Thermostats

[Bill HH]

I wanted to prevent my poly going below 10 deg c using a cheap new 2kw electric fan heater. The thermostat on it seems to have a tolerance of + or _ 20 deg. It is useless. I set it last night to just come on at 12 deg (the temp at the time) and then backed it off to just turn off. This morning my poly thermo read 5.5 deg C. I need a more accurate thermostat that I can plug in to the power and then plug into the heater which could then be set to full power. It seems such a simple wish but hard to find. Any ideas?

[bearded bloke]

Depends how much current your heater draws Bill,this will go to 10 amps & is double insulated ... Honeywell Dial Setting Room Thermostat T6360B1028 ... Potty might have a better option though

[andy_j]

The other thing is Bill....is a 2kw heater man enough to heat a badly insulated greenhouse or poly tunnel to 12 degrees when it's cold outside.

I have the same type of fan heater which kept my 10 x 8 greenhouse at 8 degrees for the past 2 nights despite being on full and being on all the time (got a British Gas energy meter which shows it was running constantly).

Might try a 3kw oil filled radiator with a small 6" clip on fan for circulation tonight

[BertieFox]

Beware of using a cheap room thermostat in a greenhouse where water is being splashed around. It IS very easy to forget something is plugged in or live and you only have to have the single accident for your life and gardening days to be over. Added to which, room thermostats will be lucky to last one season in the humidity and damp, as I know from experience. So it really is a false economy. Buy a proper greenhouse thermostat that is designed for the job. That will last many years and although they are absurdly expensive, at least you will not kill yourself using them!

I agree with the other comments that unless you have a TINY greenhouse, a fan heater will run all night and be lucky to raise the temperature by more than a couple of degrees. The best plan is to create a fully insulated enclosure within the greenhouse and heat that with a tubular heater or something. I used to use straw bales arranged in a square with a polycarbonate sheet over the top, but that was in a larger greenhouse. Think about some kind of plastic tent to cover your precious plants within the greenhouse.

[Kristen]

The thermostat on it seems to have a tolerance of + or _ 20 deg

Sounds more like "intolerance" to me

I think that is the main problem with cheap heaters, the hysteresis on the thermostats is pants If it overheats by 10C you will waste a lot of money on electricity, if it under-heats by 10C your plants will be dead ...

I don't think that central heating thermostats are particularly accurate.

My advice would be to splash out on a high quality [greenhouse] thermostat and plug your cheap heater (or a pair of them) into it. The thermostat will set you back 50-quid, but if you use the heater for "most of the Spring" it is likely to save its cost in a year or two just by running a tight hysteresis. Mine (not the one linked to below) keeps my greenhouse within 0.5C

(Actually looks like they are only 40-quid, unless you want one that can do cooling too)

Heat Mats Warming Cables & Thermostats

I thought these people sold one too, but they only seem to have the cooling one:

Bio Green Thermostat Thermo 2 - The Greenhouse People

Personally I only use a fan heater, it gets the heat into the corners, and when temperature is reached it cuts off immediately. "Radiators" heat up and it takes time for convection to move that heat around. Even if boosted with a fan when the thermostat cuts the power there is considerable stored-heat in the radiator, which then continues to heat the greenhouse, increasing the hysteresis, which costs/wastes money

[Bill HH]

Sounds more like "intolerance" to me

I think that is the main problem with cheap heaters, the hysteresis on the thermostats is pants If it overheats by 10C you will waste a lot of money on electricity, if it under-heats by 10C your plants will be dead ...

I don't think that central heating thermostats are particularly accurate.

My advice would be to splash out on a high quality [greenhouse] thermostat and plug your cheap heater (or a pair of them) into it. The thermostat will set you back 50-quid, but if you use the heater for "most of the Spring" it is likely to save its cost in a year or two just by running a tight hysteresis. Mine (not the one linked to below) keeps my greenhouse within 0.5C

(Actually looks like they are only 40-quid, unless you want one that can do cooling too)

Heat Mats Warming Cables & Thermostats

I thought these people sold one too, but they only seem to have the cooling one:

Bio Green Thermostat Thermo 2 - The Greenhouse People

Personally I only use a fan heater, it gets the heat into the corners, and when temperature is reached it cuts off immediately. "Radiators" heat up and it takes time for convection to move that heat around. Even if boosted with a fan when the thermostat cuts the power there is considerable stored-heat in the radiator, which then continues to heat the greenhouse, increasing the hysteresis, which costs/wastes money

I quite fancy having a "tight hysteresis"

[Bill HH]

Looks like spending again then, how many cucumbers can you buy for £40, sigh, but then we don't do it to save money primarily do we.
Its a very small poly 10x8 ish and I am only asking for maybe a 5 degree rise, in fact any rise is better than none. Thanks for all the suggestions.

[Urban]

I can highly recommend the bio green thermo 2, I'm using one myself really impressed with it so far, seems like it will last for years

I know what you mean about you could buy a lot of cucumbers for the money, but I don't think most of are growing our own because it's cheaper



Sent from my iPad using Grow Your Own Forum mobile app

[Potstubsdustbins]

Bill only one comment.

As others have said don't bother with a central heating type room stat, they wouldn't last ten minutes in the damp environment.

[Kristen]

Looks like spending again then, how many cucumbers can you buy for £40, sigh, but then we don't do it to save money primarily do we.

There's a flaw in your argument mate

You are spending £40 to save £40 on heating cost ... over X years ... thus you "Can't afford not to have it" (c) Me!

[Bill HH]

There's a flaw in your argument mate

You are spending £40 to save £40 on heating cost ... over X years ... thus you "Can't afford not to have it" (c) Me!

That is of course true, but the total sum of things I can't afford not to have, exceeds my income. I will put it off till next year but then get the one you recommend. It is just what I need.

[Bigmallly]

I've often thought of trying this Bill but have never got round to it............

Heat a room using tea candles and clay pots | Peace . Gold . LOVE

[Bill HH]

I've often thought of trying this Bill but have never got round to it............

Heat a room using tea candles and clay pots | Peace . Gold . LOVE

I got round to it, unfortunately it doesn't work. Firstly most T lights burn for three or four hours, so your heating finishes in the small hours just when it is coldest. So I bought 8 hour T lights, Secondly one T light will raise the temperature of a 10x8 poly tunnel by 0.01 degrees, so you need about ten on the go to make any difference. Thirdly if you are lighting ten while you bend down to light one, another one sets fire to your ass and fourthly if like me you place them in bread baking tins your wife hits you over the head with one when she discovers candle wax all over them. Fifthly you neighbour notices the flames and calls the fire brigade. In short I was not to impressed.

[johnjohn]

That is of course true, but the total sum of things I can't afford not to have, exceeds my income. I will put it off till next year but then get the one you recommend. It is just what I need.

How about this one at £18? It recon's a tolerance of +/-1deg C. Free delivery too.
THERMOGAURD PLUG IN DIGITAL HEATING THERMOSTAT | eBay

[Kristen]

I'm sceptical that they will control temperature accurately as heat has to reach inside the cover before it will trigger, and that will be where the socket is (rather than having a remote sensor which can be placed where the plants are).

Doesn't seem to say if it is water resistant - e.g. IPX4 rated

Might be worth a go though