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Old 11-02-2012, 07:57 PM   #1
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Installing a Garage Heater


Hi,

I would like to install a Dimplex 4000W 240V garage heater.

In order to do so, I need to install a dedicated 20A circuit.

My problem is that I am not sure how to size the breaker, my electrical inspector says the 20A breaker I was planning to install is not the right size for the receptacle and to go with a bigger 30A breaker and #10 wire. My concern is that the receptacle then becomes a hazard as the breaker will trip above the limit of the receptacle. There are no 30A receptacles that match the plug configuration of the heater, and even if there were I would be in the same situation with the safe limit of the breaker.

My question then would be, is the NEMA 6-20R receptacle safe to use on #10 wire and a 30A breaker?

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Last edited by harryreid_iii; 11-02-2012 at 08:10 PM.
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Old 11-02-2012, 08:05 PM   #2
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Installing a Garage Heater


a 6-20r receptacle is a 20 amp receptacle, and that is what it should be protected at,
Your inspector is wrong. dDd he say why?

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Old 11-02-2012, 08:18 PM   #3
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Installing a Garage Heater


Show the inspector the installation instructions. The mfg. specs are what you wire the circuit to, not the inspectors opinion.
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Last edited by Missouri Bound; 11-03-2012 at 11:02 AM.
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Old 11-02-2012, 10:19 PM   #4
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Installing a Garage Heater


A circuit is only good for 80% continuous load. Your 4000w heater is .8333 amps over that calculation. That is why. A 25A circuit is needed at minimum for the heater. Inspector is being stickey.
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Old 11-03-2012, 08:57 PM   #5
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Installing a Garage Heater


Quote:
Originally Posted by Marc05 View Post
A circuit is only good for 80% continuous load. Your 4000w heater is .8333 amps over that calculation. That is why. A 25A circuit is needed at minimum for the heater. Inspector is being stickey.
To elaborate slightly, 424.3(B) defines fixed space heating equipment as a continuous load, so all branch circuit ratings must be calculated based on 125% of the actual load. However, the same heater would not be considered a continuous load if it were not "fixed". So if it's connected by cord and plug and not attached to the structure, then a 20A circuit and #12 wire would be fine. But if you attach it to the structure or hard-wire it, then it needs a 30A circuit and #10 wire.
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Old 11-04-2012, 07:44 AM   #6
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Installing a Garage Heater


Of course you install the kind of receptacle (wall plug) that matches the factory supplied plug (cord cap) of the appliance.

In turn the breaker rating may not exceed the receptacle rating.

In this instance the 20 amp circuit and receptacle fits the above discussion excluding that referring to the inspector.

In some cases the receptacle accepts more than one plug style; the most common instance of this is a 15/20 amp receptacle intended for a 20 amp circuit.

Quote:
My question then would be, is the NEMA 6-20R receptacle safe to use on #10 wire and a 30A breaker?
No.

But it is safe to use 30 amp circuit components (including 10 gauge wiring) but still use a 20 amp breaker if the actual load never exceeds 20 amps. Except you must still use a 20 amp receptacle here (necessitating the 20 amp breaker) because the plug won't fit a 30 amp breaker.
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Last edited by AllanJ; 11-04-2012 at 07:59 AM.
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Old 11-04-2012, 08:08 AM   #7
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Installing a Garage Heater


What is the model number of this garage heater?

I found this... http://www.heatersplus.com/dgwh4031.html

Here's the slight issue, I think the manufacturer should have installed a 30A cord end, but to make it easier for the end-user, they installed a 20A and got it listed. Being that this is the way the manufacturer listed the product, you must follow their specs. Now, the AHJ has final say. If he is saying you need a larger circuit, then you will probably need to install a larger circuit with the proper cord/receptacle. Or you could hard wire it.

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