Help explaining 120/240 to a customer....

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c2500

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Ok,

I have a customer that is wanting under-tile mat heating installed. I have suggested the 240volt matts to reduce power consumption. He did some online research and says the power used will be the same whether it is 120 or 240 based off of some formula someone posted. (I have not seen it) Any thoughts on the best way to explain this? Or is there some great diagram out there that someone knows about? I have been unable to verbally explain it (He is a doctor). The wiring is not an issue as there are dedicated circucts available.

As always thanks,

c2500
 
I agree with Bob.

A 5000 watt heater at 240 volts is 21 amps a 5000 watt heater at 120 volts is 42 amps. The power consumption is the same, 5000 watts.

Chris
 
Another consideration to think about if you are under nec '08 -

120V system you'll need to supply an arc fault breaker
240V system you won't need to supply an arc fault breaker

edit- if you are installing it in an area that needs to be arc faulted...
 
alfiesauce said:
Another consideration to think about if you are under nec '08 -

120V system you'll need to supply an arc fault breaker
240V system you won't need to supply an arc fault breaker

edit- if you are installing it in an area that needs to be arc faulted...
Click to expand...

I'm not sure you would need to arc fault this type of application. It is a hard-wired installation and technically does not meet the definition of "outlet" per NEC definitions. Much the same as if you were to install a 120 volt baseboard heater (hard-wired), anyone think that BB would need arc fault protection?

I reread 210.12 after posting, I could be eating crow for Thanksgiving..................

As to the OP's question, your H.O. is correct, power consunption would be the same, regardless of the voltage. A watt is watt. FWIW, I always sell the 240 volt rated mats just because you can get more mat per circuit.
 
Last edited:
Jljohnson said:
It is a hard-wired installation and technically does not meet the definition of "outlet" per NEC definitions.
Click to expand...
Yes it does. An outlet is any point at which current is taken from the premises wiring system to supply utilization equipment, regardless of whether the current is taken via a plug & cord connection or a hard wired connection.
 
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