Compressors DKRCC.pf.000.G3.02 520H6345
Transcript of Compressors DKRCC.pf.000.G3.02 520H6345
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Fitters Notes Compressors
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Compressors
Contents Page
Household compressors general inormation 3
Household compressors how to handle 21
Household compressors special requirements or R290 systems 39
Commercial compressors general inormation 49
This chapter is divided into our sections:
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Fitters Notes Danoss compressors
Notes
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Contents Page
1 0 G e n e r a l 4
20 Compressor 4
2 1 D e n o m i n a t i o n 5
22 Low and High starting torque 623 Motor protector and winding temperature 6
24 Rubber grommets 6
25 Minimum ambient temperature 6
30 Compressor check-up 7
31 Winding protector cut-out 7
32 PTC and protector interaction 7
33 Check o winding protector and resistance 7
40 Opening the rerigerating system 7
41 Flammable rerigerants 8
50 Mounting 851 Connectors 8
52 Driting out connectors 10
53 Tube adaptors 10
54 Brazing alloy 10
55 Soldering 11
56 LOKRING connections 12
57 Driers 12
58 Driers and rerigerants 13
59 Capillary tube in drier 13
60 Electrical equipment 14
61 LST starting device 14
62 HST starting equipment 15
63 HST CSR starting equipment 17
64 Equipment or SC twin compressors 17
65 Electronic unit or variable speed compressors 18
70 Evacuation 18
71 Vacuum pumps 19
80 Charging o rerigerant 19
81 Maximum rerigerant charge 19
82 Closing the process tube 19
90 Testing 2091 Testing o the appliance 20
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When a compressor has to be installed in newappliances normally sucient time is availableto choose the right compressor type romdatasheets and make sucient testingContrary when a aulty compressor has to be
replaced it can in many cases be impossible toget the same compressor type as the originalIn such cases it is necessary to compare relevantcompressor catalogue data
Long lietime or a compressor can be expectedi the service work is done in the right way andcleanness and dryness o the components aretaken into consideration
The service technician has to observe theollowing when choosing a compressorType o rerigerant, voltage and requency,application range, compressor displacement/capacity, starting conditions and cooling
conditionsI possible use the same rerigerant type as in theaulty system
The programme o Danoss compressors consistso the basic types P, T, N, F, SC, SC Twin and GS
Danoss 220 V compressors have a yellow label
with inormation o the type designation, voltageand requency, application, starting conditions,rerigerant and code number
The 115 V compressors have a green label
LST/HST mentioned both means that the startingcharacteristics are depending on the electricalequipment
I the type label has been destroyed, thecompressor type and the code number canbe ound in the stamping on the side o thecompressor
See picture Am0_0025b
Composition o line 1:
H4485: Compressor type inormation(eg 102H4485 = H4485)
C: internal code
Composition o line 2:Production date(week, year, day, hour eg 051D11)
2.0Compressor
1.0General
Am0_0024
Am0_0025
Am0_0025b
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Compressors
2.1Denomination
Compressor platormBD, P, T, F, N, S, GS
Protection locationL, R, C = Int Winding protectorF = Ext Winding protectorLV = Variable speed
Optimization levelE = Energy optimizationS = Semi-direct intakeX, Y, U = High energy optimized
Nominal displacement in cm3
(15/15 = TWIN compressors)
N L E 9 FF R 7,5 G KS C 15 CN X . 2
GenerationBlank, 2, 3, 4
K = Low Starting Torque (capillary tubes)X = High Starting Torque
Application RangeC = LBP R22CL = LBP R404/R507CM = LBP R22CN = LBP R290D = HBP R22DL = HBP R404A/R507, R407CF = HBP/(MBP) R134aFT = LBP tropical R134aG = LBP/MBP/HBP R134aGH = Heat pumps R134aGHH = Heat pumps optimized R134aK = LBP/(MBP) R600aKT = LBP/(MBP), tropical R600aMF = MBP R134aMK = MBP R600aML = MBP R404A/R507MN = MBP R290S = LBP/HBP (service) R426A, R401A/R401B, R409A/R409BST = LBP tropical (service) R426A, R401A/R401B, R409A/R409B
The rst letter o the denomination (P, T, N, F, Sor G) indicates compressor series whereas thesecond letter indicates motor protection placing
E, U, Y and X mean dierent energy optimizationsteps S means semi direct suction V meansvariable speed compressors On all thesementioned types the indicated suction connectorhas to be used Using the wrong connector assuction connector will lead to reduced capacity
and eciencyA number indicates the displacement in cm3,but or PL compressors the number indicates thenominal capacity
The letter ater the displacement indicates whichrerigerant must be used as well as the eld oapplication or the compressor (See example)LBP (Low Back Pressure) indicates the range olow evaporating temperatures, typically -10Cdown to -35C or even -45C, or use in reezersand rerigerators with reezer compartments
MBP (Medium Back Pressure) indicates the rangeo medium evaporating temperatures, typically
-20C up to 0C, such as in cold cabinets, milkcoolers, ice machines and water coolers
HBP (High Back Pressure) indicates highevaporating temperatures, typically -5C up to+15C, such as in dehumidiers and some liquidcoolers
T as extra character indicates a compressorintended or tropical application This means highambient temperatures and capability o working
with more unstable power supplyThe nal letter in the compressor denominationprovides inormation on the starting torque I,as principal rule, the compressor is intended orLST (Low Starting Torque) and HST (High StartingTorque), the place is let empty The startingcharacteristics are depending on the electricalequipment chosen
K indicates LST (capillary tube and pressureequalization during standstill) and Xindicates HST (expansion valve or no pressureequalization)
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2.2Low and High startingtorque
Description o the dierent electrical equipmentsshown can be ound in the datasheets or thecompressors See also section 60
Low starting torque (LST) compressors mustonly be used in rerigerating systems having
capillary tube throttling device where pressureequalization is obtained between suction anddischarge sides during each standstill period
A PTC starting device (LST) requires that thestandstill time is at least 5 minutes, since this isthe time necessary or cooling the PTC
The HST starting device, which gives thecompressor a high starting torque, must always
be used in rerigeration systems with expansionvalve, and or capillary tube systems without ullpressure equalization beore each start
High stating torque (HST) compressors arenormally using a relay and starting capacitor as
starting deviceThe starting capacitors are designed or shorttime cut-in
17% ED, which is stamped onto the startingcapacitor, means or instance max 10 cut-ins perhour each with a duration o 6 seconds
2.3Motor protector andwinding temperature
Most o the Danoss compressors are equippedwith a built-in motor protector (windingprotector) in the motor windings See alsosection 21
At peak load the winding temperature mustnot exceed 135C and at stable conditions thewinding temperature must not exceed 125CSpecic inormation on some special types can
be ound in the collection o data sheets
2.4Rubber grommets
3327-2
9
Compressor bas rommet sleeve
Washer Nut M6
Cabinet base Screw M6 x 25 Rubber grommet
Stand the compressor on the base plate until itis tted
This reduces the risk o oil coatings inside theconnectors and associated brazing problems
Place the compressor on its side with theconnectors pointing upwards and then t therubber grommets and grommet sleeves on thebase plate o the compressor
Do not turn the compressor upside down
Mount the compressor on the baseplate o theappliance
Am0_0026
Am0_0027
2.5Minimum ambient
temperature
Allow the compressor to reach a temperatureabove 10C beore starting the rst time to avoid
starting problems
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3.0Compressor check-up
I the compressor does not operate, it could havemany reasons Beore replacing the compressor, itshould be made sure, that it is deect
For easy ailure location, please see the sectionTrouble shooting
3.1Winding protector cut-out I the winding protector cuts out while thecompressor is cold, it can take approx 5 minutesor the protector to reset
I the winding protector cuts out while thecompressor is warm (compressor housing above80C) the resetting time is increased Up toapprox 45 minutes may pass beore reset
3.2PTC and protectorinteraction
The PTC starting unit requires a cooling time o 5minutes beore it can restart the compressor withull starting torque
Short time power supply cut os, not longenough to allow the PTC to cool down, can resultin start ailure or up to 1 hour
The PTC will not be able to provide ull actionduring the rst protector resets, as they typicallydo not allow pressure equalization also Thus theprotector trips until the reset time is longenough
This mismatch condition can be solved byunplugging the appliance or 5 to 10 minutestypically
3.3Check o winding protectorand resistance
In the event o compressor ailure a check ismade by means o resistance measurementdirectly on the current lead-in to see whetherthe deect is due to motor damage or simply atemporarily cut out o the winding protector
I tests with resistance measurement reveal aconnection through the motor windings rompoint M to S o the current lead-in, but brokencircuit between point M and C and S and C thisindicates that the winding protector is cut outThereore, wait or resetting
M S
C
Start winding
Winding protector
Main winding
Am0_0028
4.0Opening the rerigeratingsystem
Never open a rerigerating system beore allcomponents or the repair are available
Compressor, drier and other system componentsmust be sealed o until a continuous assemblycan occur
Opening a deect system must be done indierent ways depending on the rerigerant used
Fit a service valve to the system and collect thererigerant in the right way
I the rerigerant is fammable it can be releasedoutside in the open air through a hose i theamount is very limited
Then fush the system with dry nitrogen
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4.1Flammable rerigerants
R600a and R290 are hydrocarbons Thesererigerants are fammable and are only allowedor use in appliances which ull the requirementslaid down in the latest revision o EN/IEC 60335-2-24 (To cover potential risk originated rom the
use o fammable rerigerants)
Consequently, R600a and R290 are only allowedto be used in appliances designed or thisrerigerant and ull the above-mentionedstandard R600a and R290 are heavier than airand the concentration will always be highest at
the foor The fammability limits are approx asollows:
Rerigerant R600a R290
Lower limit 15% by vol (38 g/m3) 21% by vol (39 g/m3)
Upper limit 85% by vol (203 g/m3) 95% by vol (177 g/m3)
Ignition temperature 460C 470C
In order to carry out service and repair on R600aand R290 systems the service personnel must beproperly trained to be able to handle fammablererigerants
This includes knowledge on tools, transportationo compressor and rerigerant, and the relevant
regulations and saety precautions when carryingout service and repair
Do not use open re when working withrerigerants R600a and R290!
