Page 1 of 3 123 LastLast
Results 1 to 13 of 34
  1. #1
    Join Date
    Apr 2011
    Location
    Florida
    Posts
    107

    3 phase ac compressor

    Just put a new comp in this unit roof top package. Wires everything up push contractor in and the comp comes on but not pumping. How do I know I have the wireing on the correct terminal? It's late and I'm having a brain fart. Thanks in advance
    Aire Force A/C and heating
    Florida
    since 1988

  2. #2
    Join Date
    May 2011
    Location
    Western, KY
    Posts
    3,226
    Quote Originally Posted by biggi View Post
    Just put a new comp in this unit roof top package. Wires everything up push contractor in and the comp comes on but not pumping. How do I know I have the wireing on the correct terminal? It's late and I'm having a brain fart. Thanks in advance
    Switch two legs and you should be good to go.

  3. #3
    Join Date
    Oct 2012
    Location
    Wisconsin
    Posts
    4,123
    If its a hermetic, rotation doesn't matter. If its a scroll and the rotation is backwards, it won't really pump, the pressures will be way off. If its a scroll try swapping two wires and see if it works better.

  4. #4
    Join Date
    Dec 2002
    Location
    Arizona
    Posts
    4,416
    Quote Originally Posted by Mike19 View Post
    If its a hermetic, rotation doesn't matter. If its a scroll and the rotation is backwards, it won't really pump, the pressures will be way off. If its a scroll try swapping two wires and see if it works better.
    What he said.
    Make your expertise uniquely valuable.

    Make your influence uniquely far-reaching.

  5. #5
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,071
    Quote Originally Posted by Mike19 View Post
    If its a hermetic, rotation doesn't matter. If its a scroll and the rotation is backwards, it won't really pump, the pressures will be way off. If its a scroll try swapping two wires and see if it works better.
    You mean reciprocating doesn't matter?

  6. #6
    Join Date
    Oct 2012
    Location
    Wisconsin
    Posts
    4,123
    Quote Originally Posted by Core_d View Post
    You mean reciprocating doesn't matter?
    Yes, phase rotation doesn't matter on reciprocating compressors. Either way they spin, the piston still moves up and down.

  7. #7
    Join Date
    Dec 2012
    Location
    Lowell,MA
    Posts
    51
    have also seen copeland scroll compressor that did not pump reversed and still did not pump and by chance took a copeland screw class and asked the teacher about this compressor and he said " take a 2x4 and wack the top of compressor there is a seal inside the compressor that sometimes does not seat right at the factory and this will solve it for good"

  8. #8
    Join Date
    Apr 2011
    Location
    Florida
    Posts
    107
    Thanks everyone. I swapped two terminals and it was fine. It's been a long day no doubt summer has hit in FL. But is that the only way to tell if its wires correctly. There has to be a way to know BEFoRE you turn power on.. Right?

  9. #9
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,071

  10. #10
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,554
    It doesn't hurt anything to find out the old fashioned way, so why invest in a meter? Just be resolved to the fact that the 50-50-90 rule will apply: you have a 50-50 chance of getting it right, but Murphy's law will have it wrong 90% of the time...

    If you want, just pay attention to how the wires came off of the old compressor.

  11. #11
    Join Date
    Dec 2012
    Location
    columbus, OH
    Posts
    2,071
    Quote Originally Posted by cjpwalker View Post
    It doesn't hurt anything to find out the old fashioned way, so why invest in a meter? Just be resolved to the fact that the 50-50-90 rule will apply: you have a 50-50 chance of getting it right, but Murphy's law will have it wrong 90% of the time...

    If you want, just pay attention to how the wires came off of the old compressor.
    Agreed, no need to run out and buy a meter here. But thats how you would do it if need be.

  12. #12
    Join Date
    Aug 2006
    Location
    Mixing oil and fire with a big spoon.
    Posts
    4,438
    Quote Originally Posted by Mike19 View Post
    If its a hermetic, rotation doesn't matter. If its a scroll and the rotation is backwards, it won't really pump, the pressures will be way off. If its a scroll try swapping two wires and see if it works better.
    hermetic means sealed without nuts and bolts and gaskets and o-rings and such. scrolls are hermetic too.


