Gas greenhouse heaters

Hi
I feel in need of a rant here!

I have used paraffin to heat my greenhouse for years but because of rising prices I thought i would look into the cost of gas greenhouse heaters.

They are so dear! Almost a hundred pounds for one - even on ebay!

Does anyone know where I could get one cheaper?

 

Hi wilroda. I'm no expert, but £100 for a gas heater sounds quite reasonable, to me. Just out of interest, are you planning on heating the whole greenhouse ? Gas too has become very expensive and in the depths of winter/early spring, I'd imagine the costs of running would be astronomical. Cheers...freddy.

 

Years ago I had a gas heater, inherited with the greenhouse (8x6) it eventually died a death. For a few years though it worked great. I only used one cylinder of gas( bbq size) for the whole winter, keeping frost off initially then for seedlings etc. That worked out at about £20 for the winter.
Thats why I am tempted now, with prices so high for electricity and probably paraffin too.

 

Wilroda - I am not recommending electricity, as I have never used it to heat a greenhouse - but you may not want to rule it out totally.

My own experience is that I have a 10' by 8' wooden summerhouse with a complete glass front. I fill it with borderline plants over the winter and heat it with electricity. All I want to do is keep the frost off. So the thermostat is set to about 1C.

Its not that hot in Yorkshire, but over the last two winters it has only cost me £1 each year to heat it. I know the figures exactly as I have an energy meter that measures it. I was surprised how low it was. I think the reasons are

1) Being largely wood it is obviously much better insulated than a greenhouse. Also I lined it with bubble wrap, and there were no draughts. Insulation is very important.

2) I used an external electronic thermostat, which was precise. I didn't use the thermostat inside the heater, as they are very cheap and don't switch on and off at the set temperature. I also checked what was going on by using two max/min thermometers inside the shed and two outside.

3) By using a thermostat, power is only used when it was needed. Most nights it never switched on at all. By contrast a parafin heater would be on every night, even when it wasn't needed. There is also the benefit of being able to go away for a weekend or longer and not worry about it.

4) by setting a very low temperature (just enough to keep my plants alive, the heat didn't need to come on very often. Simply raising the temperature a couple of degrees could have used 10 or 20 times as much power, as it would have to come on so many more times.

 

I agree with Peter.

Electricity is really the best, its so controlable.

Dont ask how to get the power to the greenhouse though, it could be a long debate.:D:D

 

Perhaps I'm being a big thick here, but if you used an external electronic thermostat...how does that tell you the internal temp?:confused:

Ah...just re read it...you only meant a thermostat that was external to the one in the heater....sorry, makes sense now.

Time for bed methinks, heh,heh.

 

Thanks everyone!
PeterS your post is so interesting. I really was of the opinion that electric greenhouse heaters were expensive to run.

I dont heat my greenhouse except to keep the frost off until about February so it may be worth looking into a bit more. I think I will invest in one of those meters to check how much you are using costwise as well though just to be sure I am not using too much electricity!

 

Hi Wilroda. The set up I had was a 2Kw Parasene FrostGuard heater http://www.garden4less.co.uk/proddetail.asp?prod=594 - but you can buy it cheaper than this.

controlled by an external thermostat http://www.tlc-direct.co.uk/Products/SMET05.html

And this was the energy meter http://www.maplin.co.uk/module.aspx?ModuleNo=38343&doy=4m6&QV=Y

I found this from an old post of mine - however the cost of electricity is a bit more now:-
--------------------------------------------------------------------------------

I know it is off topic - but I finally got my wattmeter this morning, which I was told was out of stock earlier. I bought it to monitor the power used heating a greenhouse. As with any new toy I had to have a play. But I thought the results might be of general interest. The following values are for the power consumed in watts:-

TV standby .............................. 1
TV on .................................... 61
Video standby .......................... 8
Video on ................................ 10
Video recording ....................... 13
Freeview standby ...................... 8
Freeview on ............................. 9
Computer ............................... 82
CRT Monitor black screen .......... 69
CRT Monitor windows ................ 76
CRT monitor white screen .......... 87
Radio........................................ 1
Propagator - narrow windowsill ..... 9
Propagator - 2 normal seed trays . 20

Remember 100 watts at 10p/kw will cost 1p per hour, or £1 every 4 days of continuous usage. For instance TV, video and freeview on standby for a year costs £15, so switching off at night will save up to £10.