Danoss compressors or the fammablererigerants R600a and R290 are equipped with ayellow warning label as shown
The smaller R290 compressors, types T and N, areLST types These oten need a timer to ensuresucient pressure equalization time
For urther inormation, please see the section
Practical Application o Rerigerant R290Propane in Small Hermetic Systems
R600a
R290
5.0Mounting
Soldering problems caused by oil in theconnectors can be avoided by placing thecompressor on its base plate some time beoresoldering it into the system
The compressor must never be placed upsidedown The system should be closed within 15minutes to avoid moisture and dirt penetration
5.1Connectors
The positions o connectors are ound in thesketches C means suction and must always beconnected to the suction line
E means discharge and must be connected tothe discharge line D means process and is usedor processing the system
TL
E
Cor
D
Dor
C
PL
C
E
D
NL
C
ED
FR
E
CD
SC
D C
E
C D
E
TLSCD
E
GS
Am0_0029
Am0_0030
Am0_0031
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Most Danoss compressors are equipped withtube connectors o thick-walled, copper-platedsteel tube which have a solderability whichcomes up to that o conventional copperconnectors
The connectors are welded into the compressorhousing and weldings cannot be damaged byoverheating during soldering
The connectors have an aluminium cap sealing(capsolut) which gives a tight sealing The sealingsecures that the compressors have not beenopened ater leaving Danoss production lines Inaddition to that, the sealing makes a protectingcharge o nitrogen superfuous
The capsoluts are easily removed with anordinary pair o pliers or a special tool as shownThe capsolut cannot be remounted When the
seals on the compressor connectors are removedthe compressor must be mounted in the systemwithin 15 minutes to avoid moisture and dirtpenetration
Capsolut seals on connectors must never be letin the assembled system
5.1Connectors(continued)
Am0_0032
Oil coolers, i mounted (compressors rom 7 cm3displacement), are made o copper tube and thetube connectors are sealed with rubber plugs Anoil-cooling coil must be connected in the middleo the condenser circuit
SC Twin compressors must have a check valvein the discharge line to compressor no 2 I achange in the starting sequence betweencompressor no 1 and no 2 is wanted a checkvalve has to be placed in both discharge lines
Am0_0033
In order to have optimum conditions orsoldering and to minimize the consumptiono soldering material, all tube connectors onDanoss compressors have shoulders, as shown
Am0_0034
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5.2Driting out connectors
It is possible to drit out the connectors havinginside diameters rom 62 mm to 65 mm whichsuit 14 (635 mm) tube, but we advise againstdriting out the connectors by more than 03 mm
During driting it is necessary to have a suitablecounterorce on the connectors so that they dontbreak o
A dierent solution to this problem would be toreduce the diameter o the end o the connectortube with special pliers
Am0_0035
5.3Tube adaptors
Instead o driting out the connectors or reducingthe diameter o the connection tube, copperadapter tubes can be used or service
A 6/65 mm adaptor tube can be used where acompressor with millimetre connectors (62 mm)is to be connected to a rerigerating system with14 (635 mm) tubes
A 5/65 mm adaptor tube can be used where acompressor with a 5 mm discharge connector isto be connected to a 14 (635 mm) tube
Am0_0036
Am0_0037
5.4
Brazing alloy
For soldering the connectors and copper tubes
solders having a silver content as low as 2% cantheoretically be used but with 15% is preerredThis means that the so-called phosphor solderscan also be used when the connecting tube ismade o copper
I the connecting tube is made o steel, a solderwith high silver content which does not containphosphor and which has a liquidus temperaturebelow 740C is required For this also a fux isneeded
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5.5Soldering
The ollowing are guidelines or soldering osteel connectors dierent rom soldering copperconnectors
During heating, the temperature should be kept
as close to the melting point o the solder aspossible
Am0_0038
Use the sot heat in the torch fame whenheating the joint
Distribute the fame so at least 90% o the heatconcentrates around the connector and approx10% around the connecting tube
Am0_0039
When the connector is cherry-red (approx 600C)apply the fame to the connecting tube or a ewseconds
Am0_0040
Continue heating the joint with the sot fameand apply solder
Am0_0041
Overheating will lead to surace damage, sodecreasing the chances o good soldering
Draw the solder down into the solder gap byslowly moving the fame towards the compressorthen completely remove the fame
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5.6LOKRING connections
System containing the fammable rerigerantsR600a or R290 must not be soldered In suchcases a LOKRING connection as shown can beusedNewly made systems can be soldered as usual,
as long as they have not been charged withfammable rerigerant
Charged systems are never to be opened by useo the fame Compressors rom systems withfammable rerigerant have to be evacuated toremove the rerigerant residues rom the oil
Assembly jaws
Bolt
Tool
Tube LOKRING LOKRING Joint
Tube LOKRING LOKRING TubeJoint
Beore theassembly
Ater theassembly
LOKRING union joint
5.7Driers
Danoss compressors are expected to be used inwell-dimensioned rerigerant systems including adrier containing an adequate amount and type odesiccant and with a suitable quality
The rerigerating systems are expected to have adryness corresponding to 10 ppm As a max limit20 ppm is accepted
The drier must be placed in a way ensuring thatthe direction o fow o the rerigerant ollowsgravitation
Thus the MS beads are prevented rom movingamong themselves and in this way making dustand possible blockage at the inlet o the capillarytube At capillary tube systems this also ensures aminimal pressure equalizing time
Especially pencil driers should be chosen careully
to ensure proper quality In transportable systemsonly driers approved or mobile application areto be used
A new drier must always be installed when arerigeration system has been opened
Am0_0043
Am0_0042
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5.8Driers and rerigerants
Water has a molecular size o 28 ngstrmAccordingly, Molecular Sieves with a pore sizeo 3 ngstrm will be suitable or normally usedrerigerants
MS with a pore size o 3 ngstrm can besupplied by the ollowing,
UOP Molecular Sieve Division (ormer Union Carbide)
25 East Algonquin Road, Des Plaines
Illinois 60017-5017, USA 4A-XH7 4A-XH9
R22, R502
R134a
HFC/HCFC blends
R290, R600a
Grace Davison Chemical
W.R.Grace & Co, P.O.Box 2117, Baltimore
Maryland 212203 USA 574 594
R22, R502
R134a HFC/HCFC blends
R290, R600a
CECA S.A
La Deense 2, Cedex 54, 92062 Paris-La Deense
France NL30R Siliporite H3R
R22, R502
R134a
HFC/HCFC blends
R290, R600a
Driers with the ollowing amount o desiccantsare recommended
Compressor Drier
PL and TL 6 gram or more
FR and NL 10 gram or more
SC 15 gram or more
