Could a kind soul give me a steer as to how to replace an existing HR92 in my system? The original installation and set up was done by an engineer who is no longer available.

I have fitted the new TRV to the radiator. My problem is how to get the wifi controller to treat it as having replaced the old HR92.

The radiator is in what I will call Room A, which is on the same circuit of water pipes as two other rooms. The flow of hot water from the boiler into the pipes is triggered by a wireless relay box for the circuit. [I'm not sure it matters, but Rooms B and C just have a single radiator each, with a HR92 on each radiator. Each room is a separate zone in Evohome. The room C HR92 has no batteries, so is permanently off, as the room does not need to be heated.] Room A has two radiators, each of which had HR92s, and there is a DT92 wall thermostat which I understand acts as the sensor for Room A. The two radiators are controlled together and I assume the controller has been set up so that it knows which wireless relay to trigger for the pipe circuit that runs through Room A. One of the HR92s in Room A died, so I am replacing it with a new HR91.

If I follow the instructions that came with the HR91, it seems to make me set it up as a new zone. This worked, once I gave the new zone a name. The HR91 bound (binded?) correctly. But what I want is for the HR91 to be part of the existing Room A zone, so it is controlled in tandem with the other radiator in Room A, using the wall sensor for that zone and the relevant wireless relay. Is this possible? I assume I need to use the Zone Configuration for Room A at the Controller screen, but then what? I would have expected it to show me the existing configuration for Room A: two HR92s, DT92 sensor and relay. But I can't decipher it. [Heating Type says Radiator Valve. Temperature Sensor says Remote Sensor. RF Device Binding says Devices Bound.]

Can I add the new HR91 to the existing zone? Or, do I have to delete the whole zone and set up the sensor and both TRVs again? How do I tell it which wireless relay to use?

I don't want to use the wizard, as it looks as if this will require me to set up all the other zones as well.