I have been thinking hard about a heat source for next year. I have a 110 outlet in my greenhouse that icomes from the garage 50 feet away. I have a 14 gauge under ground wire hooked to a single plug between both greenhouses & I use the electric only ocasionally!
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A 10 gallon trailer type hot water tank with a small pump and thermostat connected to it will solve all my problems even for a sweat box! Just heating the water at night in one of my 50 gallon tanks to 70 and putting it inside a insulated sweat chamber will give me all the heat I need and moisture at a very low cost! I could even use a baseboard heater in ther sweat chamber that circulated from the water in the 50 gallon drum! It would be easy to conect and would not be dangerous using plastic pipe! The heat excaping from the sweat chamber would add a little heat to the greenhouse.
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I would also make another mini inside green house around the sweat chamber to put the new seedlings during the feb cold weather then expand later! The cole crops would not need to be in the mini greenhouse! What do you think of my plan?.?
I like your plan! Here I am talking to myself again! I did look into the hot water tank and am making plan now to get it set up over the summer Using plastic pipe will make the tank much more safe! I can also set the hot water tank to move hot water into several 50 gallon barrels to keep a small section of a inside smaller greenhouse warm so that the early plants will be at 40 or above at night cheaply! Thanks DD for the sweat chamber idea which will work great with the small hot water tank!. I can have the top of one barrel open to give more moisture to the sweat chamber!