In commercial systems larger solid core driers areoten used These are to be used or the
rerigerants according to the manuacturersinstructions I a burn-out lter is needed in arepair case, please contact the supplier or detailinormation
5.9Capillary tube in drier
Special care should be taken when soldering thecapillary tube When mounting the capillary tubeit should not be pushed too ar into the drier,thus touching the gaze or lter disc, causing ablockage or restriction I, on the other hand,the tube is only partly inserted into the drier,blockage could occur during the soldering
This problem can be avoided by making a stopon the capillary tube with a pair o special pliersas shown
Am0_0044
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6.0Electrical equipment
For inormation on the right starting devices,please see Datasheets or the compressorNever use a starting device o and oldcompressor, because this may cause acompressor ailure
No attempt must be made to start thecompressor without the complete starting
equipment For saety reasons the compressormust always be earthed or otherwise additionallyprotected Keep away infammable material romthe electrical equipment
The compressor must not be started undervacuum
6.1LST starting device
Compressors with internal motor protector.The below drawings show three types o deviceswith PTC starters
Mount the starting device on the current lead-ino the compressor
Pressure must be applied to the centre o thestarting device so that the clips are not deormed
Mount the cord relie on the bracket under thestarting device
On some energy optimized compressors a runcapacitor is connected across the terminals N andS or lower power consumption
Pressure must be applied to the centre o thestarting device when dismantling so that theclips are not deormed
Place the cover over the starting device andscrew it to the bracket
N
N LC
b
d
a1
a1
Winding protector
Start windingMain winding
g
10 11
1312
14
b
d
a2
c
c
Main winding Start windingWinding protector
N
N LC
b
d
a1
a1
Winding protector
Start windingMain winding
Am0_0045 Am0_0046
Am0_0047 Am0_0048
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6.3HST CSR starting equipment
Mount the terminal box on the current lead-inNote that the leads must ace upwardsMount the cord relie in the bracket underterminal box Place the cover (See g F)
6.4Equipment or SC twincompressors
The use o a time delay (eg Danoss 118U0082) isrecommended or starting the second section (15seconds time delay)
I time delay is used, the connection on theterminal board between L and 1 must beremoved rom the compressor no 2 connectionbox
I thermostat or capacity control is used, theconnection on the terminal board between 1 and2 must be removed
Am0_0058
M
12
10 11
13
14
12
14
10 11
13
1
2
N
L
1
2
N
L
1 1
2 2
N N
L L
2 1 3
BA
1 2
C
D
E
F
5 2
14
5 2
14
1 1
2 2
N N
L L
1 1
2 2
N N
L L
M
B
2 1 3C
D
E
A
F
1
A: Saety pressure controlB: Time delay relayC: BlueD: Black
E: BrownF: Remove wire L-1 i time delay isusedRemove wire 1-2 i thermostat 2is used
Am0_0059
Am0_0060
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6.5Electronic unit orvariable speed compressors
The electronic unit provides the NLV compressorswith a high starting torque (HST) which meansthat a pressure-equalization o the system beoreeach start is not necessary
The variable speed compressor motor iselectronically controlled The electronic unit hasbuilt-in overload protection as well as thermalprotection In case o activation o the protectionthe electronic unit will protect the compressormotor as well as itsel When the protection has
been activated, the electronic unit automaticallywill restart the compressor ater a certain time
The compressors are equipped with permanentmagnet rotors (PM motor) and 3 identical stator
windings The electronic unit is mounted directlyon the compressor and controls the PM motor
Connecting the motor directly to AC mains, byault, will damage the magnets and lead to dras-tically reduced eciency, or even no unctioning
Am0_0061
7.0Evacuation
Ater brazing, evacuation o the rerigerationsystem is startedWhen a vacuum below 1 mbar is obtained thesystem is pressure equalized beore the nalevacuation and charging o rerigerantI a pressure test has been perormed directlybeore evacuation, the evacuation process is to
be started smoothly, with low pumping volume,to avoid oil loss rom the compressorMany opinions exist how evacuation can becarried out in the best wayDependent on the volume conditions o thesuction and the discharge side in the rerigerationsystem, it might be necessary to choose one othe ollowing procedures or evacuationOne-sided evacuation with continuousevacuation until a suciently low pressure in thecondenser has been obtained One or more shortevacuation cycles with pressure equalization inbetween is necessaryTwo-sided evacuation with continuousevacuation until a suciently low pressure has
been obtained
These procedures naturally require a gooduniorm quality (dryness) o the componentsusedThe below drawing shows a typical course oa one-sided evacuation rom the process tubeo the compressor It also shows a pressuredierence measured in the condenser This
can be remedied by increasing the numbers opressure equalizationsThe dotted line shows a procedure where twosides are evacuated simultaneouslyWhen the time is limited, the nal vacuum to beobtained is only dependent on the capacityo the vacuum pump and the content o noncondensable elements or rerigerant residues inthe oil chargeThe advantage o a two-sided evacuation isthat it is possible to obtain a considerably lowerpressure in the system within a reasonableprocess timeThis implies that it will be possible to build a leakcheck into the process in order to sort out leaks
beore charging the rerigerant
Am0_0062
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The below drawing is an example o a pre-evacuation process with built-in leak test
The level o vacuum obtained depends onthe process chosen Two-sided evacuation isrecommended
7.0Evacuation(continued)
Am0_0062
7.1Vacuum pumps
An explosion-sae vacuum pump must be usedor systems with the fammable rerigerantsR600a and R290
The same vacuum pump can be used or allrerigerants i it is charged with Ester oil
8.0Charging o rerigerant
Always charge the system with type andamount o rerigerant recommended by themanuacturer In most cases the rerigerantcharge is indicated on the type label o theappliance
Charging can be done according to volume orby weight Use a charging glass or charging byvolume Flammable rerigerants must be chargedby weight
8.1
Maximum rerigerant charge
I the max rerigerant charge is exceeded the oil
in the compressor may oam ater a cold start andthe valve system could be demaged
The rerigerant charge must never be too large
to be contained on the condenser side o thererigeration system Only the rerigerant amountnecessary or the system to unction must becharged
Compressor Maximum rerigerant charge
R134a R600a R290 R404A
P 300 g 150 g
T 400 g* 150 g 150 g 400 g
N 400 g* 150 g 150 g 400 g
F 900 g 150 g 850 g
SC 1300 g 150 g 1300 g
GS 2000 g 2000 g
SC-Twin 2200 g 2200 g
*) Single types with higher limits available, see data sheets.
