need help wiring a thermostat to a Junkers KN 12-8 KP

[Cashflood]

hi all,
I would need help in connecting an aliexpress bought RF Receiver to a Junker KN 12-8 KP boiler. It's a kit coming with a thermostat. I know the boiler it's old but I can't replace it anytime soon as I just spent all my money in buying the place. Please find the picture below for the boiler electric schema and wiring, the internal panel and receiver picture with his wiring schema.

Many thanks to anyone having the time to look into this.

LE: the TRZ 12 seen on the picture is where one should plug in the native Bosch TRZ 12 thermostat. I've included the wiring schema for that receiver if that helps.

 

[stem]

I'm not familiar with Junker boilers and my German is not good either. However, from your description and the diagrams, TRZ are the connections for the room thermostat, [Raumtemperaturregler?] Therefore terminal 4 will be the live (out arrow) and 5 is the switched live (in arrow). I am referring to the terminal numbers hidden below the wires, not those in ( ) above.

Then, the thermostat receiver terminals 2 and 3 (OPEN and COM) are the switching terminals.....

.....so the thermostat receiver could be connected as follows:

Normally when there isn't a room thermostat fitted with many boilers, certainly here in the UK, there is a wire link fitted between the thermostat terminals to allow the boiler to operate. Maybe not for a Junkers.

 

[Cashflood]

Thank you very much stem, very kind of you. That seems about right and I was thinking the same wiring scheme. I was expecting to find out a bridge/strap there too but I have to look for it somewhere else.

I have identified it on the drawing but I can't seem to identify it phisically. I have underlined it on the drawing.

Probably I have to trace the wires and un/plug to see effects.

 

[stem]

The drawings are a bit confusing there are a couple of links called BK1 & BK2 but I can only see them in the schematic drawing and not in the wiring diagrams to determine what they do. If you have the boiler installation manual it should say somewhere what they are for.

 

[Cashflood]

That's it. I've look in the manual, it's the BK1. I'll attach the schematic it anyone else may be interessted in the future.

Many thanks stem, as soon as I have some spare time I'll wire the thermostat and get back with a confirmation.

I do still have a question: I know that in this configuration I have to keep the boiler on the whole time and control it wih the thermostat. I'm thinking on powering the receiver from the mains before the on/off switch so that in the summer i can shut it off without losing the synk inbetween receiver and thermostat.

I know the schematic will look a bit differnt but it's fine. Wouldn't it be better this way, any isssues?

 

[stem]

I'm guessing you want to isolate the whole boiler during the summer months as you don't use it.

Here in the UK, heating systems and their external controls are normally fed from the same fused connection unit so that when the engineer comes to service them everything is isolated by one switch. Most boiler MI's also stipulate it.

What you suggest would work though, and maybe it won't be an issue in Germany.

As I said before I've neve seen a Junkers boiler, does it not have an on/off switch on its control panel? [S1 on the wiring diagram on your last post] If it does and you switch it off there, the main live feed into the boiler [L] would still be live and would keep the receiver powered.

 

[Cashflood]

Here in the UK, heating systems and their external controls are normally fed from the same fused connection unit so that when the engineer comes to service them everything is isolated by one switch. Most boiler MI's also stipulate it.

From this point of view I fed it like you said earlier, I guess it's safer.

I plugged the thermostat, removed the BK1 strap and chage the operation mode from the switch accordingly (Betriebarten-Schalter) and all works fine. There's an electric buzz noise though when not heating, something like an old transformer buzz. That was not present when the boiler was running in manual mode. I dont' know where it's coming I have see how annoying it will be.

However many thanks againg for your support stem. I've posted this on 3 forums : a german one, a romanian one and here wehre I actually solved it.

 

[stem]

The buzzing does sound odd, from an electrical circuit point of view nothing really should have changed. Is there a possibility it's the the thermostat receiver that's making the noise.

 

[Cashflood]

I checked but nope, the receiver it's silent. It could be that the buzz was present and I didn't noticed it because of the burner noise. So far after 9 hours on nothing burned.