Are there any thermostats with a good range of user adjustable hysteresis?

[ericmark]

It is called droop and is causes a hysteresis, my thermostat used to brew beer has option to adjust ½ - 30ºC.

I also have an oil boiler, so simple on/off, and I also had a problem with over shoot, caused more by thermostat location than any fault with the thermostat, located in my hall around centre of the house, and hall radiator is other end of hall near to the door.

So we see these pictures, but that simply does not work in my hall, and the thermostat is located where the builder decided to put the wires for it, no real option to move it.

So attempt one was to raise the temperature in stages, rather than move from 17ºC to 20ºC in the morning, it went 17.5ºC for an hour, then 18ºC for an hour and so on until reached 20ºC so the boiler runs once an hour, so all the TRV heads have a better chance to control each room, it did help, and Nest Gen 3 will allow it to be set that way, however clearly if in the morning the house had not cooled to 17ºC then clearly the heating did not come on.

Nest Gen 3 UK version (USA version is very different) has no ability to monitor more than one place, so the easy option was to have a thermostatic system that does allow monitoring multi places to decide when the boiler should run. I did not like the idea of wireless, last thing I want is no central heating because two AA batteries have gone flat, but as a second system not so bad, so decided to have a second thermostat in parallel with the Nest Gen 3 so if either detected low temperature the boiler will fire.

Since a second thermostat no problem putting it in a room with the open fire, if it shuts off, the Nest in hall will still fire up the boiler for the rest of the house, and clearly better to have a system that will take multi inputs as to home temperature. So Hive was out, as that is limited to 22ºC to accept demands for heat, so if fire lit, then likely it would not take a demand for heat from elsewhere in the house.

So I went for the Drayton Wiser, I did not realise with Wiser there is no need for a wall thermostat, the hub can connect direct to the TRV's, however since two radiators and TRV's in the main living room, a wall thermostat is likely the best option.

It came with a stand so could go anywhere, like on a table, so we tried it in multiple places, but cat sleeping on it caused heating to switch off, so decided it does need to be wall mounted. Now with two thermostats it is a lot better, I thought the Nest Gen 3 would only actually work the domestic hot water (DHW) but sun in the living room windows has some times resulted in living room being warm, but rest of house cool, so the old Nest Gen 3 does still some times turn on the boiler.

But now we have Wiser, it is easy to add to it with linked TRV heads, so if wife's bedroom ends up cool, I will just swap the programmable TRV head she has, for a linked TRV head, as it stands the 9 programmable TRV heads stop any room over heating, and the two thermostats do seem to be working stopping the living room from getting cold.

The history with the Nest shows it still brings on the heating, when living room warm from the sun, Wiser also produces a chart, as to what it tells me not so sure, I assume the bar graph shows when it fired up the boiler, however it works, and I can expand if I want latter. Had I gone for Wiser first, likely would not have needed the Nest, but I have used the CH only version of Wiser, it does not run my DHW, and it is unlikely it could run my DHW without a lot of messing around with relays etc.

Hive could have run the DHW, but that 22ºC limit would be a problem, I have a C Plan, and not seen a way to configure Wiser with a C Plan.

However I in summer heat the DHW with excess solar, and simply can't turn DHW off in winter even if I wanted to, so it would not really be a problem not being able to get DHW in summer.

Nest Gen 3 do not publish how to set up C Plan, this is how Nest Gen 3 can work with C plan, will not work with wiser as no access to the Com terminal.

 

[ericmark]

Oh as a P.S. Nest shows me as I walk towards it temp set and temp now, and the built in PIR also sets it to occupied if using geofencing, although since only control with geofencing is the comfort and eco temps, not very good. Not tried Wiser geofencing, I know it uses IFTTT but never set it up. And to read the wall thermostat you need to press a button, and then it shows current, target, and humidity on display, which is a lot smaller than the Nest display.

In the main all the bells and whistles have been turned off. I did try the Nest learning system, but it set up a daft schedule, so turned it off, together with the anti legionnaires how that can work with no tank thermostat I don't know.