8.2Closing the process tube
For the rerigerants R600a and R290 the closingo the process tube can be done by means o aLOKRING connection
Soldering is not allowed on systems withfammable rerigerants
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9.0Testing
Hermetic rerigerating systems must be tight I adomestic appliance shall unction over areasonable lietime, it is necessary to haveleak rates below 1 gram per year So leak testequipment o a high quality is required
All connections must be tested or leaks with aleak testing equipment This can be done with anelectronic leak testing equipment
The discharge side o the system (rom dischargeconnector to the condenser and to the drier)must be tested with the compressor runningThe evaporator, the suction line and thecompressor must be tested during standstill andequalized pressure
I rerigerant R600a is used, leak test should bedone with other means than the rerigerant, eghelium, as the equalizing pressure is low, so otenbelow ambient air pressure Thus leaks would notbe detectable
9.1Testing o the appliance
Beore leaving a system it must be checked thatcooling down o the evaporator is possible andthat the compressor operates satisactory on thethermostat
For systems with capillary tube as throttlingdevice it is important to check that the system isable to pressure equalize during standstill periodsand that the low starting torque compressor isable to start the system without causing trips onthe motor protector
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Contents Page
10 General 23
11 Fault location 23
12 Replacement o thermostat 24
13 Replacement o electrical equipment 2514 Replacement o compressor 25
15 Replacement o rerigerant 25
20 Rules or repair work 27
21 Opening o the system 27
22 Brazing under an inert protective gas 28
23 Filter drier 28
24 Moisture penetration during repair 29
25 Preparation o compressor and electrical equipment 29
26 Soldering 30
27 Evacuation 3128 Vacuum pump and vacuum gauge 31
30 Handling o rerigerants 32
31 Charging with rerigerant 32
32 Maximum rerigerant charge 32
33 Test 33
34 Leak test 33
40 Replacement o deective compressor 34
41 Preparation o components 34
42 Removal o charge 34
43 Removal o deective compressor 34
44 Removal o rerigerant residues 34
45 Removal o lter drier 34
46 Cleaning o solder joints and reassembly 34
50 Systems contaminated with moisture 35
51 Low degree o contamination 35
52 High degree o contamination 35
53 Drying o compressor 36
54 Oil charge 36
60 Lost rerigerant charge 37
70 Burnt compressor motor 38
71 Oil acidity 3872 Burnt system 38
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Notes
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Repairs o rerigerators and reezers demandskilled technicians who are to perorm thisservice on a variety o dierent rerigerator typesPreviously service and repair were not as heavilyregulated as now due to the new rerigerants,
some o which are fammable
Fig 1 shows a hermetic rerigeration system withcapillary tube as expansion device This systemtype is used in most household rerigeratorsand in small commercial rerigerators, ice creamreezers and bottle coolersFig 2 shows a rerigeration system using athermostatic expansion valve This system type ismainly used in commercial rerigeration systems
Repair and service is more dicult than newassembly, since working conditions in the eldare normally worse than in a production site or ina workshop
A precondition or satisactory service work isthat the technicians have the right qualications,ie good workmanship, thorough knowledge othe product, precision and intuitionThe purpose o this guide is to increase theknowledge o repair work by going through thebasic rules The subject matter is primarily dealtwith reerence to repair o rerigeration systemsor household rerigerators in the eld but manyo the procedures may also be transerred tocommercial hermetic rerigeration installations
1.0General
1.1Fault location
Fig. 3: Pressure gauges, service valve, multimeter and leak tester
Beore perorming any operations on arerigeration system the progress o the repair
should be planned, ie all necessary replacementcomponents and all resources must be availableTo be able to make this planning the ault in thesystem must rst be known For ault locationtools must be available as shown in g 3 Suctionand discharge manometer, service valves,multimeter (voltage, current and resistance) anda leak tester
In many cases it can be concluded rom the usersstatements which aults could be possible, and
or most aults a relatively accurate diagnosis canbe made However, a precondition is that theservice technician has the necessary knowledgeo the unctioning o the product and that theright resources are available An elaborate aultlocation procedure will not be gone throughhere, however, the most common aults wherethe compressor does not start or run arementioned in the ollowing
Main switch releasedOne potential ault may be a deective use, andthe reason may be a ault in the motor windingsor in the motor protector, a short circuit or aburnt current lead-in on the compressor Theseaults require the compressor to be replaced
CompressorStarting device and compressor motor may bea wrong choice Compressor motor or windingprotector may be deective, and the compressormay be mechanically blocked
Frequent reasons or reduced rerigerationcapacity are coking or copper platings dueto moisture or non-condensable gases in thesystem
Blown gaskets or broken valve plates are due totoo high peak pressures and short-time pressure
peaks as a result o liquid hammering in thecompressor, which may be due to a too highrerigerant charge in the system or a blockedcapillary tube
Fig. 1: Hermetic rerigeration system with capillary tubes
Fig. 2: Hermetic rerigeration system with expansion valve
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1.2Replacement othermostat
The voltage may be too low or the pressure toohigh or the compressor Non equalized pressurecauses the motor protector to cut out ater eachstart and will eventually result in a burnt motorwinding A deective an will also aect the
compressor load and may cause motor protectorcut outs or blown gaskets
In case o unsuccessul start and cold compressorup to 15 minutes may pass until the windingprotector cuts the compressor out I the windingprotector cuts out when the compressor is hot upto 45 minutes may pass until the protector cutsthe compressor in againBeore starting a systematic ault location it is agood rule to cut o the voltage to the compressoror 5 minutes This ensures the PTC starting device,i any, to be cooled suciently to be able to startthe compressor
Should a brie power ailure occur within therst minutes o a rerigeration process, a confictsituation (interlocking) may arise between theprotector and the PTC A compressor with a PTCstarting device cannot start in a system that isnot pressure-equalized, and the PTC cannot coolso quickly In some cases it will take up to 1 houruntil the rerigerator runs normally again
High and low pressure switchesCut out o the high pressure switch may be due totoo high condensing pressure, probably caused bylack o an cooling A cut-out low pressure switchmay be due to insucient rerigerant charge,leakage, evaporator rost ormation or partial
blockage o the expansion device
Beore replacing the compressor it is a good ideato check the thermostat
A simple test can be made by short-circuitingthe thermostat so the compressor gets powerdirectly I the compressor can operate like this thethermostat must be replaced
For replacement it is essential to nd a suitabletype, which may be dicult with so manythermostat types in the market To make thischoice as easy as possible several manuacturers,
ie Danoss, have designed so-called servicethermostats supplied in packages with allaccessories necessary or thermostat service
1.1Fault location(continued)
The cut out may also be due to a mechanicalailure, wrong dierence setting, wrong cut-outpressure setting or irregularities in pressure
Thermostat
A deective or incorrectly set thermostat mayhave cut out the compressor I the thermostatloses sensor charge or i the temperature settingis too high, the compressor will not start Theault may also be caused by a wrong electricalconnectionToo low a dierential (dierence between cutin and cut out temperature) will cause too shortcompressor standstill periods, and in connectionwith a LST compressor (low starting torque) thismight lead to starting problemsSee also point 12 Replacement o thermostat
For urther details please reer to Fault locationand prevention in rerigeration circuits with
hermetic compressorsA careul ault determination is necessary beoreopening the system, and especially beoreremoving the compressor rom the system Repairsrequiring operations in a rerigeration system arerather costly Beore opening old rerigerationsystems it may thereore be appropriate to makesure that the compressor is not close to breakingdown though it is still unctionalAn estimation can be made by checking thecompressor oil charge A little oil is drained in toa clean test glass and is compared with a newoil sample I the drained oil is dark, opaque andcontaining impurities, the compressor should be
replaced
With eight packages, each covering one type orerigerator and application, service can be madeon almost all common rerigerators See g 4The application area o each thermostat coversa wide range o thermostat types Moreover,the thermostats have a temperature dierentialbetween cut in and cut out sucient to ensuresatisactory pressure equalization in the systemstandstill periods
In order to achieve the requested unctionthe thermostat sensor (the last 100 mm o the
capillary tube) must always be in close contactwith the evaporator
When replacing a thermostat it is importantto check whether the compressor operatessatisactorily both in warm and cold position, andwhether the standstill period is sucient or thesystem pressure equalization when using a LSTcompressor
