Fermentation fridge build

[ericmark]

I do understand what you are saying as to air temp v brew temp however it is the brew temp which is important not the air temperature. So to my mind there are two methods.
1) Have a varying air temperature which starts low and climbs as the brewing goes on to compensate for the heat generated by the brewing.
2) Limit the amount of energy removed or applied so that any move is slow.
With mine the air temperature during heating does not come into the equation as the heating tile has the fermentor sitting on it so all heat transferred by conduction and convection within the brew and at just 18W there is little or no over shoot. Only the cooling goes vie the air. With the cooling there is a lower limit of 5 degs C at which the fridge turns off so the air temperature will be at 5 degrees until the brew becomes cold enough.

So the sin wave diagram is wrong it will have the troughs with a flat base as it reaches 5 degrees and the peaks will not be as steep as the troughs as far less energy is put into heating than into cooling. To reduce the trough there are two methods. 1) reduce the amount of cooling by using a timer so 15 minutes cooling is followed by 45 minutes rest giving more time for the heat to leave the fermentor before cooling air again. The other is to raise the minimum temperature to over 5 degrees.

If we consider 40 pints that is a large mass. calorie is a metric unit so to start with we need to convert 40 pints into grams so 22730.45 grams so to raise or lower the temperature by 0.5 degrees C will need 11365.23 calories to be removed or added. However the Joule is the unit required so divide by 4.2 and we get 2706 Joules. Now by definition a watt is a Joule per second so to raise the brew using 1 watt will take 45 minutes. So using 3 watts will take 15 minutes or using 5 watts it will take 9 minutes. This clearly does not allow for losses as energy either enters or leaves the fridge to the outside so likely we are going to have to use at least a 10W heater which with losses will take around 5 minutes to raise the brew by 0.5 degrees C.

At 10W the raise in temperature is slow so at 1 degree between on and off even when the heater is not in direct contact with the fermentor it will keep the brew at 1.5 degrees of the set temperature. However measure the air temperature and the brew will at the start be more like 5 degrees above the set temperature. Simply because of the energy realised by the brewing.

As I said before heating is easy one can select a 10W bulb and if not hot enough swap it for a 20W bulb so inexpensive and easy to adjust by trial and error. If you don't want the light then 2 x 40 watt bulbs in series will give 10W of heat.

It is the cooling which causes the problem as the motor is either on or off and at 100W it will take 30 seconds to drop the temperature by 0.5 degrees. So a 2 minute burst will drop the temperature by 2 degrees but it will take a lot longer than 2 minutes for that energy to leave the fermentor.

So how to get around the problem. Using something like an Arduino one can program the temperature starting at 5 degrees below what you want and over 5 days gradually increase the temperature to what you want. So you measure air temperature and allow for the difference between air temperature and brew temperature. You could manually adjust moving one degree per day. Or you use a second temperature controller so the air temperature is only allowed to go 5 degrees below the brew temperature before the fridge motor stops. This would stop the over shoot. Or the third option is to have a larger difference between upper and lower limits set.

I have decided not to brew in the summer. I do all brewing in the winter so only need a heater and I can set it and walk away for 2 weeks then bottle. If I find my stocks are not enough then I will buy a second temperature controller and monitor both fermentor and air temperature.

What I can say is with a 18W heater under the fermentor measuring the wall of the fermentor temperature (which from experiment is within 0.5 degrees of centre of brew) the over shoot is at worst 0.1 degrees during the winter months. The sensor is insulated with a sponge from the air temperature.

Using either heat or cooling but not both together and using a sensor on the fermentor is not a problem. Only when one tries to use both is there a problem. So with the set up in question since only cooling is required at this time of year sensor on fermentor will work well with heater unplugged.

With my brews under 19 degrees they nearly stop and by 25 degrees you start to get off tastes allowing 1 degree error centre to fermentor wall then I have 5 degrees to play with so setting a temperature controller at 2 degrees between heating and cooling it's unlikely to cause a problem measuring the fermentor wall. However since my controller will only either heat or cool not both I will need a second controller to allow for the odd hot day.

 

[as13]

I'm seriously contemplating doing a how-to guide on this.

