Predictive Maintenance Programs (PMP's) In Small HVAC ... · Predictive Maintenance Programs...
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ESL-TR-94/04-07 Predictive Maintenance Programs (PMP's) In Small HVAC Applications: Analysis of Available Products and Technology Jim Watt Research Assistant Energy Systems Laboratory Texas Engineering Experiment Station, Texas A&M University College Station, Texas 77834-3123 INTRODUCTION Maintenance of HVAC&R systems and scheduled replacement of components to avoid costly down time, degraded comfort conditions, or health hazards is not new. In fact, designs have not changed dramatically in many years. However, new regulations placed on CFC emissions and other environmental and energy conservation concerns are causing changes. On the traditional side of things, cost for down time for any HVAC&R system whether it be for an industrial process or commercial function can add up very quickly and often results in thousands of dollars worth of spoiled goods or uncomfortable customers, tenants or employees. Even the slightest deviation from the operational norm of the refrigeration system can result in spoiled goods. It is also worth mentioning lost revenue in sales or productivity and even the possibility of coming under a civil suit in situations where HVAC systems go down in occupied buildings. Obviously, avoiding such situations would be desirable to say the very least. In the past, this has been accomplished by what is known as preventative maintenance. In the past preventative maintenance programs have been the only means by which a company could avoid the costly alternatives listed above. The thing is, these scheduled maintenance programs can also be very expensive. They too, often require a certain amount of downtime and unfortunately don't always prevent untimely failures. Many man hours of maintenance time, down time, and inefficient system operation could be avoided with the help of a relatively new method of maintenance called predictive maintenance. With computers getting smaller and more efficient and the electronics involved in monitoring systems becoming generally less expensive, predictive maintenance is coming within reach to industry as well as the private sector. Someone said, "An ounce of planning is worth a pound of work." If HVAC&R systems could be economically monitored and their operation predicted in a literal sense, then many dollars worth of unnecessary maintenance cost as well as down time could be prevented. This paper offers an overview of predictive maintenance technologies available. With the exception of the considerably more complex and expensive control type systems (e.g. the AKCESS 25 from Danfoss), all of the predictive maintanence systems presented here basically rely on comparative temperature measurements. The list of PMP's presented here is not to be considered exhaustive. EXISTING PRODUCTS Since service and replacement of components of HVAC&Requipment based on a predictive strategy is a relatively new field, there are many types of PMP's evolving. In this report, a predictive maintenance program will include fully automated as well as semi-automated systems. A fully automated system is one which requires very little or no knowledge of the operation of HVAC&R systems to operate. A semi-automated system is one which requires at least some knowledge of the monitored system to operate effectively. Table 1 lists the products and services uncovered during the research for this report. All information contained in the table and in the remainder of the report was extracted primarily from product data sheets and telephone interviews. FLUKE 52 The first item on the list is the FLUKE 52 made by the Fluke Manufacturing Company. This device is not really a PMP in itself. It is presented here simply because its functions allow it to provide much the same type of data utilized by bona fide PMP's to arrive at predictive maintenance decisions. Fluke makes many different hand held metering devices but this particular unit offers a couple of features which make it a handy tool for not only spot checking
Transcript of Predictive Maintenance Programs (PMP's) In Small HVAC ... · Predictive Maintenance Programs...
ESL-TR-94/04-07
Predictive Maintenance Programs (PMP's) In Small HVAC Applications:Analysis of Available Products and Technology
Jim WattResearch Assistant
Energy Systems LaboratoryTexas Engineering Experiment Station, Texas A&M University
College Station, Texas 77834-3123
INTRODUCTION
Maintenance of HVAC&Rsystems and scheduled replacementof components to avoid costlydown time, degraded comfortconditions, or health hazards is notnew. In fact, designs have notchanged dramatically in manyyears. However, new regulationsplaced on CFC emissions and otherenvironmental and energyconservation concerns are causingchanges.