With most thermostats it is possible to obtaina higher temperature dierential by adjustingthe dierential screw Beore doing this it isrecommended to seek advice in the thermostatdata sheet which way the screw must be turned
Another way o obtaining a higher dierentialis to place a piece o plastic between the sensorand the evaporator, since 1 mm plastic results inapprox 1C higher dierential
Fig. 4: Service thermostats
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1.3Replacement o electricalequipment
1.4Replacement o compressor
The cause or aults may also be ound in theelectrical equipment o the compressor, where itis possible to replace starting relay/PTC startingdevice, motor protector, starting or run capacitorA damaged starting capacitor may be caused
by too low thermostat dierential setting, sincethe starting capacitor must maximum cut in 10times/hour
I a ault is ound on the winding protector builtinto many hermetic compressors the entirecompressor must be replaced
When replacing a compressor the electrical
equipment must be replaced as well, sinceold electrical equipment used with a newcompressor may cause a compressor breakdownlater
I the ailure is a deective compressor, thetechnician must take care to select a compressorwith the correct characteristics or the applianceI a compressor corresponding to the deectiveone is available, and i it is intended or a nonregulated rerigerant, no urther problems willarise However, in many cases it is impossibleto provide the same compressor type as thedeective one, and in this case the service
technician must be aware o some actorsI it is a question o changing rom onecompressor manuactured to another it canbe dicult to select the correct compressor,and thereore dierent parameters have to beconsideredCompressor voltage and requency mustcorrespond to voltage and requency on locationThen the application area must be considered(low, medium or high evaporating temperatures)The cooling capacity must correspond to the oneo the previous compressor, but i the capacity
is unknown a comparison o the compressordisplacements will be applicable It would beappropriate to select a compressor slightly largerthan the deective oneFor a capillary tube system with pressureequalization during the standstill periods a LSTcompressor (low starting torque) can be used,and or a system with expansion valve or nopressure equalization a HST compressor (high
starting torque) is to be chosenO course a HST compressor may also be used ina capillary tube systemFinally the compressor cooling conditions mustalso be considered I the system has an oilcooling arrangement, a compressor with an oilcooler must be selectedIn a service situation a compressor with anoil cooler instead o a compressor without oilcooler can be used without problems, since thespiral can be completely ignored when it is notrequired
1.5
Replacement orerigerant
The best solution or a repair is to select the same
rerigerant as used in the present systemDanoss compressors are supplied or weresupplied in versions or the rerigerants R12, R22,R502, R134a, R404A/R507/R407C and or thefammable rerigerants R290 and R600aThe rerigerants R12 and R502, which are coveredby the regulations in the Montreal Protocol,may be used in very ew countries only, and thererigerants will eventually be phased out oproduction altogetherFor heat pump systems the rerigerant R407C isnow used instead o R22 and R502The more environmentally acceptable rerigerantR134a has replaced R12, and the rerigerantsR404A and R507 have replaced R22 and R502 in
many applications
The ammable rerigerants R290 and R600aMaximum charge o these rerigerants in asystem is 150 g according to todays relevantappliance standards, and they must be applied insmall rerigerators only
Blend rerigerants
Rerigerant Trade name Composition Replacing Application area Applicable oils
R401A Suva MP39 R22, R152a, R124 R12 L - M Alkylbenzene
R401B Suva MP66 R22, R152a, R124 R12 L Alkylbenzene
R402A Suva HP80 R22, R125, R290 R502 LPolyolester
Alkylbenzene
R402B Suva HP81 R22, R125, R290 R502 L - MPolyolester
Alkylbenzene
The famable rerigerants must only be used in
rerigeration systems meeting the requirementso EN/IEC 60335-2-24 or -2-89, including demandsor fammable rerigerants and the servicepersonnel must be specially trained or thehandling This implies knowledge o tools,transport o compressors and rerigerant as wellas all relevant rules and saety regulationsI open re or electrical tools are used near thererigerants R600a and R290, this must take placein conormity with current regulationsThe rerigeration systems must always be openedwith a tube cutter
Change rom the rerigerants R12 or R134a toR600a is not permitted, since the rerigerators are not
approved or use with ammable rerigerants, andthe electrical saety has not been tested accordingto current standards. The same applies to changerom the rerigerants R22, R502 or R134a to R290.
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Rerigerant blendsAt the same time as the new environmentallyacceptable rerigerants (R134a and R404A) wereintroduced, some rerigerant blends or servicepurposes were also introduced They were better
environmentally acceptable than the previouslyused CFC rerigerants (R12 and R502)In many countries the rerigerant blends wereonly permitted or a short period, which meantthat they were not widely spread in connectionwith small hermetic rerigeration systemsUse o these rerigerants cannot be recommendedor series production but they can be used orrepair in many cases, see the table on the previouspage
Add inThis designation is used when lling up anexisting rerigeration system with anotherrerigerant than the one originally charged
This is especially the case when problems arisewhich must be solved with as small an operationas possibleCorrespondingly, R22 systems were replenishedwith a small amount o R12 in order to improvethe fow o oil back to the compressorIn several countries it is not allowed to add in onCFC systems (R12, R502, )
1.5Replacement orerigerant(continued)
Drop inThis term means that during service on anexisting rerigeration system ie > 90% o theoriginal mineral oil is poured out and replacedby synthetic oil, and a new suitable lter drier is
mounted Furthermore, the system is chargedwith another compatible rerigerant (ie blend)
RetrotThe term retrot is used about service onrerigeration systems replacing the CFCrerigerant by an environmentally acceptableHFC rerigerantThe rerigeration system is fushed, and thecompressor is replaced by an HFC compressorAlternatively the compressor oil is replaced by asuitable Ester oilThe oil must be changed several times ater shortoperating periods, and the lter drier must bereplaced
In case o oilreplacement a statement romthe compressor manuactorer on materialcompatibility is necessary
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2.0Rules or repair work
To enable a hermetic rerigeration system to workas intended and to achieve a reasonable servicelie the content o impurities, moisture and noncondensable gases must be kept on a low levelWhen assembling a new system these
requirements are relatively easy to meet, butwhen repairing a deective rerigeration systemthe matter is more complicated Among otherthings, this is due to the act that aults in a
2.1Opening o the system
rerigeration system oten start disadvantageouschemical processes, and that opening arerigeration system creates possibilities orcontaminationI a repair is to be carried out with a good result
a series o preventive measures is necessaryBeore stating any details about the repair work,some general rules and conditions have to beexplained
Fig. 5: Hermetic rerigeration system with capillary tube
I the rerigeration system contains a fammablererigerant like eg R600a or R290, this will appearrom the type label A Danoss compressor will beprovided with a label as shown in g 6
Fig. 6: Label on compressor or R600a
Service and repair o such systems demandspecially trained personnel This impliesknowledge o tools, transport o compressor andrerigerants as well as the relevant guidelines andsaety rulesWhen working with the rerigerants R600a and
R290 open re may only occur as described inexisting guidelinesFig 7 shows a piercing valve or mounting onthe process tube, thus enabling an opening intothe system or draining o and collecting thererigerant as per instructions
Fig. 8 Recovery unit or rerigerants
Beore starting to cut tubes in the rerigerationsystem it is recommended to clean the tubeswith emery cloth in the places to be cut Thusthe tubes are prepared or the subsequentsoldering, and entry o dirt grains into the systemis avoided
Only use tube cutter, never metal-cutting saw, orcutting tubing in a rerigeration system
Merely a small burr let in the system can cause asubsequent compressor breakdownAll rerigerants must be collected as perinstructions
When a capillary tube is cut it is essential notto admit burrs or deormations to the tube Thecapillary tube can be cut with special pliers (seeg 9), or with a le a trace can be produced in thetube which can then be broken
Fig. 9: Special pliers or capillary tubes
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Fig. 7: Piercing valve
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2.3Filter drier
The lter drier is adsorbing the small wateramounts released through the lie o the systemBesides, it acts as a trap strainer and preventsblocking o the capillary tube inlet and problemswith dirt in the expansion valve
I a rerigeration system has been opened the
lter drier must always be replaced to ensuresucient dryness in the repaired system
Replacement o a lter drier must always bedone without use o a torch When heatingthe lter drier there is a risk o transerring theadsorbed moisture amount to the system, andthe possibility o a fammable rerigerant beingpresent must also be consideredIn case o a non-fammable rerigerant, however,a blowpipe fame may be used but the capillarytube must be broken and then dry nitrogen mustbe blown through the lter towards the open airwhile the lter drier is detachedNormally a lter drier can adsorb a water amount
