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.

HDCochran I used a vent free propane heater with my daylilies last winter. The plants did not suffer but I sure did! The heater kept using up all the oxygen in the greenhouse (8'w x 17' L) and snuffing out. It was a royal pain!

MollyD

All kinds of heaters here

http://www.greenhousemegastore.com/products.asp?dept=1013

Also try Charlies greenhouse supplies

Resurrecting this thread...

I have a small, 8x 8x 8 greenhouse. Last year I tried heating it with an electric space heater. I ended up with some frosty plants :^( The heater I had just wasn't made for that application.

I'm thinking of this
http://www.greenhousemegastore.com/prodinfo.asp?number=HT%2DPAR%2D591

I just basically use my greenhouse (this is it's 2nd year) to move my veggie seedlings to until I can stick them in the ground in June.

Any thoughts?

Michelle in Michigan

Michelle, it is an unvented heater. You must accept the risks associated with unvented heaters. Also (and maybe I just missed it) I didn't see a BTU rating on that heater. That concerns me a little bit. You would want to know how many BTU you are getting. The space heaters are 5120BTU at 1500W and so if it isn't any bigger than that, it probably won't do.

We just bought this one:

http://www.greenhousemegastore.com/prodinfo.asp?number=HT%2DRCH

Haven't gotten the greenhouse completed yet so it's still waiting to be fired up.

Ken in Glassboro, NJ

I wish I had anticipated heater problems when my son built my 8 X 8 X 8 orchid greenhouse. I haven't been able to keep it warm on cold cold nights. On the coldest nights, the outside temperature gets down to 23ºF. It's barely above freezing in the greenhouse even with the space heater on all night. This year I've added 4 large black garbage cans full of water. That's raised the temperature by 3 degrees. I have room for about three more. I also need to put up the bubble wrap for added insulation. Has anyone ever run a 220 line to the greenhouse so that 2 space heaters can be used? That may solve my heat problems or I could wait for global warming to place me in a warmer zone. Haha!

bettydee I think you should run two separate lines off two different breakers for that kind of use. You'll avoid having the system trip when you're sleeping or away from home and it shouldn't be that much more expensive if both are done at the same time.
edited to say I'm not referring to 220's here!

MollyD

This message was edited Jan 16, 2008 9:17 AM

bettydee--you may be able to fix your problems by upgrading to a better heater. I have a 5x9 GH, and I have a heater from Charlie's Greenhouse and it works fine. Granted my temps don't get quite as cold as yours, most nights are around 35 or so but we've had some that got down close to 25, and my greenhouse has stayed at a toasty 60 degrees no problem (and the heater's not even running constantly). So you might consider upgrading--especially if yours is an indoor space heater those aren't very safe in outdoor situations where there's water around anyway. Here's the one that I have, it's electric and plugs into a standard outlet, no need for the 220. http://www.charleysgreenhouse.com/index.cfm?page=_productdetails&productid=4045&cid1=201&cid2=264&cid3=-99

ecrane3, thank you for that link. The space heater I have in there now is an indoor heater because it was an emergency purchase. My old heater didn't work when I plugged it in late last month.

I wonder if the one Charleys Greenhouse sells is identical to one being sold at Wally World for much less. Charley's does tend to charge more.

Wouldn't surprise me if it's the same--the thing to check is first of all that it's an outdoor heater (if it's not, then it's not the same) and then check the BTU output, that tells you if it'll put out the same amount of heat or not. If the WM one has less BTU's, then it won't have the capacity to put out as much heat. If it's just a little different then you're probably still OK, but if it's half the BTU's or something then you probably ought to splurge for the Charley's one.

Check out ACF, they ahave a variety of heaters for greenhouses. Here is the website: http://www.littlegreenhouse.com/accessory/heater-compare.shtml


"Stay Happy and Keep Gardening"

Don't know if I'm too late on this thread or not, but all plug in heaters (that run on 120V) have the same maximum BTU and watts. One of the nice things about electric heat is there is no such thing as an efficiency rating. Watts used are directly proportional to the heat given off - there is no waste. Although Charley's heaters are nicer looking and probably better built, they don't put out more heat than the Wally World 1500W "milk house" heater.

