DIY: 10.7 KW space heater

I recently finished a project that I thought I'd share in case someone might like to copy it.

When I replaced my furnace, I kept the blower out of the old one, and made an adjustable base for it with a 4 speed switch. It makes a nice fan for the garage.

When we replaced the washer & dryer, I kept the heating element from the dryer. I wanted to rig up a container to hold the dryer element in front of the fan. But I wasn't sure one heating element would be enough, so I scrounged up a second heating element.

Here's some pics of the metal box I welded up to hold the two heating elements. Its upside down in the first pic. The top has holes drilled in the top for the heating element contacts. The bottom of the box is removable for access/replament of the elements.
(pay no attention to the plywood welding table on a cardboard box)



The tabs in the photo above are positioned to line up to the mointing points on the two heating elements:


The electrical connections on top required two square boxes to have enough room to work the 6 guage cord. There's one switch for each heating element, so they can be turned on separately (high/low). And also I needed two switches because standard wall switches are rated for 20 amps, and each element pulls about 22-22.5 amps. Pulling 44 amps through one switch is more than I'd care to do




It slides into the front of my blower fan nicely:


The air comes out noticeably warm, but not hot. The air moves fast enough that it doesn't feel very warm on bare hands, but if I stand in front of it for a few seconds my jeans are toasty. It heats up my 3 car garage fairly quickly. After an hour I'm sweating and need to turn it off. 10.7kw with our local $0.08/kwh means it costs almost $1 per hour to run.

Its also nice for painting projects. I can heat stuff up to paint in winter, and bake it dry.

EDIT: mods - I didn't see the garage/workshop forum. If this belongs there, please move

 

I wonder how long of a life the elements will have ??

Do you have a cool down to cool the elements off slowly once power is removed??

The thermal cycling is what kills them.

 

I just make a point to turn the fan on first, and off last, so the elements are not powered without moving air. By doing that, there is sometimes a very faint glow on the coils, but not much. I think the air is moving fast enough that they can't get very hot.

I usually see the coils on space heaters glow a lot more, so I think this pretty light on the thermal cycling.

If the coils get turned on without the fan, that would be an issue.