breaker loading

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jociha

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I have a 480v 3p breaker size 125a. The customer wants to add to it. Must i always stay below 80% load or is that only on continous loads. My new load will be 90a continous load and 16a non continous load is this legal. john
 
Take a look at 215.3.

By my calculations the load exceeds the breaker rating.

The total calculated load would be 128.5 amps.

(125% of the 90 amps continuous plus 16 amps non-continuous= 128.5)

Chris
 
I would say no. 125% of 90 is 112.5. Add 16 and you get 128.5. That exceeds 125. Not allowed, per 210.19(A)(1).
 
For the record, I typed my reply before Chris posted his. But I had to pause to look up the code article. :roll: :grin:

By the way, I took the question to be refering to a branch circuit, not a feeder.
 
If the continous load were 85a would it be legal. it is hard to determine continous load. one example is a a/c unit, the fan is continous but the compressor or humidifier is not. john
 
jociha said:
one example is a a/c unit, the fan is continous but the compressor or humidifier is not.
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If you could show that that were true, you could take advantage of the situation, to get the calculated load below the 125 amp target. But I would not even call the fan a continuous load. Does it run for more than 3 hours without stopping, even on a hot summer day? I tend to doubt it.
 
charlie b said:
For the record, I typed my reply before Chris posted his. But I had to pause to look up the code article. :roll: :grin:

By the way, I took the question to be refering to a branch circuit, not a feeder.
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Thats OK, I had to pause to get my code section as well, but had a brain cramp and posted the reference for a feeder and not a branch circuit.:D

Luckily both feeder and branch circuit overcurrent devices are sized the same way.

Chris
 
raider1 said:
. . . but had a brain cramp and posted the reference for a feeder and not a branch circuit.
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You might be right. The original question did not say one way or the other. But beween us, we have the issue covered. :grin:
 
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