o approx 10% o the desiccant weight In mostsystems the capacity is not utilized, but in caseso doubt about the lter size it is better to usean oversized lter than one with too small acapacityThe new lter drier must be dry Normally thisis no problem but it must always be ensuredthat the lter drier sealing is intact to preventmoisture collection during storage and transportThe lter drier must be mounted in a way thatfow direction and gravitation have an eect inthe same direction
A system charged with rerigerant must neverbe heated or soldered, especially not when thererigerant is fammableSoldering on a system containing rerigerant willcause ormation o rerigerant decomposition
productsOnce the rerigerant is drained o an inertprotective gas must be lled into the system Thisis done by a thorough blow-through with drynitrogen Beore the blow-through the systemmust be opened in one more place
2.2Brazing under an inertprotective gas
Filter driers with a pore size o 3 ngstrm in
relation to rerigerant:In connection with service on commercialrerigeration systems Danoss DML lters arerecommended
Compressor Filter drier
P and T 6 gram or more
F and N 10 gram or more
SC 15 gram or more
GS 22 gram or more
I the compressor is deective it would beappropriate to cut the suction and pressuretube outside the compressor connectors, notopening the process tubeI, however, the compressor is unctional,
it is recommended to cut the process tubeBlow-through must be done rst throughevaporator and then through condenserAn inlet pressure o approx 5 bar and a blow-through o approx 1-2 minutes would beatisactory on appliances
Thus it is prevented that the Molecular Sieve(MS) balls wear each other and produce dust,which may block the capillary tube inlet Thisvertical position also ensures a quicker pressureequalization in capillary tube systems See g 10
Since water has a molecule size o 28 ngstrm,
molecular sieve lters with a pore size o 3ngstrm are suitable or the normally usedrerigerants, since the water molecules areadsorbed in the pores o the desiccant, whereasthe rerigerant can reely pass through the lter
Fig. 10: Correct location o lter drier
I a lter withaluminium oxide is required or
the suction line, Danoss type DAS burnoutlters or the rerigerants R134a and R404A arerecommended
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A repair must always be done quickly, andno rerigeration system must be open to theatmosphere or more than 15 minutes to avoidmoisture intake Thereore it is a good rule tohave all replacement components made ready
beore the system is opened
2.4Moisture penetrationduring repair
Rubber grommets are to be mounted in thecompressor base plate while the compressoris standing on its base plate I the compressoris placed upside down oil will gather in theconnectors, which leads to soldering problemsNever use rubber grommets rom a deectivecompressor since they are oten aged and harderthan new rubber grommetsRemove the cap (Capsolute) rom the processconnector o the new compressor and soldera process tube into the connector Leave thecompressor closed until it is to be soldered into
the systemBesides, it is recommended to plug all connectorson compressor, lter drier and system i or somereason the repair is delayed
The aluminium caps on the connectors must notbe let in the nished system
The caps are only intended to protect thecompressor during storage and transport and donot provide tightness in a system under pressureThe caps make sure that the compressor has notbeen opened ater it let Danoss I the caps aremissing or are damaged, the compressor shouldnot be used until it has been dried and the oil has
been replaced
Never reuse old electrical equipment
It is recommended always to use new electricalequipment with a new compressor, since use oold electrical equipment with a new compressormay lead to the compressor soon developingdeectsThe compressor must not be started without acomplete starting deviceSince part o the starting circuit resistance liesin the starting device, start without completestarting device does not provide good startingtorque and may result in a very quick heating o
the compressor start winding, causing it to bedamaged
The compressor must not be started in vacuum
Start o compressor in vacuum may cause abreakdown inside between the pins o thecurrent lead-in, since the insulation property othe air is reduced at alling pressure
Fig 11 shows a wiring diagram with PTC startingdevice and winding protector A run capacitorconnected to the terminals N and S will reduceenergy consumption on compressors designedor this
2.5Preparation ocompressorand electrical equipment
I it is impossible to complete the repaircontinuously, the open system must be careullysealed o and charged with a slight overpressureo dry nitrogen to avoid moisture penetration
Fig. 11: Wiring diagram with PTC and winding protector
Fig 12 shows a wiring diagram with startingrelay and starting capacitor as well as a motorprotector mounted outside the compressor
Fig. 12: Wiring diagram with starting relay and startingcapacitor
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2.5Preparation o compressorand electrical equipment(continued)
Fig 13 shows a wiring diagram or large SCcompressors with CSR motor
Fig. 13: Wiring diagram or CSR motor
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2.6Soldering
Creation o the correct soldering t is important
Recommended soldering gaps or brazing joints
The connectors o most Danoss compressorsare copperplated steel tubes welded into thecompressor housing, and the welded connections
cannot be damaged by overheating duringsoldering
Please see the section Mounting instructionsor urther details about soldering
Material Material
Solder alloy Copper tubes Steel tubes
Easy-fo 005 - 015 mm 004 - 015 mm
Argo-fo 005 - 025 mm 004 - 02 mm
Sil-os 004 - 02 mm Not suitable
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2.7Evacuation
When a rerigeration system is assembled it mustbe careully evacuated (remove air rom thesystem), beore it is charged with rerigerant Thisis necessary to achieve a good repair resultThe main purpose o the evacuation is to reduce
the amount o non-condensable gasses (NCG) inthe system, and secondarily a limited drying willtake placeMoisture in the system may cause ice blocking,reaction with the rerigerant, ageing o theoil, acceleration o oxidation processes andhydrolysis with insulation materialsEvacuation o rerigerating systemNon-condensable gasses (NCG) in a rerigerationsystem may mean increased condensing pressureand thus greater risk o coking processes and ahigher energy consumptionThe content o NCG must be kept below 1 vol %The evacuation may be done in dierent waysdepending on the volume conditions on the
suction and discharge side o the system
I evaporator and compressor have a large volumeone-sided evacuation may be used, otherwisedouble-sided evacuation is recommendedOne-sided evacuation is made through thecompressor process tube but this method
means slightly worse vacuum and slightly highercontent o NCG From the discharge side o thererigeration system the air must be removedthrough the capillary tube, which results in asubstantial restriction The result will be a higherpressure on the discharge side than on thesuction sideThe main actor or the NCG content aterevacuation is the equalized pressure in thesystem, which is determined by the distributiono volumesTypically, the volume on the discharge sidewill constitute 10-20% o the total volume, andthereore the high end pressure has less infuenceon the equalized pressure here than the large
volume and low pressure on the suction side-
Fig. 14: Evacuation process
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2.8Vacuum pump andvacuum gauge
For stationary use a two-stage 20 m3/h vacuumpump can be recommended but or service asmaller two-stage 10 m3/h vacuum pump isbetter suited due to its lower weightA hermetic rerigeration compressor is notsuitable or the purpose since it is not able toproduce a suciently low pressure, and also acompressor used as a vacuum pump would beoverheated and damagedThe insulation resistance o the air is reduced at
alling pressure, and thereore there electricalbreakdown at the current lead-in or in the motoro the hermetic compressor will quickly occur
In order to perorm a sucient evacuation a goodvacuum pump must be available See g 15
Fig. 15: Vacuum pump
The same vacuum pump may be used or alltypes o rerigerants provided that it is chargedwith Ester oilA fameproo vacuum pump must be used orrerigeration systems containing the fammablererigerants R600a and R290
There is no point in having a suitable vacuumpump available i the vacuum obtainedcannot be measured Thereore it is strongly
recommended to use an appropriate robustvacuum gauge (g 16) able to measure pressurebelow 1 mbar
Fig. 16: Vacuum gauge
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To ensure a reasonable rerigeration system liethe rerigerant must have a maximum moisturecontent o max 20 ppm (20 mg/kg)Do not ll rerigerant rom a large container into alling bottle through several container sizes, since
with every drawing-o the water content in thererigerant is increased considerably
Flammable rerigerants R290 and R600aR600a must be stored and transported inapproved containers only and must be handledaccording to existing guidelines
3.0Handling o rerigerants
3.2Maximum rerigerant charge
3.1Charging with rerigerant
I the permissible limit o rerigerant chargestated in the compressor data sheet is exceededthe oil will oam in the compressor ater a coldstart and may result in a damaged valve system inthe compressorThe rerigerant charge must never exceed theamount that can be contained in the condenser
side o the system
Compressor
TypeMax. rerigerant charge
R134a R600a R290 R404A
P 300 g 120 g
