Redrose wrote:

Hello, at the moment I am heating my greenhouse by a 3 kw Electric heater. but
the electric bill is getting rather large!

I am thinking of switching to a Propane Gas heater of 2 - 3 kw, has anybody any
thoughts about this?


electric is the most expensive of all options. If you use electric
ensure its on an rcd, or for a permanent install, an rcbo for each
circuit. Electrics in greenhouses are different to electrics in the
house, and leakages due to water, damp, bugs and dirt are to be
expected. Use toughened glass bulbs (eg PAR38), enclosed fittings, or
preferably fl/cfl. GLS and halogen bulbs are liable to shatter.

Bottled gas works well and is pretty safe. With 2 cylinders and a
changeover valve you can ensure it doesnt freeze now and then and you
dont waste gas.

Paraffin is the cheapest, but isnt really safe. CO ouput is something
they do unless you keep a proper eye on them at all times, a wick that
isnt kept trimmed and shaped will produce CO. They can get knocked
over. Nearly all are spill proof but if you screwed the cap on askew it
wont be, and there are heaters that arent spill proof. Daytime
ventilation before entering the greenhouse is good practice with
paraffin. When these heaters were used in houses, deaths occurred.

The 2 other options are solar thermal and insulation. A layer of
polythene of bubble wrap will reduce heat loss day and night, and an
external sheet of silvered mylar can reflect more heat and light in
during the day. Raising daytime temp increases the night time minimum,
more so if youve got insulation.

Directing central heating boiler exhaust into the greenhouse is an
effective option rarely used, and is as safe as portable gas heating.
Might not be very effective if youve got a 95% efficient boiler though.

Controlled house ventilation with the exhaust to the greenhouse is one
last option.


NT