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I am planning on installing a Garage ceiling heater, which has a fan, and 240 volt coil electric heater. This unit is 26 amps, and 6000 watts, and will be installed in my garage, 60 feet from my main panel. Can you tell me what size wire, and breaker I need to feed this heater?

  • Are you sure it's 26 amps? What does the installation instructions say? I ask because 6000 watts is right on the cusp... Also do you need any other electrical service in that garage? – Harper Jan 15 '18 at 21:07
  • The literature with heater says it is 26 amps.. I do not need any other electrical service in this garage – Richie M Jan 15 '18 at 21:14
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    Does the installation instructions say anything about what wire size to use? As things are now, it looks like you'll need 8 AWG because you are 1 amp over the limits for 10 AWG. However the instructions could override that (under UL's watchful eye, as the instructions are approved as part of the UL approval for the machine). – Harper Jan 15 '18 at 21:34
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    I'm just surprised a builder would make a machine 25A when they could make it 24A and allow you to use smaller wire... Unless they had gone to UL and gotten UL to grant them a variance?... Hence my interest in the instructions. – Harper Jan 15 '18 at 21:49
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    @fixer1234 depends how it's insulated. 6kw of heat isn't that much. It's a lot of power, but it's not a lot of heat. – Harper Jan 16 '18 at 0:12
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For a 26A nameplate load, Code will require #8 wire and a 40A circuit breaker. There really isn't any legal way around it.

Not what you asked, but by code you also must have 8 ft. from the bottom of the heater to the garage floor, because you have to avoid igniting any potential gas leaks from your car (remember, technically a "garage" is for a car, although few of use use them for that). If your garage has an 8 ft. ceiling, that isn't going to fit.

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Google finds plenty of links. For example: https://www.thespruce.com/matching-wire-size-to-circuit-amperage-1152865

AWG 10 would seem to do. Once you pick the gauge, you must use the appropriate breaker for the wire. There might be, in your code some extra you must factor in. @harper points out, this is NEC 424.3b and adds 25%. This increases it to 8 AWG.

You can calculate the voltage drop at sites like http://www.calculator.net/voltage-drop-calculator.html

If I got your situation correct, that would only be a 3-volt drop. Looks acceptable.

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    Except this is a continuous load. NEC 424.3b. See, this is a classic example of what happens when people learn electrical by asking questions on Google... How would you even know to ask the "continuous load" question? You wouldn't. – Harper Jan 15 '18 at 21:41
  • @Harper you are totally right on the perils of learning by asking on the internet. Personnaly, I know stuff from the theoretical side and had no idea about code. Thanks for sorting that out. Also, I can only guess what the reasons would be for someone to want this kind of heating power in a garage while not wanting to ask a professional. There's probably a reson. Anyway, with the edit, the OP should be able to make something not TOO dangerous. – Jeffrey Jan 15 '18 at 22:58
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    Jeffrey code is the minimum requirement so that is the not Too dangerous level we go to. If the mtg states that the heater can be installed with #10 that would be legal and not TOO dangerous, however if no instructions are provided on the branch circuit size 125% of continuous loads is a requirement, fixed heating as defined by code are a continuous load. – Ed Beal Jan 16 '18 at 9:42

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