If you use the probe to monitor the temp of the brew (either in the brew or attached to the FV) it will cause the controller to cycle between heat and cool. This is because the fridge has to heat or cool by several degrees to shift the brew by a fraction of a degree. With a 10 litre brew and the stc set to switch at +/- .3 degrees the fridge will vary by +/- 5 degrees and brew will actually vary by +/- 1.5 degrees as it overshoots.

With the probe in the fridge the air temp will vary by +/- .3 and due to the thermal lag of the brew it will only vary by .1 degree.

Below are graphs I posted in an earlier thread :-

Probe monitoring the brew, fridge bouncing between heating and cooling and the brew varying in temp.

Probe in the Fridge, fridge air temp varies a small amount, variation in brew temp barely measurable.

There seems to be some debate ongoing here!

I've bought a fridge, got an STC-1000 and am planning on setting it up in the next few days.

Prior to getting the fridge I was using only the heating side of the STC with the probe on the FV side.

To clarify (to be fair, I think you've made it pretty clear already, but want to make sure I'm not being stupid) your advice, based on your graphs and experience is to have the probe 'floating' in the fridge so as to measure and control air temperature, thus in turn controlling the brew temperature?

Makes sense to me, but there seems to be some disagreement!

 

[Twostage]

There seems to be some debate ongoing here!

I've bought a fridge, got an STC-1000 and am planning on setting it up in the next few days.

Prior to getting the fridge I was using only the heating side of the STC with the probe on the FV side.

To clarify (to be fair, I think you've made it pretty clear already, but want to make sure I'm not being stupid) your advice, based on your graphs and experience is to have the probe 'floating' in the fridge so as to measure and control air temperature, thus in turn controlling the brew temperature?

Makes sense to me, but there seems to be some disagreement!

Yes, Mainly because it wasn't until his last post that Ericmark revealed that he was using a heating mat (at least I think that is what he is saying). With a heating mat you are heating the brew directly therefore your only option is to control it using the probe either in or attached to the FV. Mind you if he's doing that and not using the cooling part to operate the fridge I'm not sure why it's in a fridge at all :hmm:. I'll reply to his last post later as the direct heating means that what he says earlier now makes more sense.

So yes, I use 40watt bulbs (not energy savers) as a heat source, the fridge on max, a pc fan to circulate the air and the probe dangling and it just looks after itself. The only thing to remember is that during the peak of fermentation the brew is its own heat source and can increase the temp of the brew by 2 degrees. So if the target fermentation temp of the yeast is 18-20 then set the stc for 18.

A useful addition is one of those £2.99 digital thermos from fleabay stuck to the side of the FV with the cable fed through the door gap so you can read it without opening the door. They tend to be a bit out temp wise but they are useful for watching the progress of fermentation. When it tells you that the temp is falling you can start increasing the STC temp so that fermentation will complete quicker and more completely.

 

[Twostage]

Thanks for the above, if you get time to write a how to guide, I think it could be super useful for a lot of people.

RE the above, did you find that the fridge/heater cycles on and off more often than having the temp probe attached the FV, as the air heats and cools quicker?

I only mention this as it happened to a friend of mine, that had a FC built, and had the thermometer dangling for the ambient temperature and he found that the ambient temp would fluctuate a lot more quickly. For instance, it would take long for the fridge to be equal to the 20 degrees he set it to, but the brew temp would be less than this initially, and then the temperature would drop within a couple of hours to 19.5 and the heat would kick in. I think the residual heat would continue to heat the ambient temp so it would then kick the fridge in at 20.5 and then it would fall back to 19.5 and so on.

Looking at your graphs one presumes this didn't happen for you? I settled on the thermometer to the FV as it seemed the consensus around the www was that temperature of the brew would remain more consistent and so the fridge/heater wouldn't kick on and off as often.

Re: your friend, having the heating operate every few hours is exactly what you'd want. During that time the brew would have dropped even less so it would receive regular nudges to keep it in the zone. In my example when the air temp has dropped enough for the heating to operate the brew has only dropped .1 degrees.

So the graphs clearly show that the brew temp is far more consistent with the dangling method (varying by a fraction of a degree). With the attached to the side method either the heating or cooling is nearly always on. Looking at the top graph for nearly the whole of the time the temp is above the yellow line the fridge is operating and when it is below the heating is on.

With the dangling method the cycling will depend to some extent on the outside temperature. On a cold day the fridge will never come on, it will heat, cool down, heat. Vice versa on a hot day.

