Need a very small heater with thermostat control

[AquaHydroChem]

OK so the project is beer brewing, and I need to keep the brewing temperature high enough for the yeast to work best
The experts tell me the correct temperature is between 20-22C

The plan is to find a broken fridge out of the scrap yard and use it as an insulation box to hold my 5 gallon brew bucket inside it
Then I plan on putting inside the fridge a very small heater that can by tempratured controlled by a thermostat

Any ideas please?
Thanks

 

[Iggifer]

@ericmark is your man, believe he's a fellow homebrewer

 

[ericmark]

The STC-1000 has been the main device used for this, however there are two new devices the Inkbird which is ready built and forget the name of the other like the STC-1000 but with touch controls and allows different gap between on/off for heating and cooling.

I have found in my attached garage it needs just 5W to maintain the temperature even on the coldest days we got last year, I use an 8W bulb, which is ample in size.

So the heater needs to be small so heat gain is slow so it does not over shoot, it also needs to be a small mass again so it will not over shoot, the sensor needs to be on the fermenter not in free air or contacts will be opening and closing every few minutes plus it's the brew temperature you want correct not the air temperature.

This time of year it will work A1 in a garage or shed, but as the summer comes back without the fridge working you will have a problem. I did so I can't see how you will get away with it.

I will explain, in a room in the house at say 19°C the brew will start well raising maybe to 21°C then slow down and the heat generated by the fermenting goes into the room.

However with a fridge with a STC-1000 set at 18°C with the outside temperature at 17°C the brew will raise to 24°C with the heat from the fermenting as the heat can't escape. As outside temperature of 14°C yes it will work OK but over 14°C it will overshoot. You can open the door of course but then you lose the automatic thing.

Now many people use a simple fish tank heater, that works well. That is the simple method. But it does not cool. You will need to put more or less insulation on the fermenter summer and winter, body warmers work well with the air lock out of the neck, and a 60W it is a bit of over kill but the mass is so small and it heats brew direct. Because it is inside the brew it's heat goes directly into brew not into the fridge.

I used a fridge/freezer, the fridge will never cool, as freezer never gets cool enough for the fridge to get any cooling, so my method is start a brew in the freezer at 20°C for 5 to 10 days, then transfer to fridge wait one day, then transfer into clean fermenter, and in the fridge I use 22°C does not really matter at that stage if it goes to 26°C as this is cleaning stage, so I can have two brews at different stages running together.

The fridge/freezer was condemned the thermal insulation has gone, but works A1 for brewing, at first I tried to use just the fridge, but then found it always would over shoot in first few days which is exactly the time you don't want it to over shoot, my first electronic temperature controller was a MH1210A looks like the STC-1000 but will heat OR cool not heat AND cool, so that now works heater an old under floor demo tile to keep brew warm after the first 5 to 10 days. The STC-1000 runs an 8W bulb and the freezer compartment. I expected the freezer to over shoot, but it does not over shoot even 0.1°C, maybe because it's a frost free freezer so a fan moves the air around?

So the freezer motor runs for such a short time not really worried about it, with a brew at 24°C and set at 19°C it will run for nearly an hour to get the brew down, but after that point it cuts in for 5 minuets every 4 to 5 hours so cost of running is very low. I looked at other ideas to cool the brew, but really not worth the effort of making them. The fridge or in my case freezer is so cheap to run.

So either use a fish tank heater and put coats or body warmers on the brew varying how many according to time of year, or go the whole hog and get a working fridge. With the latter use Inkbird if your not into DIY electrics or STC-1000 if your into a little DIY. (Or new one sorry can't remember the name think E1000)

 

[AquaHydroChem]

OK so at a brief look at your post; are you saying that-
The difference is the variations of temperature in the thermostat heater and the difference in the conductivity of heat transfer between water and air is enough to make the beer to cold and/or too hot?

I have heard about using this fish tank thing before, but I just don't see how it would work. Because you would have to float it at the top of the tank/ brew and as heat rises to the bottom of the brew it will never get warm.
You mentioned on this idea to wrap the brew up with blankets; my idea hear was to use the broken fridge as the insulator/ blankets

 

[slippyr4]

Aren't you overthinking it? I have used a brew belt type heater before and it's just worked.

If you wanted to go up a step you could insulate a cupboard (cheap high line kitchen base for example) with polystyrene and then wire the brew belt in series with a central heating thermostat installed in the cupboard.

