propane heat

I have bought my first 6x8 Gardener's Greenhouse. I don't know the poly thickness. I live in central east Texas. Can I use a Mister Buddy propane gas heater if needed on nights of prolonged below freezing temps?

Since your greenhouse is only 48 sq. ft., you really only need something as simple as a space heater to heat your greenhouse. Your Mister Buddy should be fine, and is probably even overkill depending on the size. Of course, the ability and cost to heat your greenhouse effectively in the winter will depend on your covering and its heat loss properties. But in your region it shouldn't be a problem.

igcusa, thanks for the reply. It's a small Mr. Buddy, only uses a 1lb bottle. I won't have electricity to the greenhouse so a space heater would not be an option. I had all my plants on my front porch last winter covered with sheets and they made through some high 20's for night temps and 30's during the day. I'm figuring that the greenhouse will keep frost off of them and if watered they shouldn't freeze. I hope.

You may have problems with the auto oxygen shutoff. Depends on how tight the GH is. I would run an extension cord, and use one of those electric oil radiant heaters. Thats what I'd do.

fourks, would I be able to use an extension cord on that heater? I know on the electric ones they tell you not to. Sounds like something I'd like to try. I never knew there were electric oil heaters.

I had one electric oil heater. It was nice. Looked like an old radiator type that went into houses. Easy to clean and efficent. Lent it out to someone and never got it back. Went out last year to buy one again and could not find one.

Well, if you give me the run in feet from power. Gauge of wire of extesion cord. and wattage of heater. I can look it up in uglies book. Or just start with your propane, and see how it works out. Home depot sell the eletric oil heaters. looks like a radator. Pretty safe unit.

I went to D'Longhi's web site and read their instruction manuals. They said I could use a No. 14 AWG extension cord rated not less than 1850 watts. That was a minimum. So I will get a D'Longhi electric oil heater and that extension or one greater than that.

Schickenlady, Lowes carries D'Longhi electric oil heaters on their website. They can check to see if they have it in a store near you. If not, then you can order it on line.

Thanks fourks for the heads up on oil heaters.

Last year they had electric oil heaters at Home Depot. I hope they have them this year as I am going to have to have more heat than I had last year... and more efficient heat also. If I could get a depndable thermostat and a drip irrigation system I would be a very happy woman!

The wire size you need depends on three factors:
1) The rated voltage of the heater - a 240 volt heater will draw half the amperage of a 120 volt heater
2) The current flow (amperes) which sets the minimum wire size based on the wire rating. Approximately, #14 ---> 15 amps, #12---> 20 amps, #10--->30 amps (these are typical for non-metallic wire, i.e. romex - many extension cords will be rated less.)
3) The distance (really the resistance of the wire since the voltage will drop in proportion to the amperage)

For example, 1850 watts @120 volts --->15.4 amps (but only 7.7 amps @240 volts) so #12 is needed (for a reasonably short run)
(of course the heater won't actually get 120 volts because of the voltage drop in the wire, thus it won't deliver the rated 1850 watts nor will it pull the 15.4 amps)

I think a #14 extension cord is too small.

For #12 romex (120 volts), using 1.6 ohms/1,000' (average figure) a 100' run (total of 0.32 ohms both legs) will drop 4.8 volts, probably acceptable.

I would be sure to use a grounded (3-wire) cable and a ground Fault Interrupter circuit breaker (or at least a GFI receptacle) in the greenhouse. For a permanent solution, you probably would want to use UF (direct buried cable) in the ground.

dd (electrical engineer)

Dave, thanks for all the info. So the smaller the number...#14, #12 and so on the greater the amps. I didn't know that. I agree that buried cable would be the best. But I doubt that will happen this year. Now this is the part where you shake your head and say dumb female, but....I was planning on running the cord from an outdoor receptacle to the electric oil heater directly in the green house. The oil heater I'm thinking of getting has a GFI built into it. Is this unadvisable? The greenhouse is approx 35 ft. from the receptacle.

The smaller the number, the larger the cable/wire.

Thanks dd for doing all the math! I would recommend that you use a GFI. Just make sure you check the circuit often. I use this kind of heater along with eight 55 gallon water filled steel barrels here in Colorado. I grow from March to early November, and the GH is 12x20 with only double wall polycarbonate panels.

Texasgrower
I have a small GH 14 X 16 and use the electric heaters. Mine is polycorb but I also line it in winter with plastic. Usually does well other than those few really cold nghts. It will keep things alive but not growing much. Mine will be stuffed this year since I went crazy with tropicals. You can see how I do things when you come over to visit.
David

David,

Hi! Did you enjoy the RU? Thanks for all the plants you gave us! I have a question about the above post. How do you attach the plastic when you line the greenhouse with it? I also have a poly greenhouse DH made for me... Most things did well in it, but I had some damage on the night we got down to 17*.

Carol

Carol
Your GH looks about the size of mine. I use the 4 ply plastic to cover all 4 sides of mine. This forms a 4 inch barrier between the poly and the plastic. I also drop my ceiling to about 7 foot since heat rises this help a lot too. I hang the plastic on the inside so the thinner plastic works fine. I only use it for winter and remove it when it warms up in spring. Your GH looks like it has a wood 2 X 4 frame as mine does. At most lumber yards that sell bulk nails, look for the nails with the plastic caps. I use the shorter ones with orange caps. I stretch the plastic tight and fold about an inch over where I nail at top and bottom. I cover all 4 sides and the ceiling. This helps to keep the heat inside the GH and forms the 4 inch barrier. For heat I use the cheap electric heater with the fan built in. I also use a box fan mounted high to curculate the air. On warm days you may need to open the door so as to cool things down a bit ( Texas weather). I found that the plastic makes about a 10 degree difference. On the few very cold nights, 17 degrees or so, I use 2 heaters. This keeps things above freezing. Some things will go dormant. This works well with seeds and cuttings I start in late Feb. and March. Hope this helps.
I always enjoy the RU's, meeting new and old friends. I like to do seeds and cuttings so usually have plenty to share. Hope that you can make the one in the spring here in Jacksonville. I hope the plants you got from me thrive and do well. If you are ever in the area, drop by and see me and my attempt at gardening.
Keep in touch and look forward to seeing you again.
DD

David,

What kind of poly did you use? I mean is it the double or is it single sheets? We used the single sheets from Hoem Depot, but he put a second layer inside. But last year we had to bring stuff in before he finshed the 2nd layer in some places. When it got down to 17* I had some damage, but I think it was mainly where the second layer was missing. He has finished it now so hopefully...

I hope to get to go to the RU in spring. The plants I got from you are doing well, but I have forgotten where they go, sun or shade so right now they are under an oak tree. I don't know which can be planted now and which should go in the greenhouse. And it may be too late to plant anything because ther might not be time for it to establish before a freeze. We are getting down to the 40's at night now.

Carol

I have decided to give the Mr. Buddy a try after all. I read the box and it can be used indoors, RV's, shacks, workshops, fish shacks, garages and the like. I figure if it can be used indoors it can be used in the greenhouse. It has a low oxygen emergency shut off. So I will leave a vent partially open and try it. Then I won't have to worry about extension cords and overheating.

I posted some info regarding propane heat on this posting:

http://davesgarden.com/community/forums/t/827836/

Yep I read that thread and even commented on it. Great info!.