    Quote Originally Posted by cjpwalker View Post
    It doesn't hurt anything to find out the old fashioned way, so why invest in a meter?...
    you should buy one because you want it done right and you want to know WHY it is right. just because it is pumping properly on 1 compressor doesn't mean that ALL of them are pumping properly due to proper phasing or broken parts. i have seen times where the manufacturer gets 1 wired properly and the other 1 or 2 NOT wired properly. if the phasing is correct, then you know the problem is in the unit. if the phasing is incorrect, then you know it is the electricians issue and you are done until he gets it right. if you 'correct' his improper phasing (on the units side of the terminal block) then you have violated the wiring diagram and that usually means that you don't get warranty anymore.

    i had a new mall start up of 48 rooftops where the installing contractor didn't want to wait for our start up. he turned them all on and checked the condenser fan rotation to 'make sure that phase rotation was correct'...the problem with that was the fact that the condenser fan was single phase. in that case, we proved that they jacked everything up by using a phase rotation meter...it was an electrician that turned everything on and they only had 1 phase rotation meter in the whole company? i personally own 2!

    not all compressors can run for days in reverse rotation without any problems. some are toast in as little as 15 minutes.

    now if you start working on screws and centrifugals...phase rotation is critical. at start up, the chillers controls will usually see reverse rotation using the motor amperage phases, however, it only takes a few rotations in the wrong direction to turn those compressors into boat anchors.
    How to make the perfect "Half-Hitch" knot or any other boyscout knot in 3 easy steps...

    1. Remove your meter leads from the meter and very carefully return them to their storage case or bag.
    2. Wait 2 seconds
    3. Very carefully remove your meter leads from their storage place and enjoy your new knot!

  13. #13
    Join Date
    Oct 2004
    Location
    Central WA
    Posts
    1,554
    Quote Originally Posted by jayguy View Post
    hermetic means sealed without nuts and bolts and gaskets and o-rings and such. scrolls are hermetic too.




    you should buy one because you want it done right and you want to know WHY it is right. just because it is pumping properly on 1 compressor doesn't mean that ALL of them are pumping properly due to proper phasing or broken parts. i have seen times where the manufacturer gets 1 wired properly and the other 1 or 2 NOT wired properly. if the phasing is correct, then you know the problem is in the unit. if the phasing is incorrect, then you know it is the electricians issue and you are done until he gets it right. if you 'correct' his improper phasing (on the units side of the terminal block) then you have violated the wiring diagram and that usually means that you don't get warranty anymore.

    i had a new mall start up of 48 rooftops where the installing contractor didn't want to wait for our start up. he turned them all on and checked the condenser fan rotation to 'make sure that phase rotation was correct'...the problem with that was the fact that the condenser fan was single phase. in that case, we proved that they jacked everything up by using a phase rotation meter...it was an electrician that turned everything on and they only had 1 phase rotation meter in the whole company? i personally own 2!

    not all compressors can run for days in reverse rotation without any problems. some are toast in as little as 15 minutes.

    now if you start working on screws and centrifugals...phase rotation is critical. at start up, the chillers controls will usually see reverse rotation using the motor amperage phases, however, it only takes a few rotations in the wrong direction to turn those compressors into boat anchors.
    In the HVAC/R industry "hermetic" refers to a welded, hermetically sealed reciprocating compressor. http://www.emersonclimate.com/en-us/...mpressors.aspx They are often also called a "recip" or a "tin can," although usually made of steel with other components made of copper, plastic, etc.

    A scroll compressor, although technically welded shut, is commonly referred to as a "scroll."

    I carry a lot of tools, but I don't work on screws or centrifugals, and I don't carry a rotation meter. I don't unclog toilets at work so I don't carry a plunger on my van either.

    When I startup a three phase piece of equipment I will of course verify that all components are operating as designed -- every good technician does. A scroll compressor can run reversed briefly without damage, and often the manufacturer's literature addresses this. A hermetic compressor (welded hermetic reciprocating compressor) can operate in either direction.

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