Installing evohome - BDR91 + Worcester Bosch Greenstar 30si + DT20RF

[GreenMonkey]

Hello,

I'm new to the forum so apologies in advance for any newbie questions!

I'm looking to install 8x HR92s along with wiring up the BDR91 relay box to my Worcester Bosch Greenstar 30si boiler which currently has a DT20RF RF programmer attached on the front panel.

My plan is as follows:

1. Leave the DT20RF set to "always on" and leave the DT20RF connect to the boiler.

2. Wire the BDR91 relay box into the boiler using the following diagram from http://www.ultimatehandyman.co.uk/fo...t=73938&start=

Screenshot 2021-12-08 at 20.02.42.jpg

Use 5 core 0.75mm cable like this: https://www.screwfix.com/p/time-3095...10m-coil/391pf

3. Connect the HR92s to all radiators except one of the hallway ones and the kitchen radiator (this has an old TRV are so doubt compatible with the HR92). These will act as bypass radiators.

Does this make sense?

Also, I have two radiator in the through ounge/dining room (one in each room) - do you set this up as one zone or two?

Many thanks!

[therealfronty]

I can't comment on your wiring, when I added Evohome I left the programmer in place (set to constant) and connected a BDR across the roomstat terminals in my wiring centre (and disconnected the roomstat wires obviously) and connected a second BDR across the cylinder stat terminals to control the DHW.

I left the bathroom rad constantly open (no TRV) to act as a bypass, I had to open the lockshield a bit to allow more flow else the boiler wouldn't fire (not enough flow).

I have two rads in my living room, it is configured as a single zone. For your lounge/dining room, I'd probably do them as a single zone, although no harm trying them as two separate zones and see how you get on.

[MajorDanby]

What is your system currently? Specifically do you have any zone valves and what currently calls for heat from your boiler?

Isn’t the dt20rf for a system set up? If you have a combi then it should t be needed??? You have a thermostat and bdr91 to call for heat on the CH and the DHW calls for heat when the boiler senses a flow

[rd99]

I can't comment on your wiring, when I added Evohome I left the programmer in place (set to constant) and connected a BDR across the roomstat terminals in my wiring centre (and disconnected the roomstat wires obviously) and connected a second BDR across the cylinder stat terminals to control the DHW.

I left the bathroom rad constantly open (no TRV) to act as a bypass, I had to open the lockshield a bit to allow more flow else the boiler wouldn't fire (not enough flow).

I have two rads in my living room, it is configured as a single zone. For your lounge/dining room, I'd probably do them as a single zone, although no harm trying them as two separate zones and see how you get on.

If I may cut into your conversation briefly: Thanks for the info - I have pretty much the same setup and wish list as the OP and was wondering if I could do exactly as you have done that is to wire the BRD91 to the wiring to the old Honeywell roomstat and just leave the programmer unit always On. Saves opening up our WB Greenstar 30Si combi - in the winter - where, if I mess things up it will be the devils job to get an engineer round to fix. Thinking about it, I might leave linking the boiler relay still spring just fit the 91 or 92 TRV' and the controller and a thermo or two - the boiler is on 24/7 at the moment anyway with the Danfoss TRV's turned right down in rooms we use little.

Richard

[GreenMonkey]

I'm going to have a go at wiring the BRD91 into the boiler this weekend, so I'll let you know how that goes.

On the question of bypass radiators - I'm assumes I'm okay to have 2 in the "system".

Thanks.

[GreenMonkey]

Well I actually got around to wiring up the BRD91 yesterday. No problems so far. My original plan was to "1. Leave the DT20RF set to "always on" and leave the DT20RF connect to the boiler." This didn't work so I removed the DT20RF panel and disconnected the ribbon cable.

The wiring diagram is slightly wrong though - it shows the 240v live going to the right L but it should be the middle L.

I also used 5 core cable but had to cut a small section out of the BRD91 back box so that the boiler switching cable could feed through, as the box is designed for 2 cables (power and boiler).