Dynamic glycol temperature setpoint

I am experimenting with a dynamic glycol temperature setpoint. Basicly what I want to do is make the glycol temperature related to the beer setpoint with a static offset, for example the glycol must be 10 degrees cooler that the beer setpoint.

Well I got that working but the think I am struggling with is that my glycol chiller won’t go lower that -2,5 degree. I want to implement a minimum setpoint for the glycol to prevent the compressor from running constantly because it cannot reach the setpoint of below -2,5 degree.

Is this possible?

It may be doable with some convoluted combination of Setpoint Driver and constraints. If not, then node-red is also an option.

I do have to ask: what is the expected benefit here? I have a hard time seeing how the extra variable would improve beer temperature control.

Well my idea is that it is not neccesary to have the glycol always at 0 degree for example. If the temperature difference is always the same between glycol and beer the response with cooling should also be the same at any given temperature of the beer. (Room temperature is also a factor, didn’t take that into account here :slight_smile:)
For finetuning the controller it is also better I expect, because respone is always more or les the same.

You could run some tests to verify. Use identical setpoint profiles for glycol and beer setpoints (with glycol offset 10*C, and kept >-2.5*C), and check control response.

That would provide useful data without having to overhaul your control logic.

I wouldn’t the simplest way be to set the internal temp control of the glycol to -1 to have an absolute minimum?

Then a setpoint driver can set the glycol setpoint in Brewblox to beer setpoint minus 10.

Yes that is fine. Is this an existing parameter?

You can create a setpoint driver block for the 10 degree offset.

By internal temp control of the glycol, I meant the thermostat of the chiller.
We can add an absolute minimum and maximum to the setpoint driver in software too, but it doesn’t exist yet.

My glycol chiller does not have a thermostat itself, so that is not an option unfortunately.

Okay, then I think that until we add the absolute minimum, you will need to manually keep an eye on the offset.
If you have a minimum and maximum on the setpoint driver, it will be limited to beer setpoint ± 10 for example.
If you set the beer to 4 degrees, I would just temporarily disable the setpoint driver and set the glycol to a constant -2.5.

oke thanks. I’ll keep an eye on the ofset indeed.