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  1. #14
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    Quote Originally Posted by ryan1088 View Post
    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.
    Normally true, but 208 vs 230 is most often an exception.

    Many commercial buildings receiver their low voltage service form 208Y/120v service, either as single phase or all three phases depending on needs.

    240v (which is expressed as 230, just like 120 expressed as 115) service is offered in residential or some commercial buildings, but that's power company's decision.

    240v/120 high-leg delta exists, but it's less common. It's too much of a burden to have to offer 208v service and 240v service models, therefore 230v motors is assumed acceptable for 208 and 240v service. You shouldn't have to use a transformer. 208v is by far the more common service.

    It's the same deal with single phase A/Cs. Houses usually get 120/240 from single phase transformers. Large apartment complexes usually get three phase service and feed two legs of service to each unit. This means 208v is available but not 240v.

    To avoid having to make apt/office bldg models separate from house models they're rated to accept 208-230.

    For larger stuff, power comes from 480Y/277v. Larger refrigeration runs on 3ph 480v. Lighting runs off of single phase 277v. You don't see 240/277v units, because there is no need for it like 208/240v model.

    Running equipment on 20A circuit when it calls for >20.1A minimum is not code compliant, so if conductor size allows for it, you should have the breaker changed to next highest.

  2. #15
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    First, your overcurrent device size is governed by NEC article 440. Get your electrician to explain it to you.

    Second, the NEC prohibits running 230 volt equipment on a 208 feed. Your choices are to install a transformer or replace the condensing unit. 10% voltage variance does not apply in this case

  3. #16
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    Quote Originally Posted by lifeline View Post
    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 wire is only current limited in residential environments.

  4. #17
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    Wires are still currently limited by temperature rise for safety, but for motor starting you need to look at volts available at motor under LRA.

    If it falls too low, it can't rank over therefore it stalls and trips the breaker.

    This is a single phaser so you might be able to use a hard start kit to increase the available torque.

  5. #18
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    Quote Originally Posted by timebuilder View Post
    #12 wire is only current limited in residential environments.
    Not true, #12 is limited to 20 amps in all situations except for specific conductor applications. A/Cs, motors, welders, capacitor banksare all exceptions to the 20 amp rule. Office lighting and receptacle loads are under this rule. Read 240.4d and 240.4g for more info.

  6. #19
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    Quote Originally Posted by wanttosee View Post
    Not true, #12 is limited to 20 amps in all situations except for specific conductor applications. A/Cs, motors, welders, capacitor banksare all exceptions to the 20 amp rule. Office lighting and receptacle loads are under this rule. Read 240.4d and 240.4g for more info.
    I was referring to his 16 amp reference, which is an 80% current limitation. Yes, 240 D 1 through 7 gives 20 amps as the upper limit for 12 wire, except for applications listed in E or G.

    But, I was not talking about the 20 amp limit on 12, just the 16 amp 80% limitation. The 16 amps is an ampacity limitation, rather than an overcurrent protection limitation.

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  7. #20
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    How far is the wire ran from panel to compressor ?

    1st thing i would do , install 10 guage wire on a 30

    They are just asking for trouble maxing both the 20 amp breaker and the 12 guage wire 24/7

  8. #21
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    Quote Originally Posted by Snapperhead View Post
    How far is the wire ran from panel to compressor ?

    1st thing i would do , install 10 guage wire on a 30

    They are just asking for trouble maxing both the 20 amp breaker and the 12 guage wire 24/7
    Larger wire will help eliminate a part of the problem.

    However, I think the indication is that this is a 230 volt condenser, and not a 208-230 volt condenser, and it's a 208 feed. If that's the case, it is a violation to run the 230 "only" machine on 208.

    I'd get the manufacturer info straight from the horse's mouth, and see what the MCA and MOD ratings are, along with the manufacturer permissible voltage, and start from a point of firm knowledge about the unit, and take the appropriate corrective action based on THOSE numbers.
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  9. #22
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    Quote Originally Posted by timebuilder View Post
    I was referring to his 16 amp reference, which is an 80% current limitation. Yes, 240 D 1 through 7 gives 20 amps as the upper limit for 12 wire, except for applications listed in E or G.

    But, I was not talking about the 20 amp limit on 12, just the 16 amp 80% limitation. The 16 amps is an ampacity limitation, rather than an overcurrent protection limitation.

    Check out 210.23. An individual branch circuit can supply any single load up to 100% of the overcurrent protection value. Since I doubt the freezer is cord and plug connected and supplies other things I believe you aren't limited to 16 amps.

  10. #23
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    First post says it pulls 27 amps , and takes 30 seconds to drop to 17

    Why push the limits on a 20 ....

  11. #24
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    Quote Originally Posted by wanttosee View Post
    Check out 210.23. An individual branch circuit can supply any single load up to 100% of the overcurrent protection value. Since I doubt the freezer is cord and plug connected and supplies other things I believe you aren't limited to 16 amps.
    No he is not limited to 16 amps (as someone mentioned above) but he has already exceeded 20. And, his branch circuit must be sized to 125% of RLA, which is the basis for the MCA value.

    Without knowing the MCA and MOD figures, we don't know what conductors or overcurrent devices would be appropriate for this unit. We do know that he has to follow 422, 430, and 440 to do it correctly.

    And, we already know that he can't run a 230-only rated appliance on a 208 line because that conflicts with manufacturer standards and UL testing parameters. A buck and boost transformer is probably the least expensive fix, along with the proper conductor and overcurrent device as permitted by the nameplate.
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  12. #25
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    Quite true, though technically #12 wire is rated at 25 amps according to 310.16 and so the wire is still suitable for the aplcation. I still contend that the real problem is the improper voltage and upsizing wiring and breakers while it may stop the symptoms is not a valid or proper fix for the freezer

  13. #26
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    Quote Originally Posted by wanttosee View Post
    Quite true, though technically #12 wire is rated at 25 amps according to 310.16 and so the wire is still suitable for the aplcation. I still contend that the real problem is the improper voltage and upsizing wiring and breakers while it may stop the symptoms is not a valid or proper fix for the freezer
    Yep. He'd have a little work if the unit was 208-230, but more to do now since it is 230 alone.
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