Individual Branch Ciruit

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mwm1752

mwm1752

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Aspen, Colo
2 -50 amp appliances. 1 - range & 1- steam unit. Contractors has only one 50 amp circuit and wants to use a manual transfer type switching that would allow only one of the appliances to be energized at a time. Both appliance require an individual branch circuit.

Does the contractors proposal comply with the NEC?

If so please be specific
 
I personally have never seen anything wrong with selective load shedding myself.

JAP>
 
Nothing wrong with doing that, but a manual transfer switch may be overdoing it. A subpanel with two 50 amp breakers (one for each device) is probably sufficient. If the feeder to the subpanel can only handle 50 amps, the breaker for the subpanel will trip if both devices are used simultaneously.
 
Coppersmith said:
Nothing wrong with doing that, but a manual transfer switch may be overdoing it. A subpanel with two 50 amp breakers (one for each device) is probably sufficient. If the feeder to the subpanel can only handle 50 amps, the breaker for the subpanel will trip if both devices are used simultaneously.
Click to expand...

Does the feeder to the sub-panel need to be sized according to the calculated load?
 
It's not selective load shedding, it's selecting a load.

Unless it's Friday and I am getting too ready to head home and am thereby forgetting something, I will say that the NEC never requires an individual branch circuit. It allows them, and allows you to bypass other rules if you use them, but I can't think of a circumstance in which it is required. Example: kitchen outlets must be on 20 amp circuits, except that you can power the fridge with an individual 15 amp branch circuit.

Now a separate issue is whether you would be violating the manufacturer's requirement for an individual branch circuit. I say no, because with the manual switch in either position, the load that is thereby selected is not sharing the circuit with any other load.
 
Rob, isnt that like when we size based upon heating and cooling? We take the largest of the two...so in this case the two are identical...
a Sub Panel sized at 50 amps with only two breakers, both of them being 50 amps... may seem to be overloaded but it definitely should trip if both are used at same time.
However, if one can run the cable for it, would prefer to run 100 amps to the sub panel and then allow the two 50 amps from there... is it a case of the panel being full? Or the service itself being full?
 
mwm1752 said:
2 -50 amp appliances. 1 - range & 1- steam unit. Contractors has only one 50 amp circuit and wants to use a manual transfer type switching that would allow only one of the appliances to be energized at a time. Both appliance require an individual branch circuit.

Does the contractors proposal comply with the NEC?

If so please be specific
Click to expand...
I say it complies with the NEC as there is nothing to prohibit the install.
I hope you are well, mwm!
 
I like the sub-panel idea but I don't see how you get around this section when the two loads are connected to the sub-panel.

215.2 Minimum Rating and Size.
(A) Feeders Not More Than 600 Volts.
(1) General. Feeder conductors shall have an ampacity not
less than required to supply the load as calculated in Parts
III, IV, and V of Article 220. Conductors shall be sized to
carry not less than the larger of 215.2(A)(1)(a) or (b).
(a) Where a feeder supplies continuous loads or any
combination of continuous and noncontinuous loads, the
minimum feeder conductor size shall have an allowable
ampacity not less than the noncontinuous load plus
125 percent of the continuous load.
(b) The minimum feeder conductor size shall have an
allowable ampacity not less than the maximum load to be
served after the application of any adjustment or correction
factors.
Click to expand...
 
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