I must admit to scratching my head about all this, on a daily basis we stick stuff in the fridge and know that when we take it out it is going to be fridge temperature. We don't stick probes in our butter. I know that fermentation generates a bit of heat but you just compensate by setting the stc a couple of degrees lower.

 

[Twostage]

@ericmark (didn't want to have a huge quote).

Rather than go through your post responding to various points I thought I'd ask a simple question :-

On Thursday night I had a bottling session and wanted to carbonate them at 19c. So I set the stc to 19 and just left the monitoring probes laid on the fridge shelf. Today the stc and both probes are reading 19 +/- .5 degrees. If I attached one of the probes to one of the bottles what temperature would it show ?

 

[ericmark]

I see your point with mine the fermentor is sitting on an 18W heating tile so heat as direct as I can get it goes into the fermentor not the fridge space. The fridge is a really good insulator so even with garage at 5 degrees C 18W is ample to maintain the temperature at 20 degrees C.

The problem is at the start there is a lot of heat from the brewing so either one needs to measure the brew or allow for the heat it produces. At first I brewed in the kitchen without any auto control and I noticed summer brews were not as good as winter brews yet the stick on thermometer never went above 24 degrees which was within the limits the kit manufacturer set for my brews.

What I realised was the outside of the fermentor may have been within 24 degrees but the centre was exceeding that temperature. Only when I moved to using a fridge with the sensor under a sponge did I realise there was a big difference when the brew starts between the stick on thermometer and the sensor under a sponge. As the brew continues then the two match, but by then I have messed it up using just the stick on thermometer.

With my brews with room at 18 degrees C during day and 16 degrees at night they seemed to go well to start with but then stall. At this point I started using a heater or moved closer to radiator. However when I put it in the fridge at 18 degrees it completely stalled. I had to raise it to 19.5 degrees for it to run well. As time went on I realised it was where I was measuring rather than the temperature which had changed. With sensor under a sponge I was getting closer to the brew temperature than simply strapped to side and since the temperature strip is just stuck on the side of the fermentor during first few days it is reading lower than the brew is actually reaching.

Heating is easy. Just use a small heater so it does not over shoot. Cooling is a problem as it is far more heat being removed per unit time. Personally I just give up brewing in the summer. To my mind one needs two thermostats so the fridge will not go too low, already we have it set at 5 degrees but if that is raised to for a brew held at 19.5 to say 14 degrees it will reduce the hysterias of the wave form you show.

But for me much easier to just brew extra in the winter when no cooling is required.

 

[marinali29]

you need a temperature controller which heating and cooling at the same time?

For an example, you set
target temperature value: 18 degree,
heating differential value: 5 degree
Cooling differential value: 3 degree
When temperature reach 23 degree, the heating plug works, if temperature drop down to 15 degree, the heating plug works. :thumb:

Very neat job well done. I used a grid switch plate so I could snap in two independent sockets to a standard double socket plate. Only then to find got the wrong temperature controller and it will only either heat or cool not do both together. However since using an old fridge/freezer don't really want to have freezer running.

Now you have the hard bit working out the settings. For heat I found 0.1 degrees worked well with little or no overshoot with sensor held to side of fermentor however when I tried cooling I found 0.5 degrees differential required and a 5 minutes delay start or motor would trip out after trying to start before the pressure had dropped and also the sensor needed to be in a pocket or taped to side of fridge not on the fermentor.

Since I could not run both together for me this is not a problem. However running both heater and fridge without them cycling needs some careful setting. I found when holding the sensor under a sponge onto side of fermentor it was within 1 degree of the centre of the brew temperature but when I tried measuring air temperature inside the fridge the difference to centre of fermentor was at start of brewing 5 degrees. But as brew completed this would drop to zero. However setting the temperature 5 degrees low to start with didn't work as brew simply too cold so did not start. Hence why now used elastic band and a sponge with sensor pressed against side of fermentor.

My heater is 18W which in garage is ample even on the coldest night to maintain the temperature. With larger heaters the over shoot is more of a problem. Air heats and cools quickly so maintaining air temperature is not a problem. However the 20 litres of beer takes a lot more heating and cooling.

