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#101113 - 02/09/07 01:56 PM AC's
dilydalyer Offline
Member

Registered: 01/08/07
Posts: 59
Loc: tennessee
If my nameplate on a residental outside ac unit says 20 amp min fuse,2o amp max fuse,13.6 running amps.....does that mean I could in theory pull a 14 home-run AND put it on a 20 breaker if I wanted to?

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#101114 - 02/09/07 03:01 PM Re: AC's
George Little Offline
Member

Registered: 01/18/04
Posts: 1492
Loc: Michigan USA
Probably yes. Even tho you might be terminating in a 60┬░ terminal. Look at the name plate again because it seems strange to have the Min fuse of 20a. and the Max fuse as 20a. Unless I read your post incorrectly.
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#101115 - 02/09/07 05:00 PM Re: AC's
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
Yes, #14 THHN/ THWN could be used on an A/C Condensing Unit that requires a 13.6 minimum amperage rating based on article 240.4 (G). The overcurrent protective device (OCPD) should always be what the nameplate calls for based on 110.3 (B). It should also be noted that if the nameplate calls for 'MAX FUSE' then you'll need a fused disconnect. Those aren't as common as they used to be 20 years ago (or so they tell me).

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#101116 - 02/10/07 08:49 AM Re: AC's
dilydalyer Offline
Member

Registered: 01/08/07
Posts: 59
Loc: tennessee
Tks...I am wanting to make sure that this is one of the exceptions to 310.16 that allows you to alter from putting 14 only on a 15 amp breaker and so forth with the 12 and 10 wire

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#101117 - 02/10/07 10:26 AM Re: AC's
CTwireman Offline
Member

Registered: 02/07/02
Posts: 839
Loc: Connecticut, USA
With the new federal regulations that mandate 13 SEER minimum efficiency, I am seeing a lot of AC's that only require a minimum circuit ampacity of 15 or 20.

Peter
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#101118 - 02/15/07 06:26 AM Re: AC's
dilydalyer Offline
Member

Registered: 01/08/07
Posts: 59
Loc: tennessee
I posted this topic a week or so ago and by coincidence,me and my helper were sent to another persons job(we've been slow lately) to change an AC feed.It is a remodel with 3 ACs,all new,using the exsisting feeds.Well,the AC in question had a no.10 pulled to it and the info on nameplate was as follows..23.9 min.ampacity,40min breaker,40 max breaker....could the no.10 have been used?

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#101119 - 02/15/07 02:24 PM Re: AC's
earlydean Offline
Member

Registered: 12/22/03
Posts: 749
Loc: Griswold, CT, USA
dilydaler,

440.6(A)tells us to size the conductors based on the nameplate rated load current. The exception says: "Where so marked, the branch-circuit selection current shall be used instead of the rated-load current to determine the rating or ampacity of the ....branch-circuit conductors..."

440.32 tells us to size the conductors at 125%.

Assuming your AC unit was not "so marked for branch-circuit selection current", then the #10s are good for the 23.9 x 1.25 = 29.875 amps.

The #10s could have been used, IMHO.
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#101120 - 02/16/07 11:15 AM Re: AC's
ShockMe77 Offline
Member

Registered: 06/11/05
Posts: 823
Loc: Rahway, New Jersey
 Quote:
Well,the AC in question had a no.10 pulled to it and the info on nameplate was as follows..23.9 min.ampacity,40min breaker,40 max breaker....could the no.10 have been used?



Absolutely. The nameplate tells you all you need to know. The minimum ampacity, and the maximum breaker size.

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#101121 - 02/16/07 11:25 AM Re: AC's
JBD Offline
Member

Registered: 07/12/01
Posts: 599
Loc: WI, USA
 Quote:
Tks...I am wanting to make sure that this is one of the exceptions to 310.16 that allows you to alter from putting 14 only on a 15 amp breaker and so forth with the 12 and 10 wire.


Actually, the restriction for limiting the protection for #14, 12, and 10 is not in table 310.16 it is in 240.4(D). But 240.4(D) is not applicable if you have one of the permissable loads in 240.4(G). Most motor and HVAC loads are covered by 240.4(G) and so they can use these size conductors at their maximum table 310.16 values (as restricted by the equipment terminations).

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