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Roughly how much paraffin do you need to use in your greenhouse heater, on a cold night?

elderberryelderberry Posts: 118
in Problem solving
Mrs Elderberry is convinced that using a tealight will keep the frost off the plants, but I can't see any way that anything that small could make an impact. Seeing as a tealight is also made of paraffin, it's be nice to have the relevant information to be able to settle the discussion.

Posts

  • BraidmanBraidman Posts: 274
    I stopped heating my 10 x 8 some years ago as I could only get paraffin in 4 lts pre packs costing between £9.99 or £11.99 per pack in local GCs, much, much too expensive, it would have been cheaper to let the more tender plants die and re purchase the next season.

    I reckon on cold nights I had two heaters going to keep the frost out, and I used 5 litres on each every 3 nights.

    Hope this helps!

  • BenCottoBenCotto Posts: 4,718
    A tealight will burn for two to three hours. Is Mrs E happy to get up at 2.00 am to light candle 2, and 5.00 am for candle 3? That might win you the argument.

    Of course a bigger candle will do the trick but that will cost more. Have you heard about the terracotta flower pot over the candle refinement? This site is aimed at American preppers so has a whiff of weirdness but you might find it interesting.

    https://www.skilledsurvival.com/clay-pot-candle-heater/

    Some people put heat retaining bricks from scrapped night storage heaters in their greenhouses. I’m not sure what they do with them but Mr Google will.
    Rutland, England
  • Blue OnionBlue Onion Posts: 2,995
    Or large black containers of water?  They retain heat, and water is dense enough to release it slowing through the night.  
    Utah, USA.
  • elderberryelderberry Posts: 118


    I reckon on cold nights I had two heaters going to keep the frost out, and I used 5 litres on each every 3 nights.


    Sorry, are you saying you needed to use 10 litres in 3 nights? Over 3 litres in total per night?
  • elderberryelderberry Posts: 118
    I’d say a cupful a night is about enough for a greenhouse 6’x8’.

    Thanks for the reply. A mere cupful sounds very modest compared to some other replies I've had...what about on really cold nights?

  • elderberryelderberry Posts: 118
    Blue Onion said:
    Or large black containers of water?  They retain heat, and water is dense enough to release it slowing through the night.  

    Yes, that would work well. It's a good idea to keep a water butt inside the greenhouse for this reason: it only warms up to a low temperature, but the volume of heat in that water would be great.
  • elderberryelderberry Posts: 118
    Candles are surprisingly hot.


    The word 'hot' needs scrutiny in this case though. Yes, they reach a high temperature, but they don't actually put out much volume of heat, which is what you need. (full disclosure: I've studied thermodynamics)

    Think of the high temperature that's achieved by the electric spark that lights a gas cooker, it's high enough to ignite gas, but you couldn't warm your hands on it.
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