Wiring BDR91 to worcester greenstar 37cdi combi

[G_4ce_uk]

Good evening. I have recently brought a Honeywell EvoHome system and need some help with wiring in the BDR91 wireless relay box.
I have a Siemens room stat that has 2 wires and need some help on how to wire the BDR91.

 

[G_4ce_uk]

There is a red wire going to L and a black wire going to Y1

 

[RandomGrinch]

There is a red wire going to L and a black wire going to Y1

Can you post a picture of the wires?

 

[G_4ce_uk]

Yes sure. Here are the wires

 

[RandomGrinch]

Thanks for the photo.
I'm afraid your new BDR91 requires a permanent Live and Neutral connection.
As you've said, your existing stat is 2 wire, having a live and switched live, going back to the boiler.
The cable feeding it is also 2 core and earth - there isn't a spare core that could provide a neutral.
Ideally, you would have a 3 core and earth flex, connected back to the boiler.
Also unfortunately, Worcester in their wisdom, hide the wiring connections behind the cover that forms part of the boilers room sealng. After accessing the wiring connections, the boiler should be checked for safety by a gas fitter.

Does the wiring to the stat pass anywhere near the boilers fused connection unit?
If it does, it may be possible to provide a permanent live and neutral from there.
Is there a separate programmer used for timing the heating?

 

[G_4ce_uk]

Hi RandomGrinch, thank you for your reply. The wiring to the stat is not far from from a socket where a permanent live and neutral could be taken. I assume that would be fine.
Once I get a permanent live and natural to the N & L connections on the left, would the existing black and red wires go to A & B on the right side?
BDR91 image attached from the web
Thanks again.

 

[G_4ce_uk]

Reference timer, there is one inside the boiler, but that is permanently on and never been set to timer mode. It’s a digital one.

 

[G_4ce_uk]

I am sure the timer was a Worcester DT20- Digital Timer

 

[RandomGrinch]

The wiring to the stat is not far from from a socket where a permanent live and neutral could be taken. I assume that would be fine.

Ideally, the supply should be provided from the same source as the boiler - i.e. it's FCU. This would provide a single point of isolation for both boiler and controls.

Once I get a permanent live and natural to the N & L connections on the left, would the existing black and red wires go to A & B on the right side?

Yes, the existing red and black wires would connect to A and B. The order doesn't matter, and don't add a link to the L terminal, as you may see in some wiring diagrams.

I am sure the timer was a Worcester DT20- Digital Timer

Once the EvoHome is up and running, set the DT20 to permanently on, this should allow the EvoHome to take over the C/H scheduling.