Bought a new heater

I pondered long and hard over what to buy, fuel wise, but eventually chose electric.
It will need a cable from a nearby shed, now installed, and the 2kw fan heater has its own thermostat. How accurate we shall see.
Paraffin is the stinky option and since few places stock it it's also expensive. I did consider experimenting with 23sec boiler oil. Got a 1250 L tank of that for C/H.
I cook with Calor Gas and have 4 x 47kg cylinders so this almost won, but the 1.5kg heater I looked at had just the one setting so lacked controllability. The next model up was 3kw so too much for my 8 x 6.
Electric it is then, and came with a free thermometer. At £45 it was the cheapest, and has 1 and 2kw settings. Arrives Monday so plug and play Monday evening. Time will tell.

Paul G

 

I bought one, looks the same but a different name on it, works well, but mine at one stage (After one year) the fan cut out and the heating elements just got hotter and didn't cut out, so keep an eye no it, i took mine a part but couldn't find any problems but after putting it all back together it has worked fine (may be a bad earth) but i will not leave it alone, it may have been just mine but i thought i would just say

 

Doesn't yours have a thermal cut out @Jiffy.

I've got a couple of similar heaters to that @BFOSP ,you may find that the in built thermostat doesn't give a very even temperature, if that turns out to be the case you could get a more sensitive thermostat that also saves a bit of energy and money.

 

I bought the heater from The Greenhouse People and this is a cut & paste from the blurb.

Paul G

" New 2019 Model with external, more accurate thermostat probe. Now also comes with temperatures listed on dial* "

 

Have you tried heat mats, not the over priced Harrod Horticulture, or cheap Chinese ones on ebay/Amazon, or a DIY version, below is a link if you wish to give it a go, 4.5m with wireless thermostat is £145, wire the mats to a 3 pin plug, and roll out on bench, cover with Baco foil, then with a good quality polythene, like cut compost bags, then a layer or irrigation matting, plug in, set the temp from the living room. I wish I had known this last year, as I bought 2 new professional Horti mats from hotbox which combined cover a space 4x30m with a thermastate on each, cost just under £2K, and its basic components are the same, except mine were already covered in a metallic cover, great for seeds, cuttings, and over wintering my Bourgainvillea, Pandorea, even Coleus.

Mesh Mat Electric Underfloor Heating | Heating Under Tiles | Purely Electrique |

 

Yes it does, the swicht on the right works but it's not very accurate, it also has a knock over swicht in side, but the fan stop working and the heat elements didn't swicht off, but that mite be i seen it quickly and swichted off at the wall, but it just a bit of a warning that things can go wrong, if i didn't see the fan stop working and left it what would have happern if the thermal cut out didn't work as well, i may have been lucky

 

@Cuttings
Haven't tried anything yet as I only bought my greenhouse (second hand) before Christmas.

I have been warned that in the event of my seeds germinating the weather dollies delight in telling you at 6pm that there's going to be a frost tonight.

I don't intend to try to sow seed too early but just grow what I can when I can.
Maybe next year with a little experience gained will be another story.

Paul G

 

Was supposed to arrive Monday but was on the front doorstep at 6pm last night.
A sharp frost over the greenhouse at the moment so might go out and test.

Now where's my teeshirt and shorts?

Paul G

 

I did a test Sunday morning.
It was -2 outside and +1 inside the greenhouse. Roof covered in frost. 8 am.

I set the thermostat to 15deg C, switched on and left.

2 hrs later frost cleared from the roof. Heater was off, and the temperature inside was 10.1deg C
on the max/min thermometer on both the "what it was then" and the "max it had been."

I think I need another experiment when I set it up on an evening when frost is forecast later in the night.

Paul G

 

Hi @BFOSP,

Bit surpised that you had set the thermostat to 15c , thats going to cost you a lot in electricity!

You do not mention the size of your greenhouse or the temp you need for your plants ? but we set ours at 4c which will allow most plants to survive over winter, using cheaper to run smaller heated propagators for seeds and cuttings.
We run our heater from a power meter so can check what its costing each week during the worst weather.

To get the best from your heater at any temp, you ideally need an electronic thermostat which are much more accurate than the several degrees C change than a typical mechanical stat in such heaters. Some such devices even come with wifi so you can monitor the temp from indoors.

You can buy electronic ones like the Inkbird range, but like anything electrical it must be suitable for the greenhouse and correctly installed for safety.

Do you have insulation in your greenhouse ?v it can make a big difference.

 

@ricky101 I think he mentioned a 4x8 greenhouse. Interesting size.

 

I've got the exact same model, in a 12' x 6' non-insulated greenhouse, been testing it over the last 2 months. The thermostat probe is fixed on the back of the unit, so the unit doesn't stay on for very long because as soon as the back of the unit gets warm from the heating element the thermostat trips it off. So don't pay much heed to the temperatures on the thermostat, just fiddle around until you find the right setting.
I've been setting mine on the 1KW setting at around 15 degrees (not because I want my greenhouse to be 15 degrees) and I'm finding it's been generally keeping the greenhouse about 5 degrees above the outside temperature at nighttime when outside lows are in the range of -3 to +5. Above that range (at night) the temperature uplift is less. Below -3 we just haven't had this year yet. For daytime it's harder to say what the heater's doing (because whenever the sun shines the greenhouse is naturally warmer anyway) but at least on cold overcast/rainy days I can say it's keeping the greenhouse a few degrees warmer.
Finally it's worth understanding how the temperature varies in different parts of the greenhouse (regardless of sun vs shade - I'm talking about nighttime lows here, to ignore the effect of sun). I've placed max-min thermometers in 4 different positions and there's about 3 degrees difference at night between the coolest spot (on the ground right next to the glass off to the side) and the warmest spot (table-top level at the opposite end to the fan, but away from the glass). I've checked the thermometers read the same when they're in the same spot. The fan is on the ground in the middle of one end, directly opposite the door and blowing towards the door. I never checked the temperature in the direct line of the fan, as I wouldn't place plants there anyway.

Hope this helps!! Obviously in a smaller greenhouse it should have a much bigger effect

 

Me Bad. That was supposed to read 6'x8'. Sorry.

Paul G

 

If the heater is on the floor where it's coldest , and its thermostat is attached to the rear (rather than being on the end of a cable placed say at staging level), then setting it at 15 Deg C should produce a temperature 2 or 3 Deg C higher at staging level, and another 2 or 3 Deg C more at high level (I have both staging, high level slatted shelving plus put plants on the floor overnight when hardening off outside during the day).

So it's odd that your heater set at 15 Deg C only registers 10 Deg C elsewhere on a thermometer. I had expected to discover it was underpowered, but that's now clearly not the case.

My 2 kW heater has 1kW and 2kW settings, is your's on 2kW?


P.S. You haven't got it directed at some window(s) fitted with auotovents by any chance, so they warm up and let the heat straight out?

 

My greenhouse is an 8x6, bought second hand in December so as yet has nothing inside it.
It runs east-west (door faces east) so I like the idea of insulating the side facing north with some bubble wrap that I have as this is the place that the sun never shines; if you pardon the expression. This is where the bench is.

AdrianBg mentions that the thermo probe is on the back of the heater so I'm temped to add perhaps a layer of insulation between the probe and the heater body, maybe 3mm cork.

Paul G