WiFi relay and Vaillant Combi boiler heating

[LucasCh]

Hi guys,

I am thinking of getting my heating control a little bit smarter. Currently, I have "old" Salus RF thermostat with touch ring, but not connected to any hub, so I can't control it outside of my house.
I was thinking about getting micro usb powered d1mini development board with relay switch which can handle up to 240V. I am already using smart home system, so I have that side covered.
Now, going to the bottom... Because its a boiler, I need a gas safe engineer. Would he/she even considered such installation?

I have Vaillant Ecotech Pro 831. I search for installation of external thermostats and I have found 2 possible solutions. Option 1 seems more possible than option 2.
I made some drawings, so I could better "describe", what I would like to achieve.

Thanks.

 

[wannocks]

You can close a switch across either RT and a 230v supply or just across the 24v RT terminals. Do not connect 230v to the 24v terminal. The ebus connection is only for connecting Vaillant controls. Putting a switch across this will not work.

 

[LucasCh]

@wannocks
Thanks for your reply. So basically your first suggestion is my option 1.
When it comes to your second suggestion... There is now a jumper wire at 24V RT terminal, which either way, I am gonna have to get rid off. So what you are saying is, connecting two wires from WiFi switch to both ends of 24V RT terminal will call for heating? If that's the case, why having a jumper wire in that terminal now, doesn't call for heating all the time then? Is it because of current thermostat, who (i don't know) has a priority over it?

Also, I know more than likely, it won't be possible to use old thermostat along with a switch, unless I am wrong?

 

[wannocks]

Does the Salus stat have a receiver plugged into the front fascia of the boiler? This will control the boiler if nothing is wired. The 24v link tells the boiler to run in heating mode. A plug in control or ebus control then tells it to stop.
If the 24v link is open the boiler will stop. If there is 230v on RT the boiler will run.

 

[LucasCh]

Yes, current stat has rf receiver in front facia of the boiler. I believe it has to be somehow integrated with main PCB, as there are no wires plugged in to 240V RT nor 24V RT (only short jumper cable between two 24V RT terminal).

 

[wannocks]

You need to remove the salus plate from the front of the boiler to use external controls.

 

[LucasCh]

@wannocks
Thank you far that. So the best conclusion is...
Wire between Mains L and NO terminal at the switch
Wire between Com terminal at switch and 240V RT
Remove jumper at 24V RT
Remove rf receiver at front of boiler.