Load Calculations, commercial buildings

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jimegg

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How do you define what is a continuous load in a commercial building? Are welders with a 5% duty service considered continuous or other loads? How about circulating water pumps? these were on Washington State load calculations exam that I just took and failed.
 

charlie b

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Lockport, IL
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Retired Electrical Engineer
Re: Load Calculations, commercial buildings

A ?continuous load? in one that runs for 3 hours, regardless of the type of facility.

A welder is not treated as a continuous load. It has its own set of demand factors in Article 630, and they are based on the type of machine and its duty cycle. You do not add a 25% factor for the possibility that a person might work a continuous 4 hour shift with the welder. The fact that a welder cycles on and off for that entire shift is part of what makes up the related demand factors.

Similarly, a motor is treated in accordance with Article 430. This separate set of rules will sometimes add a 25% factor to a motor?s calculated KVA. However, that 25% factor is assigned to the single largest motor, and not because any given motor might be running for more than 3 hours.

Short answer: neither of these loads is treated as a ?continuous load,? in the sense that you do not add 25% for the ones that run more than 3 hours.

p.s. Sorry to hear about your test results. I also failed the first time, but I passed the second time.
 
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