Cheap heating

Ive just come accross this..
http://www.dailymail.co.uk/sciencet...-TEALIGHTS-FLOWERPOTS--costs-just-8p-day.html
Has anyone tried and tested the method with good results? i cant afford to heat the GH so this looks an ideal way Thanks x

 

This was on FB - definitely worth a try.

 

It's a good idea, but I don't think it will work in the greenhouse, the coldest time is overnight when you need heat most. I think he said the candles burn for up to four hours Joolz and that means getting up to replace them during the night.

 

Maybe church candles could be used.....some burn for 150 hours. I've seen them for sale on Amazon.

ETA....just seen some short fat church candles which burn for 50 hours!

 

Complete waste of time IMHO, although it has long been used as a method.

A Tea-light is 20 watts ... it takes 100 watts to raise a 10' x 8' greenhouse by 1C (rough figures).

For journalists that advocate using tea-lights I'd love to ask what their plan is for when it is -10C outside? That would need 50 Tea-lights burning in a 10' x 8' - not very practical! and that would be 4 quid, probably about the same as the bottled gas / paraffin you'd use.

My choices for Greenhouse heating would be:

1. Extension of house central heating - this is the cheapest heat source.

2. Electric fan heater plus spend £50 on a very accurate thermostat (otherwise you will waste more than £50 per annum using the cheap thermostat in the heater which will probably have a 10C hysteresis). Snag is the cost of getting electricity to the greenhouse if it is far from the house ... like on an allotment for example!!

3. Bottled Gas - thermostatically controlled, but the thermostat is crude [bi-metallic strip or somesuch] so again a poor/wide hysteresis. I have one as a backup for power cuts.

4. Paraffin - no thermostat (on cheap greenhouse style heaters) so light it on nights you think will be cold and then pay for heating even when not cold enough. Risk that the wick burns unevenly out and blackens the whole greenhouse. This is the most expensive.

0. But above all insulate the greenhouse. Bubblewrap will reduce heat requirement by nearly half. Insulating the North (no sun that end ) wall with proper house-insulation will help a lot too. Try to increase the thermal mass - to "store" heat from day that can be radiated at night.

 

How many people will burn there hand lifting of the pots? if it get's that hot

 

I totally agree with Kristen.

For a frost free greenhouse, I would suggest that electricity is the most practical way because, if its controlled by a thermostat, it only turns on when its needed. And that could be as little as one hour in a mild week. Obviously more in cold weather.

In the past, I set up a 1 kw heater run off an external thermostat to heat a 10' by 8' summer house, where I overwintered plants. I also ran it through an energy monitoring device. In the first winter the cost was just £3. The highest cost was £30 in the very cold winter a couple of years ago. That year the external thermostat failed and I had to use the higher hysterises internal thermostat in the heater (as Kristen mentioned), which will have caused some of the increase.

Electricity is expensive, but it is so easy to control and you use so little to maintain frost free, that I suspect that it is the best method. However if you want higher temperatures needing a lot more energy, I suspect that a Propane heater with a thermostat would work out best.

My gut feeling, and I saw some supporting evidence recently, is that you heating cost doubles for every 2 or possibly 3 degrees that you maintain.

 

could you explain how external thermostat turns the fan heater off? Also where could I buy one and what is it called. I have a fan heater but have never used an external thermostat, didn't know about it until I read this thread, helping to save money is always welcome.

 

External thermostats have a plug, which you plug into the electricity, and a socket - and you just plug your fan heater into that. You will need to turn the heat on your fan heater up to maximum, so that it will come on when the thermostat asks for it, and then the new thermostat controls the heater rather than its cheap internal & inaccurate thermostat.

Only downside is that you do need to buy an accurate external thermostat (or more correctly one with a very small hysteresis [the difference between the temperature when it switches on, to the one where it switches off]), the one that I have keeps the temperature to less than a degree Min to Max, and they tend to work out at around £50.

I reckon you could easily save that in a year - particularly a year like this one where temperatures have been very mild, as it would be easy for a less accurate thermostat to keep the heat on for longer, each time it came on, than absolutely necessary. On a really cold night the heat will be on pretty much flat out, whatever thermostat you have ... but of course we get plenty of borderline nights, and that is where I think electric heaters and good thermostats win - even though the cost of electricity may be more, per unit, than other fuels.

I favour the digit type, as you can "dial in" the temperature you want like this one:


£40 http://www.jungleseeds.co.uk/contents/en-uk/d106.html

(That is a good price, they are normally nearer to £50)

but there are also capillary ones like this:

£60 http://www.greenhousewarehouse.com/pre-wired-electronic-thermostat.html

but they have a "1-to-10" type dial, so you will have to sit in the greenhouse waiting for it to get to the exact temperature and adjust it to come on at that temperature which is a bit of a faff ... I have one like that on one of my heaters and it does indeed control the heater very accurately, but I find it controls it to slightly different temperatures on different nights - although it then keeps it within a degree or so. I'd prefer to set a specific temperature using a digital thermostat and then forget about having to adjust it

Make sure it will cope with the capacity of your heater - most fan heaters are 2kW - 3kW, but there are plenty of the cheaper thermostats can only control up to 750W (1kW = 1,000W)

 

What you need is two greenhouses side by side with a cheap-and-nasty heater in one of them ... and letting us know the difference