electrical exam question

[Jhaney]

Took my Ky electrical exam and unfortunatly I was a few points shy of passing, I did well on motors, generators, transforms and such but for residential load calculation I had a few issues.
Anyway to my main question I had a residential load question that stumped me.
The question went like this: calculate the load for the following for residential, all hardwired, dishwasher, garbage disposal, microwave, and one other device but I can't remember what it is. Non of the devices had any form of power rating to go with them. I started figuring for 1500va per item and was way way off. None of my calcuations came close. How do you calculate a load for these items?

 

[wbalsam1]

How about Example D1(b) One-Family Dwelling in Annex D page 70-763 in the '08 NEC or page 70-717 in the '05. ?:smile:

 

[Jhaney]

in that example and other examples I'm not seeing a microwave or is the micorwave considered one cooking unit like in example D2(b) rated at 5100VA?

 

[wbalsam1]

in that example and other examples I'm not seeing a microwave or is the micorwave considered one cooking unit like in example D2(b) rated at 5100VA?

Yes, microwave would be 5.1kw. You found a better example. :smile:

 

[Jhaney]

Okay now on the test for all 4 appliances there was not one answer over 4600va and the microwave by itself surpasses that is there a derating that I'm not seeing? I'm confused I thought I had studied this section fairly well and now I'm as lost as a blind seeing eye dog.

 

[wbalsam1]

Either you're missing something (forgetting the exact details on the question in the test) or the test question may have been too ambiguous. Typically if the question contains 4 or more appliances then Article 220.53 comes into play and permits a 75% application.

 

[Jhaney]

Thanks for your help I believe 220.53 was exactly what I missed. I wish I could have wrote the question down but they frown on that sort of thing, and after 5 hours and 100 questions my brain was a little fuzzy. But I'm tracking down and studying my week areas for next year. Sadly the areas that really kicked my butt were control devices, mescellaneous, and special occupancies and uses.

 

[wbalsam1]

Thanks for your help I believe 220.53 was exactly what I missed. I wish I could have wrote the question down but they frown on that sort of thing, and after 5 hours and 100 questions my brain was a little fuzzy. But I'm tracking down and studying my week areas for next year. Sadly the areas that really kicked my butt were control devices, mescellaneous, and special occupancies and uses.

Good luck to you. Season's greetings.

 

[badjeepr]

It would appear spelling may be 1 of those areas that require special attention...