Two days ago with heaters unplugged for some weeks with just some bottles conditioning sitting in the fridge waiting for me to label before moving to shed the temperature was 19.8 degrees inside the fridge so without using the fridge too warm to start brewing another batch. I was considering making another controller which will heat and cool so I can use the fridge when required. Hence why interested in how you set it up.

 

[ericmark]

you need a temperature controller which heating and cooling at the same time?

For an example, you set
target temperature value: 18 degree,
heating differential value: 5 degree
Cooling differential value: 3 degree
When temperature reach 23 degree, the heating

? think you mean cooling

plug works, if temperature drop down to 15 degree, the heating plug works. :thumb:

Until I got a STC-1000 that was my thoughts. However the STC-1000 has the same slewing range both heating and cooling. So target temperature 18ºC with smallest slewing which is allowed heating will start at 17.7ºC and switch off at 18ºC and fridge will switch on at 18.3ºC. With heating one has the option of using a small heater with a small thermal mass so it is unlikely to over shoot. I found an 8W bulb was enough to maintain temperature at 20ºC with an ambient of 5ºC.

However with cooling there is little one can do about compressor size so monitoring the fermentor likely the fridge will reach 4ºC when it's own built in thermostat will stop it.

There are two options, that's to monitor air temperature and use a circulation fan, or use two controllers so the heating and cooling slewing can be independently set.

With my brewing I am looking for 20ºC in the main I only require heat, only on the odd day will I ever need to cool. So cooling is that infrequent not worried if it over shoots.

With lager not sure if there is really a problem if it over shoots in the same way as proper beer? At 24ºC starting to get off flavours and at 18ºC near enough stalled so only a 6ºC window. I think there is a much larger window with Lager?

 

[marinali29]

ericmark,sorry I do not mean that there's the functions I mentioned with STC-1000(actually it will not do that). Some some temp controller can do. :grin:

Yes,there's compressor delay on STC-1000,which to protect your cooling device. And you can set the value yourself. Usually, the default value is 2 degree C, but you still can change to 0 if as long as you need no delay.

But do all the metioned job can be finished with just 1 temp controller as long as you need it.

? think you mean cooling
Until I got a STC-1000 that was my thoughts. However the STC-1000 has the same slewing range both heating and cooling. So target temperature 18ºC with smallest slewing which is allowed heating will start at 17.7ºC and switch off at 18ºC and fridge will switch on at 18.3ºC. With heating one has the option of using a small heater with a small thermal mass so it is unlikely to over shoot. I found an 8W bulb was enough to maintain temperature at 20ºC with an ambient of 5ºC.

However with cooling there is little one can do about compressor size so monitoring the fermentor likely the fridge will reach 4ºC when it's own built in thermostat will stop it.

There are two options, that's to monitor air temperature and use a circulation fan, or use two controllers so the heating and cooling slewing can be independently set.

With my brewing I am looking for 20ºC in the main I only require heat, only on the odd day will I ever need to cool. So cooling is that infrequent not worried if it over shoots.

With lager not sure if there is really a problem if it over shoots in the same way as proper beer? At 24ºC starting to get off flavours and at 18ºC near enough stalled so only a 6ºC window. I think there is a much larger window with Lager?

 

[Twostage]

However with cooling there is little one can do about compressor size so monitoring the fermentor likely the fridge will reach 4ºC when it's own built in thermostat will stop it.

No it won't. If you set the fridge to its maximum setting it is quite capable of going sub zero. I regularly get my fridge to -2.

See this from previous post on this thread where the fridge gets to -5c:-

[/IMG]

 

[ericmark]

I do see the point that setting the fridge start delay to maximum it can over shoot and return before compressor can start. But in the grand scheme of things 10 minutes is not very long.
There is a list of variables all which can alter the end result.
1) Small heater is going to help.
2) Size of fermentor will alter things, 4.7 litre demijohn will react quicker than 22 litre.
3) How the heat is administered, using my tile which puts heat directly into the fermentor will be different to one which transfers through the air or one placed in a water bath.
4) The design of the fridge some will over shoot more than others.
5) Where air temperature is used size of fan.
6) Settings allowed for controller.
7) Ambient temperature of room.
My point is it's not a fixed result, there will be some who have the skill required to program an Arduino to pulse both heating and cooling giving a near perfect result. But using a simple STC-1000 or any other simple controller which can't slowly reduce energy supplied or removed but simply switches on and off it is a compromise which will vary. What works A1 for one person may not work for another.