On the traditional side ofthings, cost for down time for anyHVAC&R system whether it be foran industrial process orcommercial function can add upvery quickly and often results inthousands of dollars worth ofspoiled goods or uncomfortablecustomers, tenants or employees.Even the slightest deviation fromthe operational norm of therefrigeration system can result inspoiled goods. It is also worthmentioning lost revenue in sales orproductivity and even thepossibility of coming under a civilsuit in situations where HVACsystems go down in occupiedbuildings. Obviously, avoidingsuch situations would be desirableto say the very least.
In the past, this has beenaccomplished by what is known aspreventative maintenance. In thepast preventative maintenanceprograms have been the onlymeans by which a company couldavoid the costly alternatives listedabove. The thing is, these
scheduled maintenance programscan also be very expensive. Theytoo, often require a certain amountof downtime and unfortunatelydon't always prevent untimelyfailures. Many man hours ofmaintenance time, down time, andinefficient system operation couldbe avoided with the help of arelatively new method ofmaintenance called predictivemaintenance. With computersgetting smaller and more efficientand the electronics involved inmonitoring systems becominggenerally less expensive, predictivemaintenance is coming withinreach to industry as well as theprivate sector. Someone said, "Anounce of planning is worth a poundof work." If HVAC&R systemscould be economically monitoredand their operation predicted in aliteral sense, then many dollarsworth of unnecessary maintenancecost as well as down time could beprevented.
This paper offers an overviewof predictive maintenancetechnologies available. With theexception of the considerably morecomplex and expensive controltype systems (e.g. the AKCESS 25from Danfoss), all of the predictivemaintanence systems presentedhere basically rely on comparativetemperature measurements. Thelist of PMP's presented here is notto be considered exhaustive.
EXISTING PRODUCTS
Since service and replacementof components ofHVAC&Requipment based on apredictive strategy is a relativelynew field, there are many types ofPMP's evolving. In this report, apredictive maintenance programwill include fully automated aswell as semi-automated systems. Afully automated system is onewhich requires very little or noknowledge of the operation ofHVAC&R systems to operate. Asemi-automated system is onewhich requires at least someknowledge of the monitored systemto operate effectively. Table 1 liststhe products and servicesuncovered during the research forthis report. All informationcontained in the table and in theremainder of the report wasextracted primarily from productdata sheets and telephoneinterviews.
FLUKE 52The first item on the list is the
FLUKE 52 made by the FlukeManufacturing Company. Thisdevice is not really a PMP in itself.It is presented here simply becauseits functions allow it to providemuch the same type of data utilizedby bona fide PMP's to arrive atpredictive maintenance decisions.Fluke makes many different handheld metering devices but thisparticular unit offers a couple offeatures which make it a handytool for not only spot checking
Table 1: PMPproducts and services available.
Service technician is still required to verify and resolve suggested problems.List prices. Substantially lower costs are available.Does not include cost of database for programming or sensors and cabling.
**•* Not Available
performance of an hvac system butalso provides the means for somevery limited short term monitoring.
The FLUKE 52 is basically athermocouple reader with K or Jtype capability. Some of its specialfunctions are dual sensingcapability (T1 & T2), differencemode (T1-T2), hold mode whichdisplays only the highesttemperature detected whileconnected, and finally record modewhich allows a limited amount oftemperature data to be recordedand recalled for a particularprocess, for instance start up. Thisdevice does not diagnose possibleproblems by itself. Rather, itrequires operation by a trainedservice technician to utilize thedata obtained using the device todetect system operatingirregularities and thereby diagnosepossible impending system orcomponent failure.1
Software based predictivemaintenance
A predictive maintenancesoftware program developed bycomputer programmer Jim Whiteand service technician Jeff Jonesboth of Portland, Oregon combines
the speed of computers with digitalmultimeters and temperatureprobes to predict air conditioningor refrigeration component failure.A complete description of thesystem appears in the Aug. 16,1993 edition of Air Conditioning,Heating & Refrigeration News.2
The PMP requires installationof temperature sensors located atstrategic locations throughout thehvac system as shown in Figure 1.The sensor connections are routedto an easily accessible box wherethe service technician can
periodically connect a temperaturereader and obtain data quickly.The data is then entered into thecomputer software. The programcompares the new data to old dataand with known operatingparameters for particular types ofequipment and performs a systemanalysis of specific conditions orcomponents to inspect (i.e. "checkcondenser coil"). The softwarealso can provide informationalcharts and graphs of the diagnosisas well as ordering information forparts.
