I would like to add a garage heater (Cadet "The Hot One" – 5000/3333watts – two settings)
I currently do not have any 240v access in my garage.
My main panel is in my basement and my garage is attached so if I measure from my main panel to the interior wall of my garage where the electric would feed from the main panel the run is about 22 feet – The electric heater would be mounted about 20" from the garage ceiling so the receptacle could be above or below so that would put that full run at about 25 feet.
I have a 200 amp service and currently have 9 slots available in my panel.
My understanding is the cadet heater needs a 30amp breaker, NEMA 6-30R outlet and I think I can run it with 10/2 cable.
I would run the line up through the garage wall plate and have the cable behind the drywall and run it into a metal box for the NEMA 6-30R outlet.
I am unclear if the 10/2 is sufficient, I believe it is, and then about grounding the box receptacle box.
Best Answer
These heaters need what the UL-approved instructions say they need. However this heater is rated for a 20.8A draw.
For heaters, we must provision 125% of that, or 26 amps. That is too much for a 20A circuit, and appropriate for 30A.
10/2 will get the job done for this one task. But it'll do more for your resale if you use 10/3, because that will allow you to fit a dryer or subpanel here in the future. (a subpanel is an easy solution to the old saw + dust collector problem and many other problems you get as you develop your wood or machine shop). You can go ahead and use a NEMA 6-30 receptacle, and just cap off the neutral.
Speaking of over-wiring, there is certainly no harm in using 8/3 or even 6/3 cable, which would allow larger heaters or full development of that subpanel. The ultimate "future expansion" option is to fit 3/4" conduit instead of cable, and simply throw the wires into the pipe that suit your needs at the moment.