Page 1 of 3 123 LastLast
Results 1 to 13 of 32
  1. #1
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332

    Ac help?, heil high pressure cutout

    I'm working on my uncles heil 3 ton condensing unit.

    I do mostly residential gas and oil but am learning ac this year.

    My uncle has been complaining of a hard start so I went over to check it out.

    The unit is a r-22 condensor here is the plate Name:  ImageUploadedByTapatalk1373841557.390837.jpg
Views: 439
Size:  70.1 KB

    This is the build sheet from the goodman a/h it's attached toName:  ImageUploadedByTapatalk1373841615.984135.jpg
Views: 320
Size:  61.6 KB

    I attached my testo 570 manifold to monitor the pressures on start up.

    Before starting the unit sits at about 130 psi equal with maybe a few pounds difference.

    On start up the high side climbs to 350+ and hits the high pressure switch and kicks the compressor.

    The compressor restarts and climbs, but starts dropping before it hits the switch. The second run cycle the compressor reaches running pressure and sounds smooth. Today with a temperature of 80 outside I had 105* saturation temp on my liquid line which I understand to be good for r-22.

    My evaporator temp seemed really low at 27-28* which made me think the unit was under charged or had leaked, but after more investigation I found he only had one central return with a 14x14 opening directly into the plenum that sounded like a vacuum cleaner.

    We added two more 8" return flexed out about 15' and that helped pull much more air across the evap and raised the evap temp up to around 37-38*. I noticed through as I ran some liquid into my gauges that it had a reddish color for a second that I have never seen before.

    So, now my low pressure sits around 65-70* with a saturation temp of 38*, my high side around 220 with a saturation of around 105-107*.

    Once the unit is running it is fine but the really hard start and hitting the high pressure switch has me stumped.

    I notice on the condensor it says txv Indoor and the unit has a piston orifice. I tried putting a hard start kit on the unit and a new turbo 200 cap just as a easy yes or no and it made no difference.

    The filter drier on unit is a copper tube about 3/4 diameter brazed into liquid line. I've never seen one like this and am wondering if maybe it is restricted?

    Any help or advice would be appreciated. I've asked some of the senior techs at my shop but won't be back in till tommorrow and not knowing is driving me crazy!!!

  2. #2
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    More info,

    Compressor amp draw
    12 amps
    Indoor temp at testing 74* DB
    Outdoor DB 80*

  3. #3
    Join Date
    Jul 2013
    Posts
    63
    The hard start could be liquid refrigerant in the compressor. Check your temp drop before and after the filter drier. Should have more than a degree or so. I think. How's it cooling now that you've corrected the airflow problem?

  4. #4
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    It cools really well, 20* across the evap coil.

  5. #5
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    One of my coworkers suggested the lack of return could be what was causing the liquid refrigerant coming back on the low side due to incomplete evaporation. Adding the two 8" returns didn't change the hard start at all though and the problem with it hitting the Hp switch seemed to get worse after that.

  6. #6
    Join Date
    Jul 2013
    Posts
    63
    Check your SH and SC. Over charge can cause hard starting. Is it a rotary compressor?

  7. #7
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    Scroll compressor.

  8. #8
    Join Date
    Jul 2013
    Posts
    63
    I've had some of those that are loud or have become loud.

  9. #9
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,401
    First get your charge correct.
    Then figure out why and what to do about flooded start. Check crankcase heater also.

  10. #10
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    Quote Originally Posted by socotech View Post
    First get your charge correct.
    Then figure out why and what to do about flooded start. Check crankcase heater also.
    Well, the condensor calls for 9* subcooling with indoor txv. The air handler is fixed orifice. So my 9* subcooling won't work. I need to charge to superheat right? And how many degrees superheat would be an acceptable starting point?

    The compressor has a crank case heater installed that seems to be working.

  11. #11
    Join Date
    Nov 2007
    Location
    Mississippi
    Posts
    1,401
    Do you know indoor wet bulb?

  12. #12
    Join Date
    Sep 2012
    Location
    thomaston, ct
    Posts
    332
    No I don't have a psychrometer yet but I will set my guitar hygrometer in the house to find RH and report back tommorrow with the WB. Maybe try and pick up a psychrometer tommorrow.

    Would an overcharge cause the unit climbing to high pressure cutout on startup?

  13. #13
    Join Date
    Apr 2010
    Location
    working overtime
    Posts
    851
    why not recover your charge and weigh in your charge pe the nameplate. while i had the charge out i would check my piston size. make sure you weigh your charge as you recover it. if you pull 19 lbs out of a unit that should only have about 10 then you can start looking for your restriction. is there a drier inside the condenser.

Page 1 of 3 123 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event