Hermetic refrigeration compressor

[superdave02]

What size branch-circuit short-circuit and ground fault protection is required for a 16 amp 240 volt single phase refrigeration motor compressor??

 

[hbiss]

Well, you make it sound like you have a refrigeration compressor sitting on your desk and that's what the label says. Compressors are part of a condensing unit or part of the refrigerator or freezer. The condensing unit, refrigerator or freezer itself should have the electrical requirements listed on the tag and that's what you go by.

-Hal

 

[infinity]

Sounds like this is what you're looking for.

440.22 Application and Selection.
(A) Rating or Setting for Individual Motor-Compressor. The motor-compressor branch-circuit short-circuit and ground-fault
protective device shall be capable of carrying the starting current of the motor. A protective device having a rating or
setting not exceeding 175 percent of the motor-compressor rated-load current or branch-circuit selection current, which‐
ever is greater, shall be permitted, provided that, where the protection specified is not sufficient for the starting current of
the motor, the rating or setting shall be permitted to be increased but shall not exceed 225 percent of the motor rated-
load current or branch-circuit selection current, whichever is greater.
Exception: The rating of the branch-circuit short-circuit and ground- fault protective device shall not be required to be less than 15 amperes.

 

[superdave02]

so if this were a test question would the answer be 25 amp or 30 amp? Asking for a friend

 

[ptonsparky]

so if this were a test question would the answer be 25 amp or 30 amp? Asking for a friend

Read infinity’s post. ”...not exceeding...” They are both acceptable. It could be smaller.

 

[don_resqcapt19]

The maximum based on the rule would be 28 amps, but that is not a standard size and 440.22 does not permit rounding up to the next standard size OCPD. So you would have to try the 25 amp device and if that would not permit the compressor to start, you could increase the OCPD to 35 amps.

This is something that would be very rarely done in the field as almost all such equipment has the minimum circuit ampacity and the maximum permitted OCPD listed on the nameplate.

 

[Eddie702]

In the old days pre 1970s ish

There were a lot of "built up" or field built systems. I have seen old jobs with the compressor (just the compressor) in the basement of a store, air cooled condenser on the roof and an air handler somewhere else. Then the wire size and OCPD would have to be calculated by the electrician

This is rarely seen anymore

But then when I started we worked on roof top units with standing gas pilots that had to be light with a match.

It was great for a service call when the wind started blowing

 

[ptonsparky]

Worked on and help installed a few back when

 

[hbiss]

This is something that would be very rarely done in the field as almost all such equipment has the minimum circuit ampacity and the maximum permitted OCPD listed on the nameplate.

That's because compressors are not used alone. There will be condenser cooling fan(s), a crankcase heater and maybe some solenoid valves that make up the condensing unit.

So if this is a test question there is your answer but don't expect to use it unless you are a manufacturer of HVACR equipment.

-Hal