FIGURE 1 - Taken from Air Conditioning, Heating & RefrigerationNews, August 16, 1993 issue.
April 1994. ESL Report from paper prepared for MEEN 662
Jones currently services 31customers with his system with 90more pending.3 A telephoneinterview with Mike Anderson ofBoise Cascade, one of Jones'primary customers, revealed thatinstallation of this system hadindeed reduced downtime andproblems with their hvac systems.4
Jones offers some otheradvantages to implementing thissystem which would apply to anyof the other systems mentioned inthis report including reduced needfor pressure gauge connectionswhich result in refrigerant losses.Also, maintaining the equipmentoperation within its designed statewill result in longer equipment life.
Paraguard EC9000This system, manufactured by
Paragon Electric Company Inc. ofTwo Rivers, Wisconsin, providesearly detection of adverse operatingconditions within a commercialrefrigerant system by monitoringelectrical current and the first fiveseconds of equipment start-up.The system requires noprogramming, and alarmconditions are displayed via LEDstatus indicators.5
Other features includecontinuous monitoring ofefficiency and performance,irregular cycling, and comparisonto previous cycles to detectchanging conditions. The systemcan be applied to conventional andparallel refrigeration systems andis compatible with existing securityalarm monitors, building controlsystems and refrigeration controlsystems.
Installation requires only a 2step setup for the defrost durationand compressor selection, andrequires no special tools orprogramming.
Alarm indicators and faultcodes used in conjunction with atroubleshooting guide help identify
what type and where alarmconditions occurred in the system.
Cool Guard Model ACM-88Manufactured by Dencor, Inc.
in Denver, Colorado. The ACM-88 utilizes four temperaturesensors installed on the air sideonly (no penetration of refrigerantsystem required) and a water levelsensor in the drain pan to monitorcompressors, condensers,evaporators, heating units, fans,and condensate drainage. It willidentify such problems asrefrigerant leaks, dirty filters, fanand blower failure, excessivelyhigh or low temperatures, lowefficiency, and high water incondensate pan.6
The display station showsoutdoor temperature, return airtemperature, coil outputtemperature, cooling factor, heatpump factor, auxiliary heat factor,impending alarm conditions andhas seven fault indicator lamps:1. high temperature limit. 2. lowtemperature limit. 3. coolingoutput low. 4. heat pump outputlow. 5. auxiliary heat output low.6. low air flow. 7. high waterlevel.
The ACM-88 also has andelectronic memory module whichkeeps the data during poweroutages without the use ofbatteries.
AKCESS 25A lot of HVAC&R control
systems are available on the marketsome of which may or may nothave the same capabilities as thisexample.
The AKCESS 25manufactured by DanfossAutomatic Controls in Baltimore,MD actually controls the operationof commercial refrigerationsystems such as cut-in/cut-outcontrol, temperature-modified rateof change control, screwcompressor control, condenser
control, and defrost control. It canoperate as a stand alone device orbe interfaced with a local PC ormodem for remote access. Thesystem can be programmed to havediagnostic capabilities to identifypotential problems such ascompressor failure, coil frosting,dirty filters, ahead of time with theproper sensors installed.7
MMS-1 (MaintenanceManagement System)
This system takes a slightlydifferent approach to the predictivemaintenance problem. It utilizesadvanced computer technologycombined with experience fromover a dozen HVAC&R experts towatch the unit for changes orpatterns which may indicate aproblem. When a potentialproblem is observed viatemperature probes the monitordecides what the most likely causeof the problem is and theinformation stored in its on-boardmemory. By pushing a button onthe monitor, a serviceman can viewwhat problems the unit hasobserved and the suggested causes.
