Overcurrent Protection Conductor Bundling Clarification

[erickench]

125% continuous plus non-continuous rule would not be applied in the case of a residence as the examples in the back of the code show. As I stated in another thread the reasoning is that in a dwelling, lighting and receptacle loads are calculated together and not separately. If receptacles are non-continuous then how would you separate the continuous from the non-continuous calculated loads? Besides in most residences the service is usually 240/120 Volt single phase 3-wire. You could not apply the derating factors to these cases either.
You could apply the 125% continuous plus non-continuous rule in a store building where the lighting and receptacle loads are calculated separately as shown in annex D of the code but because that particular case is three wire the derating factors would not apply.

 

[infinity]

125% continuous plus non-continuous rule would not be applied in the case of a residence as the examples in the back of the code show. As I stated in another thread the reasoning is that in a dwelling, lighting and receptacle loads are calculated together and not separately. If receptacles are non-continuous then how would you separate the continuous from the non-continuous calculated loads? Besides in most residences the service is usually 240/120 Volt single phase 3-wire. You could not apply the derating factors to these cases either.
You could apply the 125% continuous plus non-continuous rule in a store building where the lighting and receptacle loads are calculated separately as shown in annex D of the code but because that particular case is three wire the derating factors would not apply.

Eric,

Where are you getting the continuous and non-continuous from in this example? The load here is a continuous load as outlined in the OP, therefore it's ampacity of 25 amps must be taken as 25 * 125%.

 

[erickench]

Okay it's continuous. You would have to apply the 125% rule. But if it were a residence you would not be able to apply it. The branch circuit ratings in a residence are pretty much standardized. And as for the feeder of the residence, you would not be able to separate continuous load from the non-continuous loads.

 

[benaround]

Eric, In article 422 you will find that a 120 gallon or less electric hot water tank 'shall be'

treated as a continous load, res., comm., or indl.

side note: In this Forum it's a good idea to look before you leap.

 

[eeRyanC]

Why are you using circuit load of 35 amps in your calculation? You said that the circuit load is 31.25 amps in step 1.

In order to comply with 2008 NEC 240.4, the conductors must be protected against over-current. Therefore, I am working backwords from the OCPD protected load (35A) rather than the calculated load (31.25A) in step 3.

 

[erickench]

Water Heater

Water Heater

Eric, In article 422 you will find that a 120 gallon or less electric hot water tank 'shall be'

treated as a continous load, res., comm., or indl.

side note: In this Forum it's a good idea to look before you leap.

Benaround, it's true that NEC 422.13 specifies that 120 gallon or less water heaters are continuous. But if you look at example D2(c) in the codes annex the 125% rule is not applied to the water heater of that problem. Now why is that?