Fermentation Temperature Control

[adm]

I've basically finished up the first of my temperature controlled fermentation chambers today. I've still got to figure out how to fit the door permanently as right now there's no hinge or anything. I've also left out any form of cooling for now, but have done the wiring ready in case I can work out how to cool the bugger. Right now it's not necessary as it's about 5C in the garage. I'll take some pics tomorrow.

I've basically insulated the whole thing in 50mm Kingspan, plus 2 lots of 4 inch cavity wall mineral wool for the floor and one of the sides where the wiring is. I've got a 120W tube heater in there and it's controlled by one of the Craftbrewer TempMate temperature controllers - which is a lovely piece of kit. It's basically the same as an ATC800, but has a larger range (-50C to +125C) and a finer difference control (goes to +/-0.5C). It's also one quarter the size and the interface is slightly easier to use. All in all - seems good so far.

So....my question is, where is it best to measure the chamber/FV temperature?

I can see two possible approaches:

1) Sensor in the FV itself (maybe in a sealed corny dip tube for a thermowell). This would give the most accurate control of the actual FV temperature, but my worry is that if the sensor is in the middle of the FV, there is a large thermal mass (25-50L of liquid) between the ambient air and the sensor that has to change temperature - this could mean that the chamber temperature goes to extremes of heat or cold before the temperature at the sensor changes. Potentially, the beer on the outside of the FV could get too hot or too cold and would be likely to do so in cycles.

2) Sensor in the ambient air of the chamber. The downside of this is that the air in the chamber will change temperature quickly, so the heater will be cycling on/off quicker. However - the liquid in the FV will tend to keep a stable temperature despite the chamber air cycling through a few degrees +/- of the setpoint and will act as a thermal mass itself, keeping the overall temperature stable.

The downside of the second approach will be that I don't know exactly what the temperature of the fermenting beer is - and as it tends to be hotter in the FV than the actual ambient temperature, then there is the risk of the FV getting too hot.

To deal with this, I would think that I could simply set the temperature, then leave it all to equalise and measure the actual temperature of the fermenting wort, then reduce the temperature setpoint on the controller by the delta. For example, if the chamber temp is set to 20C, but the FV measures 22, then I set the chamber to 18C to achieve 20C in the FV.

Does that sound about right?

[hoppingMad]

That sounds about right. I have a probe that sits inside a half litre jar of water, the digi readout being on the outside of the fridge. When it reads 7.5 C I know the FV is 9C because of the yeast activity. This works well for most applications.
However, as I sometimes lager at 1 degree C, I want to know the temp of the glass carboy acurately so as to make sure I'm not freezing the beer so I place the probe on the side of the glass carboy and insulate it with a rubber pad and this gets taped onto the side of the carboy when still warm to prevent condensation under the tape.
I don't think it matters much where the probe is most of the time.
Hopp.

[adm]

Thanks Hopp,

Nothing for it but to run a test and see what the difference is, right?

I'm going to do an EKG based single hop brew today with S04 as a trial. I think I'll aim to ferment it at 20C, it says anywhere between 16 and 24C, so I'll go the middle ground.....

I filled an FV with cold water last night, set the chamber to 20C and left it overnight. This morning, it's smack on 20C in the FV, so it all seems to working well anyway.....

[adm]

Here's a few pics for anyone that's interested.....the plan is to have two separate chambers when done, but right now I've just done the first one


Adding cavity wall insulation to the floorspace. The middle area will be the second chamber and the bit under the sink will just be under sink storage space. Everybody needs a "cupboard under the sink", don't they ?


Then I figured that full FVs might be a bit heavy and I could do with some more bracing. That's fitted and another layer of insulation.


Ply floor going in


Bit of a jump here.....but the walls and top are now lined with insulation, I've wired in a plug socket for the heater and put the wiring in (but no socket yet) for electrical cooling if I can figure out a way to do it and fixed in a 120W tube heater


Here's the insulation slab for the door area


And the exterior ply door skin. I need to sort out a hinge and locking clip arrangement. Plus stick a good coat of boat varnish over all the exposed wood here, inside the chamber and over the rest of the brewery frame for good measure. The grey insulation board is a temporary bodge to hold the rockwool in place until I cut a ply skin and fit the electrical sockets for the second chamber.


TempMate controller wired up, set and working. I've left the space in the box for a couple of PIDs and assorted switches for my HLT and Mash Tun controllers when I get around to that....

[sexysouthwest]

This is how i aim to run my fermentation chamber
http://www.hawco.co.uk/LAE-Digital-Ther ... 142_p.aspx
I have got a stainless foster nhr 220 u fridge which has a fan inside in which runs warm and am hoping this will keep it warm and the chiller will cut in to keep it maintained at temp, If not then i will add a small hetet such as a tube heater and the controller will operate both.