Greenhouse heaters

[Tee Gee]

Hi all hope you had a goog christmas.

I am after some opinions on fan assisted electric greenhouse heaters.

Over christmas I made a check on my 'autoheat' fan heater which has served me well for many years and found that the heating element is not working (fan is) so I am thinking on purchasing another.

Trouble is to replace this model it is going to cost over 150 quid, and I am not prepared to spend that much, particularly when you consider I only use it on the coldest of nights which in the recent past has been well under ten times a growing season.

I have been looking at three potential models and wondered if any of you had any experience with these? they are

Frostshield 2Kw and 3kw models

Bio green 2kw model

And the Tropic Electric 2kw model

I look forward to your replies...Tg

[Tee Gee]

[laurieuk]

I have a Parwin heater that I bought in 1979 still going strong. I did bye a new thermostat for it this last spring. I use it right through the winter as you can set to to just above freezing.It is very economical with the electric having a fan that can be running all,the time or just when heat is required. If the fan runs all the time the fact of the air moving stops odd corners going cold and is more effective that way. I have sat with a thermometer and stop watch to check best settings. You can onlybuy them from Parwin but Google will find them.

[james1]

Tee Gee

Why don`t  you purchase a replacement heating element.
Or dont they stock them anymore...... :)

[Tee Gee]

Thanks to you both for your replies.

Had another go at repairing it this morning and found the trouble.....the thermostat expansion plate was corroded.

Cleaned it and got the heater working so I put it all together again and tried it.

The heater went red hot, then there was a cloud of acrid smoke then the power went off (fuse presumably)

Didn't check didn't want to risk the appliance, I have had two greenhouses burn down in the past with faulty equipment. Once was a gas heater blew a flame back up the supply tube creating a bunsen burner effect and burned the greenhouse down.

The other was the heating element in a propagator that was faulty ( a manufacturing defect) the makers replaced it with better and gave me some compensation and my house insurance covered the rest!

Now back to the heaters;

I have looked in here http://www.garden4less.co.uk/greenhouse-heaters.asp and I am considering the following;

Bio green Montana

Bio Green tropic

but the hotbox elite is similar to what I have been using over many years.

Had a look at the Parwinshttp://www.parwinheatersukltd.co.uk/page/1j0wv/Heaters_Prices.html and they look very good.

I like the RC 01 but I don't know if I can justify the extra expense.

As I said I only use the fan heater as a supplementary heat supply my propagating heat supply is in the form of an 7'-6" x 2'-6" hotbed so I only need the additional heat on exceptionally cold periods when I have seedlings on the go i.e. to keep the air temperature above freezing.

Descisions ? Descisions? what do you think guys?

[laurieuk]

Wow I have just had a look at the Parwin list the prices seem to have gone up slightly.When I bought mine it was £27.30 admitted that was 30 years ago. Several people have bought after seeing mine and no one has been disappointed, the fact of the fan running in dendent of the heat elements does mean it is more economical. I am not connected with the firm/.

[Tee Gee]

When I bought mine it was £27.30

When I bought my hotbox it was just over £30 as I recall so these too have gone up by about 5 times over the years.

I am more or less convinced that I will be going for a 'Parwin' but can't decide on which thermostat to get i.e. the 'electronic' or the capillary.

I have e-mailed Parwin to find the difference.

From what I see the 'electronic' is more accurate so this fact may give me better control over heat output/management then in this way I can justify the more expensive equipment.

The cheaper varieties kick in at +/- 5°C which I consider too high for 'frost protection' then when you add in their accuracy of +/-2°C I could be heating the greenhouse to around 45°F (7°C)when 35°C will do.

Plus the cheaper ones look a bit flimsy.

By the way Laurie! What type of thermostat do you have and where do you locate it relative to the heater?

I plan on putting my heater in the same place as in the picture below and the thermostat near to where my thermometer is situated on the left. or perhaps a similar place on the right side (north) of my greenhouse.

What do you think?

[colt]

Hiya Tee Gee i use one of the fan heaters you can buy at comet and have had no problems have a look here

http://www.comet.co.uk/shopcomet/product/769523/DELONGHI-HVE134-WHITE

Or you could use one of the oil filled heaters, not used one myself but a friend of mine as used one for years with great results have a look at this one

http://www.screwfix.com/prods/84978/Heating-Cooling/Electric-Heating/2000W-Portable-Oil-Filled-Convector-Heater-With-Timer

[laurieuk]

Hi Tee Gee    When I bought my parwin it had a built -in thermostat. The problem with built- in thermostat is that the body of the heater retains heat and so it does not come on when the air temperature drops and you need to set it higher. Last year I bought an electic thermostat which has a good long lead and I have that almost centre of the greenhouse and it works very well. I can controlthe temp. within a few degrees,

[northener]

Argos have a sale on TG might be worth a look.

[Tee Gee]

Hi guys thanks for the replies!

Firstly let me reply to Colt;

The 'Comet' one seems to to have limited control and the oil filled one is too big a unit for the size of my greenhouse.

I have had a look at what Argos have and they are mainly domestic types.

Can I ask you another question Laurie?

Do you use your heater for 'propagation' or just general heating?

Why I ask is; my main source of propagation heat is my 'hotbed' so I don't need a great deal of ambient heat as such around 4°-8°C (40°-45°F) seems to meet my needs.

