[barbarella]

I want to use a small thermostatic fan heater in our new greenhouse this winter just to keep it frost free.  We happen to have one already which we don't need indoors - will it be okay to use?   In Hessayon's Greenhouse Expert it says 'Electric Fan Heater - Horticultural Type' - does anyone know what the difference is?

[poultrygeist]

Hi barbarella.

I would imagine it's to do with how waterproof it is. If you drip water onto your indoor one, it will no doubt catch fire and do untold damage.
A horticultural one may well be waterproofed and be more robust. You also need to have safe, legal wiring already installed to your greenhouse.

Rob

[pushrod]

Any electricity supply to a greenhouse should be rcd protected, if it is that should give sufficient protection. As poultrygeist says one that is marketed as horticultural should be more robust and possibly some degree of drip/damp proofing maybe double insulated. I would not use a metal casing one in your greenhouse if it is not a proper supply.

Why you want to keep your greenhouse frost free is a whole different argument - are you trying to help all the pests survive winter 

[tode]

I've found that fan heaters don't seem to last very long, even in the house. Its usually the motor that conks out.

This winter I used an an ordinary convector heater and maintained a minimum of 5 -7 °C (for citrus trees etc).  Worked well.
It may not distribute the heat as well as a fan heater, but I think it must get a reasonable circulation going. (Obviously, the GH musn't be packed full of plants).

One thing to watch out for, is that not all heaters (fan or convector) have a thermostat that covers the 0 -10 ° range. Many only work from about 15°, which means they'll be going full blast until that temp. is attained.
How big is your GH?

[poultrygeist]

Assuming all the rest is in place, you could wire a domestic central heating thermostat in series which would give you a full range of temps.

Obviously all work carried out by a competant person, suitably qualified.

Rob

[yorky]

Slightly off topic, but if you use a fan heater then lining the greenhouse with bubble wrap realy comes into its own. You keep the heat in and you don't need any ventilation because the fan keeps the air moving.

[barbarella]

One thing to watch out for, is that not all heaters (fan or convector) have a thermostat that covers the 0 -10 ° range. Many only work from about 15°, which means they'll be going full blast until that temp. is attained.
How big is your GH?

Many thanks for all your useful replies.  Sorry it took me so long to acknowledge them - I forgot to check the 'notify of replies' box.

GH is 8 x 10ft, cedar, glass on three sides and half timber on one long side. 

I think I will use the fan heater until it conks out anyway, check the temp range when I have hiked it down from the loft,  and add another thermostat if necessary.  At least him indoors will.  He is a qualified electrical engineer which will come in useful 

When the tomatoes and peppers have finished, all that will be left are some late sown French beans, lettuce, some cuttings and some overwintering bits and pieces from hanging baskets.  But after Christmas, the seed sowing will start.  I've got a couple of small electric propagators and two cold frames.  One of them will be open most of the time for my sweet peas.  So I am thinking I will need a frost free environment to bring seedlings on during the spring.

[gillie]

I would try and clear the greenhouse completely, if only for a week, while you fumigate it with a sulphur candle.

I am not convinced about bubble plastic, it must cut down the light an awful lot.

Cheers,

Gillie

[Kristen]

"Sorry it took me so long to acknowledge them - I forgot to check the 'notify of replies' box."

In case it helps:

Profile : then under "Modify Profile" select "Notification and Email" : tick "Turn notifications on when you post or reply to a topic" and that box will be ticked, by default, when you post / reply.