have 10x16 temporary shed as 'man cave'; spray foam insulation walls & loft; partially wall boarded to 8' level. Only heated during 2-4 hour periods of occupational use. Power to shed via extension cord for 120V/15A circuit.

I've used small propane heater for warming in cooler months, yet realize this produces some undesirables such as increased H2O vapor & bad air components.

Supplemented by occasional small ceramic electric heater is not adequate and raises power bill considerably.

Considering an oil-filled finned electric heater .

What's a better choice? May need heating several hours per day, maybe 2 or 3 days per week thru cool/cold season.

I use an oil filled electric "radiator" in my foamed dog kennel room when it gets cold. 12' by 6' with 7' ceilings and the ceiling is foamed too. It is capable of running you out of that space so I obviously dial it back, usually only using it on the low setting with the stat about halfway.

The right way to do it is:

run a direct burial power line between main electric panel and shed, install a small panel in shed, and connect to a larger amperage breaker on the main panel.

Then, install a small minisplit in shed. 9000 btu mini-split kits are $700 to $850.

It's more money up front but it's safer (asphyxiation and fire), code compliant, more energy efficient, and will last much longer. You'll also have AC so could use it as a man cave year around.

quote:

Originally posted by signewt:
Considering an oil-filled finned electric heater .

Those portable oil-filled radiators put out a lot more heat than a ceramic space heater.

We used to have one at our old office, and it could sweat you out of a good-sized room (larger than 10x16).

whats the ambient outside as that really determines what works.

Electric heater on an extension cord, hell no!

Unless you buy an oversized SJ cord (10 ga etc) depending on length requirements. But then you still have the restrictions of where that plugs into, unless you have it wired to an appropriate outlet or panel.

quote:

extension cord, hell no!

this is a heavy gauge round 10~12 gauge 3 wire outdoor power cord like painters/contractors/carpenters job site use. Local electrician felt it was adequate for the purpose. A/C is not ever involved.

ignore that extension cord crap. Per my post above how much heat rise is necessary.

Why is that TV ad about the lady's "she shed" going up in flames coming to mind? Whatever you do, do it safely! (Yes, I know it was lightning.)

flashguy

The biggest problem I see is your 120v x 15a circut is 1,800 watts. That's the high setting on most portable electric heaters, including the rolling hot oil ones. And that's before the additional draw of the extention cord comes into play. An additional issue is the liquid filled heaters heat by convection, and they're slow to heat when starting from a cold start. They do an excellent job once they are on and up to temp, but in cooler weather it could take several hours to bring the space up to temp.

I've had good success with similar spaces using propane heaters that run off of the one pound bottles. The blast type heating is much quicker than waiting for a liquid filled unit to come up to temp, and some of the propane units have circulation fans so the heat circulate that much quicker.

How about a little wood stove made from an old propane tank?

quote:

how much heat rise is necessary

looking for rise inside the 10x16 from upper 40s to upper 50s.

I've long used a 2# propane jug during cold spells. My old cave was originally built into the hill side as a 1930s era root cellar. A few upgrades along the way, and it became easily 20* warmer in winter & 20* cooler in summer. Now a pump house/still room for garden canning. Primitive concrete floor & shoulder walls adequate for some uses, inadequate for others.

I can always put more thermal shorts on in the new cave, and continue to use periodic propane.
Supplement with oil fins when right temp range is attained might well serve the purpose.

quote:

a little wood stove

not in this setting; space use is tight & at a premium. We heat the house with wood so I'm familiar with the possibilities.

quote:

Originally posted by hrcjon:
ignore that extension cord crap.

Sure, ignore it. That's why so many houses burn to the ground.

But, go ahead, ignore it.

thanks for the tips; gotta a lotta work ahead of me.

quote:

That's why so many houses burn to the ground.

they don't burn to the ground from someone using a properly sized (he says 10g, outdoor rated cord), properly circuit protected at a load it can support on a temporary basis. Ok I'll agree there are some unknowns like the distance involved, the connections, etc, but on the surface it doesn't seem a code issue. And if the "local electrician" felt it was adequate I'm guessing its not connected in a risky way if that really meant he understood what the OP was doing.

Use one if these vent free heaters in mine all the time with a box fan. It will heat my 20x20 from cold to take your coat off in about 20 min. They are supposed to not light and shut off if there is a problem with carbon monoxide. I still have a monitor in the shed. I use a 100 pound cylinder that i refill at tractor supply. Wall propane heater

quote:

Originally posted by Excam_Man:

quote:

Originally posted by hrcjon:
ignore that extension cord crap.

Sure, ignore it. That's why so many houses burn to the ground.

But, go ahead, ignore it.

This aint a house, it's Signewts He-shed......

Personally I would use a propane heater like a 3 panel ventless wall mount unit. Mount a carbon monoxide alarm if you want.