Heat Pump Wire Size

[MICHAEL S. SNOW]

I recently completed the Conductor Sizing and Protection Calculations Course and have the following question in regards to example 6.10, page 248:

When wiring a heat pump, where in section 440 does it allow for exceeding 240.4(D), i.e. 15A for #14, 20A for #12? I need to be able to share this with a local inspector.

Thanks, I'll wait for your response.

Mike

 

[bphgravity]

In the first sentence of 240.4(D), it states, "Unless specifically permitted in 240.(E) or 240.4(G)...."

In Table 240.4(G), Article 440 is listed. If the heat pump falls within the scope of that article, the rule in 240.4(D) does not apply.

 

[iwire]

Start at the beginning.

240.4 Protection of Conductors.
Conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.15, unless otherwise permitted or required in 240.4(A) through (G).

240.4(G) Overcurrent Protection for Specific Conductor Applications. Overcurrent protection for the specific conductors shall be permitted to be provided as referenced in Table 240.4(G).

If I could post Table 240.4(G) you would see it lists 440.

 

[623merlin]

I was not aware that we werer allowed to exceed 240.4(D) on inductive load circuits (motors).

 

[infinity]

Look at table 240.4(G), it lists the applications that are not subject to 240.4(D).

 

[infinity]

That was quick. Mike was waiting for your responses and got four two minutes apart.

 

[jwelectric]

If I could post Table 240.4(G) you would see it lists 440.

I hope that I can get this to upload;

Well I did good!!

 

[Bea]

If there is a listing on the unit or the manual for the heat pump those spec must be followed as per NEC 110.3 Other wise th ampacity of the OCD should in no case exceed 225 percent of the branch-circuit selection current NEC 440.22.