Topic: ADVICE REQUIRED ON GREENHOUSE HEATING

[Duke Ellington]

Could you give me your opinions on greenhouse heating. I would ideally like to use an electric heater and was thinking of buying one like this~

http://www.alertelectrical.com/Electric-Heating-Fixed/Multi-Purpose-Heaters/4ft-180w-Tubular-IP55-Greenhouse-Heater---Green-HYTH4545G-.asp

I have an 8ft x 6ft greenhouse. Would this be a good heater for a greenhouse of this size. My aim is to keep the greenhouse at a reasonable temperature on cold nights.

Duke

[Tee Gee]

In my opinion Duke its a waste of money its only 180 watt or put another way its the equivalent of a couple of light bulbs.

You would be better investing in a soil warming cable which is about the same wattage and is used to give bottom heat to your plants but not heat the greenhouse.

You need something in the region of 1KW + for this.

Its only an opinion .........lets see what the others have to say!

[tonybloke]

I have recentley aquired a 120 watt 'glen' tubular greenhouse heater. I place a piece of 3" xtratherm board on the floor (aquired from builders skip), and stand the heater on that. certainley keeps a frost at bay.  they are VERY fuel efficient, and if mounted below a bench will act as a heated bench. you can run them from a central heating thermostat. ;)

[tim]

What are you growing, Duke - & when?

I'm with TG for most situations. Heat the smallest area you can. A large propagator type thing or a(covered) heated bench.

Tube heaters - fuel efficient? Without being carpy, little heat=little fuel?

Our 2mX1m mat is 300W, but is temperature controllable to give gentle bottom heat - &, at the same time, some overall warmth. I cover parts that need more warmth. Veg only.

It also has capillary watering.

[tonybloke]

[attachment=1]
the 'xtratherm' board means all heat is deflected upwards, not into the floor ;)

[kt.]

I use a parafin heater lit on cold nights for my 8x6ft greenhouse.  1 gallon lasts 4 - 5 nights and only costs £4.  You can also insulate with bubblewrap for extra warmth so less heat escapes,  meaning less fuel required.

[Duke Ellington]

Thanks for all your replies.:)

*Tim I am really looking to keep my greenhouse frost free during cold nights. At the moment I am not looking to grow anything in the greenhouse during the winter months.

Duke

[Barnowl]

It doesn't appear to have thermostatic control.  So you would have to be around to switch it on and off which I see as a disadvantage.

I use a bio-green Tropic heater on its frost free setting. It may be 1kw (switchable to 2 kw) but only comes on for brief periods as necessary and gives me the option (although I admit I've never used it for this  :) ) to maintain the greenhouse at higher temperatures. The fan also moves the air around which is no bad thing. It is a bit pricey but I think anything with a thermostat will cost more.

A 2m heat mat would take up most of my (8ft x 6ft hexagonal)GH space and be a bit inflexible. I need some cells at at 25+ degC and others at 18degC - not sure if that heat differential is achievable on the same heatmat but Tim and TeeGee may elucidate.  I find it more flexible to have smaller propagators running above the frost free heater.

[Tee Gee]

not sure if that heat differential is achievable on the same heatmat but Tim and TeeGee may elucidate. 

I have a cable rather than a mat but it is the same principle so far as I know and no! you can't vary the heat as such.

Having said that I have had to do a bit of experimenting this year because my themostatic propagator broke down (element I think) so I propagated everything on the hot bed. Like  you Barnowl I liked to use my propagator for high temperatures and the hot bed for lower temperatures.

This is how I conducted my experiment;

High heat; Tray directly on to the hot bed with a propagator cover over it.

Fairly high heat; as above without cover.

Lower heat; I sat the propagating tray on top of an upside down standard tray meaning it was about an inch and a half above the hot bed. I also used a propagator lid or left it off as required.

As you can see in the picture each tray contained 4 sub trays (punnets) and on occasions these were sub divided meaning on occasions I had 12-16 varieties on the go in one tray.

This is feasible when you have a rough idea of germination times i.e. you can propagate plants with similar germination times.

I must say; I was quite happy with the results so I won't be forking out around £70 for a new propagator.

[Barnowl]

Cunning!  :)

[tonybloke]

you can use something like this for automatic operation.http://www.uk-plumbing.com/drayton-invensys-frost-thermostat-rts3-p-1389.html
but , as duke only wants to be able to use a heater  on an as-and-when situation, there's no need. ;)

[chriszog]

Got to agree with the parafin heater, only use it when you need it, not had mine on this month and coldest nighttime temp was 12 have good insulkation throughout.

[Two Choices]

Rather than heat my whole greenhouse I have a100w cable buried in 3 inches of sand. This gives me a heated area 24 inches by 42 inches and the tray is on the bottom of my aluminium staging (with extra support by the way of bricks to stop it sagging in the middle). To start with it is on 24 hours a day and I drape bubble wrap from the top over all four sides and place a piece over the top. This is like a small heated greenhouse within the greenhouse.  If that makes sense!!! The as the weather improves I only have it on at night and I leave the top off during the day and eventually all the time.
As the seeds get transplanted into trays and I need more space I use a cheap Wilko plastic mini  greenhouse which I heat with a thermostatic fan heater on the minimum setting between sunset and sunrise. Again, this is inside my greenhouse.  Main thing is to remember to open it during the day, especially if you go off to work as the seedlings will easily cook on a nice day.
I reckon this is about the cheapest way of starting things early and not risking the frost getting them as I run out of space.
Hope this helps.  :)
Would show you a pic if I knew how to upload them ??? ???