Hive Dual Channel To Replace Honeywell BDR91 & ST9400s

[Jme_]

Morning all,

Apologies, I'm aware this set up has been discussed here before.

I'm looking to replace my Honeywell BDR91, ST9400s and wireless thermostat to control heating and hot water (cylinder) with Hive dual channel.

I understand the ST9400s and the Hive Dual Channel Receiver have exactly the same connections, however my current installation doesn't have (1) Hot water off or (2) Heating off used. The ST900s does currently control both the heating and hot water.

The other point which threw me off is the earth core used for terminal B, I'm assuming the original installer didn't bother sleeving this.....

Based on what I've read, my plan was to remove the BDR91 wiring and link out the A and B wires where they originate (double pattress JB) and install the Hive Receiver wiring as per the ST9400s.

I should also add, I have John Guest UFH but this is controlled via a separate thermostat and controller.

Any advice would be much appreciated, please see attached pictures.

Many thanks,
Jamie

 

[stem]

my current installation doesn't have (1) Hot water off or (2) Heating off used. The ST900s does currently control both the heating and hot water.

Perfectly normal, and commensurate with many other heating systems in the UK. terminals 3 & 4 are the important ones hot water 'on' and heating 'on' if it's working correctly now, that's all you need.

The other point which threw me off is the earth core used for terminal B, I'm assuming the original installer didn't bother sleeving this.....

Indeed bad practice but seen frequently I'm afraid

Based on what I've read, my plan was to remove the BDR91 wiring and link out the A and B wires where they originate

That's the way to do it.

 

[Jme_]

Perfect, thank you for your help!

 

[Jme_]

Hello again, just a query on linking out the A and B terminations, do these just have to be linked on their own or linked with another particular terminal?

The reason I ask is B (earth core) is terminated with another wire which will be left unconnected if the wire for B is removed from the choc block (if that makes sense?).

I've attached a picture with A and B cores marked.

Thanks again,
Jamie

 

[stem]

BDR terminals A and B are just a switch. When the BDR turns the heating on A and B are electrically connected, and when the heating turns off they are not. So when the wires that go to A and B are removed at their origin, in your case the other ends of these, need to be joined to complete the circuit.

So if the other end of these wires are the wires you have indicated with the arrows, only remove the black and green/yellow wires you have highlighted and add a link between the two terminals thay have been taken out of. Leave all the other wires exactly as they are.

 

[Jme_]

Thanks for confirming that Stem, much appreciated!