 

Hi, we have always used electricity in out green house and it is not too expensive if you use the frost setting, bubble wrap etc. We even put on of those little plastic green houses in ours one year( it was very cheap in the sales). We have electricity all the way down to our greenhouse and pond:thumb:

 

Bob - I didn't look very closely at the Parascene heater, but I assume that there is a very cheap bimetalic strip thermostat. With any thermostat you get what is called hysteresis. This simply means that the temperature at which it turns on and the temperature at which it turns off are not the same.

I spent quite a lot of my working time working with temperature controllers, so I am basing my comments on my gut feelings and experiance rather than anything specific about this particular heater. If you set say 2C on a cheap thermostat, it might one day come on at 2C and turn off at 7C, ie you are heating the greenhouse 5C higher than you wanted, which is expensive. On another day it might not come on until the temperature has dropped to minus 2C.

The manufacturers would assure you that this does not happen, but a bimetallic strip only costs about 20p, so it is unlikely to be as good as the one mentioned above at £16. And that cheap - you can pay a lot more!

Also the heater thermostat is actually in the heater, and is not neccessarily measuring the temperature of the greenhouse. Its a bit like strapping your house thermostat to the radiator - its not neccessarily telling you what the temperature of the room is. With a seperate thermostat you can place it anywhere in the greenhouse - I had it on an extension lead, rather than plugged into a wall socket.

Yet another reason is that in the Parascene heater the frost guard setting is a standard settin that you can't alter - they say it is 4C. On my independant thermostat I could adjust the setting in tenths of a degree, and I adjusted the figure so that my max/min thermomiters inside the shed registered 1C min.

The internal one might work well enough, though I suspect that it would have cost more to heat the summerhouse over the winter. I do have a habit of doing a proper job, when something cheaper might do. Perhaps the real reason is that I like to be in control and I like toys. :D

 

Good advice regarding the outboard thermostats, much higher quality and accuracy than the cheap and nasty onboard bi-metal strips.
Being able to site the sensor exactly where you want is reason enough on its own

 

This is so interesting! Thanks so much PeterS!
The plug in thermostat looks great. What has concerned me was the possible inaccuracies of an electric heater " with built in thermostat" One of my reasons for thinking about gas.
With all the energy price increases I have been trying to find ways to cut - or even have some more control over my greenhouse heating but using your "set up" it seems that I would have no worries.

Any other tips? lol!

Maybe we should have a page on "greenhouse tips" because if, like me people use the "Heath Robinson" technique in their greenhouse - and garden for that matter - it would prove very interesting reading!


Thanks again!

 

Its more economical to heat the floor/soil rather than the air.
Plants don`t mind an air temperature of 40F or less if they have roots in 60F soil
More expensive to install than an electric heater but in the long term will pay for itself as energy prices continue to increase...which they will :D

 

Thanks Wilroda and others for your comments. I think greenhouse heating is a subject that will run and run. I remember some good threads on storing heat in drums of water, painting walls black to absorb more sunlight, and the effects of radiation at room temperatures. All good stuff.

Hex, thats a good point about heating the soil. I have a question for you - but will put it in another thread on home build greenhouses.

 

I can see where your coming from Hex, but it occurs to me that you would need to heat the soil to a fairly high temperature to be sure of keeping frost away.

A temp of 60F as you suggest could well cause plants to continue growing when they should be dormant, and any top growth would be very weak in mid winter.

Also most people move pots into the greenhouse for winter protection, how do you heat these?
Yards of soil warming cables wound around pots?