NEC 220.51 allows the heating loads of feeders to be calculated at 100% of the load if I am reading that right. It is a typical install in my area to supply a boiler or a furnace that has two or more breakers installed on the unit with a “feeder” to an encloser and use the 10 foot tap rule to supply the 2 breakers. (Assume two 9kW loads on one furnace, 37.5 amps each for a total of 75 amps. I run a number 3 AL to the box and a number 6 AL to each of the 50 amp breakers on the furnace.) However, I was questioned by an inspector who stated the number 3 AL was not a feeder as tit did not supply a branch circuit as required in NEC 100 definitions and so had to be calculated at 125% of load. Is he correct?
Tap rule for heating loads
- Thread starter wyboy
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- Location
- Connecticut
- Occupation
- Engineer
See if 424.22(D) applies to your case.
I'm not sure that taps would be compliant with 210.19, however.
I'm not sure that taps would be compliant with 210.19, however.
- Location
- Connecticut
- Occupation
- Engineer
Yes
- Status