Priority for multiple TRVs in one room

[MalcolmS]

If you have a large room with multiple Wiser TRV-controlled radiators, how does Wiser determine when to stop calling for heat?  When all the TRVs have reached the set temperature or, just one or does it have an algorithm to calculate a temperature taking into account all the TRV temperatures?

Also, I have one room, again with multiple TRVs, that I was sure was never getting to temperature despite Wiser recording it as at temperature and shutting off the heat.  I installed a temperature recording device in the centre of the room and at the time Wiser was showing 21°c it recorded temperatures of only between 18°c and 19.5°c.

Am I correct in saying there is no way to calibrate the TRVs to another temperature and the only way around this problem is to up the temperature cut-off point by 2-3°c to allow the room to get to 21°c?

[robertwigley]

See here for details on how it calculates temperature in different scenarios. Short answer, yes, you need to up the target temperature to compensate as there is currently no offset and even if there were, the iTRVs do not calculate temperature with a linear offset. See here for analysis after I added Room Thermostats recently. There's lots of useful information in that thread. Probably more so than in this forum.

[MalcolmS]

Thank you Robert, that's extremely interesting.  I did not appreciate the value of the Wiser Room Thermostat.  I have one in the hallway at the moment fo no other reason than that's where the thermostat in the old system was!  My Living Room is currently 19°c according to my temperature unit yet the Wiser TRVs tell me it's 21°c. I think I'll move the Room Thermostat into the Living Room. If only they weren't so expensive I might buy some others for the main rooms

[robertwigley]

No problem. Yes, you are definitely best moving your existing one from the Hallway to the Living Room. They do make a big difference. They are stupidly expensive for what they are, but I now consider them essential (at least for the main living areas). If you're going to buy a few more, I suggest you have a look on eBay, I got mine for a lot less than RRP on there. Still expensive, but much more stomachable than the RRP.