Heater for Small Greenhouse
 

My orchid collection has outgrown my orchidarium and I am building a small 12' x 12' greenhouse and will need about ~10,000 Btu/hr of heat to keep it warm enough next winter. I cannot find a ~10,000 Btu/hr vented propane heater. Does anyone know of a source? Alternatively, can anyone provide reliable information on any detrimental effects on orchids of using a vent-free propane heater? I've read arguments on both sides of this question.

I ran across this supplier while checking on other items (lights) Electric & Gas Heater Comparison Chart and Information Guide I'm not a greenhouse person, but maybe there's something here? I'm sure others will jump in as well cause we've had some lively discussions regarding venting vs not venting.

I can gladly chime in on this for you. I have a small greenhouse (8x15) and really wanted to go propane too. After much searching, if I wanted something vented, it seemed as though the purchase, installation and permits would have been three times what I paid for the greenhouse. (Nearly $1500) I found and opted for a setup using a "Mr Buddy" vent free unit along with (2) 20lb cylinders and the necessary lines and filters. It offered three heat settings at 4,000, 9,000 and 18,000 btu's. Well, within 6 nights at it's lowest setting, all buds blasted and a huge amount of my plants old growth turned yellow. Going in the greenhouse just made you sick. I returned everything to Lowes and opted to go electric. I ran a 240 volt line out to the greenhouse and got a 4000 kw wall pack that has worked wonderfully. I still need to contemplate a backup system.

Your big problem is ethylene which is a by-product of burning propane. Natural gas doesn't have the same problem so if you have the option, go with gas. If propane is still your choice, go vented! If you don't find a 10k btu unit, it doesn't hurt to go oversize on your heater and run it at a lower setting.

Even if one uses Natural Gas there is still carbon monoxide to deal with. I would never consider a ventless gas heater of any sort of brand for use in a closed area. I have seen a ventless propane unit that needed as much free air coming from outside as it blew out of the heater. So what is the point then? Electric is still the safest, but the highest operational cost for a heater. Vented gas would be the cheapest to operate (but still not inexpensive). :twocents:

try looking at Rinnai. I have a small GH that I heat very happily wit ha vented Rinnai natural gas heater. IT does require electricity for the ignition thou

What about one of those heaters that attatches to a 5 lb bottle of propane? looks like a metal plate on its side with piping going into it. Like this one I found online: at
Google Image Result for http://www.hardwarestore.com/media/product/166751_front200.jpg
It goes from 10,000 to 15,000 btu

I just use a 45,000 btu gas grill in my smallest greenhouse 24X66 , I put my ceiling fans on reverse and let it go. Heat will dry out the flowers, I soak down the greenhouse floor with water the night of heating. (ps I am in Stuart ,Fl)

HD, by now you may have resolved your heating situation. I live in Michigan with night time temps between -5 and 20 deg. I have a standalone twin wall acrylic GH (8 x 15) and use a vent-free NG 20,000 Btu heater I purchased at a big box store for about $200.00 I ran a 1/2" gas line inside a PVC sleeve from my home to the GH (underground) and I've been toastie warm all winter. I have had NO problem with CO. Of course as would be expected there is lots of additional water vapor from the combustion of the NG along with CO2, but the plants eat that up and no GH is so tightly constructed that there isn't some air leaks...just my 2 cents worth. The red box to the right of the heater is the 15,000 Btu 240v electric heater that came with the GH and used as a back-up heat source.