As I have said before heating is easy. One can adjust size of heater to suit conditions likely between 5 and 25 watt, but this is easy to vary to suit.

The problem is cooling, The motor has a fixed rate of cooling and is designed to cool to 4ºC the closer to this the unit is set to the better it will work. So it will work better with lager than with a cask ale. What is needed is a method to result the over shoot. I have considered many methods.
1) Limit run time.
2) Second thermostat.
3) Measure air temperature and compensate for difference to fermentor temperature.
The Arduino program would likely use time. We can easy work out energy removed or added to temperature change, for a 40 pint fermentor 15W will alter temperature by 1ºC per hour. OK cooling using a heat pump is a little more efficient, but if set to 1ºC slewing then with a 60W motor needs to run just 15 minutes in an hour, in theory a simple time switch which switches on for 15 minutes every hour should reduce over shoot to a minimum.

However when as an experiment I put an independent sensor in to monitor the air temperature when controlling fermentor temperature I found there was a huge gap between theroy and practice. I am sure others doing the same will get different results as it's all down to the 7 points above which will vary. Each person will need to do their own experiments and decide what is required, there will not be a one size fits all.

For cask ale type I have worked out what temperature I need. Below 18.5ºC my brew stalls, above 22ºC start to get off taste. As to the range with a lager I will not pretend I know. But this is really the big issue. John Palmer states 45-55°F that's around 7 ~ 13ºC however when I tried I found at 13ºC it was completely stalled I need more like 16ºC before anything happened. OK likely I was using wrong yeast, but this is the whole problem until you try one is not sure what is required.

To me the whole idea of temperature control is to be able to avoid what makes a bad beer and to replicate what makes a good beer. If the control is hit and miss then not much point. As far as I am concerned lager is a non starter. To make lager means boiling, to use a kit is a non starter, one simply can't ensure water out of the tap is going to gain alcohol quick enough to ensure wild yeasts will not take over. The whole idea of lager is long shelf life the brewery can produce a steady output and storage caterers for demand changes. This is why large multi nationals do well with lager and the micro brewery excels with cask ales. For home brewing we are super micro brewing with 40 pint batches so to lager beer seems the wrong approach. We can make a lager like ale using standard yeasts with temperatures of 18 ~ 22ºC lager is a process not just a light ale, you can also make dark lagers.

I want a beer which tastes the same every time, is easy to make, and is cheap. Making lager is a skill and labour of love, it's not easy or cheap. To go to all the work required and have a temperature controller which is hit and miss just to me seems a waste of time.

 

[ManseMasher]

I like brewing beer. Most types of beer. Beer is beer. Then you break it down, like money (1p, 2p, £1 coin, £10 note, Krugerrand). If you want to equate this to your brewing, decide which 'money' you want to go for, design/find a recipe that hits it, and voila - there you have it. If you think lager is not for you, don't go there. But please don't focus on easy and cheap, the bar is not very high there, and for an extra couple of quid (literally) you can end up with 'wow' rather than 'meh'. I would love to hit krugerrand, will be happy with a sixpence, and I try not to focus on what the experts tell me, because, after all, this is home brew. My home, my brew, my choice and taste. That is what makes this hobby so unique. We all want the same thing, but the variables are infinite. If my next door neighbour were to start brewing (same water, air, pollutants etc.) and we shared/started the exact same recipe, do you think we would hit exactly the same brew? The same taste every time in home brew is probably achievable, depending on how picky you are, but why worry? Aim for nice beer, not disappointment because it wasn't what you expected....

 

[Twostage]

It really isn't that complicated. The below is a graph of my last brew, the orange line is the fridge temp and the blue is the FV. It uses a STC100 controller using the probe in the fridge. It was an Ordinary Bitter using Gervin GV12. I set the STC1000 to 18. I pitched at a low temp and you can see it catch up and then fermentation kick in. The brew peaks at 'A' at just below 20. As the fermentation slows and the brew temp drops I up the STC to 19 at 'B' which kicks it back into life. It starts to slow down again at 'C' as fermentation and the clean up stage finishes so shortly after (at 'D') I cold crash it. You can judge points A and C by watching the bubbler.

