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#205568 03/09/12 05:18 PM
Joined: May 2010
Posts: 30
B
Bravo Offline OP
Member
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

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Joined: Dec 2000
Posts: 4,294
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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.

Joined: May 2010
Posts: 30
B
Bravo Offline OP
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#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?

Joined: Jan 2004
Posts: 1,507
G
Member
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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