If you run 240V to the greenhouse you can definitely put more heat in there which is what I did. But you shouldn't just run 2 of the 1500W heaters, especially if it's wired up like I think you're talking about. If you use a single 2 conductor plus ground wire and hook it up as 2 different 120V lines, that's a big mistake. You will be using the ground wire as a common wire, but for 2 different lines. You will overheat the wire and possibly start a fire! A better option is to buy a heater that is meant to run on 240V. I use a 5000W heater. It only draws slightly over 20A because it's running on 240V versus 2 milk house heaters giving only 3000W, but drawing 25A. Electricity and heat is simple math: volts x amps = watts which is directly proportional to BTUs which is also directly proportional to your electric bill :)

That heater looks EXACTLY like the heater I bought at a local hardware store for $29.95! Mine is definately not an "outdoor unit", but it's worked just fine for me for the past 3 years. I do put a little table over it to somewhat protect it from roof drippings, but other than that precaution (and being careful not to soak it when watering plants), the little thing has done the job. We've only had 2 nights in the 20's here this year, but the lowest it's gotten in the little greenhouse (6'x6' "CostCo Special") was 48.5 degrees. Colder than the citrus I'm storing in there like, but poo on them if they can't a joke for a few hours! (And they can---they're all sprouting new leaves, some are flowering!).

My experience with the inexpensive 1500W (5120 BTU) WM heaters is that they will work fine for a couple of years and then for unclear reason, they just quit. You kind of get what you pay for with these heaters. Don't get me wrong, I use them, but with the understanding that they don't last that long.

Stressbaby, You are right about that. My old heater lasted just about three winters. It quit toward the end of the third winter.

Yup! I get 3-4 yrs out of these things, then goodbye. I replace them. Never spent the time to calculate the true economics of the thing, but probably should! My gut feel, though, is I'm beating the system. If the heaters last an average of 3 yrs and cost $30per unit, that's a sunk cost of $10/yr. I can live with that, to keep my citrus growing and producing. Unless the "outdoor" rated units last twice, or three times as long, economically I'm ahead(assuming other aspects equal---energy consumption, efficiency, thermostat reponse/range, etc,). And I think that's a pretty safe assumption, since they're identical units in most observable ways.

If they last 2-3 years and "quit" that is fine as long as they don't "quit" in the middle of the night when the outside temperature unexpectedly drops into the teens.

Doug

Doug from what I've read here and on other greenhouse forums that can happen even with the high priced "greenhouse" heaters!

MollyD

Scary stuff! I guess it is a good idea to have some kind of backup system or alarm to alert you to a malfunction. I'm petrified of losing some of my tropicals that I've had for years to a bad heater.

Doug

I have been using a heater that looks just like the one you find at Charlies it is called a barn heater. Farmers use them all the time in there barns for chickens or whatever. It works excellent, got it on sale for $19.99. After I got mine at Orscheln Farm & Home Supply I noticed Wal Mart had them also.

It's a good idea to have an alarm system to warn you of temperatures that are too high or too low no matter what heating system you use. I had a good one which has become unstable so I'm looking to buy another one this year.

MollyD

I have a wireless temperature and humdity sensor in the greenhouse. Then I set the main weather unit to sound an alarm if the temperature goes beyond the perimeters I set. It works pretty well although it drives me nuts during the summer.

Bettydee, where might I find this wireless temperature and humdity sensor? What's the brand name, as I might have to purchase it off the internet.

I've had good luck with Oregon Scientific. I've had one unit for over 6 years and don't remember where I purchased it. I purchased the other one from Amazon.com late last year. I got a good bargain, but you may be able to find them cheaper even with shipping. I use the unit that can receive information up to 300 feet, but there are units that receive work at shorter distances. Be sure to get the unit that receives both temperature and humidity because some remote sensors can only send temperature.

This message was edited Feb 22, 2008 10:43 AM

I've been looking for an alarm system that can cover a distance of 800 feet for years, Bettydee. Haven't found one. You haven't run a cross one by any chance, have you?

Line of sight distance for these one is 1000':
http://www.weathershack.com/davis-instruments/davis-vantage-pro2.html
http://www.ambientweather.com/61wivaprowif.html
http://www.scientificsales.com/Davis-6152-Wireless-Vantage-Pro2-p/6152.htm

MollyD -
I'm a new small greenhouse enthusiast and a new subscriber. I believe I read in another thread (which I now have forgotten) that you posted info on converting a non-venting propane heater to a vented one. Hope I'm not wrong about that but I can't find the thread where the info was originally posted. Can you steer me in the right direction? My propane heater is adequate but I'm learning this winter what plants really dislike it. I do use an electric heater on warmer nights (not many of those here) but when it's below 20 degrees, I rely on the propane.
Thanks for the help.

Cindy it was someone else who posted it for me to see. Let me look around and see if I can find it.


