workshop heating

While that is true of course, you can get more heat out than electrical power in by using a reversible air conditioning unit. They draw heat out of the cooler outside air into the building so do not break the laws of physics.

Russell.

I envy those of you who live in an area with 'sane' temperatures! Here on the Canadian prairies winter temperatures often get down to the range of -30C for prolonged periods and heating a shop is neither cheap nor easy.

My shop is detached and about 28 x 20 feet. The first thing I did when I bought my place (1997) was to insulate and sheet the walls (2x4 construction). The original owner had relocated the oil furnace from the house to the workshop when the house was converted to wood/electric and the much-oversized furnace was great! Within 15 minutes of flipping on the switch, the furnace would be blowing HOT air and the shop would be shirt-sleeve warm within 30 minutes.

Unfortunately the price of heating oil had increased significantly and the cost of filling the tank had risen above $1,000. Even though a tank of oil would last more than a year, $1,000 is a HEAVY touch for a pensioner and the insurance costs and regulatory B.S. for having a 200 gallon oil tank was becoming a problem so last year I had only a 4 KW electric heater. Over the course of 4 month last spring, the electric heater also cost quite a few hundred dollars.

Last summer I removed and scrapped the oil furnace and installed a small air-tight wood stove. Removing the furnace freed up a lot of floor space (about 8 x 12 feet!) but I miss the speed and convenience of the oil furnace and being able to flip a switch and have lots of heat minutes later.

Now I try to turn the electric heat on a couple of hours before going to the shop to take the chill off. I light a fire when I first get to the shop but even with an old ceiling fan to circulate the warmth, it still takes an hour or two before the shop is comfortably warm.

If money was no object, I would have stayed with oil heat for the speed and convenience. Since money is a consideration, a wood stove with electric "pre-warm" is more economical.

Most people in this part of the world have their model workshop in the basement and for good reason!

I've family in France (I guess one day, my farther in law) he has his own ground source heat pump. If your're looking to save money on electric heating, its the only way I think.

Air Source are ok, but air temperature varies of course and they stop working at a certain low temperature

Now if a forum full of model engineers can't build a mini GSHP - who can?

The problem with heat pumps is the capital investment wrt service life. The running savings have to be put aside to pay for the replacement in maybe only 10 years.

However a angle I am considering is this. When I lay the concrete over insulation for my new shed I may put pipes under the insulation (in the sand blinding) to pick up ground heat at say 8C. If I leave the shed which will have 6 in of celotex insulation for a long period I may be able to connect the pipes to a radiator to keep the space above freezing.

I have a 7 metre deep borehole for watering the garden. The water comes out at 15 C summer and winter so perhaps I should make a water bath for the heat exchanger coils on my reversible aircon. Need to balance the pump running costs against the efficiency gain.

Russell.