Soil warming cable, constructed a bed

[Ruud]

i have dug down to the cable and its only warm really , no where near hot enough to warm the whole bed.

i just dont know whats wrong, its in a unheated greenhouse btw because of the weight.

[Kristen]

I think it is a good sign if it is warm. I doubt it's going to get up to 30C ... it will provide gentle heat under the roots, and I think that is all that is called for. Maybe there is a fault though if you are not getting more heat from it once it has been on, flat out, for a couple of hours? - worth asking the manufacturer perhaps?

[Potstubsdustbins]

On the packet it should give the Wattage of the cable this will give some idea of how effective it is going to be.

Colin

[Ruud]

On the packet it should give the Wattage of the cable this will give some idea of how effective it is going to be.

Colin

75w colin

[teakdesk]

It sounds to be working correctly.

I've had one of these for a few years and over a long period of time they will raise the wet sand temperature about 10 degC above the average air temperature around it. Your greenhouse is probably 5 degC or less so the sand may get to 12 to 15degC which will seem cold to your touch but will help seedlings.

Make sure you insulate everything to stop heat loss underneath and thru the sides. You will need a good cover over the seedlings. Wait 24 hours to see if sand has got warmer.



Mine feels cool to the touch but definitely germinates chillis far quicker than those not on the sand and I stood a cucumber pot on mine all summer and that plant gave more growth and fruit than 3 other plants put together.

[Potstubsdustbins]

If we work on a standard light bulb being 100 watts it then becomes obvious that a 75watt lead has got and awful lot of work to do to raise the temp in a 4ft long bed.

I would think Teakdesk as the answer it going to take some time before you can notice the warmth and of course every time you disturb the bed to investigate it would be like starting over.

If you have a thermometer stick that in for a day otherwise use the back of your hand as this area is more sensitive to heat.

Colin.

[Ruud]

think ill just sell the parts and get a Heating mat

[teakdesk]

What makes you think a heating mat will be any warmer ?

From the ones I have seen they cost around £100 for the same area that you have constructed and have the same wattage so will perform identically.



If you are wanting to put a propagator in an unheated greenhouse and get it to to 30degC in January then I think you will need to get a heater with a power of 400Watts or more.

There are plenty of suitable heaters available. I use a 400W heater in a large 4 foot home-made glass box in my greenhouse and can happily keep temperatures at 20degC - not sure if I could get it to 30degC during the current weather though.

[Ruud]

just brought a 4ft mat for £39 had 10%off and £50 voucher.
now i can use the mat in my house. which i couldnt do with the sand because of the weight.

so if anyone wants a 6M cable and a stat.......

[teakdesk]

Well done - good price!!

As you say it can be used inside, which will give you the high propagation temperatures you want, and can also go into the greenhouse once air temperatures have increased.

Can you use the thermostat with the mat ?

[Ruud]

Well done - good price!!

As you say it can be used inside, which will give you the high propagation temperatures you want, and can also go into the greenhouse once air temperatures have increased.

Can you use the thermostat with the mat ?

it comes already with one so ill probabaly be selling the other one.

Propagator - Heated Propagation Mat - Thompson & Morgan

[rana]

For indoor use I use an electric blanket. Much cheaper than heat mats and heat cables and comes with a variable heat control. Works a treat for seedlings

[Ruud]

For indoor use I use an electric blanket. Much cheaper than heat mats and heat cables and comes with a variable heat control. Works a treat for seedlings

there not waterproof tho and will get dirty quick

[rana]

there not waterproof tho and will get dirty quick

They are not waterproof but it is simple to cover the blanket with some newspaper and a sheet of plastic. The blanket remains clean and dry.

[salilah]

Rana - love that idea!!
Now to persuade OH that the bed is perfectly OK if I put down some plastic first - and to purchase a heated blanket!!
(think the second is easier...)
cheers
S