Vaillant Furnace: Connecting a Room Regulator with Dry Contact Thermostat (24V, Pins 7 8 9)

Hello everyone, I am at the stage of connecting the room regulator to the furnace but the diagram has no input for a dry contact thermostat only with 24V power supply pins 7 8 9 and I have such a regulator from a stalopal furnace and I would like to connect it to the furnace but I do not know if it is possible there is a jumper on newer models
and there is nothing I am asking you for help and thank you in advance
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There is a 3-4 jumper for the room thermostat. Just be careful, because there is 230V, but you can let it go through a regular room thermostat.

After photos I see that you have an old boiler from a dozen or so years ago, because newer ones have 7-8-9 additional eBUS connector next to them.

The 7-8-9 connectors described as 21V are used to connect the original Vaillant room regulator, e.g. VRT390, then you need a 3-wire cable, but the description shows that your case does not apply, so you can forget about 7-8-9 connectors.
In the case of typical ON-OFF room regulators, which is a whole mass on the market, 3-4 connectors are used. As mauri_b wrote, there is 230V, so the regulator must offer potential-free contacts, i.e. voltage-free and connection should be done after removing the boiler's power plug from the 230V socket.
You remove the jumper and connect the 2-wire cable in this place, the other end of the cable is connected to the room regulator.
If the room regulator wants to turn on the heating, it closes the circuit, which simulates the presence of a jumper on contacts 3-4, and if the heating is turned off, opens the circuit, which simulates the lack of a jumper on contacts 3-4.
You need to make sure that your regulator has voltage-free contacts capable of controlling the gas boiler with a 230V pulse and will close the circuit when heating or open the circuit when heating is turned off.

Thanks to all of you for the hints.
I have a TECH regulator ST-292 v3 but I don't know much about it.
I prefer to seek advice from people who know each other and suggest something wise.
Thanks for any tips.

since you don't know each other, call a specialist who will connect you to it.
I usually just need to download the user manual and a glance at the connection diagram and I know what to do, although I am an amateur.
If this is beyond you, it is better not to rummage yourself, because a layman can spoil something. In such cases, two left hands fall off.

Connecting to the thread. With the original controller on 789 contacts, can jumper 34 be controlled without fear, e.g. remotely via a contactor / relay. That is - regardless of the state of the controller 789, disconnect the contacts 34. Even how do you get with opening 34 for the moment of heating the furnace?

Targanici wrote:

That is - regardless of the state of the controller 789, disconnect the contacts 34. Even how do you get with opening 34 for the moment of heating the furnace?

They use regulator 7-8-9, according to the instructions of my boiler, contacts 3-4 must be permanently shorted.
This suggests that in the case of open contacts 3-4 heating which will not work despite the fact that regulator 7-8-9 will give a heating request.
In other words, contacts 3-4 have a higher priority than contacts 7-8-9 but without heating demand from regulator 7-8-9, the boiler will not start.
With this in mind, you can play with contacts 3-4 while using the 7-8-9 regulator if you have such a need, although I don't see any sense in it.

Thank you very much for your comprehensive reply.

BUCKS wrote:

With this in mind, you can play with contacts 3-4 while using the 7-8-9 regulator if you have such a need, although I don't see any sense in it.

There is a point.
Instead of setting the holiday mode, you can remotely control the activation of heating. All this in order to be able to come to a warm home, e.g. earlier than expected by placing a "suitcase" on the regulator. With this assumption, holiday mode may not be used, but maintaining tmp. (e.g. 15 degrees) I will set with an external regulator with a contactor connector connected to these contacts 3 and 4.

BUCKS wrote:

Targanici wrote:

That is - regardless of the state of the regulator 789, disconnect contacts 34. Even if you happen to open 34 for the moment of heating the furnace?

They use the 7-8-9 regulator, according to the instructions of my boiler, contacts 3-4 must be permanently closed.
This suggests that in the case of open contacts 3-4, the heating will not work, although the controller 7-8-9 will give a heating request.
In other words, contacts 3-4 have a higher priority than contacts 7-8-9, but without a request for heating from the regulator 7-8-9, the boiler will not start.
With this in mind, you can play with pins 3-4 while using the 7-8-9 regulator if you need to, although I don't see the point in it.

Good morning
I have a question regarding the suggestion of the predecessor, I have a 789 regulator and I would like to control the heating of the water with it, set when it should heat the water in the boiler and when not. And besides, I would like to use a 3-4 regulator to control central heating remotely using regulators generally available on the internet. Can something like this be done and it will not be so-called. Bite? Thanks for the help

kloza19 wrote:

I have a question regarding the suggestion of the predecessor, I have a 789 regulator and I would like to control the heating of the water with it, set when it should heat the water in the boiler and when not. And besides, I would like to use a 3-4 regulator to control central heating remotely using regulators generally available on the Internet

contacts 3-4 may be open, and the boiler will still heat hot water when you turn on the tap.
In other words, contacts 3-4 control only the central heating mode in the boiler.

For this reason, in my opinion, there should be no problems for the 7-8-9 controller to control the hot water heating, and the 3-4 controller to control the
The necessary condition is that the 7-8-9 controller must be set to the maximum central heating temperature, so that it constantly demands heating. Otherwise, if 7-8-9 turns off the central heating, switching on contacts 3-4 will not start central heating.

But you still need to test it in practice to make sure it works the way you want it to.

Added after 5 [minutes]:

it is worth remembering that the 7-8-9 controllers have 2 operating modes, continuous and two-state, so in these circumstances the two-state mode should be set. I do not know the algorithm of the 7-8-9 driver, so I cannot guarantee that it will work the same in all conditions. The 7-8-9 regulators had an "intelligence" that I couldn't figure out because they didn't behave predictably like a typical ON/OFF regulator.

And what exactly is the regulator plugged into 7-8-9?