Greenhouse Heater Options


We have a small greenhouse attached to the south side of our home. It's 14' X 12' with a shed roof tapering from 10' on the house side to 6'. Roughly 1,400 cubic feet. It's a 2x4 frame with double-walled polycarbonate sheeting, 10mm for the roof and 6mm for the sides. We're in Maryland, near Baltimore, so it rarely gets below the mid-teens in the winter.
We heat it with a 220V electric heater, 5,600 watts and 19,110 BTUh rating. This generally keeps it at the 50 degrees the plants require but occasionally my wife puts on a 110V supplimental heater on cold nights.
The power hasn't failed in the winter since we got the greenhouse but it's probably only a matter of time. I was thinking of getting a kerosene heater as back-up to the electrical heaters. Home Depot has a 23,000 BTU heater for $129 which seems to fit our needs. Could I use home heating oil for this or would it be better to stick with pure kerosene?
I was wondering about a propane heater; would that be more efficient than kerosene? We have a propane ball/tank for some other applications which aren't used in the winter.
Thanks in advance for any suggestions.
Paul
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For the rare occasions that you may need it, the kero heater is probably the easiest solution. It may burn on home heating oil, but it would be really dirty, stick with kero

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But if he already has a propane setup, why not use that? Or just put a bbq grille in there...
Someone recommended a petromax, for home heating oil or kerosene. petromax.com
Another possibility is to get a backup generator -- might as well power the house iffin yer going to heat the greenhouse!! More bucks, tho, but also a more general solution.
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wrote:

We have a 5,500 watt generator to keep the essentials (water pump, furnace, refrigerator, etc.) going during an outage. The heater for the greenhouse is 5,000 watts so we don't have enough to power that, too.
Paul
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Electric heater on a generator will suck a LOT of gasoline. I think you'd be best served with the kerosene heater you mentioned. I havn't tried fuel oil, but people tell me that fuel oil in a kerosene heater will smell very bad. Fuel oil is desgned to burn and be blown up a chimney, not vented into the room. Propane is very good, also. Propane has something like 21,000 BTU per pound. You'd need a wall heater, or double burner infared on a gas grill tank. A galon of kerosene, if memory serves, has about 140,000 BTU of energy. So, a galon would last about six hours at 23K per hour.
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On 12/28/2009 07:20 AM, Pavel314 wrote:

extra C02.
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What about CO levels? I wonder what a digital readout of those would be.
Steve
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Van Chocstraw wrote:

Kerosene smells.
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What will the fumes do to the plants?
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hr(bob) snipped-for-privacy@att.net wrote:

Not the plants. Human noses. My greenhouse/sunroom is heated by a heat pump when it gets real cold. Today it is ~20F outside in the sunroom it is ~60F. No need to turn on the heater.
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Been asking in rec.gardens and rec.gardens.edible, and the consensus there is that electric is good. Propane, also, but be sure the air mix has it so that the flames are blue tipped instead of yellow to keep CO levels down. I'd put a digital CO detector in there just to be personally safe, as well as know exactly what the CO levels are. The screamer models only let you know if the levels are high. If 300 is high and where it starts screaming, I'd like to know if it is hanging at 295. They have a memory, so you can reset. $25 to $50, some more, but you get what you pay for.
Steve
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wrote:

HD sells kero in a 5 gallon can -- $35.00, plus tax a couple years ago. YIKES!
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Oren wrote:

Some gas stations and fuel oil companies sell kero at sensible prices. I'd find a good source before investing in a heater for the $35 stuff.
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wrote:

was almost free when we were kids.
I see folks on craislist trying to get rid of kerosene heaters. Must be the price for fuel :)
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Electric here is near 40% more than gas, whats your electric bill. I have a big greenhouse like yours, uninsulated glass, it costs about as much to heat as the house, now I keep the plants in the house. Unvented may cause to much condensation, I have a gas vented heater. You could test unvented propane to see if condensation is an issue. For about 40$ you can get an infrared propane heater that goes right on a 20lb tank,
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Last winter was the first one with this greenhouse. I checked the electric bills for the last couple of years and did some calculations; my estimate was $300 to run the greenhouse heater for the heating season. There's probably some savings in heating oil that I didn't include as an offset. The back, north wall of the greenhouse is the outside wall of the laundry room. On a sunny winter day, the greenhouse heats up to 80 degrees or more so we open the laundry room windows and let the heat pour into the house.
Never thought about condensation; thanks for mentioning that.
Paul
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We used to heat the greenhouse with a woodstove with warm air blower on it. The warm air was blown into the family room, which was on the ground level of the tri-level house. The heat of the stove itself kept the greenhouse warm enough.
Even if the power went out, the greenhouse could be kept warm, and passive heat flow would help heat your house.
hth..... Linda H. Illinois
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Linda Hungerford wrote:

Did you let the plants see you burning the dried body parts of other plants?
TDD
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The fumes from kerosene would be bad for the plants. I had a lean-to green house off my workshop and the plants didnt like the kerosene residue at all. I noticed the leaves had an oily coating on them but unfortunately not before it was too late.
Jimmie
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