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#100026 - 10/05/06 03:12 PM A Code compliant installation?
ShockMe77 Offline
Member
Registered: 06/11/05
Posts: 821
Loc: Rahway, New Jersey
Air conditioning condensing unit has a minimum ampacity rating of 18 amps.

A maximum over current protection device rating of 30 amps.

A 60 amp rated non-fused diconnect is used and installed in a readily accessible location.

14 AWG wire is run to the disconnect, and then #14 THWN to the condensing unit.

A double-pole 30 amp circuit breaker is installed at the panel.

Is this an NEC compliant installation?
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#100027 - 10/05/06 03:44 PM Re: A Code compliant installation?
George Little Offline
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Registered: 01/18/04
Posts: 1488
Loc: Michigan USA
Absolutely Green Sticker time.
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#100028 - 10/05/06 04:31 PM Re: A Code compliant installation?
Trick440 Offline
Member
Registered: 08/15/05
Posts: 247
Loc: Waterford, MI, USA
I need some clarification on this one.

How can you use a 30a breaker to protect 14g wire?

heck I guess I need to know how 14-2 supports 18a aswell.

[This message has been edited by Trick440 (edited 10-05-2006).]
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#100029 - 10/05/06 04:41 PM Re: A Code compliant installation?
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
I agree with George.

Trick first off 14 AWG is rated anywhere from 20 to 25 amps depending on the insulation and terminations.

On typical branch circuits 240.4(D) requires us to use a 15 amp over current device.

However for HVAC units 240.4(G) applies and we can use 14 AWG up to the rating in 310.16 and the short circuit and ground fault protection can be as allowed in 440.6
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Construction & Maintenance Electrician
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#100030 - 10/05/06 04:59 PM Re: A Code compliant installation?
Trick440 Offline
Member
Registered: 08/15/05
Posts: 247
Loc: Waterford, MI, USA
Can't wait to pull this one on my boss.. lol.

Thank you for the code refs. and explanation.
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#100031 - 10/05/06 05:24 PM Re: A Code compliant installation?
ShockMe77 Offline
Member
Registered: 06/11/05
Posts: 821
Loc: Rahway, New Jersey
Trick, this is exactly why I posted this. I did an over/ under split-system A/C install today and was talking to the HVAC contractor. He saw me looking at the specs on both CU's and told me, "just run a 30 amp 10/2 wire."

So I said, "ok, but I could really just run 14 wire and it'd be ok by NEC standards."

He says, "I've never heard of that so don't so it."

^^
(this coming from the HVAC guy, not an electrician)

Of course, the better install is to run the maximum size wire and the maximum size OCPD, I'm sure most would agree. But the point is, it can be done and pass inspection, and damn it felt good to hold my own in this discussion.

Thanks ECN!
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#100032 - 10/05/06 06:10 PM Re: A Code compliant installation?
HotLine1 Offline


Member
Registered: 04/03/02
Posts: 6776
Loc: Brick, NJ USA
Ron:
Ya did good! Just keep watching the mfg nameplates. Only other consideration could possibly be voltage drop, dependent on the run. That's my opinion, when ya cut it close.

John
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#100033 - 10/05/06 08:12 PM Re: A Code compliant installation?
ShockMe77 Offline
Member
Registered: 06/11/05
Posts: 821
Loc: Rahway, New Jersey
Thanks John!
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#100034 - 10/05/06 09:44 PM Re: A Code compliant installation?
macmikeman Offline
Member
Registered: 07/16/02
Posts: 717
Loc: Honolulu, Hawaii
Most of the mini split systems I have done will list the max fuse or circuit breaker, and the minimum ampacity of the wiring. What I've noticed is they tend to want to protect thier machines from overworking and usually exceed code a bit on the minimum ampacity labeling. Code says go with what is on the label.
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#100035 - 10/06/06 06:09 AM Re: A Code compliant installation?
mountainman Offline
Member
Registered: 01/29/02
Posts: 54
Loc: Richmond Va. U.S.A.
iwire, what about 240.6? In order for this to be code compliant you would need a 25 ampere breaker to comply with 240.4(B). IMHO
thanks Joe
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