HVAC Preventative Maintenance Basics

Presented by Mike Crawleyy y

Air Handlers/Package Units:• Coils – have to be clean!• Coils have to be clean!

• The main purpose of any coil is to absorb or reject heat • If coils are dirty; air flow is restricted and minimal heat exchange is

taking place

• Evaporator Coils• Need to change filters on a quarterly basis

Rule of thumb: 1.5 square foot of filter for each ton of capacityO RTU f i ti t h t h l d t • On a RTU refrigerating system poor heat exchange can lead to: freezing up, liquid flood back to compressor, and blocked air flow in which all can damage compressor

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Air Handlers/Package Units:• Condenser Coils• Condenser Coils

• Air cooled condenser units will set outside • They need to be cleaned at least once a year depending on location• Higher condenser temps can lead to hot gas entering metering device g p g g g

and evaporator. Over a long period of time, oil breakdown can occur. The lubricity becomes thinner as the oil heats up. The low viscosity can cause compressor failure

• BeltsBelts• Belts need to be properly aligned with a straight edge or a string pulled

tight on a multi-grooved variable pitch pulley• Misalignment can be destructive to belts and pulleys wich can groove

the pulley and wear out the beltthe pulley and wear out the belt

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Air Handlers/Package Units:• Belt tension is very important!• Belt tension is very important!

Rule of thumb: Tension needs to be approximately 1/64 of an inch deflection for every inch from shaft center to shaft center

• Belt conversion Note 1:• Belt conversion – Note 1:• 4L belt to A belt = the length of the 4L belt - 2 = A belt

• Belt conversion – Note 2:• 5L belt to B belt = the length of the 5L belt – 3 = B belt5L belt to B belt the length of the 5L belt 3 B belt

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Air Handlers/Package Units:• Grease• Grease

• Motors and bearings all need grease or oil. Metal to metal contact is not good

• How much and what kind of grease? There is no rule of thumb for grease amount Consulate bearing manufacturer You can grease a grease amount. Consulate bearing manufacturer. You can grease a ball bearing until you see a slight amount of grease around the seal

• Grease type: typically a NLGI2 (national lubricant grease institute) is recommended for roller bearings

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Air Handlers/Package Units:• ElectricalElectrical

• All units have various forms of electricity from throw away relays and contactors to large serviceable starters

• Check for: corrosion, burnt wires, bubbled insulation, discoloration• With electricity locked out tagged out, check for: snug (not Godzilla With electricity locked out tagged out, check for: snug (not Godzilla

tight) fittings – consult the manufacturer for torque values. Unlike conductors (ie:copper to aluminum) should have anti-oxidant compound

• Electrical also needs to be clean! Use dry nitrogen at low pressure• Don’t use a hose off the air compressor receiver tank. Moisture and oil

may get into components • Dust and grime can get in and cause over heating on starters

Serviceable starter can be cleaned with contact cleaner • Some pitting is okay and normal needs to be monitored• Some pitting is okay and normal, needs to be monitored• Large motors 20HP+ can be megged• A megger is a hand-crank or push button DC volt generator. DC volts

are used because it is easier to control

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Air Handlers/Package Units:• Drain Pans• Drain Pans

• Cleaning will help deodorize most smells. Pan tabs and pads will help• Debris can build up and block drainage• Drain lines need to have correct fall• P-traps need to be vented on the “leaving” side of the trap• Pan seal can be used to coat older more rusted out pans• Blow through coils - no need for trap• Draw through coils - have to be trappedDraw through coils have to be trapped

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Pumps• Pumps are broken down into many categories The HVAC industry • Pumps are broken down into many categories. The HVAC industry

generally deals with centrifugal pumps• End suction pumps, close coupled pumps, and split case pumps

dominate the industry• Pumps have to be level• Check pump coupling for wear• Check for shaft seal leaks• Pump alignment is important

• Pumps can be aligned by three methods:• Feeler gauges and a straight edge• A dial indicator rim and face methodA dial indicator rim and face method• And laser alignment

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Pumps• Keep logs of pressures• Keep logs of pressures

• Head = PSI x 2.31 / specific gravity (specific gravity of water is = 1.0)• You need to make sure you maintain a net positive head

• Exercise isolation valves• Grease bearings• Check starters• Clean strainers on cooling tower applications

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Chillers• Chillers are a major investment for a facility and are costly to • Chillers are a major investment for a facility and are costly to

maintain. An in depth maintenance program can increase reliability• Facilities with a thorough PM, have found for every dollar invested in

maintenance they save $10 in operating costmaintenance they save $10 in operating cost• Daily logs can help you trend pressures, temps, etc.• Inspections can be set-up as three quarterly run inspections and

one comprehensive annual inspectiono e co p e e s e a ua spect o

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Chillers• Heat exchangers• Heat exchangers

