Support for different size of radiato

[feryllt]

Hi,
In my setup I have two independent radiators with two TRVs. The radiators have a very big difference in size, yet I intend to use both (one is close to the desk area and it is nice to have it warm).

Is there a way/need to inform/hint Better Thermostat of the different in size/thermal capacity?

Thanks

[mungo312]

I habe a very similar use case. Any information or experiences ?

[mungo312]

@wtom Is there anything in the new MPC algorithm?

[wtom]

Not yet. I first want to have it stable.
But feedback is rare. 🙂

[cl445]

Short answer: No, you don't need to inform BT about the different radiator sizes — but you also can't. BT models the room as a whole, both TRVs always receive the same target/valve command.

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What BT actually learns (room-level, not per radiator):

• heating_power (°C/min while heating is active)
• heat_loss_rate (°C/min while heating is off)
• Both are tracked per BT-instance in utils/thermal_learning.py::HeatingPowerTracker / HeatLossTracker.

These values describe the combined heat contribution of every TRV attached to the BT instance, against the room as measured by your external sensor. If one radiator is twice as large as the other, that simply shows up as a higher learned heating_power than you'd see in a single-radiator setup.

MPC:

The new MPC mode (CalibrationMode.MPC_CALIBRATION) uses the same room-level heating_power / heat_loss_rate to plan a setpoint trajectory. It does not split the model per radiator — there is one room, one model, one decision, both TRVs follow.

Practical implications for your setup:

• The combined system "just works" — the bigger radiator contributes most of the heat, the smaller one helps where it can, and BT learns the resulting room dynamics over a few heating cycles.
• The desk-area "warm" feeling is a local effect of the smaller radiator being near you; the room-average temperature is what BT regulates.
• You cannot ask BT to drive the two TRVs to different setpoints from a single BT instance. If you really need that, you would have to create two BT instances each with one TRV — but they would compete on the same external sensor, which usually doesn't help.

In short: leave both TRVs in the one BT instance, let it learn for 1–2 days, and the combined heating power will reflect your actual radiator setup.