ECN Forum Forums Code Related Discussion NEC & other Code issues A Code compliant installation?

240.(B) is not being used in this application, we are using 240.6(G)

When you read 240.6(G) you find it says 'shall be permitted'

Take that along with the sections in 440 and you get to go much larger that the next standard size.

Here is the reason this is permitted and it is safe.

The HVAC unit contains internal overload protection, if say a motor seizes up the units own over current protection will open before the conductors area damaged assuming you followed the name plate data.

The break at the panel is not being used for over current protection, it's only function is short circuit and ground fault protection.

I understand that 440 allows you to use 14 awg for this installation, but I cannot find were the code allows you to protect 14 awg with a 30 ampere breaker when by table 310.16 shows maximum of 25 amperes. This is the part that is confusing me.

Thanks

Mountan, look at 430.52

In this case look at 440.6 for the nameplate use, 440.12 for the disconnect size, 440.22 for the OC device and 440.31 for the wire size,.

But the key is the last sentence of 440.21: "They" (short circuit and ground fault OC devices) "are in addition to or amendatory of the provisions of Article 240."

Code compliant maybe, cutting it close, adding too many variables to the picture like ambiant temp, derateing, voltage drop, starting current etc. But with most inspectors, it just wont fly when you have a 3 second eye-ball inspection, or a full blown engineering calculation to go through.

Either way, we are in the buisiness of selling wire right? the bigger the better....

Mark there are always two answers, the code minimum (which the inspector must accept) or beyond code minimums.

99% of the time we run conductors that match the breaker size.

I had my outside AC unit moved from the west side of my house to the north side of my house, Granted it was a freebie job, I had done an electrical favor fer the ac guyz sister, and in re-payment he moved my ac, cut and brazed the freon lines etc, but when he moved it, he went from a 45amp 230v dissconect to the unit w/ #12 awg, that was laying out side my shed. and told my roomate, that I needed to replace it (the #12) as soon as possible..............

Is the 60 amp disconnect correct for the overload though?

Village:
Welcome to ECN.
Any size disconnect is OK, provided that the MOCP is sized properly. IF you wanted, for whatever reason, to install a 600 amp disco, that also would be OK

John