Panel feeder size

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bruce johnson

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nashville, tn
During a hotel renovation we have discovered that each room has it's own panel each with a 40 amp breaker back feeding and acting as a main. The feeders (#6 copper) come from junction boxes in the corridors. Each junction boxes services 3 rooms and these are also fed with #6 copper conductors on a 60 amp breaker in a "main" panel.
So you have #6 copper conductors on a 60 amp breaker feeding a junction box. From the junction box is 3 sets of #6 copper feeding 3-40 amp panels. Are these conductors large enough? The farthest junction box from the main panel is 200 feet.
These wires are run in 1" EMT with no separate ground wire. Two hots and a neutral with the EMT acting as a ground. The ground bars are bonded to the panels and the neutral bar are not. There are no grounding bushings.
Should there be a separate ground wire as far as codes goes?
 
The NEC allows the emt to be used as an equipment grounding conductor. So a separate conductor is not required but often used.
 
bruce johnson said:
So you have #6 copper conductors on a 60 amp breaker feeding a junction box. From the junction box is 3 sets of #6 copper feeding 3-40 amp panels. Are these conductors large enough? The farthest junction box from the main panel is 200 feet.
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Impossible to say without knowing the connected load.


These wires are run in 1" EMT with no separate ground wire. Two hots and a neutral with the EMT acting as a ground. The ground bars are bonded to the panels and the neutral bar are not. There are no grounding bushings.
Should there be a separate ground wire as far as codes goes?
Click to expand...

It sounds fine and code compliant.
 
As Bob says, you really need an Art 220 load calculation. Once I saw your panel schedule I think your concern may be warranted as it appears you actually have a dwelling unit as I see S/A circuits, cooktop, etc.
I could not read the schedule well, does the panel also supply HVAC ?
 
dkidd said:
How far is it from the junction box to each 40 amp panel?
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The farthest panel from each junction box is maybe 50 feet. The farthest junction box from the main panel is 200 feet. One set of #6 wires feeds each junction box. Each junction box feeds three of these panels.
There is a water source HVAC unit in each room. 120 volts. Not sure of amperage. There is a 1200 watt cooktop in each room, an 18 cu ft refrigerator and a microwave.
 
There are guys here far more qualified to perform Art 220 calculations than I but guessing at the room size I see no problem with the 40 amp main in each unit but the 60 amp feeder looks to me to be inadequate. Hopefully one of the
calculation gurus will chime in.
 
Conductor Size

Conductor Size

My concern in my original post was the conductor size. One set of #6 wires supplying power to 3 of these panels. It just does not seem sufficient to me.
 
bruce johnson said:
My concern in my original post was the conductor size. One set of #6 wires supplying power to 3 of these panels. It just does not seem sufficient to me.
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It may be undersized or it may be fine. The only way to know is a load calculation. The number of panels or breakers is irelevent.
 
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