Adding external Wirless thermostat to Boiler

[stem]

That's the idea

The link marked 1 & 2 goes and the thermostat wiring that replaces it is shown by the dashed lines. As well as these switching control wires, the wireless thermostat receiver will also need have separate L &N terminals for the 230V to power it, but that can come from the L & N terminals above.

If you get a wireless thermostat that will control the room temperature only and the boiler's internal timeswitch can be used to control the on and off times.

If you get a wireless programmable thermostat that will provide combined temperature and time control, in this case, the boiler timeswitch would no longer be used and would need to be set to be 'on' permanently 24/7.

 

[ianmcd]

Is the make :
https://www.heatingcontrolsonline.c...mable-thermostat-for-combi-boilers-p-350.html

It sorts of fits with it being Horstman looking at code, though I can't see manufacturers name anywhere.

that is a drayton digistat + but will be rebadged

 

[RickH]

Update - I bought a 'generic' model:
https://www.heatingcontrolsonline.c...-in Programmable Thermostat for Combi Boilers

Was very easy to fit, direct replacement for mechanical timer ... just swap over 4 push fit wires ...... took less than 5 mins.
Remote stat worked as soon as I put batteries in .... no issues with pairing/setup.

I have wall fixed the stat/programmer in the hall (where Honewelly stat was), and removed TRV valve'head unit' from the rad in the hall, seemed logical not to have 2 stats in same area.

 

[ericmark]

I have wall fixed the stat/programmer in the hall (where Honewelly stat was), and removed TRV valve 'head unit' from the rad in the hall, seemed logical not to have 2 stats in same area.

The two thermostats have different functions, at least when used in a hall, the hall will clearly cool when door opened to outside, the TRV can do a number of things depending on the head used, so with for example the eqiva eQ-3 head as the head is cooled down quickly it assumes window open and shuts down for the time programmed in, once this time has expired it then opens up to allow rapid re-heating of the hall, but before it get to the wall thermostat temperature it starts to close again so the last degree takes longer so rest of house can also heat up.

The wall thermostat is set so when you have a warm day the boiler is turned off rather than allowed to cycle off/on as the warm water returns to boiler.

They clearly do react with each other, so when a programmable wall thermostat drops from daytime temperature to over night for example the TRV needs to change temperature at the same time, however the reverse is not always true, my hall TRV turns up in the morning but my wall thermostat turns up in stages to extend the time the boiler runs for, so 8 am the TRV goes from 17°C to 20°C but the wall thermostat goes from 17°C to 19°C at 7:30 am and then add 0.5°C per hour until also at 20°C to extend the time so rest of house can heat up.

Exact times and temperatures depend on where the stairs are, and distance between radiator and wall thermostat, etc. Mothers house the wall thermostat was closer to radiator, so was able to go straight to new temperature in the morning.

But it is fair enough in a ground floor room with no alternative heating and no outside door keep reasonably cool to remove the TRV, however since you have an outside door, either the radiator is turned up too high and rest of house remains cool, or when the door opens the hall does not recover and hall says cool, so you have broken the rule of thumb by fitting wall thermostat in a room with outside door so also need to break the rule of thumb not having two thermostats in one room.

There are a few exceptions, EvoHome and Hive the TRV can send a signal to the wall thermostat to keep boiler running even when the room with wall thermostat is warm enough, however even in that case the hall could get too hot.

 

[RickH]

The guideline I have been given is that one rad must NOT be on a TRV otherwise boiler has nowhere to pump water, just closed loop.
This is a standard basic TRV.

So are you saying I should have the TRV working in the hall ?

If that is HIGH it will have boiler pushing out heat until it is satisfied (if Prog on) if set Low then it would be turning the boiler off before other rooms are warm.

 

[stem]

I have wall fixed the stat/programmer in the hall (where Honewelly stat was), and removed TRV valve'head unit' from the rad in the hall, seemed logical not to have 2 stats in same area.

The heating system should be designed with a by-pass so that there is always somewhere to allow water to flow. This may be in the form of a radiator with lockshield valves so that it can't be turned off fully, an external by-pass device, or a by-pass that is integral with the boiler.

This is a different matter to the practicality of having a TRV on the radiator in the same location as the room thermostat. The bottom line (as you have figured) is: If you have two devices trying to control the temperature in the same room, one will interfere with the operation of the other. Most thermostats come with this advice.

Hive

Mi Home Energenie

If the TRV turns the radiator 'off' before the temperature set at the room thermostat is reached, then the room thermostats control is overridden, it will not operate and therefore becomes ineffective.

 

[RickH]

That is what I expected ... so have done the right thing and removed the TRV ‘head Unit’ ... pretty sure R3 o I g the adjustment head puts it on full flow.
I’ll see if I can get a plastic cover.