• Air cooled chillers condensing coils should be cleaned regularly• Water cooled chillers tubes should be brushed annually

• Note: .002” of fowling will reduce efficiency by 20%• Anodes should be changed annually or depending on condition• Eddy Current analysis should be performed every 3 years or as

needed to both condenser bundles and evaporator bundle

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Chillers• Oil testing can be performed on an annual basis on large • Oil testing can be performed on an annual basis on large

centrifugal and screw chillers• Oil testing is a useful tool in determining internal conditions of a

compressor • Reciprocating and scroll compressors generally require a field acid test• Oil filters changed manufacturers specifications

• Leak checking chillers• All chillers should be leak checked annually • All chillers should be leak checked annually • Water flow must be maintained through the barrels• Low/High water flow=poor heat exchange

• Purge Units – low pressure chillers• Monitor pump out minutes• Check for proper operation• Change filters annually

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Chillers• Starters• Starters

• Electrical must be tight and clean • Contact points must be inspected and cleaned annually• Change the VFD or SSS coolant on manufacturers recommendations • Motor terminals must be secure in a dry environment• Motors should be megged annually

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Chillers• Panels• Panels

• Safeties should be tested annually• Sensors and transducers should be tested and calibrated on each visit• Wiring should be neat and secure• Flow switch operation should be checked annually• Parameters need to be logged and maintained

• Refrigerant and oil circuit should be logged and maintained• Predictive maintenance for chillers• Predictive maintenance for chillers

• Vibration analysis• Infra red testing• Open rotor bar test• Oil analysis• Eddy current testing

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Cooling Towers• Water treatment is very important with towersWater treatment is very important with towers

• To prevent scale corrosion sludge and biological growth• Conductivity should be high

• Monitor blow down solenoid• Blow down is used to re-circulate water to drain dissolved

solids • Make up water valve

• Ensure proper water level is in tower basin (3 to 4 inches below overflow pipe)

f b h b l d b d• Tower fans can be either belt driven or gear box driven• Grease bearings• Inspect belts and sheaves• Inspect gear box oil level – change annually

Oil samples and vibration analysis can be performed on • Oil samples and vibration analysis can be performed on the gear boxes

• Keep tower inlet screens clean• Inspect hot deck and spray headers

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Cooling Towers• Towers should be cleaned annually and inspected on a daily basis Towers should be cleaned annually and inspected on a daily basis

as well as a quarterly• Inspect all electrical connections and disconnects• Have motors tested• Freeze protectionFreeze protection

• Basin heaters maintained• Exposed piping should be insulated with heat trace• Make up water line should also be insulated with heat trace• Tower by-pass must be checked in seasonal weather

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Pneumatics• Heart of pneumatics is the air compressor• Heart of pneumatics is the air compressor• Air compressor has five components:

• Motors• Pumps• Receiver Tank• PE switches• Alternating Relays on duplex machine

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PneumaticsInspections:Inspections:• Intake filter; monthly

• Change filter annually or sooner depending on environment• Piping p g

• Check for air leaks • Relief valve

• Check for proper operationl l l• Oil level

• Change oil twice a year• Note: any 30 weight non detergent oil will work, do not use synthetic

• Verify belt condition alignment and grease motor bearings • Verify belt condition, alignment, and grease motor bearings

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Pneumatics• Inspect electrical • Inspect electrical

• Starters, PE switches, and alternating relays for proper operations and condition

• Blow down• Important to verify moisture and oil removal from tank

• Inspect coalescing oil removal filter • Inspect bypass

Air dryer• Air dryer• Ensure condensers are clean and compressor is operating• Check the operation of the dryer every six months

• Maintain main air pressure of 20 PSIa a a a p u o 0

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Pneumatics• Thermostats and VAV boxes• Thermostats and VAV boxes

• All Pneumatic thermostats are different • Thermostats are sensitive, if adjusted to much calibration will be

thrown offb b d h• Fan power boxes can be inspected each season

• PE switches , heat strips, return fan motors should all be checked• Equation for percent run time; see attachment

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VFD Notations• Common to most HVAC equipmentCommon to most HVAC equipment• Keep a copy of all start-up parameters

• Important to note any changes that are made• Once every six months VFDs should be shut down so that the

electrical can be inspected, tightened, and the drive blown out with p , g ,air in a can or by dry nitrogen under low pressure

• Check the cooling fan for operation• VFDs can damage older non-inverter rated motors

• Inverter rated motors can handle higher voltage spikes (from VFD) and l d h h h ld d brun at lower speeds which can overheat older motors damaging bearing

etc…• Bearing fluting is not a myth

• Occurs when Eddy Currents from the drive operations take a path to ground on the bearingsground on the bearings

• Some ways to counter this are to make sure drive is installed and grounded properly a grounding brush can also be installed in the motor to shield unwanted currents

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