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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Ive been experiencing some difficulties with my AC system

Customer Question

Hi, ive been experiencing some difficulties with my AC system over the past couple days. while investigating/troubleshooting elevated temps i discovered my honeywell temp controllor purge light would be illumiated for about the 5 minutes expected for Anti-Recycle, the purge light would extinguish and subsequently illumate. After replacing the air filters(which desperately needed it) the compressor and fan ran semmingly fine for the rest of the evening and the following day. Once again my compressor is turning off (some form of a trip not the bkr) so far performed the following for troubleshooting. cycled the breakers for the compressor and temp controller with similar results. checked he air filters, my wife installed them they were in backwards(corrected), did not solve problem. I just took both thermostat cooling settings to off and Fan to on (attempting to defeat the vent fan/compressor interlock for fault isolation. After appropriate purge delay the vent fan started and was running for about 10 minutes. I took the thermostat to cool, the compressor immediately turned off after starting and vent fan turned off on interlock. returned the thermostat to compressor off/fan on and the fan started after an appropriate time delay. Other possible pertinent details include the drip pan beneath the air exchanger is bone dry and the bypass damper is currently in the inline position (during my first troubleshooting attempts i found it like this so i just put it back how i found it) I believe ive narrowed down the problem as far as I can w/o tech assist
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: some background on me is I am a submarine mechanic and have performed plenty of maintenance and operations on submarine A/C plants (obv not the same) but I am very familiar with the refrigerant cycle and basic principles of A/C thermostats set to 72 downstairs 74 up and air filters are brand new and i can still see right through them
JA: Do you plan on doing the work yourself?
Customer: *worst answer possible i know* depends on the extent if it were to involve replacing a controller most likely replacing or charging a compressor or similar intrusive maintenance then most likely not
JA: Anything else we should know to help you best?
Customer: I forums have led me to believe that the potential exists that the cooling coils are frozen over causing low suction trips of the compressor but given the state of the drip pan i find that hard to believe
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Let me make sure I understand.You can turn thermostat to COOL and after the 5 minute delay all comes on and works, but compressor is shutting down before we reach desired temp. Is this correct?

Customer: replied 1 year ago.
with vent fan running took thermostat to cool green compressor indicating light illuminated < 3 seconds later compressor shut down and purge light came on repeating in the 5 minute cycle
Expert:  airheatman replied 1 year ago.

OK during the short time compressor runs feel of the large copper line at outdoor unit and tell me if it is outdoor temperature, slightly cool, sweating cold or ice cold

Customer: replied 1 year ago.
tried....compressor didnt even start, the signal went out, then the "cool" light extinguished the purge light illuminated orange and the "zone 3" green LED light lit (i only have 2 temp control zones so i believe its indicating a trip/alarm event)
Expert:  airheatman replied 1 year ago.

Sounds like this s going to be an issue with the compressor or refrigerant pressures.Compressor has most likely shut down on what is called internal overload or a pressure switch.You are most likely going to get a technician onsite to fix this.