NEC Continuous and Non-Continuous and System Size

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kerrys914

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Is the below correct?

320amp (400amp max) Meter Center Application

Lets say I have 350amps load on my 400amp MDP.
200amp continuous loads
150amp non-continuous loads

Will the 320amp meter center/socket be a correct application? My understanding as long as the continuous load is 320 or less and the combined loads (non + continuous) is 400amps or less, the 320amp meter will be fine.

Cheers
 
The check is 125% * continuous plus 100% * non-continuous <= 400A.

So 200*125% + 150 = 400, maxed out but OK.

Change your example to 250A continuous and 100A non-continuous, and it's no longer OK.

Cheers, Wayne
 
Thanks.. I also assume the 320amp meter center is okay since the 200amp*1.25% = 250amp (continuous load only) which is less then the 320amp meter socket rating for continuous load.
 
kerrys914 said:
My understanding as long as the continuous load is 320 or less and the combined loads (non + continuous) is 400amps or less, the 320amp meter will be fine
Click to expand...
That is correct*. See post 6.
 
Last edited:
infinity said:
That is correct.
Click to expand...
I don't think so as stated. Per my example, if you have 250A continuous and 100A non-continuous, that satisfies both "continuous <= 320A" and "total <= 400A", but the required minimum rating is 125% * 250A + 100% * 100A = 413A, which exceeds the 400A rating.

Unless meter ratings behave differently from breaker ratings?

Cheers, Wayne
 
wwhitney said:
I don't think so as stated. Per my example, if you have 250A continuous and 100A non-continuous, that satisfies both "continuous <= 320A" and "total <= 400A", but the required minimum rating is 125% * 250A + 100% * 100A = 413A, which exceeds the 400A rating.

Unless meter ratings behave differently from breaker ratings?

Cheers, Wayne
Click to expand...
Yes I left out the part where the continuous loads would have to be valued at 125%. My response should have been yes when it's continuous*125%+ the non-continuous.

So 320 amps continuous+ 0 non-continuous would be the maximum load permitted. For every amp the you reduced that 320 figure you could add 1 amp non-continuous.
 
infinity said:
So 320 amps continuous+ 0 non-continuous would be the maximum load permitted. For every amp the you reduced that 320 figure you could add 1 amp non-continuous.
Click to expand...
For every amp you reduce the continuous figure below 320A, you can increase the non-continuous figure by 1.25A.

Cheers, Wayne
 
HA!!
Just to clarify as it got confusing

Keeping the numbers the same below (I should have used 90amps non-continuous to make this sample under 400amps):

200amp continuous load "connected" is 200amp*125%=250amp "calculated load"
250amp is <320amp meter base rating for continuous load....All good here

Add in non-continuous load of 100amps

250amp + 100amp = 400amp max system load.

A 320amp meter center feeding a 400amp MDP meets NEC.
 
kerrys914 said:
200amp continuous load "connected" is 200amp*125%=250amp "calculated load"
250amp is <320amp meter base rating for continuous load....All good here
Click to expand...
No. Because you used a 125% factor on the continuous load, you compare the result to 400A, not 320A.

If your load is all continuous, then you instead compare the continuous load (no 125% factor) to 320A. Because 320A * 125% = 400A, so that comparison is the same as the comparison in the previous paragraph.

If you have both continuous and non-continuous loads, then the check is as specified in my first post.

Cheers, Wayne
 
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