If I wanted to add a couple of Wi-Fi controlled relays to my S Plan system, would I be correct in thinking that I?d just need to wire the relays across terminals 1 and 4 for CH and 1 and 6 for HW control?
Tim
I'd say 5 and 8, rather than 4 and 6
Yes
But the programmer will override your relays unless you remove it but I expect you knew that.
But I never use number 6. Number six is a free man.
Don?t think so. That would bypass both thermostats. I don?t want to adjust the stats remotely but I do want the existing stats to work.
Tim
That would override the stats. I assumed that he still wanted then to work and just wanted wifi control of the programmer.
Yep I appreciate that.
Not following you here? Can you expand?
Tim
I assumed he did want the wifi relays to override C/H and H/W independently?
But not the stats. Still want something to control the temperature of the house and the HW.
Tim
Please other posters tell me that I am not the only person on this newsgroup to have run along Portmeirion beach shouting "I am not a number I am a free man" whilst the wife phones the solicitor and asks for divorce proceedings to start.
Best day of my life.
Doh! Shoulda got the reference! ;-)
Tim
OK sorry, I'm coming from the mindset of a wifi programmable stat, where the timer may be on, and the room stat up to temperature, but I want a couple of degree boost for an hour if I'm still not feeling warm enough.
The way this is normally done, eg when a Hive system is installed, is to removed the timer. On modern systems ( and that can mean several decades old) the timer will probably be mounted on a Mark 14 back plate. This has a footprint the same size as a single mains socket etc. There is a row of terminals - as shown in the right hand group of your diagram- and the timer / programmer clips onto it.
Generally, to convert to a remote control system - such as Hive- you unclip the programmer, clip on a box which has relays ( or equivalent) plus the remote control interface. Sometimes minor adjustments are needed to the existing wiring but the theory is, the Mark 14 plate provides a common interface.
You should be able to adapt the idea.
Simply fit a relays wired to emulate the switching arrangement in the timer part of your diagram, removing the existing programmer and connecting your circuit to the corresponding points.
The coils of your relays will be powered by your control circuit - I assume an Arduino or R Pi.
I?m just keen to ditch the existing programmer (or at least bypass it) as it?s a pain to alter and not particularly flexible and I quite like the idea of being able to fire up the system remotely.
Basic Shelly relays are very affordable.
Tim
There's a different way of doing things, which I've seen on some smart thermostats, is you leave the programmer in place and set it to run the heating 24/7. You then set the existing 'stat to a 'frost' position, but wire the relay for the smart controls in parallel. That means the smart controller can call for heat by closing the contacts, but the system is still able to come in as a backup if the smart controller were completely disabled. You can also override it by turning up the existing stat if you want to.
This is much less work than a full programmer replacement and works even for ancient wiring (ie potentially a DIY install, against Nest etc which are often sold as professional installs).
Theo
Neat, but would mean adding another temperature sensor. That would cost another £11.99 + postage! ;-)
Tim
is the thermostat too far away to stand up and turn it up?
Read carefully. It's not the thermostat he wants to control.
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