Ferguson FS1TH thermostat how to connect to a Vaillant atmo tec pro

Hello, I bought a wifi thermostat from Ferguson FS1TH. I have a problem with connecting to the Vaillant VUW PL 200 stove? 3-3M ok and the power supply is on and the thermostat is on and hula but the problem is that I do not know how to connect the signal in the old Eurostel 2000 controller, I had 2 NO and COM cables
connected to socket 3i4 in the oven will someone help me get it? because I have no idea and I don't want to burn something

on the boiler side you have contacts 3-4 and in order for the boiler to heat, the circuit must be closed there, i.e. you have a factory bridge there, or in the case of a room regulator, this regulator closes the circuit for the heating time and opens when there is a heating break.
The boiler on these contacts 3-4 has 230V, so all connections are best done after completely disconnecting the power from the boiler, i.e. after removing the plug from the 230V socket.
The regulator should have voltage-free contacts and according to the diagram, the boiler should be connected to the RW on the thermostat side, but I am wondering about the option of 9-24V power supply on RC contacts, which is in conflict with 230V generated by the boiler.
I would check with a meter if the thermostat works "dry" without the boiler, there is no voltage on the RW contacts and if the heating on the thermostat is turned on, the circuit is closed on the RW contacts.
Without this attempt, the connection seems risky and uncertain, but the manual for a different connection option does not show.
Due to the presence of 230V, you do everything at your own risk.

It follows that the thermostat requires a separate relay.
Only instead of two power supplies and a 5V relay, I would try with a relay powered by the same voltage as the thermostat, then in theory one power supply would be enough.
You just have to take into account that low voltage limits the length of the wires, so finally two power supplies may be obligatory so that there are no too large voltage drops.

Are you sure that ~ 230V voltage appears on contacts 3-4 in the Vaillant boiler?

Is it just a normally open / normally closed contact?

From what I remember, Vaillant forbids giving ~ 230V voltage there

ls_77 wrote:

Are you sure that ~ 230V voltage appears on contacts 3-4 in the Vaillant boiler?

yes there is 230V generated by the boiler itself.
You can always download the service manual and see the diagram of this boiler.

ls_77 wrote:

Is it just a normally open / normally closed contact?

From what I remember, Vaillant forbids giving ~ 230V voltage there

The room regulator, and in fact the relay built into this regulator, should have voltage-free contacts that will only close or open the circuit in which there is 230V, because it only replaces the factory bridge, so there is no question of giving an additional 230V voltage.

The situation is different with the contacts 7-8-9 for connecting the original Vaillant room regulator, because it is a 24V section and as you know, releasing 230V there means burning the boiler motherboard.
Therefore, when connecting regulators / thermostats, replacements without a built-in relay with voltage-free contacts, you need to be careful what you do, because improper connection and additional voltage may mean problems and extra expenses.

It is theoretically necessary to provide a 3-core cable with grounding for the on / off thermostat