The process is repeatable, works exactly the same for lager (only at lower temps) and things like fan size and ambient temperature are irrelevant - the temperature of my brew shed could be 6, 26 or vary between 6 and 26 and the graph (and fermentation) would have been exactly the same. No Arduinos, no second thermostat, just a fridge with an STC1000 and a light bulb.

 

[ericmark]

No it won't. If you set the fridge to its maximum setting it is quite capable of going sub zero. I regularly get my fridge to -2.

See this from previous post on this thread where the fridge gets to -5c:-

[/IMG]

May be your fridge will go that low, however clearly a fault with the fridge to be able to do that. In the main fridges are set to around 4 ~ 5ºC by the manufacturer. Our new one the user has some options 1ºC to 7ºC with a vacation option which sets it to 15ºC but this is unusual normally you only have hi-med-low with no temperature setting.

This is my whole point however. Fridges, heaters, ambient temperature, fans, will all vary user to user. So each user has to adjust how he uses the set up.

Had some one said to me before I started you only need around 8W of heating that would have been a great help. Clearly you can use a 100W heater but likely it will over shoot. Even my 18W heater will over shoot by 2ºC.

But again how the heat transfers also matters. Air is not a good medium a heat belt will act on the brew far faster than an air heater. Ideal method would be circulating water and I suppose to have a cold water feed and a water bath which the fermentor sits in would work just as well as a fridge although rather a waste of water.

When controlling the temperature of concrete we used water cooled with a refrigeration unit and I would guess that is the commercial method with brewing.

However we are trying to do it on the cheap. I am sure an Arduino can be programmed to do an A1 job but we are using rather a Heath Robinson affair so have to allow for it's failing.

As long as we realise it's Heath Robinson and allow for it then it will work good enough for what we want. When I start a new brew if sitting at 16ºC I know it will over shoot so I set to 18ºC then slowly raise it the last 2ºC to get to 20ºC each time I check it I raise it a little.

I know the centre of fermentor is likely 0.5ºC higher than the fermentor wall even when insulated and 1.5ºC higher when not insulated, I know the air temperature is around 2~4ºC different to brew temperature and as long as I allow for that there is no problem.

Where it goes wrong is where we follow instructions to keep beer at say 20ºC but because of where we are measuring we are actually keeping it at 26ºC it's not the air temperature, or fermentor wall temperature that's important but the actually temperature of the brew.

There is however nothing wrong with setting air temperature to 14ºC and slowly raising to to 18ºC as we know from experience the brew will be at 20ºC with those air temperatures.

Where it all goes wrong is where we tell others we brew at 14ºC when we are actually brewing at 20ºC and only the air temperature is that low.

 

[ericmark]

It really isn't that complicated. The below is a graph of my last brew, the orange line is the fridge temp and the blue is the FV. It uses a STC100 controller using the probe in the fridge. It was an Ordinary Bitter using Gervin GV12. I set the STC1000 to 18. I pitched at a low temp and you can see it catch up and then fermentation kick in. The brew peaks at 'A' at just below 20. As the fermentation slows and the brew temp drops I up the STC to 19 at 'B' which kicks it back into life. It starts to slow down again at 'C' as fermentation and the clean up stage finishes so shortly after (at 'D') I cold crash it. You can judge points A and C by watching the bubbler.

The process is repeatable, works exactly the same for lager (only at lower temps) and things like fan size and ambient temperature are irrelevant - the temperature of my brew shed could be 6, 26 or vary between 6 and 26 and the graph (and fermentation) would have been exactly the same. No Arduinos, no second thermostat, just a fridge with an STC1000 and a light bulb.

I agree with most of what you say. Clearly for you it works and as I said using a small heater like a bulb it will follow the set temperature quite well. But I still feel it depends on where your fridge is, and what you are brewing, and with silly sized heaters of 60W likely it will not do as wanted.

I have not a clue why people ever use such huge heaters but it seems they do.

 

[Twostage]

Couldn't resist doing a myth busters on the 'FV wall temp is different to the brew temp' debate. So with my last brew I calibrated three USB temperature probes against each other (and against a thermapen). I put one in the middle top of the brew itself, one in my usual taped to the side of the FV and one dangling in the fridge. The graph below shows the results. One of the probes had lower resolution than the others so it looks a bit 'steppy' but it did the job. As you can see the FV probe tracked the brew probe to within a fraction of a degree. The biggest difference between the FV temp and air temp (once the brew had reached fermentation temps) was 1.5 degrees at the peak of fermentation.

