load calculations

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sleepy

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i am calculating load for a sheet metal shop, they are moving from one place to another, we have utility bills showing that there highest usage for one month was 125amp, they will be adding 150 amps of equipment. this is a shop that has a few people , and a lot of equipment. we have a connected load of 766amp old and new. we used the information that they gave us, and came up with a demand load of 256 amps so we are going with a 400 amp service.
the inspector who review this sayes that we have to follow the nec. i followed the example d3(a) in annex d and by following this i will need 800amp service, is that correct?
any help out there thanks
 
Article 220

Article 220

sleepy said:
i am calculating load for a sheet metal shop, they are moving from one place to another, we have utility bills showing that there highest usage for one month was 125amp, they will be adding 150 amps of equipment. this is a shop that has a few people , and a lot of equipment. we have a connected load of 766amp old and new. we used the information that they gave us, and came up with a demand load of 256 amps so we are going with a 400 amp service.
the inspector who review this sayes that we have to follow the nec. i followed the example d3(a) in annex d and by following this i will need 800amp service, is that correct?
any help out there thanks
Click to expand...

The utility bill (unless they have a special meter) seems useless, but calculating the load with Know values is no problem. First thing is sq.ft. of the shop and lighting, then all the general purpose outlets all in ART. 220, if they are not likely to use two pieces of equipment at the same time you don't need to add both together in the calculations. We wired a 4,000 sq. ft. shop that 200 amps was more then enough because there was never a time when more then 2 pieces of equipment were used at one time.

220.60 Noncoincident Loads.
Where it is unlikely that two or more noncoincident loads will be in use simultaneously, it shall be permissible to use only the largest load(s) that will be used at one time for calculating the total load of a feeder or service.
 
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Without seeing all your numbers, it's not easy to make this type of call. How does the utility bill tell you that the max amp draw was 125?
 
load calcu's

load calcu's

the utility gives you the max demand kw usage for that month
that divided by voltage gives amps
 
load calc's

load calc's

i thank you for the responses,
it seems that i have followed what you people have suggested
i followed the lighting calc's as you mentioned
the receptacles also
the equipment we have 282kw of connected power
i thought i followed i put down 70.4 kw load as you stated
the inspector sayes not right
any suggestions
thanks
 
sleepy said:
i thank you for the responses,
it seems that i have followed what you people have suggested
i followed the lighting calc's as you mentioned
the receptacles also
the equipment we have 282kw of connected power
i thought i followed i put down 70.4 kw load as you stated
the inspector sayes not right
any suggestions
thanks
Click to expand...

Yes read section 220.60 it may change every thing in the calculation.
It is very likely that a much smaller demand exists compared to "connected load" if you have 10 machines and 1 guy using 1 machine at a time, you would only need to add for the largest load "being used at one time"
 
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