MollyD

Cindy check these out:

http://forums2.gardenweb.com/forums/load/strucs/msg0112022018008.html

http://forums2.gardenweb.com/forums/load/strucs/msg0113461218768.html
on this thread is a guy named etravian. It was his pictures I mentioned but I can't see them now. Maybe you can contact him for them?

MollyD

MollyD -
Thanks for locating that thread for me. Now I remember reading that thread a few weeks back when I was lurking around to get alternative heating ideas. I have a Big Buddy 18K non-vented propane heater and was hoping to make the GH environment a little more friendly when I run it. I haven't had any issues with it snuffing out and I can get about 50 to 60 degrees over outside temps with it set on low. The heater has two inlets so I can set up 2 20 lb tanks and not worry about running out in the middle of the night. It's just that I get some foliage damage if I run it constantly. It doesn't have a thermostat so I'm in and out of there a couple times a day turning the thing off/on. I have an electric heater for backup or sunnier days (which can raise the temp to close to 80 inside). I left my automatic roof vents in for that very reason and I do keep a fan running 24 hours a day. I've checked out a lot of the vented heaters and they're pretty big (for my little GH) and pricey so looking for alternatives. I've got twin-wall polycarb, gravel and paver flooring, attached to heated garage (no direct access yet), faces south and I've put up the foil-backed bubble insulation on the east and west sides and rigid styrofoam on the lower half of the south-facing side. I'm trying to maintain 55 to 60 degrees minimum but I dread opening the electric bill these days. Who knew an 8 x 10 lean-to would be so expensive to heat?
If anyone has any other ideas, I'd sure be interested.
Thanks again for your help!

Cindy, unless propane heaters are properly vented, there is a real danger of combustion products accumulating inside the greenhouse. If you do go that route, get one each of these monitors, a CO and a CO2 monitors and install at the recommended height in the greenhouse as a precaution. Getting the monitors is even more important if you are going to have direct access to a living area.

This message was edited Mar 1, 2008 6:22 PM

Cindy I had the same problems with the Big Buddy so I went to a Pro Com Blue Flame which snuffed out. Now I'm using a kerosene heater with an electric auxiliary heater for the coldest months. That combination has worked very well for me this winter. I've gotten more sleep than last winter!
My kerosene heater came from Walmart (10K btu). It has a metal container that you lift out to refill. I do it in the morning and in the late evening. On cold sunny days I turn the electric heater off because it can get quite warm in there. Since we have a lot of power outages here I can't rely on just electricity.
Two box fans circulate the air rapidly in there.

MollyD

bettydee/MollyD -
My DH has a 4-gas monitor and we do test the environment from time to time. While the monitor is barely registering anything, the foliage definitely suffers when I run the propane for a prolonged period of time. Normally, the propane heater is turned off during the day and I don't work out there when it is on. I am planning on cutting a door from the garage to the greenhouse and hope that the garage heater can keep the greenhouse heat at an acceptable level next winter. A few more weeks and I shouldn't need the propane. I have seedlings indoors under lights that I'm holding off on sending out to the GH until then. I am getting GH fever now.

Cindy it's possible that it's a matter of what kinds of plants you have. I have daylilies and hostas and they never showed any kind of reaction to propane. Neither did I. The heater I was using was designed for in home use so there was no expectation that a person could not spend time around it. Some people may be more sensitive to propane and kerosene heaters. I'm not.

MollyD

MollyD -
Had a Stephanotis in there (have to grow it in a pot here) that was doing great and all of a sudden, 3/4 of the leaves yellowed. Brought that one into the house. Also had a purple shamrock (botanical name is elusive at the moment) that was loving the greenhouse, blooming like crazy and then the flowers gave up and the leaves turned yucky. Brought that one in as well. I do know that the florist Cyclamen is loving the cool greenhouse and blooming like mad for the past two months.
Re: your daylillies and hostas - do you grow them year-round or do you use the greenhouse for propagating?

Cindy I use the greenhouse to grow them from seed beginning Oct 1st till the ground here can be worked sometime late April to May. Daylilies in the north can take up to 3 years to go from seed to bloom. By growing them in the greenhouse for that time I can shorten that cycle by as much as 12 months (sometimes more). Last year I had a bloom in September on a plant that sprouted in January (same year). That's the seed to bloom cycle for daylilies grown in Florida, not upstate New York!
I shut my greenhouse down once all the plants are out in the garden and don't open it up again till October. No cooling problems for me :-)

MollyD