Fermentation Chamber Up And Running.

[Stitch]

The STC has a hysteresis band which will account for the dampening effect. Please see my original post.

As a professional automation engineer using a PID loop for on off control is sloppy and does not work. Hysteresis is the gap (effectively) between on/off and PID control. PID control should only be used for continuous output control. In the application of temperature control of wort you woild only use PI.

How it is done generally in the industry is you have a bank of chillers out back bring the temperature of a water/glycol mix fown to about 4DegC. This is then mixed at the jacket eith the return water to eith raise or lower to flow temperature of the jack. There are multiple probes measuring wort temperature. As this is continous control you can use PID. Also at the same yime the supply air is balanced with the rest of the system.

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[Ciderhead]

Please advise Greg how he can calculate the thermal mass of his wort and thermal inertia of his fridge?

Ok let's do if your way now please show us how?

[Stitch]

You can Google this and get all the formula and information.

Easiest way to get it is by trial and error. Get chamber to known temp. Add water at know temp and known volume and see how long it takes to achieve equilibrium. Do this for a few different temperatures and tabulate the results. Get the average. You must set error limits though as the small the error the longer it will take to achieve equilibrium.

CH how do you calculate your strike water temp if you don't know thermal mass of mash fun and temperature of grain. If you are an extract brewer you need not worry about this.

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[pob]

(Brewrob: Hysteresis, thanks had been racking brain for that term, long time since I needed it.)

So where do we put the STC probe in the ferment chamber so we don't get temp extremes from, eg tube heating up outside FV air before wort probe reacts, or chamber air temp but fridge cycles too much as - fridge cools, probe tells STC ok & switches fridge off (eg delay 10 mins off), mass of wort still  heating surrounding air, probe then tells fridge to cool again, etc).

Or is it we're worried too much about the progressively smaller differential between wort & chamber target temp, that over a couple of hours it balances itself out & will be fine and just have your pitching temp as close to ferment temp as possible when putting into chamber.

In other words your not really going to get funky flavours from high ferment temps if your pitching correctly & then putting into ferment chamber at close to ferment target, ie have good procedures in place to minimise errors.

[Ciderhead]

Strike temp is calculated for me by beersmith and based on grain temp mash tun temp.
I operate herms so I have it very accurate within a minute or so.
I use an ir laser probe to determine wort temp and usually hit it exactly as I prewarm glass carboy.

All this theory is lovely but I'm a practical fella, if anything my ferments have been a degree or 2 too cold, as stated above more likely to trigger the heating rather than cooling
If I use air temp the freezer is gonna be flicking on and off all the time as it chills air quickly and cuts off, heat from fermentor raises temp from an exothermic reaction and ups air temp again and it needs to cool again.
if it's insulated the freezer keeps going until the cool reaches the insulated probe and although the cooling cycle is more aggressive it's less frequent?

[Stitch]

@CH your mash is a perfect example.. You don't need to know the thermal mass because your process accounts for it. If you loose 2DegC your process automatically replaces it. Now if you have glycol jacket for your fermenter same thing. You need not directly know the thermal mass, but you pic loop will!! Tuning the loop learns this factor believe it or not.

As far as the heater only home brewers do this. Ask yourself why the "big boys" don't use heaters. You already stated yourself that fermentation is an exothermic reaction so why do you need a heater. Its like installing an AC unit in your sitting room to keep the temperature down. We live in Ireland average outside air temperature all year round is below standard required room temperature. You need heat in the chamber just use the reaction.

I have a temperature strip on the outside of my carboy and also 2 calibrated temperature probes(One NTC one thermocouple). The two probes always read at least 2DegC off the temperature strip when placed in the wort.

What you must remember here is that the fermentation chamber is a homebrew solution (not a professional) one to home brewers problem.

@pob yes I chill to about high 20DegC and drop into chamber at much lower temp. When temp equalizes I can pitch yeast. Remember though using freezer as fermentation chamber the freezer just comes on to try get down to about -20DegC. Water starts to freeze at 4DegC. Have your probe stuck between bubble wrap bad conductor and glass poor conductor can only give a false reading.

I agree with what CH has said earlier that the way he does it is the way he has seen it done. That does not mean it is the right way. However, the equipment is not the right equipment for the job but it is all we have so it must be used the best way it can.

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[johnrm]

I have PID but opted for STC with cool and heat. I have fermented at ambient temps recently but will be trying a single input either heat or cool depending on ambient to reach target temps.
I believe with too close a gap,  heating may be fighting cooling and vice versa as the heating and cooling sources take time to reach ambient themselves.

[Ciderhead]

I have PID but opted for STC with cool and heat. I have fermented at ambient temps recently but will be trying a single input either heat or cool depending on ambient to reach target temps.
I believe with too close a gap,  heating may be fighting cooling and vice versa as the heating and cooling sources take time to reach ambient themselves.

Once you set the delay to max 10 mins and differential to 1 degree and have a quality fermentation chamber you will be fine and the wort comes up/down to temp it acts like a storage heater and you get less and less input required.
If it's outside you probably won't get any cooling come on at all in this weather.