Greenhouse heating

[Cactuscat2]

Hello - I hope someone can help me before the cold weather sets in. I have a 2kw heater in my 6 x 8 greenhouse. This used to be connected to a domestic timer and came on for an hour or so several times a night in very cold weather. This year I invested in a Bio Green thermostat and plugged in the heater with the thermostat set to 7 degrees. Photo shows where I set the heater dials. The last two mornings I saw the temperate had dropped to 3 degrees (separate thermometer). It appears the Bio Green is not telling the heater to come on at all! What am I doing wrong? I hope someone can tell me! Thank you.

[Rayc11]

I use a similar set up to this using a Biogreen temperature controller, in my setup the Biogreen is set to the temperature I want the heater to come on at, the temperature control on the heater is set to maximum. On your setup it looks like the temperature control on the heater is set to a midway position. It's possible the thermostat on the fan heater is cutting in before the Biogreen one, I would suggest you turn the heater 'stat to the max setting and see what happens. I've found from past experience that thermostats on fan heaters can be very inaccurate.

[Tony R]

... and are you sure you have the Biogreen thermostat set to Heating mode H rather than Cooling mode C?

[el48tel]

I'd do the simple test I do every year when the cold weather is forecast for the following week.
I take the bag of frozen peas to the GH and apply it to the thermostat probe. If the heater comes on . If hot air comes out of the unit . I then put my hand on the probe. If the hot air stops and then the fan should eventually stop
Simple and cost-effective test

If you score less than 4 x then you need to check the wiring as in ... connected to heating rather than cooling ... easy mistake to make and correct. And the setting for the rheostat on the heater itself needs to be high enough, as described in post above.

[habanerocat]

I might add that it should be easy enough to test it.
Just increase the setting on the Biogreen until it switches on. You should see the LED turn on, hear the internal relay click and the heater should turn on.
Then move the thermostat in front of the heater and you should see it turn off again when the set temperature in reached.

Edit. Sorry Terry, more or less a double post at the same time.

[el48tel]

An additional thought. Does the output heated air flow close to the thermostat? If so it could confuse the thermostat so it switches before the desired temperature elsewhere is reached.

[el48tel]

I might add that it should be easy enough to test it.
Just increase the setting on the Biogreen until it switches on. You should see the LED turn on, hear the internal relay click and the heater should turn on.
Then move the thermostat in front of the heater and you should see it turn off again when the set temperature in reached.

Edit. Sorry Terry, more or less a double post at the same time.

No problem. We are at least giving similar ideas for tests and where problems might occur.

[Diane]

I agree with Rayc11, the heater temperature dial needs to be set at maximum. I have the same heater with a Biogreen thermostat.

[Cactuscat2]

Thank you all so much! I have done as suggested and turned the heater setting to high. Tomorrow I will do the tests as well, as suggested by several of you lovely experts! Most of my quite small cacti and succulents are in the house now for winter; it's just the bigger ones left in the greenhouse. I will report back . . .

[Stuart]

I've been using six Inkbird external thermostats for quite a few years now, bought them because they were recommended here. The only drawback is that they're limited to 2kw max but otherwise they're superb and the thermostat sensor reaches to where it should be - between the plants - rather than in the heater on the cold floor.

Stuart