For a while I've used a couple of ceiling mounted 120V electric infrared heaters in the garage shop (two car garage). It's sort of OK with outside temps in the mid-30's and higher but still need to work with a couple of extra layers. I've now mounted a new 7500W 220V forced-air electric heater which draws about 35 amps on high. I added a 50amp breaker to my main panel - also in the garage - specifically for this unit with about a 12 foot run to a NEMA 6-50 outlet. From the breaker to the outlet I have 6 gauge copper THHN wire (two live and a green ground, all the same size) in 3/4" flex metal conduit. This runs to a wall-mounted metal box for the outlet. Why an outlet instead of hard-wiring the heater? I have four machines in the garage that use 220V (band saw, jointer-planer combo, table saw, and dust collector). I figure I won't be using this heater for about the half the year anyways and during those times I can use the outlet for one of the 220V machines. So, just for convenience since with this additional outlet I now have one outlet for each machine. The heater, of course, is intended to be hard-wired. Instead, I made an extension cord with 6/3 SEOOW cable, about 10 feet long, using a NEMA 6-50 plug on one end (it's my understanding that SEOOW has a higher temp rating that SOOW cable). The other end of the cable enters the heater with a 90deg compression fitting and is wired in. Works great. The 50amp breaker and gauge of the wiring is probably overkill, but admittedly the way I have installed it is not exactly what is described in the heater's instructions...
Couple questions...one is do I need to make sure the 6 gauge green ground wire is bonded to the square metal box with a screw, or is it electrically tied to the box by way of the outlet itself (it seems to be that way when I test it with a multimeter). Second question...is there a way to still utilize the extra outlet when needed and still have the heater hard-wired according to what is intended in the instructions? Is there a switch available where I could send the power to either the heater or the 50amp outlet, but not both?
BTW, 6 gauge copper wiring is not inexpensive!
Scott
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