T 400 g 150 g 150 g 600 g
TLG 600 g 150 g 150 g
N 400 g 150 g 150 g
F 900 g 150 g 850 g
SC 1300 g 150 g 1300 g
GS 2200 g 2200 g
SC-Twin 2200 g
Do not use open re near the rerigerants R600aand R290The rerigeration systems must be opened with atube cutter
Conversion rom rerigerant R134a to R600ais not permitted, since the rerigerators arenot approved or operation with fammablererigerants, and the electrical saety has notbeen tested according to existing standardseither The same applies to conversion romrerigerant R134a to R290
Normally, charging with rerigerant is no problemwith a suitable charging and provided that theequipment present charging amount o thererigeration system is known See g 17
Fig. 17: Charging board or rerigerant
Always charge the rerigerant amount and
type stated by the rerigerator manuacturerIn most cases this inormation is stated on thererigerator type label The dierent compressorbrands contain dierent amounts o oil, so whenconverting to another brand it may be advisableto correct the amount o rerigerant
Charge o rerigerant can be made by weight orby volume Flammable rerigerants like R600aand R290 must always be charged by weightCharging by volume must be made with arerigerant charging cylinder
The rerigerant R404A and all other rerigerants inthe 400 series must always be charged as liquidI the charging amount is unknown, chargingmust be done gradually until the temperaturedistribution above the evaporator is correctThe rerigerant charge must be made withrunning compressor, rerigerator without loadand with the door closedThe correct charge is characterized by thetemperature rom inlet plus superheat equalsoutlet o the evaporator
Systems with expansion valve must be chargedwith rerigerant until there are no bubbles in thesight glass, which should be placed as close to
the expansion valve as possible
Please also reer to the compressor data sheets,as the present maximum rerigerant charge maydeviate on single types rom the statements inthe ormThe maximum charge o 150 g or R600a andR290 is an upper saety limit o the appliancestandards, whereas the other weights are stated
to avoid liquid hammer
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Beore nishing a repair the complete rerigeratormust be tested to make sure that the expectedresult has been achieved It must be ensuredthat the evaporator can be cooled down andthus enable the requested temperatures to be
obtainedFor systems with capillary tube as throttlingdevice it is important to check i the compressorruns satisactorily on the thermostat Further itmust be checked i the thermostat dierential
3.3Test
A hermetic rerigeration system must be tight,and i a rerigerator is to have a reasonablelietime it is necessary to keep any leaks below1 gram rerigerant annuallySince many rerigeration systems with thefammable rerigerants R600a and R290 havecharging amounts below 50 g, in these cases theleaks should be below 05 g rerigerant annually
This requires a high-quality electronical testequipment that can measure these small leakratesIt is relevant to test all soldered joints o thesystem, also in places where no repair has beenmadeThe joints on the discharge side o the system(rom the compressor discharge connector untilcondenser and lter drier) must be examinedduring operation o the compressor, whichresults in the highest pressuresEvaporator, suction tube and compressormust be examined while the compressor isnot operating and the pressure in the systemis equalized, since this results in the highest
pressures here See g 19
3.4Leak test
allows or sucient standstill periods or pressureequalization so an LST compressor (low startingtorque), i any, can start and operate withouttripping on the motor protectorIn areas where undervoltage may occur it is
important to test operating conditions at 85%o the nominal voltage, since both starting andstall torque o the motor will decline when thevoltage is alling
Fig. 19: Leak detector
I no electronic detector (g 19) is available thejoints may be examined with soapy water or withspray, but o course small leaks cannot be oundwith these methods
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In the ollowing a procedure or replacement o adeective compressor in a hermetic rerigerationsystem is outlined, ollowing the undamentalrulesA precondition is that there is a rerigerant
overpressure in the system and that the system isnot contaminated with moisture The rerigerant
4.0Replacement o deectivecompressor
By starting with preparation o the replacementcomponents later delays with opened systemare avoided, and thus also increased risk oradmission o moisture and impuritiesA process tube with process valve must bemounted into the process connector o the newcompressorIn some case it may be an advantage to mounta piece o connecting tube into the compressorsuction connector
4.1Preparation ocomponents
Place a piercing valve with connection to arecovery unit on the compressor process tubePuncture the tube and collect the rerigerantaccording to guidelinesFollow the rules described earlier
4.2Removal o charge
Cut the compressor suction and discharge tubewith a tube cutter approx 25-30 mm rom theconnectors in question, but previously the placesto be cut must be trimmed with emery clothpreparing the solderingI the compressor is to be tested later, the tubeends must be closed with rubber plugs
4.3Removal o deectivecompressor
To avoid decomposition o any rerigerantresidues in the system during the subsequentsoldering operations the system must bethoroughly blown through with dry nitrogen
4.4Removal o rerigerantresidues
The lter drier at the condenser outlet should becut with a tube cutter but another method mayalso be used
4.5Removal o lter drier
Soldering silver must be removed rom the
condenser outlet This is best done by brushing ito while the soldering silver is still liquidThe other tube ends are to be prepared orsoldering in case this was not yet done Take carethat dirt and metal grains are not admitted to thesystem when trimming soldered jointsI necessary, blow through with dry nitrogenwhile trimmingThe new lter drier must be mounted at thecondenser outlet, and the lter must be keptcovered until assembly can take place Avoidheating the lter enclosure itsel with the fameBeore soldering the capillary tube into the ltera slight stop must be produced on the tube asdescribed earlier to ensure the tube end to be at
the right place in the lter to avoid blockingsBe careul during soldering o the capillary tubeand avoid burnings
4.6
Cleaning o solder joints andreassembly
must correspond to the original rerigerantDuring ault nding the compressor is ound tobe deective I it turns out that the motor hasburnt resulting in strong contamination o thesystem another procedure is required
By doing so the later connection o the suctiontube to the compressor can take place urtheraway rom the compressor i mountingconditions in the machine compartment arenarrowWhen the compressor is ready process valve andconnectors must be closed Further, the correctlter drier type must be ready but the cover mustremain intact
To acilitate any analysis or guarantee repair laterthe compressor must be provided with the causeor the ault and the rerigerator production dateCompressors or R600a and R290 must always beevacuated and sealed beore they are returned torerigerator manuacturer or dealer
This is done by connecting the connection tuberom the bottle with dry nitrogen rst to the cutsuction tube and aterwards to the cut dischargetube
Produce a slight fow o dry nitrogen through thedischarge tube to the condenser and maintainthis fow while the lter is careully removed witha torch Avoid heating the lter enclosure itsel
Mount the compressor, which already during
preparation must be provided with rubbergrommetsMount the electrical equipment and connect thewires Evacuation and charge are to be made asdescribed in paragraphs 27 and 31Test to be made as described in paragraphs 33and 34When the process tube is squeezed and solderedthe process valve must be removed
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For systems contaminated with moisture itapplies that the degree o contamination may bevery varying, and the scope o the repair will varyaccordinglySystems containing moisture can be divided
into two categories, namely the ones with a lowdegree o contamination and the ones with ahigh degree o contamination
5.0Systems contaminatedwith moisture
5.1Low degree ocontamination
This deect is usually characterized by the coolingoten being interrupted due to ice blocking in thecapillary tube or in the expansion valve With heatsupply the ice blocking is gradually removed,but i the rerigerant circulates the blocking willquickly build up againThis deect may be due to ollowing reasonsThe system has not been assembled careullyenoughThe components used may have been moist
A rerigerant with too high a moisture contentmay have been usedThe system will oten be new or it has just beenrepaired Usually the moisture amounts aresmall, and thereore the deect can normally beremedied by replacement o rerigerant and lterdrier The procedure is as ollows
a) Open the system at the process tube andcollect the rerigerantIt is an advantage to rst let the compressorrun until it is hot In this way the moisture andrerigerant amount let in the motor or in the
oil is reducedWhen ice is blocking capillary tube or
expansion valve it is possible to run thecompressor hot but the system will not runI capillary tube or expansion valve areaccessible, the place o blocking may be kepthot with a heating lamp or a cloth with hotwater to obtain circulation o the rerigerant
I there is a rupture in a rerigeration system andthe rerigerant overpressure escapes, moisturecontamination will take place The longer timethe system is open to the atmosphere the higherthe degree o contamination I the compressoris operating at the same time, conditions areurther worsened The admitted moisture amount
