Construction Heater Requirements

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Old 11-09-06, 03:14 PM
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Construction Heater Requirements

Ok, so I want to use a 4800 watt, 220v, 20 amp construction heater in my garage. It says that 30 amp breakers are required. I am assuming this is because you can't have over 80% of the breakers capacity in use? Does this mean that I have to use #10 wire for 30 amps? Or could this be considered a "fixed load" so that I could use #12 with 30 amp breakers (since the load would never exceed 20 amps)? Thanks in advance!

Scott
 
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Old 11-09-06, 03:21 PM
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According to the 80 percent rule, a 20 amp 240 volt circuit can only supply 3840 watts, so a 4800 watt heater is too large. Again, applying the 80 percent rule, a 30 amp breaker at 240 volts can supply 5760 watts, which is enough for a 4800 watt heater.

So you need a 30 amp circuit. The 80 percent rule applies to the wire as well as the breaker. You need 10 gage wire.

4800 watts is right at the cusp of a 20 amp breaker. Why would you want to take chances with 12 gage wire anyway?
 
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Old 11-09-06, 04:20 PM
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I thought that 80% only applies to the breaker, not the wire. It would just be easier to buy a big roll of #12 since I'm using alot of that already. If code allows a full 20 amps on #12 then it must be safe to do so... however, I agree, better safe than sorry is always to best way to go.

Thanks for all the replies Bob!
 
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