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problems in AC land

Came in to a warm building this AM. The programable stat is mostly off on Sunday when the bldg is empty. Starts to cool at 6AM, temp was set to 73, the room was 83 at 9AM. This is a very old Singer roof top compressor. It has not been running for 2 years and when put on line it required a full charge. It has been running fine for about 2 weeks. My first thought was it leaked down and stopped cooling. I turned off the wall switch that disables the AH contactor (also breaks the roof top contactor) figuring I had turned the thing off. I could still hear a rushing sound in the AH and found that the roof unit was still running. I shut it off at the box on the roof. I also discovered that the AH coil was a block of Ice. It was no more than 10 min. before I discovered that the compressor was still running. It had atleast 1.5 inch of ice on the coil. If the compressor is running low on freon,is it likely to freeze up the coil? If the compressors contactor is sticking on when the air handler is off sounds more like the problem. Worried that the evap coil might be dirty, I cleaned it, by blowing water through the moter side and later after I cut an opening to see the other side It looked clean. I also replaced the filters. Neither was bad, but I may have cleaned more than I thought. The compressor is shutting off by the wall switch now. The stat is satisfyed and the compressor just shut off also. Any thoughts? The sight glass is circulating large bubbles through it.


  • soot_seeker_4
    soot_seeker_4 Member Posts: 22
    low charge certainly a possibility.. but also...

    "I shut it off at the box on the roof. - the compressor was still running"

    sounds like you shut-off someone elses a/c instead.......

  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398

    Low charge = Evap coil freezup?? Causes roof unit to keep running?? or are you having a bad day. Be NICE!!!
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    As I mentioned Before


    From your numerous posts, it has become more than evident that your system is indeed in need of PROFESSIONAL INTERVENTION. I applaud the fact that you are attempting to understand the operation of your system and even tinker with the controls, but I must insist that you call in a reputable professional to do complete evaluation of your system.

    Not to insult you or your technical ability, but it seems that a good portion of the system woes you are experiencing are results of your tinkering with the system.

    And yes, a low refrigerant charge DOES CAUSE THE EVAPORATOR TO FREZE and YES, a low refrigerant charge DOES CAUSE THE COMPRESSOR TO CONTINUE OPERATING.

    I must insist, for your own safety, that you call someone in to evalauate the system and make the necessary repairs. I have the funny feeling that you did call people in and did get a proposal to perform repairs, but then decided to attempt the repairs on your own. Just my opinion, but I would hate for you to get, especially since you e air conditioning system contains high pressure refrigerant and cutting holes in the ductwork to access the coils without having a complete understanding of the system and its operation is an accident waiting to happen.

    I hope that the industry professionals that post here, will heed my warning about providing information, tips or tricks to those who may obviously take this input and create a dangerous situation.

  • thfurnitureguy_2
    thfurnitureguy_2 Member Posts: 74

    Yes I do understand the risks and do take all of the responsibility for my actions. As for my motivation.. this is the last hurah for an old and dieing system one that next year is going to be replaced. This year the budget is slated to re-vamp the steam system. What I am trying to do is last through the season with what I have, and learn what it takes to design and maintain an AC system. Am I going to start a HVAC company? NO. Do I wish to be better educated on the system I have and what is available for the future? YES. I have contacted outside help on three occations prior to doing it my self only on one, did the tech do what was required to test, and make the system operable. He was here for 30 min It cost $200.bucks and I am happy! I do admit that the longer term fix would be to find the leak. I also know what kind of time is involved in doing this. On the positive side I did,rewire the 24V controls, find and install a thermostat, reconnect a economiser, all with your help. All of these work and are doing what they were intended to do. I don't see what problems I have caused with the system. It has a leak. The things that I did I'm sure could have been done easily by any of the three techs that came out. It just wasn't the thing to do when nobody took the time to see if the system even worked, Save one. BTW, his company will be the one installing the new system. I'm sorry if I make you nervous.
  • steve_93
    steve_93 Member Posts: 37

    Actually a low charge could cause a compressor to go off on safety.

    Compressors need refrigerant to keep them cool... if they heat up, their internal overload trips.
  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Controls, controls, controls

    Indeed, it all depends on what controls the system has been wired with as well as what controls have been jumped out!
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398

    Thankyou Steve. This was an odd thing I would have thought if you opened the compressor contactor switch wire (turned it off) that it would turn off. It does now and did every time before. I guess it is not a surprise that a contactor could fail in an outside environment. It is a switch that slides to operate. It also seems odd that a system would fail in an "on" position In the event of a low charge. Perhaps the Professor ment the compressor would continue to run because it would never reach the needed cooling to satisify the stat. I will ask my tech to check the contactor when he looks for the leak.
  • thfurnitureguy_4
    thfurnitureguy_4 Member Posts: 398

    Good point Professor. My observation of the distruction to the systems wiring was where the demo crew removed store fixtures cutting the stat wire. Someone along the way disabled an old timer, some other wires were disconected (24V) as well, it was quite a rats nest. I think that the High voltage and the outside stuff was not messed with. But it pays to never assume. The tech who did the initial restart did look at the top compressor wiring and made no mention of sensors or controls being jumped out or removed. It would be a good idea to have it rechecked.
  • JeffD
    JeffD Member Posts: 41

    Word to the wise, and I mean this in the nicest way. Let the technician you call do the troubleshooting. Not only are you paying the tech to fix the problem, you are paying for his or her ability to effectively troubleshoot. When you troubleshoot a problem you may be pointing the tech in the wrong direction, ie leading him to what you think the problem is. After the tech leaves and the problem remains you will blame the tech, when in fact it was you who gave the wrong diagnosis. All you need to do is tell the tech the problem symptoms the system is having and let them do the troubleshooting, that way if they misdiagnose the problem they screwed up and not you. Please let the technician do his or her job. When I have a customer like yourself who tells me what part is bad, I ignore them and troubleshoot based only on the symptoms. A lot of times the owner of the equipment gave the wrong diagnosis, and this would be a waste of my time as I would have to come back to fix the problem a second time. I had this happen the other day, homeowner was convinced that the compressor on their 2 ton unit was shot. Turned out to be a bad cap. Had I replaced the compressor the homeowner would have been out a lot of money when they didn't need a compressor at all.

  • Eugene Silberstein
    Eugene Silberstein Member Posts: 1,380
    Improper Diagnosis


    I ran into a tech that always replaced compressors as his troubleshooting process always led to a defective compressor. Needless to say, when he replaced the compressor, the contactor, capacitor and associated wiring were replaced along with the pump. The tech though he was awesome, especially since after his repair, the system worked fine.

    Needless to say, I am quite certain that a number of comprssor were replaced unnecessarily.
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