Power needed to heat FVs in cold outbuildings?

[Kev888]

I'm going to be heating a fermentation bucket located in an unheated, uninsulated shed, and I'm intending to heat it directly (rather than heat a fermentation cupboard). Because its off-grid, I'd like to get a sensible real-world idea of the power required.

Has anyone fermented ale/beer over a UK winter in an unheated outbuilding with some type of low power direct heating - such as a heat-pad, heat-belt or aquarium/immersion heater? If so I'd be keen to hear what kind of power was sufficient (or insufficient) for whatever batch size it was (and please mention whether the FV was insulated or not).

Many thanks!
Kev

[gobuchul]

Kev

When you say "off grid" I take it you mean you will have to run an extension lead from your house?

If I was you I would build a brewfridge? it solves so many problems and is the most efficient use of the electrical heater.

Mine is in the garage and the fridge rarely kicks in, as it has a computer fan which seems to draw the cold air in through the drain hole, which gets the temperature down before the fridge kicks in.

The whole set up pulls very little power and could easily be run from an extension lead.

If you don't insulate the FV some how you will be wasting a lot of heat.

[Kev888]

Hi, thanks for the thoughts. Yes, I'll certainly be insulating the FV, should make a huge difference, though I'm moving away from the fridge/cupboard this time - mostly as part of an attempt to reduce the weight and bulk of all the brewing stuff I need.

It will need to work properly off-grid if required (i.e. no mains supply) but there are all sorts of other ways that I could power it (inverters, gas etc) so that needn't be a problem. What I'm really keen to know for the moment is what sort of power is actually needed.

I've done some calculations and will probably do some experiments with some warm water and a fermenting bucket, but it would be useful to hear other people's real-world experience of the heater power they need.

Cheers
Kev

[Fil]

fwiw i had to get a 100w fishtank heater to heat a brew in the garage (23l) via a trub, the whole lot draped over with blankets/insulation wher a 25w one worked fine in the house..

for small 12v heat pads 4-6" sq look for motorcycle grip heaters on ebay,

[BenB]

Well my fermentation chamber stays at 20 degrees even when it's minus temps outside with a pathetic 60w heater. So if you insulated the bucket well it will be less than that I would imagine. Never checked what the duty cycle is of that 60w chamber heater. Rather unscientific but when I listen in via my WiFi camera to my shed I can hear the heater fan (I have a fan behind the heater tube to circulate the air) about 50% of the time. So I reckon on 720w per 24hrs. I was planning on heating my chamber via 12v but that would flatten my battery quite quickly!

[Kev888]

Thanks chaps - starting to get a useful picture

So 25w is not enough for a 25L FV even with blankets and insulation, and 60w is quite sufficient for a whole chamber. The latter backs up my own experience too, though I had no idea at all of its duty cycle or watt-hours so that rough estimate still helps.

Presumably we can say the minimum needed, assuming some insulation, is somewhere between 25w and 60w, then. Which suggests to me that my calculations may be slightly towards the perfect/optimistic side of reality.

Cheers
Kev