Jim,

Are roof cables anything like the cables you wrap pipes in to keep the pipes from freezing? If so, then they are not adequate for things like warming citrus, which needs soil temps of at least 55*F.

I suppose it might help in a situation like a cold frame.

Hopefully other will chime in here.

Robert

Can't tell you if the roof cable would be suitable, but I've looked at both and found that the cables sold for greenhouses are cheaper for longer lengths and higher wattages than roof cables.

If you already have roof cables that wish to use, I'd check with the manufacturer to see if its safe.

Thanks for the info. I priced the roof cables and you were right, they would make for expensive trial and error. Although in zone 5 I think I could always put them to good use. My hope was to help my bonsai trees survive in an unheated greenhouse and try to minimize the day/night temperature swings.

Jim:
Those roof cables will work to heat the soil but will not work to heat the air in a greenhouse. I am in Ontario also and it will take alot of heat to heat and greenhouse at night it will all depend on the size you have to heat. And for the Temp. swings you will have to exhaust in the winter on a sunny day or it will get to hot in there.

If any questions feel free to ask

Carl

Heat cables are meant ot be buried in the soil to heat the soil, they have never been meant to heat the ambient air.

Mountain-curmudgeon:

Where do you find the greenhouse heating cables you've mentioned? Anywhere online?

Hello all

My hope was never to heat the gh with the soil cables. I wanted to keep the root system from freezing and let the rest of the tree survive for itself with the protection of the gh. The roof cables can be bought at any hardware store, but they have an automatic temp. setting of 71F. I want to be able to set the temp. to just above freezing so the trees will have a complete dormancy. I took another look at them the other day, and the package said that they are not to be burried.

I have also had a thought (that didn't die of loneliness, but maybe should have) of using a waterbed heater so I could set the temp just above freezing. I know that this could be dangerous, but if one could come up with some type of bladder with water in it, it should mimic the proper use of this type of heater. What do you think?

Thanks
Jim

Thanks for clarifying that. I think in theory it's a good idea. One that I would try, BUT only if I am around said heater for a few hours, until I got comfortable with it. I once set a table in my garage on fire using a waterbed heater, so I am still a bit leery.

Jim,

Look into a submersible aquarium heater, a small table fountain type submersible pump, a rubbermaid type tote box as a reservoir and a length of flexible pipe.

I don't know if an aquarium heater can be set low enough for your needs but there are thermostatically controled stock tank heaters that will maintain water at 40f or so.

Hey Weebus

How did you set up the waterbed heater? Did you just place it on the table and put your plants on it? If so, the heater would run constantly which may have caused your problem in the garage.

We have had high winds here lately and the cover on my inground pool keeps blowing off at one spot. I will need to put on some more water bags...WATER BAGS...could it be that simple?

What if I made a box of syrofoam to insulate, put a piece of plywood on the bottom for support, place in the heater and put a couple of water bags on it. This should in fact be making a 18" x 8' waterbed. The waterbags would absorb the heat to keep the heater from getting too hot and allow the thermostat to work so I could set it at any temp I wanted. If I covered this whole thing with with plastic and then put some sand on top, would this make for a safe (most of all) and cheap solution? As you recommend, I would babysit it for a while before leaving it on all night.

What do you think?