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  1. #1

    Copeland compressor starting issue.

    Hi everyone and thanks in advance for your replies. I have been doing hvac and refrigeration for many years, and this one has got me.
    This all started last week, I have a 6 door freezer with 2 evaps and they share a common condenser. Everything is hussman, very old hussman. Anyway, I got the call last Friday, that the case had got to about 40 degrees on thursday. When I arrived, the case temperature was at 15 and all was well, so I began to dig deeper. When I walked up to the condenser, the compressor and all fans were running, I went ahead and turned the timeclock to initiate a pumpdown, the pumpdown took a very long time, but it finally did shut off, so I energized the solonoid, and it opened, and then the compressor sat there and hummed pulling locked rotor amps. At this point, I shut off power, reversed 2 legs of power (3 phase) and it took off and ran. This time I decided to do a pumpdown test, and this verified that the compressor would not pull into a vacuum, and the compressor has a loud rattle. Pressures were about 270/24 on 404a. shut off compressor, and it wouldnt start again. reversed legs, still would'nt start. Verified that I was not single phased, or that voltage was ok.. Here is the deal. I had and have 198 volts give or take 2 between all 3 legs. Pulling close to lock rotor amps. Comp nameplate says 208/230. As a final test, I used my gauges to equalize pressure on the compressor. Still won't start. So today we replaced the compressor. Now, the compressor will run and runs fine, amps are a tad high due to the low voltage I am dealing with, but two times I just hit the oil safety test switch, and it will shut off the compressor for a split second and it wont come right back on when I release the button. If I hold the button in for 2 or 3 seconds then release it, it starts without a problem. I have never had starting torque issues with a 3 phase compressor, and I have seen these things run all day long on 195 volts, which is well within 10% of 208. Here is the other question I have, I talked to my local copeland rep, and he said that these compressors don't like to start with the pressures equalized, and to me (and anyone else I have talked to) doesn't make any sense. Is the problem fixed? yes. Am I a little concerned? yes. So, if any of you have any answers, I would be more than willing to listen. I also changed the oil pressure safety and contactor. And the compressor starts fine coming out of a pumpdown. ?????????

  2. #2
    Join Date
    Apr 2010
    Location
    West Virginia
    Posts
    636
    Well, depends on your outlook, starting at low pressure is not actually pumping as much gas as starting equalized.
    Equalized you are pumping against a lower pressure.

    Freezers usually have a Crankcase pressure regulator to limit the starting pressure, so I would tend to believe not starting equalized statement.

    So, I would suspect that the CPR is bad, had been removed by someone that did not know better.

    Jim

  3. #3
    Join Date
    Jun 2005
    Location
    Las Vegas NV
    Posts
    1,139
    So we'll know what we're dealing with, what is the model number of the compressor? Any other models numbers you have would help.

  4. #4
    I will get the #'s tomorrow. I just threw it in today and it was hotter than heck on the roof and was ready to get down. Appreciate the help.

  5. #5
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,309
    Sounds like you had a bad compressor and fixed it! Bill Customer.
    Could have been open windings (intermittant) on one leg - heats up and opens which won't necessarily stop a running motor (although it will kill it eventually), but won't let it start. Did you ohm out the compressor?

    James122964, I have to disagree with you on the cpr valve. The purpose of this valve is to limit running amps during a hot pull down. That is why you set them only during a pulldown, and set them to rated amps on the compressor. When not present you would have to sit and throttle the suction svc valve until the box comes down in temp.

    Coolinggod, you also mentioned everything is VERY OLD hussman, then said 404a... Retro done properly?

  6. #6
    Join Date
    Apr 2010
    Location
    West Virginia
    Posts
    636
    Quote Originally Posted by cjpwalker View Post
    Sounds like you had a bad compressor and fixed it! Bill Customer.
    Could have been open windings (intermittant) on one leg - heats up and opens which won't necessarily stop a running motor (although it will kill it eventually), but won't let it start. Did you ohm out the compressor?

    James122964, I have to disagree with you on the cpr valve. The purpose of this valve is to limit running amps during a hot pull down. That is why you set them only during a pulldown, and set them to rated amps on the compressor. When not present you would have to sit and throttle the suction svc valve until the box comes down in temp.

    Coolinggod, you also mentioned everything is VERY OLD hussman, then said 404a... Retro done properly?
    CPR does protect the compressor from overloading by limiting the suction pressure, weather its a hot pull down or not, and by limiting the suction pressure (at the compressor) it limits the amperage and the amount of refrigerant that the compressor has to pump, thereby limiting the amperage.

    As far as throttling the valve, what happens when you are not there, and the box was shut off for whatever reason? the only option if there is not a CPR is to have a compressor that can handle it.

    Jim

  7. #7
    Join Date
    Feb 2005
    Location
    Tampa Florida
    Posts
    746
    I've never seen a CPR on a 3 Phase system.

  8. #8
    Join Date
    Apr 2010
    Location
    West Virginia
    Posts
    636
    Quote Originally Posted by jimp View Post
    I've never seen a CPR on a 3 Phase system.
    Ture, but they may have a ZP power head, does nearly the same thing.

    Jim

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