 

[ericmark]

Had I not already tried to do the same I would have said yes a broken fridge is fine. However been there and done that and I had problems. I think if I relate what happened to me this will show you the problems. The garage is integral so it has a temperature of zero to 28°C but the latter is short lived caused by sun on the tin door. My idea was the old fridge/freezer would allow me to move my brewing from the kitchen to the garage.

The temperature controller I bought was cheap, however I had made an error the MH1210A was same size as a STC-1000 but it could only heat or cool not heat and cool. i.e. one relay not two. So I built it into a box and plugged in a under floor demo heating tile, 18W this seemed ideal as heating from the bottom.

I tested the sensor, there was just 0.5°C difference between being in the brew and held tight onto side of fermenter under a sponge to insulate it from the air in the fridge. I used an energy meter to see how much power it used. And on the coldest day still average of 5W only so 18W was ample if not over kill.

I found my stick on thermometer was wrong, what I had not considered is to read the stick on it has no insulation so it shows some where between air and fermenter temperature, so I found 18°C was minimum temperature that fermentation would happen, so I would start the brew set at 18°C. In the first 24 hours the temperature would raise to 20°C maybe even 22°C and then drop again, this was with an ambient in garage of around 5°C. This was well within what I wanted and I was satisfied with results.

I found I needed to raise the temperature to around 21°C after first 5 days for the brew to complete within 21 days which I set as time I expected a brew to take. Once the first 5 days were over the brew would keep spot on temperature set.

However as Summer arrived I found 14°C ambient was the highest temperature I could start a brew at, over that and the fermenter would hit 24°C or over which was too hot. I tried to simply open the fridge door, but then it went too cold.

So since the fridge/freezer did work I bought a second controller this time a STC-1000 and set this one up to control the freezer compartment, I used an 8W bulb in the short draw and the fermenter was a tight fit in the lowest full size draw, had to remove air lock as not enough hight. The first day I tested it was really a hot day, the fermenter was at 22°C when it went in and the temperature set at 19.5°C the motor ran for 3/4 hour then stopped, by this point air temperature was 8°C in freezer and I expected it to over shoot, however as soon as the motor stopped the temperature started to raise again and after 1/2 hour motor cut in again for second time. Over the first 10 days the freezer used 0.10 kWh and never over shot, which was a contrast to heating which would regular over shoot.

After 10 days I move the fermenter from freezer to fridge, now in the cleaning stage I want a higher temperature and set at 21°C now the fermenting has nearly finished it will remain at 21°C even when the garage hit 28°C as the average temperature in garage is below 21°C even if it does peak to 28°C.

However the fridge/freezer is old, and will not last for ever, so I looked into other methods, the best seemed to be to use an old washing machine water valve and allow water to circulate when the temperature raises, but not really very good use of water and this summer my domestic water was hitting 18°C so it would need a lot of cooling water.

There are other methods but each one was a lot of messing about, and I quickly came to realise if my fridge/freezer fails, best option is get another fridge.

In the house the area is large, and with an ambient temperature in winter months of 19°C the brew works fine, without any heating or cooling, by June I would stop brewing and restart in September, although this year many got caught out with late hot spell.

So once the first 5 days have gone then the non cooled fridge will work fine, but the first 5 days you are likely to over shoot, so start in the house, then after 48 hours move to an old fridge will work fine. And in winter it will work fine anyway.

Clearly different brews want slightly different temperatures. Coopers will work hotter than most British kits, all down to yeast used, lager will need around 12°C and a fridge is a must.

But brewing does generate heat, so you must cool in first 48 hours and only warm after the first 48 hours, and it is that first 48 hours where the temperature is critical.

Once I got temperature control set up, I wondered how I ever brewed without it, I no longer need to check the s.g. although I do, but every brew is the same, they all take same time, so no longer do I need to monitor progress. Taken all the uncertainty away.

As a P.S. the fish tank heaters sit on the bottom. Never used one, but know many who do.

Be it a body warmer, cupboard, or fridge, you need control, and unless the fish tank heater is used then 95% use the STC-1000, the InkBird itc-308 is ready built and at £28 it is not really worth building your own any more. So if starting again I would get the itc-308 by Inkbird. By time you buy a box, and pair of sockets, the £7 for a STC-1000 soon hits the £28 mark with all the extras, so may as well get a ready built unit.