This heat is required to keep my pricked out seedlings & cuttings ticking along nicely after they come of the hotbed.

Which suggests any of the heaters would do.........what do you think?

Having said that; I am a bit of a control freak and what with the price of electricity these days I want to control this expense as much as I can, and the use of  thermostats is the only way I can see this being kept in check!

The other thing I look at is;  from the cheap to the most expensive they all have one thing in common they all have 1kw,2kw or 3kw ( or a combination of these) heating elements, their differences are mainly in their thermostats!and this seems to be where the 'expense' variations come in, apart from them being made of metal or plastic!

I have thought on buying a £20 model and use the £130 saving to buy electricity, which is one point of view.

Then there is 'reliablility' I could buy one every year for the next 7-8 years and not be any worse off financially!

But back to reliability; I think in terms of the number of plants I have on the go at any one time, last year I grew over 2000 plants so even at 10p a plant I risk losing £200  worth of stock if something goes wrong ( and I know it would cost a lot more than that if I had to buy them)

So do you see my predicament?

I don't necessarily want to invest at my age in expensive equipment but not to, could be equally expensive!

Decisions! Decisions! now what do you think guys?

[tonybloke]

Decisions! Decisions! now what do you think guys?

go with the quality product, reliability has got to be top priority!!

rgds, Tony ;)

[laurieuk]

Hi TG,
I do use my heater solely to heat the greenhouse I have a bed of sand with a 60 watt heating cable for propagating.I have found the parwin to be the most economical heater.You can limit the area in your greenhouse for heating by having plastic sheets as curtains and reduce the amount of air needing heat. I went for the 3 kw model in that it would take less time therefore less electricity to raise the temperature also that with a smaller one if the frost got in all the money spent to that point would be wasted. At the moment with the cold spell I am running a minmum temp of 36  F.

[Vinlander]

Edge of envelope thinking for thrifty/green people:

1) Use water heatsink/s to maintain your entire greenhouse/whatever above 0C - this relies on latent heat and the average recycled galvanised attic coldwater tank will release about 30kWH before it freezes entirely (though in reality only a 5cm layer will freeze before it insulates the rest).

Nevertheless it compares favourably with a 3kw heater on a thermostat all night. Remember that even when the outside temp is below zero, a greenhouse in anything less than deep overcast will be picking up solar energy in daytime to replenish this store.

2) Use your heater in a smaller space (propagator/cloche/mini tunnel) within this (free!) 0C area.

3) Using a heater in soil/sand under your plants makes sense - the roots are often the first to go.
    BUT why use air heating when you can get the same amount of heat from compact fluorescent lightbulbs (CFLs) - cheaper to install than heaters per watt and then provide all that plant-friendly light for free. The only problem is getting them on a thermostat, and even if you can find an electrician to do this you might still need to switch to a normal heater after 11pm if your neighbours object to annoyingly intermittent light pollution...

3) Have a small water heatsink inside this inner sanctum too - just in case the heater fails - CFLs are more reliable than heating elements but latent heat never fails.

It works!

[Tee Gee]

Thanks for that info Vinlander.

Indirectly I do this i.e. from close of season to start of a new season.

But not using as 'techie' methods as you suggest.

I never heat my greenhouse until about the beginning of January and only heat the air when new growth emerges.

Prior to that my greenhouse is lined, my watering cans are full and my plants are virtually bone dry.

By means of a 'soil thermometer' I know my plants (roots) are generally a few degrees warmer than the ambient temperature meaning they are relatively safe even if the air temp drops below freezing.

My hot bed with overhead lighting( which is on a timer not to upset the neighbours) works well for me.

It is after I have pricked my plants out that I need the increase in air temperature and this is why I have been in a quandry about the type of heater I want, rather than its heat capacity.

So to me reliability and control are my main criteria not the total heat as such.

I finally made a decision yesterday and have gone for the 3 kw Parwin PE 1 as shown here.http://www.parwinheatersukltd.co.uk/page/1j0wv/Heaters_Prices.html

But would you believe it? they are out of thermostats!! so I am going to have to wait until they take delivery of some.

I respect businesses not carrying a lot of stock to help with their cash flow, but to be completely out of the component that makes their equipment 'tick' is a bit rediculous :'(

[laurieuk]

I hope you will find the parwin good when you get it ,I am surprised with them not having thermostats. I know thefirm changed hands some years ago but once about 20 years ago mine was not running well and when I phoned they sent my by return free of charge a washer to fit , which is still going to this day.

[Vinlander]

That's an expensive bit of kit!

It's probably a good solution though - I tried several cheap greenhouse heaters in my conservatory (there's no space for a water heatsink) and they each failed within 18 months from broken element wires (metal fatigue - not burnt out).

The reason was that I left them on in summer - they shook the elements to pieces and turned out to be a very expensive solution.

Since then I installed a cheap ceiling fan for ventilation and use it all year round to keep down fungal problems.

In winter I use an even cheaper fan heater that only comes on when it goes below 0C.

No more problems...

[Chatteris]

Hi I bought  a Bio Green heater. Its ace but not sure about heating  yet as i have it set at 3 which means grenhouse is 7 degrees at night. It heats te greenhouse well and I bump it up when I am in it and it heats very quickly.

Sue