will distribute in compressor, lter drier and othersystem components depending on their ability tohold the moistureIn the compressor it will especially be the oilcharge that absorbs the water In evaporator,condenser and tubes the contamination willprimarily be determined by the oil amountspresent hereO course the largest water amounts will be incompressor and lter drier There is also a highrisk that valve coking has started damaging thecompressor Thereore compressor and lterdrier must be replaced during the normal repairprocedure
a) Remove the compressor rom the system witha tube cutter
5.2High degree ocontamination
Systems with a low degree o contamination areintact and maintain a rerigerant overpressureSystems with a high degree o contamination,however, are characterized by having been incontact with the atmosphere or moisture has
been added directly The two types o deect willbe treated independently
The evaporating temperature in the systemmay also be increased by heating theevaporator Do not use an open fame orheating
b) Ater collecting the rerigerant the systemmust be blown through with dry nitrogenNitrogen injection must take place throughthe compressor process tube, and rst thesuction side and then the discharge side
must be blown through, rst directing thenitrogen fow rom the compressor throughthe suction tube and evaporator and outthrough the capillary tube, then throughcompressor and condenser and out throughthe lter drier at the condenser outletIt is an advantage to blow through with somuch pressure that any oil in the componentsis removed
c) Replace lter drier and process tube asdescribed earlier It pays to use an oversizedlter drier
d) When the system is reassembled, evacuation
must be carried out very careullyCharge and test according to earliermentioned guidelines
b) Break the capillary tube at the condenseroutlet, and blow through the condenser withdry nitrogen as protective gasRemove the lter drierRepeat the blow-through with increasedpressure to remove oil rom the condenser, iany Cover condenser inlet and outlet
c) Treat suction line heat exchanger andevaporator in the same way The opportunityo an ecient blow-through is improved ithe capillary tube is broken o at theevaporator inlet Blow-through with nitrogenwill then take place in two paces; rst suctiontube and evaporator, then capillary tubesI the reason or the repair is a broken capillarytube the operations must be changed toreplace the entire heat exchanger
d) Reassemble the system with a newcompressor and a new lter drier in the rightsize
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5.3Drying o compressor
In some markets it may be necessary to repair amoist compressor in a workshop, and one is thenobliged to manage somehow
The drying process described here can give thewanted result, provided that the process is closelycomplied withDraw o the compressor oil chargeThen fush the compressor inside with -1 litreso a non-fammable low pressure rerigerant orsolventPlug the compressor with the solvent inside andshake it thoroughly in all directions to get thererigerant in touch with all inside suracesCollect the solvent as stipulatedRepeat the operation once or twice to ensurethat no substantial oil residues are let in thecompressorBlow through the compressor with dry nitrogen
Connect the compressor to an arrangement asshown in g 20
Plug the discharge connector.The connections to the compressor suctionconnector must be vacuum tight This can beachieved by soldered joints or by use o a suitablevacuum hose
In some cases it can be necessary to replenisha compressor with oil i it has lost some o the
chargeOn some Danoss compressors the amount o oilis stated on the type label, however, not on all, sothe present oil type and amount must be oundin the compressor datasheet
5.4Oil charge
5.2High degree ocontamination(continued)
Evacuation must be done with special care,and subsequently charge and test accordingto normal rules The outlined procedure isbest suited or simple rerigeration systemsI the system has dicult access and the
design is complex the ollowing proceduremay be better suited
e) Remove the compressor rom the system andtreat it according to point a
) Break the capillary tube at the condenseroutletBlow through with nitrogen through suctionand discharge tube
g) Mount a new oversized lter drier at thecondenser outlet Connect the capillary tubeto the lter drier
h) When the system, excl compressor, is intact
again carry out a dryingThis is made by at the same time connectingsuction and discharge tube to a vacuum pumpand evacuate to a pressure lower than 10 mbarPressure equalize with dry nitrogenRepeat evacuation and pressure equalization
i) Mount the new compressorThen evacuate, charge and test
Bring the compressor up to a temperaturebetween 115C and 130C beore starting theevacuation Then start the evacuation that must
bring the pressure in the compressor down to 02mbar or lowerThe joints in the vacuum system must be tightin order to achieve the required vacuum Themoisture content in the compressor will alsoinfuence the time or reaching the vacuumI the compressor is highly contaminated a ewpressure equalizations with dry nitrogen toatmospheric pressure will enhance the processShut o the connection to the vacuuminstrument during the pressure equalizationTemperature and vacuum must be maintainedor approx 4 hoursOn nishing the drying process the pressurein the compressor must be equalized to
atmospheric pressure with dry nitrogen and theconnectors must be sealedCharge the compressor with the specied oil typeand amount and mount it into the rerigerationsystem
Fig. 20: Drying o compressor
It is absolutely essential to use the oil approvedor the compressor in question I a lost oil
charge in a compressor must be replaced, it mustgenerally be assumed that approx 50 ccm o theoil charge will be let in the compressor when itis emptied completely by draining oil o rom aconnector
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6.0Lost rerigerant charge
The term lost charge covers cases where thewanted cooling unction is not achieved becausethere is not sucient amount o rerigerant in thesystemThe repair procedure implies a rerigerant
overpressure in the system so that thecontamination problems that may be caused bypenetrating moisture can be disregardedLost charge is characterized by the act thatthe intended cooling is not achieved Therunning time is long, and the compressor mayrun continuously The build-up o rime on theevaporator is only partly and perhaps onlyaround the injection place The compressor willoperate at low evaporating pressures, and thismeans low power and current consumption Thecompressor will have a higher temperature thannormal due to the reduced rerigerant transportThe dierence between lost charge andblocked capillary tube consists in the prevailing
condenser pressure, however, ater some timethe pressure will be the same in both casesBlocked capillary tube results in the rerigerantbeing pumped into the condenser, and thepressure will become high As the evaporatoris pumped empty, however, the condenser willbecome coldI the blocking is complete no pressureequalization will take place during standstillWith lost charge, however, the pressure in thecondenser will be lower than normalA considerable part o the repair procedureconsists o nding the cause o the deect I thisis not done it will only be a question o time untilthe deect occurs again
In case o blocking o the capillary tube in smallsystems they will normally be scrapped, buti large expensive systems are concerned areplacement o the suction line heat exchangermay be approproate
The main steps in the repair procedure can be asollows (only or non-fammable rerigerants)
a) Mount a service valve on the compressorprocess tube
Mount a pressure gauge and use this or aultdetermination
b) Increase the rerigerant pressure in the systemto 5 bar
c) Examine all joints to see i there is any oiloozing outPerorm a thorough search with leak testequipment until the leak is ound
d) Release the overpressure rom the systemBreak the capillary tube at the condenseroutletBlow through the system with dry nitrogen
e) Replace lter drier as described earlierReplace the process tube and repair the leak
) Evacuate the system and charge it withrerigerantSubsequently make a new leak test and testout the systemAter a pressure test o the system with highpressure perorm a slowly starting evacuationwith a large vacuum pump since otherwisethe oil can be pumped out o the system
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7.0Burnt compressor motor
A burnt motor has destroyed wire insulationBy burning is meant motors where the wireinsulation is decomposed
A real burning is characterized by the wire
insulation in the motor having been exposed tocritical temperatures or a long timeI the temperature conditions in a compressorare changed in a way that the insulation materialassumes a critical temperature or long time aburning will take placeSuch critical conditions may arise when theventilation conditions are reduced (eg due to adeective an), when the condenser is dirty or atabnormal voltage conditionsThe ault lost charge may have a correspondingeect Part o the motor cooling is done bymeans o the circulating rerigerant Whenthe rerigeration system loses charge theevaporating pressure becomes abnormally low,
less rerigerant is circulated per time unit, and thecooling is reducedIn many cases a motor protector mounted in theelectrical equipment cannot protect against suchconditions The motor protector is activated bothby current and by temperature I the currentconsumption is low, a high temperature isrequired around the protector to cause cut-outHowever, at alling evaporating temperatures
7.1Oil acidity
Since a burnt motor may result in contaminationo the system with acid products, the aciditycan be taken as a criterion whether the systemrequires a thorough cleaning
The compressor itsel and the discharge sideo the system up to the lter drier will be th