Fermentation fridge build

Finally got around to doing this today. Pleased with the results and the fact it works; looks forward to a brew day tomorrow!!

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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.

Will that glass shelf support a full fv? I assumed not so I'm going to build a wooden support for mine.

Looks like a great job done there (How much imput did the dog have he looks well tired ):rofl:

The dog was vital at keeping any potential threats away from the garden, you know like flies, a moth, people walking passed...

I still need to work out the best differential etc. going to give it a try today.

The glass plate is reinforced glass, I've had a full fv sat on it for 3 weeks without any problems or any signs of problems.

Bit unsure on the delay, can I have this a different delay for heat and cool?

The instructions for my controller are here http://gw7mgw.freeiz.com/Temperature-controller.html it says 0 ~ 10 minutes on mine the time is to allow the pressure to drop before the motor tries to start again so only really required for cooling.

With mine I started with a low temperature 17 degs C and found the yeast simply would not start so after some experiments I found 19 degs C was the lowest setting I could really start at. However remember the sensor was pressed against the fermentor not in free air. Before having the fridge I did it in kitchen and so had some temperature strips stuck on the side of the fermentor. When the fermentation is complete the strip and the controller match. However when starting the strip can show a couple of degrees lower than the controller I will guess because the sensor is insulated with a sponge so showing brew temperature but the strip is not insulated so showing some where between air temperature and brew temperature.

When I realised this it explained why it seemed the brews were happy at 17 degs in the kitchen they were not really at 17 degs only the outer casing of the fermentor was that cold.

For winter it worked great set at 19 degs and forget about it for a week or two. But in summer really need the cooling and the fridge/freezer is far too big if I sense on the fermentor side the fridge goes to 4 degs well before the brew has started to cool. Since I don't have both cool and heat at same time that means brew stops as it gets too cold and really I want to stop fridge when it reaches something like 12 degs not 4. Our new freezer will do that by selecting holiday mode but have a little problem with my wife she will not let me use it.

So for me it's another controller. This time the right one which will heat and cool. Hence why I am watching to see how you get on.

One thing I have considered is I have a spare plug in timer. I considered setting 15 mins on then 45 mins off so the motor will run for just 15 mins then allow some time for the brew to cool. But I would have to sit there watching the temperature to see how it worked.

Popped a brew in tonight.

Doing a quick kit to see how this works out, didn't want to do a full AG day only for the build to malfunction somehow.

Added some saaz to it and fermenting with saflager s23. Set the temp at 14 degs on the stc 1000, and currently bringing it down from 15.3 degs.

Attached the thermometer to the side of the FV with some bubble wrap and a sponge; hope that works.

So I'll see how this goes. Gonna check on it later tonight and then forget about it until Thursday Friday and see how it's getting on!

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Checked tonight and fermentation is underway, fridge keeping a stead 13.5

Ericmark,

I can't figure out why you'd want to heat and cool at the same time.

I'm not a fan of trying to control the brew temperature by sticking the probe to the FV. It just causes the fridge and heater to constantly cycle as they are heating/cooling the air in the fridge not the contents of the FV. By the time the FV has dropped to the right temp the air temp is about 5 degrees cooler and it continues to chill, goes too low and the heater switches on. That stays on until the FV has reached its temp but by that time the fridge is 5 degrees hotter than that. The FV continues to heat up and the fridge has to cut in again.

It's far simpler to just have the probe in the fridge, thats how fridges work - if your fridge is at 5 degrees then so will your milk and cheese. But take into account that during rapid fermentation the brew will be about 2 degrees above the fridge temp and thats it.

If you put the probe dangling in the fridge it will chill when the outside temp is higher and heat when it is cooler. No bouncing.

I've placed another thermometer in the fridge, and the ambient temperature of the fridge is 11.6 degrees right now, but the beer is 14.3 degrees. The heater and fridge only come on when the beer reaches either 13.4 or 14.6 respectively.

If, for example, fermentation is coming to an end and I want to increase the temperature to get a better attenuation I cannot simply increase the ambient temperature of the fridge to say 16 degrees as the temperature of the beer will be lower than this. It takes a lot more to heat up 5 gallons of beer, the same to cool it also.

the_city_of_homebrew said:

I've placed another thermometer in the fridge, and the ambient temperature of the fridge is 11.6 degrees right now, but the beer is 14.3 degrees. The heater and fridge only come on when the beer reaches either 13.4 or 14.6 respectively.

If, for example, fermentation is coming to an end and I want to increase the temperature to get a better attenuation I cannot simply increase the ambient temperature of the fridge to say 16 degrees as the temperature of the beer will be lower than this. It takes a lot more to heat up 5 gallons of beer, the same to cool it also.

Click to expand...

Have you calibrated the stc against the thermometer ? If not then that could explain the relatively high difference between them. Just detach the probe from the FV and stick it next to the thermometer and leave it for a while. Then adjust the stc to match.

Yes you can just adjust the ambient temperature. Obviously the beer will take longer than the air in the fridge to change but it will get there (it has to). The time it takes depends on the volume of beer and the amount you are changing the temperature. Increasing by two or three degrees with a 25 litre brew will take a couple of hours. I do this all the time to both increase the temp when fermentation has slowed and to cold crash. In fact I'm cold crashing some lager right now. I changed the STC from 19 down to 0 earlier tonight and i expect it will get there sometime during tomorrow.

For some of my brews I monitor the temperature of both the air in the FV and the FV itself using a tempr2 probe attached to a laptop. That way I can see when the vigorous stage of fermentation is over and start to increase the temp to help the yeast. I can post some nice graphs if you want.

Hope this helps.

Thanks for that, very informative; if you have any graphs that'd be great. Good idea RE the dual thermometer.

I have calibrated the stc-1000 and adjusted F4 to match this. In fact I did it three times! Ha-ha.