The unit has the capability tolearn how the particular systemruns when it tuned to peakperformance and detects subtlechanges in operation over time.From this data, the unit calculatesthe relative drop in performance ofthe system and displays the needfor service to the system.
Installation of the MMS-1 isrelatively simple and requires nointruding into the refrigerant orcontrol systems themselves. Theunit will then program itself bylearning the key factors for thesystem.
The state of the system isevident on the display panel whichuses a colored light informationscheme. The display providesconstant information on relativesystem performance, on/off status
April 1994. ESL Report from paper prepared for MEEN 662
of the system, and early troublewarnings.
The on-board provides ahistory of problems such as airflowrelated, refrigerant related,mechanical, and electrical. It willalso identify the likely causes ofhvac problems and record the orderin which they occurred.8
The MMS-1 is no longer inproduction due to the fact that themanufacturer, Woolery Technologypreviously based in Dallas, Texas,is no longer in business. The unitwas apparently over priced or therewas not enough of a demand tosupport the company. However,the nature of the MMS-1 and itsrelation to future diagnostic andpreventative maintenance systemswarrants its inclusion in thisreport.
SUMMARY
It is evident from the analysisof the systems presented here thatPMP's can take a number ofdifferent shapes but all have thesethings in common:1) They utilize electronicmonitoring equipment (primarilytemperature sensors) to obtainconditional data for the HVAC&Rsystem.2) They diagnose problems base onthe collected data and in somecases recommend solutions.3) They provide timely informationwhich can predict or be used topredict component failures whichmeans replacements and repairscan be made in an expedient andtimely manner.4) When properly used, they insurethe proper operation and thereforethe service life and efficiency of thehvac or refrigeration equipmentbeing monitored.
FUTURE DIRECTIONS
With computers constantlybecoming smaller and faster andelectronic monitoring equipmentbecoming more and moreeconomically feasible for industryand the private sector, systemssuch as those mentioned in thisreport will no doubt become morecommon place.
It can also be said withconfidence that these types ofsystems will become more accuratein their diagnosis of hvac systemproblems as expert systems andartificial intelligence work theirway into the framework ofPMP's.9-10-11
REFERENCES
1 Manufacturer's data. "HVAC & RSystems, Service tips with Fluketermometers and multimeters".Revision B, March 1989, JohnFluke Mfg. Co., Inc., P.O. Box9090, Everette, WA 98206, (206)347-6100.
2 Ogden, L. 1993. "Service techdevelops predictive maintenanceprogram" ,4/> Conditioning,Heating & Refrigeration News.August 16, 1993. p. 14
3 Jones, J. Western Engineers,Portland, Oregon. Personalcommunication. 25 February1994.
4 Anderson, M. Boise CascadeVibration Analysis Division,Vancouver Washington. Personalcommunication. 24 March 1994
5 Manufacturer's data. "ParaguardEC9000 Refrigeration SystemMonitor and Alarm", ParagonElectric Co., Inc., 606 ParkwayBlvd., P.O. Box 28, Two Rivers,WI 54241, (414)793-1161.
6 Manufacturer's data. "Keep AirConditioners OperatingEfficiently", Dencor, Inc., 1450West Evans, Denver, CO 80223,(800) 392-2690.
7 Manufacturer's data, "SystemHardware - NC25-4", DanfossAutomatic Controls, 4971Mercantile Road, Baltimore, MD21236-5999,(414)931-8250.
8 Manufacturer's data. "The MMS-1. A monitor for reducing yourcosts and avoiding unpleasantservice surprises", WooleryTechnology, 5520 S.Westmoreland, Suite 200, Dallas,TX 75237, (800) 962-8571.
9 Kaler, G. M. 1988. "ExpertSystem Predicts Service" Heating,Piping, & Air Conditioning.November, 1988. p. 99.
10 Brothers, P.W. 1987,"Knowledge Engineering ForHVAC Expert Systems" ASHREATransactions, 1987.
"Herrod, R. A. 1988, "AI:Promises Start to Pay Off'Manufacturing Engineering.March 1988.
April 1994. ESL Report from paper prepared for MEEN 662
