17.100 btu out put heater

[Ericst38]

I have a very well insulated greenhouse 1/4 poly on the outside then a 3inch gap for framing and lined on the inside with 5/8 poly and sealed and 5 inches of gravel on the floor i have a 60amp sevice to run a 5,000 watt,17,100 btu out put heater ,for my 10 x12 greenhouse . I was woundering what some other greenhouse growers think and will this work fine. This will be my first winter outside so i want to get it right. I also have keroscene back up heaters if any power goes out....

[msaar]

Where do you live?
What minimum outdoor temp will you experience?
What do you mean by 5/8 and 1/4 poly?
Is the roof the same?
What minimum inside temp do want to maintain?

[Ericst38]

Yes i bought a greenhouse kit and it had 1/4 double walled polycarbonate and i live in nebraska where it gets to -10 so what i did was reframe the whole in side with 2x3's and put 3/8 double walled polycarbonate from a salvage yard on the inside and last year i had it up and it held up great even with 2 foot of snow on the ground . So it gets down to-10 to -15 and i want to keep it 63 to65 degrees.The greenhouse is 10x12 and the side walls 8ft and to the peek 11 1/2 high.

[Wjs2nd]

The only thing I could find was a btu calculator that said, depending on your structor, it will only take 10,770 btu to heat your building to 65F in -10F weather. So hopefully if all your weather sealing/insulation works for you, it sounds like you'll be okay. I would get some kind of system to monitor the temp in your greenhouse. They sell wireless weather systems. Good luck!

[Ericst38]

I have two wirless temp controls one for out side and one for inside.

[msaar]

Using a quick and dirty heat loss calc, 12K - 13K btu should be adequate. The biggest variable here will be air infiltration-how well joints are sealed, louvers, exhaust fans, etc.
BTW, if you live in Lincoln, it will cost you about $525/year to heat ($.08/KWH)

[Ray]

Using this Heater Size Calculator, 400 square feet of the equivalent of an 8mm multiwall PC covering, for a -10 minimum and 60° desired interior temp, your heater is JUST enough, so personally, I'd go bigger, to have something of a safety factor.

[msaar]

If Ray used only the value for 8mm polycarbonate, his number is overly conservative; unless I misunderstood you, you have 6mm + 2.5" air space + 8mm which cuts your heat loss through the walls and roof (but not total heat loss) by more than 1/2. The biggest variable, though, is air infiltration.