Finding wattage of various appliances

flyhopJune 30, 2013

Trying to determine wattage of various items as a survey of eletrical service to home. Need information please.

Clothes dryer label shows following:
120/240V 28A

VA = watts, so which Voltage to use in calculation of wattage?

I chased the "service" (is that what you call it) from the dryer to the breaker box. It's on a 30A double pole breaker. Help me understand what I'm seeing. Is this 120V for each half of the double pole breaker at 30A each? Totalling 240V at 30A at the dryer outlet?

If so, 240 * 30A = 7200 watts. That seem really high.

Not enough attention during physics class, I guess...or Ohm's Law has faded after 32 years.

Thanks in advance.

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llaatt22

When you start your car, do you look at the highest number painted on the speedometer dial to calculate your gas consumption?

    Bookmark   June 30, 2013 at 2:09PM
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flyhop

No, but I also don't know if it is running on 4 cylinders or 8. May I assume from your post that it's 120V * 28A = 3360 watts? That seems reasonable.

So, it's a double-pole 30A breaker that feeds it. That's 120V for one feed at 15A and another 120V for 2nd feed at 15A? This is still 240V at 15A for 3600 watts? Have I got that right?

3360/3600 is over 93%. Should I change this out to a 40A breaker?

Thanks.

    Bookmark   June 30, 2013 at 2:23PM
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btharmy

30 amps it the rating of your circuit breaker. A 2 pole breaker will indicate it is feeding a 240v load. It is not 15a per leg. It is 30a per leg. And no, they do not get added together to equal 60a. So, 240 x 28 = 6720w

I am curious to know where you are getting the 28a from? The name plate on the dryer is usually marked in watts and amps.

    Bookmark   June 30, 2013 at 4:24PM
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flyhop

Clothes dryer label shows following:
"120/240V 28A"

So what is the wattage consumption by this dryer on a 240V feed?

This post was edited by flyhop on Sun, Jun 30, 13 at 16:46

    Bookmark   June 30, 2013 at 4:44PM
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weedmeister

The 120/240v means that requires a neutral so that 120v can be supplied to that portion that uses 120v instead of 240v. Probably the motor and electronics.

    Bookmark   June 30, 2013 at 8:01PM
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flyhop

Thank you, all!

    Bookmark   June 30, 2013 at 8:28PM
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