Air and fermentor temperature

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Air and fermentor temperature

Postby ericmark » Thu Jun 09, 2016 10:54

Until today I could only guess are the difference with cooling. With heating I did note a difference and how much depended on if bringing up to temperature or maintaining temperature, with the latter the difference was small with the temperature controller set to 0.1°C differential it may has stretched to 0.5°C so five times the set differential this increased when the outside was very cold and reduced when outside was near to fridge or freezer inside temperature. When there was some ground to make up, ramping from say 18°C to 20°C it was not unknown for a huge over shoot it could easy hit 24°C but holding it was quite good.

So again set to 0.1°C deferential the brew was well under temperature set when it went in, around 20 hours before it hit the 20°C set the freezer air temperature went to some where near 18.2°C not sure if it went any lower as when inspected the freezer motor had stopped only knew it had run because the energy meter showed it had run. The fermentor temperature was 19.9°C as expected with a 0.1°C deferential set. There was also a 10 minute delay on starting set.

Conclusion with a 0.1°C deferential in round figures a 2°C air temperature deferential. So if using heating and cooling at the same time one needs a 3°C between the two at least to stop it yo-yoing between heat and cool and that's with a 0.1°C with the other temperature controller a STC 1000 the smallest gap is 0.3°C so I think my self lucky to have in error got a MH1210A to start with, I kicked myself for the error as it would only do heat or cool, but in hind sight since you can't have a different differential between heat and cool and to when it starts to cool and stops cooling you need two controllers anyway.

So in my case the MH1210A on cooling as allows a 0.1°C differential set, and STC 1000 on heat with minimum of 0.3°C differential allowed to be set.

I will have to admit my errors.
1) You do need cooling, even set low to start it still needed cooling.
2) With a single STC 1000 unit you have to monitor air temperature.
Next to monitor is how low does the fermentor go? I am measuring fermentor temperature for control but have anther thermometer to see air temperature. Big question does the fermentor continue to drop or is there enough mass so it stops at 19.9°C?

Out of interest the energy meter shows I have used 0.03 kWh with what I assume was a single run, also hour and half latter the fermentor had gone to 20.1°C but the air still only 18.8°C clearly heat is from fermenting. The system must be just about to trigger again, but as yet has not. Need to go out, would love to see at what temperature the motor stops.

Well after the initial drop to 19.9°C every other visit and the fermentor temperature was 20.1°C I have never walked into the garage and found motor running but the energy meter has to start with jumped to 0.03 kWh then next day 0.04 kWh and next day 0.05 kWh so clearly the motor has run. Fact it has run at least once every day means clearly it is required.

Well it seems I had really got it wrong when I thought I could get away without using the freezer motor, each time I check it has used another 0.01 kWh now up to 0.06 kWh in total 1.8°C does not seem much, but that's the difference between freezer air temperature and fermentor temperature so once the garage reaches around the 15°C mark then likely it will need some refrigeration. I had miss-calculated how much heat the fermentation released.

What I do need to do is swap the two temperature controllers over in the boxes, the MH1210A has only one relay so only needs one socket, and the STC1000 has two relays so needs two sockets. As it stands can't use the STC1000 for cooling and the MH1210A has an unused socket. Otherwise I would as an experiment have swapped them around and seen what a 0.3°C differential would have made. I have seem it flashing between 20.1°C and 20°C and on 20.1°C but other than first time it ran the fermentor seems to have stayed steady even though the air temperature in freezer has been between 18.2°C and 19.5°C next is also to taste beer.

It also seems I had miscalculated the mass inside the freezer, two days both fermentor and garage ambient have been higher than freezer air temperature by over 1°C, so the brew is still being cooled from refrigeration motor running, with 2°C between heater coming on set at 18°C and refrigeration motor running set at 20°C not a problem. But had I been using the same controller for heating and cooling then by now heating would have come on.
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