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San Jose [email protected]

Some basic electrical calculations.

watts X volts = amps 1500 watts X 120V = 18 amps this is a full circuit, and even an overload.

you are only supposed to use 80% of your breaker capacity, so 16 amps is the max you should use for a 20amp breaker, and 12 amps for a 15 amp breaker.

12/1/2008 9:24:03 PM

Winston Salem NC

Not trying to be mean or anything but that formula isnt correct. At 18 amps a bathroom heater would kick any breaker for receptacles in most houses. Most are wired with 14 awg wire on a 15 amp breaker for wall outlets. With 12 awg wire you would use 20a receptacles which have one vertical prong one horizontal prong and a ground and give you a 20 amp breaker. Also the heater would have to have 12 awg cords when most are 14-16 awg. Here is a correct formula, although none are exactly correct because
watts and amps are not the same. Its like converting gallons to miles. I majored in electronics and work with stuff in my job is the only reason I know this.
The conversion of Watts to Amps is governed by the equation Amps = Watts/Volts

For example 12 watts/12 volts = 1 amp
1500w/120v=12.5a

12/1/2008 10:11:41 PM

Ohio

The calulation I've used is that for every 100watts you will pull or need .8 amps. Which is pretty close to Max's calculations. Still looking for some space heaters around 300 or 400 watts. If they are even out there. Don't really need anything stronger than that. When you are running 4 of them anything stronger begings to flip the breakers.

Thanks for the input guys.

12/1/2008 10:53:20 PM

Eugene, OR

Max is right in that amps times volts equals watts but the equation itself is not like converting gallons to miles. The units do indeed cancel out like they should, making the equation valid.

As for wire sizing, just refer to the NEC ampacities table. Even 14AWG copper wire is capable of handling 20 amps but they specify that overcurrent protection must not exceed 20A for 12AWG wire and 15A for 14AWG. When in doubt, the National Electric Code has the answer.

12/2/2008 12:07:01 AM

Oz

Remember that motors draw more amps at start up.
Heaters,lights,etc,do not have a large start up current.

12/2/2008 10:45:40 AM

Ohio

Still looking for some space heaters around 300 or 400 watts.

If anybody knows of such a thing drop a line. Thanks a bunch.

12/2/2008 4:56:28 PM

Utah

http://www1.shopping.com/xPF-Soleus-MS-12-Reflective-Heater

http://www1.shopping.com/xPF-Soleus-Air-MS-11-Two-Setting-Oscillating-Reflective-Heater

http://www.campingworld.com/shopping/item/oscillating-reflective-heater/33496

http://www.walmart.com/catalog/product.do?product_id=10554692
has a adjustable heat setting.

http://www.walmart.com/catalog/catalog.gsp?cat=133026&adid=1500000000000006955330

12/2/2008 7:35:35 PM

Winston Salem NC

I replied to your original post with some.
Rick

12/2/2008 9:43:50 PM