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 mysterd429 09-25-2012 06:50 PM

Calculating load on a circuit based on appliance labels

Hi all,

I've been reading the forum for a little while and just registered. My wife and I recently bought our first home, built in 1937, which we believe is a kit house. We just had our basement refinished--it was previously and poorly finished--and I've got two electrical questions. (I made a different post for the other.)

All of the outlets in the basement are on one 15-amp circuit. There are about eight of them. We have a TV, a dehumidifier in the summer, a microfridge, and some electronics. The amperages listed on the appliances total only to a few amps. Are those the peak currents listed, or are they some kind of average? I can't quite get Google to give me what I'm looking for.

Thanks!

 Daniel Holzman 09-25-2012 09:00 PM

Electric motors often have high start up current, so the current listing on the nameplate for an electric motor typically gives a variety of currents, including startup, locked rotor, and sometimes no load amperage. Most appliances do not have large electric motors, so the current listed is usually the full load current. I am a little surprised that your total amperage is only a few amps, usually a dehumidifier draws a fair amount of current, of course you may have a small capacity unit.

 Stubbie 09-25-2012 10:17 PM

Quote:
 Originally Posted by mysterd429 (Post 1017307) Hi all, I've been reading the forum for a little while and just registered. My wife and I recently bought our first home, built in 1937, which we believe is a kit house. We just had our basement refinished--it was previously and poorly finished--and I've got two electrical questions. (I made a different post for the other.) All of the outlets in the basement are on one 15-amp circuit. There are about eight of them. We have a TV, a dehumidifier in the summer, a microfridge, and some electronics. The amperages listed on the appliances total only to a few amps. Are those the peak currents listed, or are they some kind of average? I can't quite get Google to give me what I'm looking for. Thanks!
Your question would appear to be concerned about having to many devices operating on one 15 amp branch circuit. You would want to total the appliance nameplate amperages then determine how many would be operating at the same time to see if the total exceeded 15 amps. The micro fridge will cycle so take that into account. If your breaker is tripping then the most likely cause is too many appliances operating at the same time or some other combination that is overloading the 15 amp branch circuit. It is quite common to have general purpose receptacle branch circuits on 15 amp circuit breakers. The nameplate wattage or amperage is the operating amperage under normal loads or it would be fair to call it peak amperages.

 SeniorSitizen 09-26-2012 12:11 AM

There is an electric measuring gadget on the market called Kill A Watt that I've found useful. Each appliance could be measured and totaled for a maximum current draw. It just wouldn't record start up amps / watts.

 mysterd429 09-26-2012 11:48 AM

Thanks for your replies. Yes, the concern is overloading the circuit and tripping the breaker, which hasn't happened yet, though I was curious about the nameplace listing anyway. My biggest doubt was over fridge, which lists its current at 0.9 amps. When I said the appliances total to a few amps, I meant that the 'fridge and dehumidifier (5 amps) leave enough room for any of the other things we're likely to do at once.

Since the current draw on the nameplate is a maximum based on your replies, question answered! Thank you very much! :thumbsup:

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