Greenhouse heaters

[Slug Killer]

OK this is not a problem as such but just a question related to heating. Just wondering if anyone uses the gas greenhouse heaters and how economical they are compared with others. Only looking at frost protection as I seem to have lost quite a few plants late last year with early frost.

I currently have a couple of paraffin heaters but the fuel is expensive locally.
Thanks in advance for any advice.

[David Nicholson]

Dave, how do you deal with the fumes that paraffin and gas heaters produce please?

[majallison]

Slugkiller, I'm not sure about gas heaters, but I've found that paraffin costing about £6 for 4 litres whether from the internet or a local horticultural trade supplier, was about 1/3 of the cost of running an electric heater to keep the greenhouse frost-free.

David ~ as for the fumes, I quite like the smell of paraffin; burning it does produce a lot of water vapour, so have to keep the greenhouse reasonably ventilated (this also I guess to avoid producing carbon monoxide)

Malcolm

[David Nicholson]

Thanks for that Malcolm. Does paraffin burning produce enough water vapour to actually run down the glass or just to mist up the greenhouse?

[Slug Killer]

Thanks for that Malcolm. Does paraffin burning produce enough water vapour to actually run down the glass or just to mist up the greenhouse?

If you don't vent the area it will cause water to run down the windows but normally just mists them if vented. The other problem with paraffin heaters is the wick. I found out once if adjusted incorrectly they burn with black smoke and then nicely colour my white shading grey

The reason I am thinking of using a gas heater like this one on eBay is that they are fully thermostatically temperature controlled coming on at the temperature you select and therefore possibly cheaper to run.

http://cgi.ebay.co.uk/LIFESTYLE-1-9KG-CALOR-PROPANE-LPG-GAS-GREENHOUSE-HEATER-/220725001132?pt=UK_Home_Garden_Garden_Structures_Fencing_CV&hash=item33643c3bac

 

[wooden shoe]

Just for everyone who is interested: I did some calculations for a very small (6m2) greenhouse constructed of 16 mm polycarbonate plate (2.4 W/m2).
Of course the energy consumption is higher if you want to heat to a higher temperature thus I have been calculating for 6 different temperature regimes in the range of 0 to 5 °C.
The calculations are based on the temperature observations in Central Netherlands from 1 Oct 2009 till 1 Oct 2010 which I must admit was a cold year.

To concede: If for instance I were to keep my glasshouse to +3°C during that year I had the heater on for 1727 hours. On average on those hours I had a difference of 4.0 °C with the outside temperature resulting in a yearly energy consumption of 98 kW.

°C	hours	avg dT	kW/year
0	1013	2.6	38.2
+1	1253	3.0	54.7
+2	1518	3.4	74.9
+3	1727	4.0	98.4
+4	1966	4.4	125.0
+5	2273	4.7	155.7

This is all theory and I hope I did the calculations well, but it might give an idea to what the energy consumption might be if you were to buy even a very small greenhouse and the influence of the choosen temperature regime.

[Maren]

Hi, I use calor gas for both my pleione houses. You may have seen the construction in my thread on Restoring a Victorian greenhouse.

Consumption varies depending on the weather, naturally. I aim to keep the houses frost free. The gas heaters have a built in physical thermostat (no electricity available), which is not terribly accurate but good enough. Each house has two bottles with a change-over device, which automatically switches to bottle 2 when bottle 1 is empty. This means that the heating is never interrupted, provided I get a new bottle when one is empty. Automation is essential because I live quite a distance away from the nursery. This is was my annual usage last year:

House   Width m   Length m   Height m   Space m³      No of bottles   Capacity   Total   
 1           2.80         6.00        2.50           42.00                    6            19kg     114kg   
 2           3.50         6.00        3.20           67.20                    4            47kg     188kg   

These houses have enough gaps under the doors to provide the required ventilation.  Pleiones don't seem to mind this kind of heating.

However, in another house (on my allotment), where I keep my cymbidiums at a minimum of 10 degrees C, I found that the leaves on the plants turned yellow. That was until someone smashed one of the larger panes, which I patched up rather inexpertly leaving a few gaps. The resulting increased ventilation seemed to suit the cymbidiums much better , although the heating costs went up rather alarmingly .

[Slug Killer]

Slugkiller, I'm not sure about gas heaters, but I've found that paraffin costing about £6 for 4 litres whether from the internet or a local horticultural trade supplier, was about 1/3 of the cost of running an electric heater to keep the greenhouse frost-free.

Malcolm

Malcolm I don't think its cheap at £6.00 for four litres, just glad my car does not run on paraffin at £1.50 a litre as petrol at £1.25 is bad enough.

Thanks for all the replies. I have now just bought a gas one and I'll see how I go and how long one 19kg bottle lasts me on frost control.

[angie]

Thanks for all the replies. I have now just bought a gas one and I'll see how I go and how long one 19kg bottle lasts me on frost control.

I would find it interesting to see how long your gas bottle will last. When I looked into heating l couldn't make my mind up between electric or gas. I ended up going for electric just because it was easier for me. I try and keep my greenhouse between 3 - 5 degrees and try and not think what it would cost, my only worry is what would happen if I had a power cut.
It's good to hear what others options are.

Angie

[Brian Ellis]

Just spotted this thread and thought the calculator here might be useful?
http://www.jungleseeds.co.uk/HeaterCalculator.htm

[ArnoldT]

Speaking of greenhouse heating.  We're expecting 8F on Friday evening.  I have an electric 'dairy barn' heater which so far has functioned just fine.  This will be the test.  I have a graph of my electric consumption going back ten years.  I should be able to put a number to the cost for heating a 7 by 12 Ft. lean to greenhouse.

[John85]

For those afraid of power cuts:here is what I saw at a commercial nursery.They were tins under the tables with a wick in them .If needed they were filled with methanol.It burned through the night and saved the plants.Please handle with care!
Nobody seems to go for the green option and do his little bit to save the planet.I try.Using a log burner suits only people who are working from home or who are retired  but it gives you a good  excuse for visi ting the greenhouse twice a day.I am building now an improved version of it where the fumes will go through pipes in a large lump of clay.It provides a gentle heat by radiation and reduces the fluctuations in temperature.There is a electric heater in stand- by in case of illness.Next step will be to build a larger furnace that can takes stumps and miscanthus.Free wood!
PS It is a lean-to so it was easy to build the chimney.

[ArnoldT]

Brian:

I ran the numbers on the Greenhouse calculator.  Came up with a number of 5500.  Is this watts per unit time.

Could you explain how this would translate into practical terms.

Thanks,

[Brian Ellis]

Brian:

I ran the numbers on the Greenhouse calculator.  Came up with a number of 5500.  Is this watts per unit time.

Could you explain how this would translate into practical terms.

Thanks,

Arnold, If you look under the products, the heaters are listed with their output.  I am assuming that you would be needing to use heaters of the equivalent wattage to achieve your heating needs at those parameters.  The time element would, of course be variable according to the amount of boosting the glasshouse/tunnel would need according to the severity of the weather.  Hope that helps.

[ArnoldT]

Brian:

Thanks, noticed that i forgot to convert to F degrees.  Requirement was much lower.