Results 1 to 9 of 9
  1. #1
    Join Date
    Apr 2011
    Location
    michigan
    Posts
    168

    Vertical pie display cooler

    I have a customer who has a vertical pie display cooler. It is an older unit from 1988, originally had r-12 in it, time clock has 409a wrote on it. The complaint was the cooler will work fine for a few days, then it will run around 60 box temp, customer leaves the cooler off overnight and starts it the next day and it seems ok for a day. I noticed everything seems to be original except for the fact someone replaced the start components. My customer has only had the cooler for about 6 months, bought it used at an equipment auction. The unit had been off for 2 weeks when I worked on it, started it up, it pulled down to 34 or so and cycled off quite quickly, was off a few min and cycled back on from the pressure switch, pulled back down to temp and cycled off, everything was working fine until the 3d time it tried to cycle on, the compressor tried to start but tripped the o.l. as soon as the o.l. reset it started fine. The customer had the cut in set at 25#, diff was at 10#. I set the cut in at 35# and increased the differential to 20#. This helped the compressor have more off time and I thought it would be ok but the last time it cycled on it again tripped the o.l. The start cap tests fine, electrical all is ok, I can make the compressor fail to start very intermittently by cycling the power switch on/off, the compressor will start right back up most if i shut it off then right back on with no delay, other times if i leave the power off several min. the compressor will fail. I believe the compressor is just wore out and if it stops in the right position it fails mechanically to move and tripps the o.l. I thought about a larger start cap or a time delay relay but even if it makes it run ok now I think it is just a matter of time before it fails completely. Any other ideas that I may have over looked??

  2. #2
    Join Date
    Aug 2002
    Location
    Southold.calm
    Posts
    4,846
    Having an ohm reading and #'s on the comp would be a big help.

    After 25 years it may be time to rebuild or put it to rest.

  3. #3
    Join Date
    Jun 2001
    Location
    Michigan
    Posts
    12,077
    what kind of start? CSIR or CSCR? PSC or RSIR? The later two start configs would perhaps be why you would possibly need to look at equalization pressures causing you an issue. You adjusted the pressures I am assuming thinking you were attempting to get more off time, more equalization.

    The Overload trips and it depends on your start config in which direction to start troubleshooting. Tecumseh and Copeland electrical Handbooks have excellent information you can study to learn exactly how to identify the problem. Free to download.
    Last edited by Dowadudda; 03-23-2013 at 08:06 AM.
    People who think they know everything are a great annoyance to those of us who do.

  4. #4
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,296
    No voltages, amp draws, pressures, or SH readings?
    What brand unit? Static coil(s) or fans? Sounds like the pump can't overcome the pressure difference. I've had instances where refrigerant changes had changed capacity on units with static coils. Solution was to upgrade to the next higher hp condensing unit.
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    It was working when I left...
    Liberalism-Ideas so good they mandate them

  5. #5
    Join Date
    May 2009
    Location
    The Pas, Manitoba Canada
    Posts
    200
    Sounds like your customer gambled and lost. Make sure he knows there might be no easy fixes before you get in too deep. Buying a 1988 vehicle and expecting to drive to Alaska would be a good comparison
    Last edited by K_Neil; 03-23-2013 at 04:32 PM. Reason: more ideas

  6. #6
    Join Date
    Apr 2011
    Location
    michigan
    Posts
    168
    The Unit is 120 Volt, I forgot to write down my amp draw, but it was below the nameplate fla. It is a fan coil, I have the compressor #, but not with me right now, I did not ohm the compressor windings, was running short on time that night, but the windings seem ok at least my amp draw was ok except when it intermittently draws lra and tripps the ol. I made pressure adjustments to allow the compressor more off time, which so far has allowed the cooler to work, the cut in pressure needs do be lowered a tiny bit the customer said the cooler is right at 40-41 when the compressor cuts in which is at the high side of his temp. range, other than that he said it is working fine now. I still think the compressor is mechanically on its way out as it starts fine even if I short cycle it most of the time its just once in a while it acts like there is a tight spot in the motor causing it to "lock up". If I go back on the unit I will ohm the windings and see what they ohm out at, but so far the customer is happy. I agree it may be time to put this thing to rest, I believe I can get a new compressor for it but probably not to cost effective to replace it in a unit this old, especially when it will loose some capacity by switching refrigerants. Thanks for the input!!

  7. #7
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    425
    The customer had the settings too cold. You increased the cut in to 34#, cut out at 20#. This is perfect for R409. You could even go 32# & 18# but risk icing the evap or getting SH too low. But verify with your stubby gauges if you go back.

    Another thought, is R409A kind of like R414 where you should only charge to 80% of sight glass for old R12 units? I typically be very careful not to overcharge small R409A units. I scale and never mind the bubbles in the glass.

    How old is the compressor? We all like to think a pump is good till it dies but sometimes they die a slow death.

  8. #8
    Join Date
    Apr 2011
    Location
    michigan
    Posts
    168
    the compressor is a 1988. Right now the unit is cutting in around 34 and cuts out at about 14, I increased the differential to 20, the differential was only 10# and was short cycling pretty bad. The cooler has not missed a beat all week been working perfect the customer said, I still warned him the compressor may lock up, even though it is working now I do not believe the compressor will last long especially when summer gets here, but it has lasted this long, the customer is happy with it I found out he paid about 150 for the cooler. Thank you for the help!!

  9. #9
    Join Date
    Oct 2011
    Location
    Chicagoland Area
    Posts
    4,296
    Keep your fingers crossed
    Officially, Down for the count

    YOU HAVE TO GET OFF YOUR ASS TO GET ON YOUR FEET

    It was working when I left...
    Liberalism-Ideas so good they mandate them

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