service manual for 6700, 7000, 8000 & 9000 series air conditioners

More documents

Recommendations

Info

Question:Answer:“What could cause the compressor to drawovercurrent or to overheat?”in coming to a conclusion.The indications of non-condensables in the systemare:1. “Dirty condenser coil.”Check the appearance of the coil. If it is coated withlint, cottonwood fuzz, leaves, etc., it is insulated andit cannot give up its heat to the outside air. A dirtycondenser will cause high head pressure which willin turn cause both high current draw and hightemperature at the compressor.2. “Condenser fan does not come up to speed.”Check fan blade, fan motor and capacitor.3. “High or low voltage.”High voltage can drive excessive current through themotor windings. Low voltage can cause thecompressor to slow down, overload and drawexcessive current. Check the voltage between “C”and “R” terminals on the compressor while it isrunning. The volt meter must read between 103.5volts and 126.5 volts (domestic USA models - plusor minus 10%).4. “Overcharge or non-condensables in the system.”Either an overcharge of refrigerant or noncondensablesin the system will cause high headpressure and consequently, excessive current. Beespecially suspicious if you discover evidence of thesystem having been open (service valves in thesystem, extra pinch off marks, etc.).The indications of overcharge are:a) Overcurrent which may be checked aspreviously outlined.b) Cooler than normal suction line. With anovercharge, the suction line will usuallysweat all the way to the compressor.c) Cooler than normal discharge line. Thedischarge line should be highly superheatedand therefore, at high temperature.Feeling lines with your fingers is a very inexactmethod of gathering information and cannot beconsidered accurate. So use this information only toform preliminary judgements in your diagnosis oftrouble and consider as many indicators as possiblea) Overcurrentb) Higher than normal discharge linetemperaturec) Higher than normal liquid line temperatured) Higher than normal compressor temperature5. “Low Charge.”This very rarely occurs and should be consideredonly after all other possible causes have beenpositively eliminated.The compressor is dependent on a good supply of coolsuction gas for cooling. If the system charge is low;there will be less than a normal amount of refrigerantpassing through the compressor, less compressor heatwill be carried away by the refrigerant, and therefore,the compressor will overheat. NOTE – LOWCHARGE WILL NOT CAUSE OVERCURRENT.It will, in fact, cause the current to be low.Indicators of low charge are:a) The evaporator will be starved for liquidrefrigerant so the suction line and a portionof the evaporator coil will be warmer thannormal. This is the condition we refer to astoo much superheat. How much of theevaporator coil will be starved for liquidrefrigerant depends on the degree ofundercharge.b) The active portion of the evaporator coilwhich does have some liquid refrigerant willbe colder than normal and many times willfrost because the suction pressure will below. How much of the coil is active dependson the degree of undercharge.c) The compressor temperature will benoticeably higher than normal.Note: Low charge situations may bemimicked by problems such as dirty filters,dirty evaporator coils, air flow restrictionsand low load conditions. Do not attempt totap into the system unless you arespecifically trained in refrigeration systemrepairs.18
6. “Plugged up cap tube.”A cap tube can become stopped up by oil sludge orcontaminants in the system. This will only occur ifthe system has been open to allow moisture or othercontaminants to enter the system or if thecompressor has been overheated for a lengthy periodof time.It is difficult to determine the difference between a stoppedup cap tube and a low charge because the symptoms will benearly the same.ProblemTo repair either a low charge or stopped up cap tube,we will have to install service valves and attachgauge manifold. If after the correct amount ofrefrigerant has been charged into the system, and ithas low charge symptoms, we will know the cap tubeis plugged and will have to be replaced.12. No heat - Heat Strip.The customer says that he has turned the selector switch to“Heat” position and the blower works OK, but no heat.Question:“What are the possible causes of “no heat”problem?”Answer: 1. “The limit switch or the heatingelement could be open.” Checkwith continuity.2. “The selector switch could be open(See page 7).”entering the return air grille of the air conditioningunit.3. Subtract from this temperature the temperature of theair immediately leaving the supply air louvers (if it isa ducted air conditioning unit, use the closestdischarge register and make sure the temperaturesensing device is measuring supply air temperatureonly).4. A properly running air conditioning unit should havea temperature difference of approximately 18 to 22degrees F. Note: Slightly less temperature differencesare possible under extremely humid conditions. (Theunit may have to run longer to remove moisture).5. Temperature differences greater than 22 degrees arepossible in warm dry weather. Restricted air flowover the evaporator may also cause greater than 22degree temperature differences.6. Compressor running amps should be checked asfollows. Note the amperage listed on the airconditioner rating plate (RLA) is determined atdesign conditions only. These conditions are 95degrees outdoor temperature and 80 degrees indoortemperature.Since the outdoor temperature is mostly responsiblefor the amount of compressor amperage, this figurewill have to be adjusted for changes in outdoortemperature approximately 1 amp for every 5 degreesin temperature change (from 95 degrees) up or downaccordingly.3. “The thermostat could be open(See page 7).”In all three cases, turn off power and checkfor continuity with an ohm meter.Problem13. Cooling Performance CheckMake sure the filters, the evaporator coil and the condensercoils are clean and all supply air registers are open wide.1. Start the air conditioning unit and allow it to run forat least one-half hour. Possibly longer if it isextremely warm outside (the objective is to saturatethe evaporator coil before we begin running atemperature test).2. With a standard dial type or digital thermometer,measure the temperature of the air immediately19
Page 3 and 4: TABLE OF CONTENTSBasic Components a
Page 6: 5. Suction LineThe suction line is
Page 9 and 10: 9. Run CapacitorsThe purpose of the
Page 11 and 12: 1. Ammeter And Its UseAn ammeter is
Page 13 and 14: 1. Most all electronic leak detecto
Page 17: The customer turns the system to fa
Page 21 and 22: 6798-7XX, 6798A7XX SERIES6799-7XX,
Page 23 and 24: CEILING ASSEMBLY WIRING DIAGRAMS675
Page 25 and 26: WIRING DIAGRAM9330X713, 9330X714 CO

service manual for 6700, 7000, 8000 & 9000 series air conditioners

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?