I read some where about thermostats changing the frequency being used, so would buy as a pair.
As to make and model hard to say which is best, there is a problem where the thermostat has no fail safe, from memory the BDR91 would auto close down if not signal in ½ hour so one the the better type.
However it also had from memory anti-hysteresis software, which is really good with an old oil boiler, it stops the temperature over shooting, but with a modulating gas boiler designed to extract the latent heat from flue gases not a good idea, as every time the boiler is switched off/on it often does so at maximum output rather than the reduced output appropriate when the home is nearly to temperature.
So a wall thermostat is selected to suit your home, which may be very different to my home. Now is the time to select which best suits your home.
Basic idea is normally that the TRV (thermostatic radiator valve) controls the room temperature, and if the lock shield is set up well, then can do a very good job, but they have a problem, the basic TRV can turn boiler down, but not off, so we want a device which when the weather is warm, will turn off boiler, this could be a hub collecting info from electronic TRV heads, or a wall thermostat, but it needs to work with the TRV, not against the TRV.
Add to this we often want the home cooler over night, or when out at work, so often we need some timer built into the TRV or the wall thermostat to switch off or down rooms or complete systems when not required.
There are some very clever systems on the market, but in the main a couple of linked TRV heads to a master hub/wall thermostat is enough, the rest can be unlinked so much cheaper. You can set it up with no links, just careful setting and positions, so often it is a case of the more you pay the easier to set up, but given time to set up even the cheap systems can work well.
So it is a balance money paid against time to set up to work well, there are some thermostats which are analogue, a far better system, it turns the boiler up/down rather than on/off, but not all boilers can use them, also some makes one needs to either have analogue control or linking, the boiler will not allow both, so selecting a replacement thermostat depends on boiler as well as home.
Sons house (my old one) is open plan, and one centrally placed thermostat can control the whole house, the house I had before that was hot air central heating, again one thermostat could control whole house, but this house has things called doors, with no vents in the doors, so each room is controlled independent.
So we select controls to suit boiler and home, there is no one type suits all. So what is your home and boiler like?
