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  1. #1
    Join Date
    Oct 2005
    Posts
    4

    Walk-In Freezer trouble

    I just spent the past 3 days getting beat up by a walk-in freezer. I have a 3 HP Copeland semi-hermetic compressor that is single phase, rated for 230 Volt, and has a water cooled condenser. Unit has 404 freon, and is rated at 20.1 Min circuit amps. It is on a 20 Amp circuit wired in 12 AWG. When it starts, it pulls 27 amps and works it way down to 17.2 amps in about 30 seconds. In doing so, it will occasionally trip the 20 Amp breaker. If the unit doesn't stay off for at least 6 minutes, it will trip the breaker instantly. After pump down, the pressures equalize a bit causing the compressor to kick back on in about 30 seconds and the breaker instantly trips. So as a tempory fix, I rewired the control circuit adding a contactor and time delay relay set for 8 minutes. That seems to work for now. My question is if a unit is rated at 230 volts, not 208/230, how critical is it to have the 230 volts? I only have 208 Volts from the panel. Will that cause rough compressor starting? The compressor is brand new as is all start components. I left there today with the understanding that the electrical circuit will need replaced. I still will only have 208 volts, but atleast it will have proper wire size and breaker size. Do I need to put a boost transformer in? Thanks for any help!

  2. #2
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
    Posts
    516
    Rule of thumb is 10% of voltage plus or minus. 10% of 230volts is 23volts. 230-23=207volts minimum voltage, 230+23=253 volts maximum.
    Do you have a CPR valve to keep the amperage to an acceptable level until suction pressure drops enough? Especially important after defrost but will help now as well. If you do, then adjust it to restrict the suction pressure of the compressor so the amp draw does not exceed the rated load amps of the compressor.
    What else can you tell us about this system, SH, SC, SP,DP,Etc?
    You can't provide too much info...

  3. #3
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    24,970

  4. #4
    Join Date
    Mar 2009
    Location
    Mid-Mo
    Posts
    3,427
    I would agree with jp but also I am concerned with you are being fed 230 and only getting 208. Yes it will run within those parameters but your amp draws will be higher.

    Probably everyone here has been on the call that someone put a 230 volt only motor on and it would run for a while then trip the thermal overload. One person I wok with did it and paid dearly for it.

  5. #5
    Join Date
    Oct 2005
    Posts
    4
    The incoming voltage from the utility company is only 208 volt. The compressor tag voltage reads 230 Volt. I agree that my amps would drop 10% if my voltage would increase 10%. That is making me think I should put a step up transformer in. I also agree that at CPR valve would be a great idea to install on this application. I wish I would have done that first. Once I get over that initial demand, the voltage settles down as does the compressor. I think that will be my next step. Thanks!

  6. #6
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,081
    My old Copeland book states the 230V compressors have an allowable range of 207-253V, whereas the 208/230V models have a range of 187-253V.

    With that undersized feed, you'd likely see a pronounced voltage drop from 208V during starts, further aggravating the situation.

    I had a customer with a 230V Copelametic on a 208 service which ran for years with only occasional starting troubles, but with age they became more frequent. I installed a suitable buck/boost transformer which brought the supply up to about 240V and solved the problem.

  7. #7
    Join Date
    Oct 2005
    Posts
    4
    Do you have any idea the price on a boost transformer that size?

  8. #8
    Join Date
    Feb 2008
    Location
    California
    Posts
    2,057
    Quote Originally Posted by kwagner View Post
    Do you have any idea the price on a boost transformer that size?
    We had a chain install Vendo cases that had a starting problem. The Acme buck n boost was the manufactures fix for it.
    http://www.vendoco.com/Documents/RD%...0CONDITION.pdf

    You could check these out.
    http://www.acmepowerdist.com/pdf/Page_104-109.pdf
    http://www.platt.com/CutSheets/Acme%...ansformers.pdf

    Maybe choose the T-1-81058.

    If it don't work, looks like your upgrading the power distribution to the unit.

  9. #9
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,081
    Quote Originally Posted by kwagner View Post
    Do you have any idea the price on a boost transformer that size?
    You could probably get by with a .50 KVA transformer, but for a few buck more, a .75 KVA would be a better choice. No pricing allowed in this open forum, but if you do a Google search for a Schneider Electric 750SV43F, you'll get some results.

    Note that they're rated for 240/480V primary and 24/48V secondary, but can be connected for a 10% boost for a 208V to 230V application. Here's a link: http://static.schneider-electric.us/...000-323-01.pdf

  10. #10
    Join Date
    Oct 2009
    Location
    Florida
    Posts
    162
    If you're drawing 20.1 amps at 208 volts that equates to 4180 va. You'd need a 4.2kva buck boost transformer rating at a minimum to do that properly. A .5kva sized bb transformer would accomplish that for you.
    Last edited by wanttosee; 09-04-2012 at 10:03 PM. Reason: hit send prematurely

  11. #11
    Join Date
    Sep 2012
    Location
    British Columbia, Canada
    Posts
    17
    If your only problem is a tripping breaker you need to increase the circuit size to the unit. #12 wire wire is rated for 20 amps but not allowed to be loaded above approx 16A. Have a #10 circuit run with a 30amp breaker. I also agree about the CPR so that the comp doesn't get overloaded

  12. #12
    Join Date
    Feb 2004
    Location
    British Columbia, Canada
    Posts
    516
    "I left there today with the understanding that the electrical circuit will need replaced. I still will only have 208 volts, but atleast it will have proper wire size and breaker."

    So did you put in a larger circuit as you were saying in your original post? I am assuming you were going with 10 gauge and 30 amp breaker as well.

    I am thinking that the original system drew less amperage due to its age and being worn out. What was the original minimum circuit ampacity of the old system?

  13. #13
    Join Date
    Apr 2010
    Location
    Richmond, Virginia
    Posts
    304
    Quote Originally Posted by koolkahuna View Post
    "I left there today with the understanding that the electrical circuit will need replaced. I still will only have 208 volts, but atleast it will have proper wire size and breaker."

    So did you put in a larger circuit as you were saying in your original post? I am assuming you were going with 10 gauge and 30 amp breaker as well.

    I am thinking that the original system drew less amperage due to its age and being worn out. What was the original minimum circuit ampacity of the old system?

    I would take a look at that breaker and make sure it is the proper one with a time delay!!

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