Table 220.55

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Hoyt

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I am attempting to better understand table 220.55. of the N.E.C.

I have a multi family dwelling unit (Dorm) w/ 50 units. I am attempting to diversify the electric stove. I do not know what stove is being used, but was told it is a standard "Res" stand alone electric stove - full size.

I believe the NEC defines it at 4.5 kw...?

So...if that is true I can use column B. I have 50 stoves...so I can diversify by 20%. That would be a load of 900 watts per stove.

Did I intrepid this correctly...math correct?

Thanks,


Hoyt
 
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Hoyt said:
but was told it is a standard "Res" stand alone electric stove - full size.
I believe the NEC defines it at 4.5 kw...?
Click to expand...

This is not correct. The nec does not define a typical stove since there is no such animal. Most standard ranges are 12kw, I believe, but you really need to get info on the stove.
 
Ok...well if 12 kw, then Column C would apply. Correct.

I am having trouble understanding how Coumn C would be calculated.

50 stoves at 12 kw.
 
Yes, thats what I get as well...a total demand. But I divide the total demand 62.5 by total number of stoves (50) and get 1.25 kw per stove. This is the load i would place in my panel scheds? Seems so low....
 
Hoyt said:
Yes, thats what I get as well...a total demand. But I divide the total demand 62.5 by total number of stoves (50) and get 1.25 kw per stove. This is the load i would place in my panel scheds? Seems so low....
Click to expand...

That is only the figure you need to calculate your service size.
 
I have 10-15 dewling units per floor, each unit will have its own panelboard. I have a distribution panel on each floor (6 floors) to serve that floors dewling unit panelboards.

I am attempting to keep the distribution panelboard size as small as possible...due to the shear quantitiy of units. So can I deversify on my distribution panelboard? 10-15, 12kw stoves per floor is reallying killing the size of my distribution panelboard.
 
Notes:
4. Branch-Circuit Load. It shall be permissible to calculate the branch-circuit load for one range in accordance with Table 220.55.

For each individual range you can use 8kW. IMO
 
So...even though i have 50 ranges in the facility I can only deversify on my service calc and for my panelboard calcs I need to view this as 1 electric range not over 12 kw..thefore branch circuit calc for 1 range would be 8 kw.

For some reason that dosent seem right. But if that is the intent, I guess that is it.
 
At each individual panel the maximum load of 8kW will only be applied if the tenant is using all 4 burners and the oven. Normally it will be much less. Plus, all the elements cycle.

At each floor distribution panel it is doubtful that even half the ranges will be in use at the same time and those that are in use will have loads varying from around 1kW (one burner) to 3kW (broiler) to 8kW (everything on). Diversification tells us that this panel will only see the loads allowed in Column C.

Or at least that is the way I interpret it.:D
 
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