I think the idea behind taping the thermometer to the FV instead of having it dangling in the fridge for the ambient, at least for me, was to ensure that I was getting the temp of the beer itself and not vice versa. If the fridge temp gets to, say, 13.4 degrees, the beer may be at the required 14 degrees but the heat would kick in and I was worried this may impact the beer. As we know it takes the FV a lot longer to heat and cool down that the ambient in the fridge so I'd rather know k have the right temp of the beer itself rather than worry about the fridge temp. However this is obviously the first time I'm using my new toy so I'll see how it goes.

Checked on it last night and fermentation is well underway [emoji3]

Temperature chart of the current lager brew :-



I haven't calibrated the two sensors against each other for a while so they are a bit adrift. Anyway, purple line is the air in the fridge temp and yellow is FV. You can see at the start that the FV temp and air temp were the same until fermentation kicked in and the FV got warmer than the air. I then started to ramp the temp up and you can maybe see there are occasional blips where the FV temp went above air as the yeast burst into activity. You can also see the air temp drop when I left the door open to take some carbonating bottles out. Then last night I set the temp to 0c and disconnected the bulbs that provide heat. The fridge went sub-zero and the FV was at 6c by 8am this morning and was around 2c when I screen grabbed the graph.

At those temperatures at this time of year you can disconnect the heater it's not required. Measuring on the fermentor side means air temperature will drop to 5 degrees C until brew has reached required temperature but there is so much mass in the brew it will quickly warm up the fridge again once the motor switches off. The brew temperature may dip below required temperature but not for long. As long as no heater is connected then it will settle down to correct temperature.

Heating is far easier as unlike the fridge motor you have control of the size of heater. So using a small heater in my case just 18W it does not over shoot as much. I found on heating measuring air temperature and brew temperature about 3 degrees difference at start of brewing but measure side of fermentor to centre of brew was just 0.5 degrees so on the side of the fermentor is clearly best option.

I am not brewing lager but bitter so for me looking at 19 degrees and this time of year this is a problem. From 12 to 5 degrees is not so bad but from 19 to 5 once the fridge has cooled it enough then that 14 degrees means it gets too cold so for me I need some more control. What I intend is to buy a second controller so one will limit the lower point to around 16 degrees rather than the simple 5 degrees pre-set of the fridge.

[At those temperatures at this time of year you can disconnect the heater it's not required.]

Depends what you are brewing and where you are in the process. Round here the night time temperatures are still dipping quite low (especially in my brew shed). At ramp up and carbonation I'm looking for 20+ so I need the heating.

[Measuring on the fermentor side means air temperature will drop to 5 degrees C until brew has reached required temperature but there is so much mass in the brew it will quickly warm up the fridge again once the motor switches off. The brew temperature may dip below required temperature but not for long. As long as no heater is connected then it will settle down to correct temperature.]

Sorry, took a while for me to get the 5 degree bit. Yes, a fridge set to 'normal' 4 or 5 on the dial will set it to around 5 degrees. But when you control it using an STC you whack it up to max (7 on mine). That way you have complete control of the temperature down to its physical minimum (below zero on mine).

Yes, during a cold crash the FV will act as a brake on the cooling (as does the air surrounding the fridge on warm days) but it will get pulled to the target temperature. This is true whether the probe is attached to the FV or free floating. If the probe is attached to the FV you will get the overshoot you mention as when the FV gets to target the fridge will be below that target and drag it further. As you say with the heater disconnected it will drift back up.

There are two major differences here between the stick on the side and leave it floating in the fridge methods. The stick it on the side will chill the FV faster as the fridge will stay on until the FV is at the desired temp and then the FV will overshoot below. The floating method will chill the FV slower as it gradually gets to the air temp and not overshoot. Either will work depending on what you are trying to achieve.

[Heating is far easier as unlike the fridge motor you have control of the size of heater. So using a small heater in my case just 18W it does not over shoot as much. I found on heating measuring air temperature and brew temperature about 3 degrees difference at start of brewing but measure side of ferPmentor to centre of brew was just 0.5 degrees so on the side of the fermentor is clearly best option. ]

Before fermentation kicks off the FV and fridge will be the same temp (clearly visible on my graph). Once it starts the FV will get around 2 degrees higher than air temp and then cool again once it dies down. I use this effect to monitor progress of the fermentation. I set the controller to the lower end of the desired temp range and let it get on with it. When the FV is back to ambient I start to ramp up the temp a few degrees to accelerate the final stages of fermentation.

[I am not brewing lager but bitter so for me looking at 19 degrees and this time of year this is a problem. From 12 to 5 degrees is not so bad but from 19 to 5 once the fridge has cooled it enough then that 14 degrees means it gets too cold so for me I need some more control. What I intend is to buy a second controller so one will limit the lower point to around 16 degrees rather than the simple 5 degrees pre-set of the fridge.]

I do beer too. Are you saying that when you chill from 19 to 5 the FV overshoots a lot or you are actually aiming for 16 ? If you set the fridge on max (which you should) then the temperature is entirely controlled by the STC. If you want the FV to be 16 then set the STC to 16.

Checked on the brew again this evening and it's well and truly on the way. Temp of the fridge is a steady 13.9 degrees.

i just started brewing and seen the treads about one of these controllers

and as you lot are arguing or discussing where to put the thermometer / sensor couldn't you put in to the fv so the reading of the team is actually the ale not the fv or fridge ?????

ddeighton_1 said:

i just started brewing and seen the treads about one of these controllers

and as you lot are arguing or discussing where to put the thermometer / sensor couldn't you put in to the fv so the reading of the team is actually the ale not the fv or fridge ?????

Click to expand...

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.

Ok that's useful info

Twostage said:

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.

Click to expand...

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.