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#205568 - 03/09/12 01:18 PM mca and mocp nameplate
Bravo Offline

Registered: 05/04/10
Posts: 30
Loc: NY, USA
Hi have a chiller rated 208V, 3P, MCA: 46.1, MOPD: 80, RLA: 30. Its been awhile for sizing motor branch ckts but any idea how to size the ckt. & OCPD?

Correct me if I am wrong but last I remember based on the nameplate info conductors can be #6 with 60A circuit breaker?
MCA = minimum current ampacity
OCPD = maximum over current protection device

Where in the NEC doesnt reference sizing ckts per nameplate?

thanks in advance

2014 / 2011 NEC & Related Books and Study Guides
#205569 - 03/09/12 01:43 PM Re: mca and mocp nameplate [Re: Bravo]
electure Offline


Registered: 12/24/00
Posts: 4226
Loc: Fullerton, CA USA
NEC Article 440 is the one you want to read for this.

You can use #8 for a MCA of 46.1, with up to an 80 amp hacr breaker or fuses for the MOPD.

#205570 - 03/09/12 01:49 PM Re: mca and mocp nameplate [Re: electure]
Bravo Offline

Registered: 05/04/10
Posts: 30
Loc: NY, USA
#8 is good for 40A in the 60deg C column of table 310.16. I think I need to use this for equipment rated 100A or less?

#205571 - 03/09/12 07:53 PM Re: mca and mocp nameplate [Re: Bravo]
George Little Offline

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Make sure the terminals in the Chiller are rated for 75° C if you plan on using #8 copper wire. Most equipment of this nature are only rated for 60° C and that would call for a #6. As for the line side of the disconnect (assume it is separate from the Chiller) it probably would be rated 75° and #8 would be fine. The 80a. overcurrent device is proper in either case.
George Little


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