You can see the fermentation (or at least yeast activity) kicks off every time I ramp the temp by a degree.

By the way you can see when I open the fridge door as the fridge temp does big dips :)

 

[ericmark]

My records are not as accurate as not recorded by computer but were similar. I too found with a simple car wash sponge to insulate the sensor on the fermentor wall the centre of fermentor was very close to wall temperature close enough to ignore.

I also found air and fermentor side temperatures varied and realised much depended on size of heat and position of heater and if a fan circulated the air. But the big difference was outside air temperature. When the garage is cold the over shoot seems very small so set to 18 it may hit 19.5 but when the garage was warmer then it hit 23.5 which was more than I had allowed for.

In winter I really see no problem. It's as summer gets closer that we have to take care not to allow the temperature to over shoot as it then seems to stay high unless fridge is used. And all we need to do is use a small heater and all works A1. I had considered my 18W heater as small but in light of tests that is quite large really half that is big enough even on coldest nights.

 

[ericmark]

Summer is here at last and now I have actually used the refrigeration option. I must apologise the results were not as I had expected. I set the differential to 0.1°C with the MH1210A and starting with both air and fermentor probes the latter connected to the controller, showing same temperature, I started monitoring a new brew.
I expected an over shoot but this happened just once the first time the freezer cut in. After that the fermentor stayed at the temperature set to +0.1°C so 20 or 20.1°C every time I looked, the freezer always showed lower than the fermentor once the fermentation had started and freezer had run. It started at around 2°C lower and slowly reduced to 1°C lower,
I wondered about using the STC-1000 with the 0.3°C minimum differential so day 5 I decided as a test to set the unit 0.3°C less than it was now at and see what it did.
Time – Air – fermentor
12:01 – 16.1°C – 19.3°C
12:05 – 16.5°C – 19.3°C
12:07 – 16.5°C – 19.2/19.3°C flashing
12:10 – 16.9°C – 19.2/19.3°C flashing
12:12 – 17.1°C – 19.3°C steady
12:20 – 17.3°C – 19.3°C steady reset temperature back to 19.9°C test complete
12:40 – 17.8°C – 19.4°C
Now that was not what I expected, I expected a massive over shoot. First two readings near same because seems there is some software in fridge/freezer which resulted in a few seconds burst of running followed by 4 minutes wait before it started to run again. In a frost free freezer compartment of a fridge/freezer so there is a built in circulation fan. The test shows a STC-1000 with 0.3°C differential would work fine, having a single STC-1000 working heat and cool with sensor on the fermentor wall under a sponge for insulation would work fine. No need for two controllers one for heating and one for cooling.

I do see when doing something other than maintaining a temperature there could be a over shoot problem using the sensor on the fermentor when cold crashing one may need to remove sensor from under sponge while it goes down to new temperature. But it will clearly hold a temperature without a problem on the fermentor which means no need to alter temperature set as difference between air and fermentor is not important, all we want is for the fermentor temperature to be correct.

Odd but the fridge temperature did not alter during the test, OK I know that the freezer has built in fan where most fridges don't, but it ran for just 6 minutes dropping air temperature from 18.6°C to 16.1°C with fermentor dropping 0.3°C that is a rapid drop would not expect a stand alone fridge to drop that quickly.

 

[ericmark]

OK hands up I got it wrong. The STC-1000 with sensor on the fermentor once the freezer was used kept the fermentor near enough spot on the 18.5ºC set, I used an 8W bulb as heater. The Air temperature went from 5.8ºC to 22ºC the former when first switching on with 2.5ºC to drop on fermentor with the longest run of 40 minutes. But all my theorising was wrong. On cool it did not over shoot and on heat it did not over shoot. Sorry.

I will point out very small heater just 8W and in a freezer so there is a built in cooling fan has to be frost free with upright as non frost free you would never get the fermentor in the freezer.

 

[Sharky]

I use a bird controller- planning on doing a similar job. With the bird you can put the probe into the brew as if outside on the FV you get ambient temp and also plan to use my Harris heat pad. Bird controller has 13 amp sockets built in for heat and cool bout £35, with a good length of cable and the pribe cable is plenty long enough .