UK Replace Drayton Digistat SCR with simple manual on/off switch

[Freelance]

I have a Firebird oil boiler that is controlled by a Honeywell timer (no thermostat) that has channels for hot water and central heating. Additionally, there is a Drayton Digistat RF thermostat and receiver (SCR) that controls the central heating; I always leave the Honeywell c/h channel on continuous and just control the c/h on the Drayton programmer/thermostat.

My house is quite large and I want to have multiple 'zones' rather than a single thermostat that doesn't ever seem to be in the right place for everyone. I don't want to buy into any of the smart heating packages because they seem very expensive for what I need. I have found a set of wifi thermostats and a programmable button pusher from Switchbot that are much cheaper. All I need is for the boiler to come on when any of the zones drops below its minimum temperature and to go off when all zones are at their comfortable temperature. I have worked out how to program this in the Switchbot and the Google home app. The Switchbot products I refer to are here:

SwitchBot Bot | Make Your Switch Smarter | SwitchBot International

Upgrade your switches with SwitchBot Bot. Transform any button or switch into a smart control in seconds. No tools required. Experience the convenience of a smarter home today.

www.switch-bot.com

The part of the system that I think needs replaced is the Drayton SCR, with a simple manual rocker on/off switch (to be pushed by the Switchbot bot). My problem is that the SCR has 5 wires including live, neutral, earth and 2 others. Is there a switch I can use to take over the position the SCR plays or do I need to replace the 5-wire cable with something else? Here are pictures of the Drayton SCR and its wiring:

3 new items by Nigel Simpson

photos.app.goo.gl

Thanks for any advice. I don't mind if the answer is to get a professional electrician but I'd like to know what to ask them to fit and if I've misunderstood the complexity of this.

 

[baldelectrician]

I added a zone on to my heating, I had to add a second motorised valve for the heating- I have a S Plan system

You need a valve for each heating zone, the 'other' wires in the motorised valve usually go to a microswitch which brings on the boiler sequence

You will need to get someone who knows heating to install the valves and alter the pipe work / wiring

 

[Freelance]

I added a zone on to my heating, I had to add a second motorised valve for the heating- I have a S Plan system

You need a valve for each heating zone, the 'other' wires in the motorised valve usually go to a microswitch which brings on the boiler sequence

You will need to get someone who knows heating to install the valves and alter the pipe work / wiring

Thanks for the helpful reply. It makes me realise I have misdescribed my objective. I don't want multiple zones with separate heating. I only want my one zone heating system to react to any of the independent thermostats by switching the boiler on if any of the thermostats drops below <configured temperature for thermostat> and to switch it off only when all of those thermostats reach their configured temperature. I have standard TRVs (non-smart) on every radiator but they won't call for the boiler to switch on/off which is the function I am trying to introduce (by replacing the single Drayton wireless thermostat & receiver). Does that change the advice?

 

[brianmoooore]

5 wires on the SCR are a live and neutral to power the receiver, plus three terminals ( common, normally open and normally closed) for a simple change over switch which is electrically separate from the live and neutral.
If I understand correctly, you are looking for a traditional heat operated thermostatic radiator valve with an electrical contact that switches as the valve opens or closes. I don't think such a thing exists.
What I've done with my own heating system is to replace the thermostatic valve heads with actuators that are normally used to control flow on UFH manifolds, or, in some cases used an inline electric valve in the radiator feed, and control these with room stats in each room. These are all hard wired and go back to a central point, where (ongoing project) I intend to switch them in groups, depending on the time of day.

 

[Freelance]

5 wires on the SCR are a live and neutral to power the receiver, plus three terminals ( common, normally open and normally closed) for a simple change over switch which is electrically separate from the live and neutral.
If I understand correctly, you are looking for a traditional heat operated thermostatic radiator valve with an electrical contact that switches as the valve opens or closes. I don't think such a thing exists.
What I've done with my own heating system is to replace the thermostatic valve heads with actuators that are normally used to control flow on UFH manifolds, or, in some cases used an inline electric valve in the radiator feed, and control these with room stats in each room. These are all hard wired and go back to a central point, where (ongoing project) I intend to switch them in groups, depending on the time of day.

It's not the TRVs that I want to control the boiler. I have bought 6 Switchbot thermostats that I have placed in the same rooms as the TRV-controlled radiators, and no connection between them. I want these 'smart' Switchbot thermostats to replace my single wireless thermostat to make the boiler on/off control more granular than whole-house as at present. I hoped there would be a simpler approach to this (i.e. just replace that one boiler switch) than buying into one of the branded and locked-in Smart Heating paradigms with expensive and proprietary thermostats and TRVs.

 

[brianmoooore]

Do these switchbot thermostats transmit a switching signal via wi fi?

 

[Freelance]

Do these switchbot thermostats transmit a switching signal via wi fi?

Yes, I have successfully programmed them, using Google Home, to send an 'on' trigger when any one of them drops below their respective minimum temperatures, and to send an 'off' trigger when all of them reach their respective maximum temperatures. I have proved this using the Switchbot 'bot' which is just a smart switch pusher device. It is a stick-on attachment for placing on a standard rocker switch and it either pushes or pulls the switch on activation from the program. However, my boiler does not have such a manual switch but instead has this Drayton wireless thermostat receiver (with 5 wires) that I want to replace.

 

[Freelance]

Yes, I have successfully programmed them, using Google Home, to send an 'on' trigger when any one of them drops below their respective minimum temperatures, and to send an 'off' trigger when all of them reach their respective maximum temperatures. I have proved this using the Switchbot 'bot' which is just a smart switch pusher device. It is a stick-on attachment for placing on a standard rocker switch and it either pushes or pulls the switch on activation from the program. However, my boiler does not have such a manual switch but instead has this Drayton wireless thermostat receiver (with 5 wires) that I want to replace.

Actually, a minor correction. I have not successfully programmed them using Google home, but using Switchbot's own mobile app. I don't think that changes anything but just in case it makes a difference.

 

[brianmoooore]

You need a wi fi switch that is compatible with your switchbot thermostats. Remove the SCR, use the neutral and live to power the wifi switch, and the wifi switch's switched output to control the boiler.
The SCR has 'volt free' switch contacts, which may or may not be required to control your particular boiler. From recent research, looking for a wifi switch with volt free contacts, I found that most do not, although, with the help of this forum, I was pointed towards one that did.
If you cannot find one that is volt free, and volt free is required, a small relay can be used to solve the problem.