Heating a small solar greenhouse ideas!

[Bobberman]

I am planning on keeping my solar my 12 by 16 greenhouse between 35 and 40 at night all winter! There is no problems doing the day bt after about 9 pm the temp drops quick! I considered a small tankless 2.5 gallon hot water ank but aftering seing some things at tractor supply today I may have found something better! I don't need alot of heat since I have the bottom 2 foot perimeter insulated with 2 inch styrofoam and blue board all the way around! I have 250 gallon of water in 50 gallon drums plus some small containers! After dec is when the cold gets bad especially when it cloudy and cold for a week!
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Tractor supply has a plug for $12 that turns on when the tem goes down and reaches 35 degrees. The plug is made to keep water for animals from freezing by turning on just about anything on a 110 circuit! I can put the plug in a location so it will go on and off as the temp climbs only 5 degrees!They also have 110 volt products that will heat water for the animals that could keep one of my 50 gallon drums at a nice 75 degrees while I have a fan blowing on the drum! keeping the top of the drum slightly open will give me the moisture I want! I may keep the drum nder my weat chamber for a two purpose use! This is exciting for me to see how it works!--- Any other suggestions that will generate a small amount of heat using electric?
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I will also have a fan that kicks on and blows air againt the water barrels when the day temp reaches 50 deg or above! to raise the temp in the barrels quicker!

[Dillbert]

Bobberman -

do pay attention to volts/amps ie wattage as you get into this stuff.

the "plug in thermostats" ie "line thermostats" have a maximum amperage/wattage in their design. if overloaded, they fail - sometimes in flames.

there are reasonably inexpensive thermostats adjustable by knob or screwdriver - much more flexible than the plug in at one temp thing. typically they can be use to "switch on" when the temperature rises or switch on when the temp falls - "double throw" is one term used for the switch description - but be aware - they signal "constantly" rise or on fall - it is telling your system either "heat" or "cool" at all times - there is no "deadband": ie no "now heat - for temp x-y do nothing - now cool" type setting. such thermostats are available but they tend to be a bit pricey.

heat from electricity: first - there is no free lunch.
one thousand watts (1 kilowatt = one kW) converted with no losses to heat will get you 3,413 BTU

whats a thousand watts? watts = voltage times amps (that's 'pure' for direct current, there's a fudge factor for alternating current - which your local utility provides) - but unless you're dealing in megawatts, you can ignore that bit of inaccuracy.

so.... 110 volts times 10 amps = 1100 watts = 1.1 kW
if you look in your breaker/fuse box you'll see in modern houses 15 amp circuits with a couple 20 amp circuits for the kitchen / dedicated appliances. 'older' electrical installs vary big time.

so just be sure the cords, wires, switches, thermostats, etc are rated for the wattage you hang on the end. 'overloads' generally produce un-pretty to disastrous results.

[Bobberman]

Thanks for the info!! I will watch!

[iwilde]

http://www.reuk.co.uk/Solar-Greenhouse-Heat-Sink.htm