Y Plan - Wiring Help

[quinla01]

I bought the "Honeywell evohome Wi-Fi Connected Value Pack A" plus an additional 4 HR92's a while back. I've not had time over the past couple of months to attempt to wire everything up but did manage to get the the controller and HR92's working in 7 different zones (one has two HR92 in a zone). This works in tandem with my existing heating system and does a half decent job of controlling the room temperature but of course it has no control over the boiler / hot water system.

Anyway - I finally got around to taking a look tonight. I was pretty shocked at the amount of existing cabling used in the system. Long story short the heating system has been upgraded several times over the years. I only moved in to this house a few months back so inherited a bit of a mess. The boiler ( brand new Worcester Greenstar 30 CDi Classic regular gas) lives in the garage. Originally the old boiler was was a wired system that lived in a cupboard in a utility room that had separate heating and hot water timings. It was then upgraded to a Salus wireless thermostat that has a wall mounted controller in the hallway which is wired back to the system somehow. The legacy controller still controls hot water and it looks like it also controls heating as it's set to be permanently on however the salus system must be switching the heating on and off somewhere down the line.

My pump, valve and hot water tank are all in a airing cupboard on the 1st floor. I removed the face plate of the double wall box in the airing cupboard used to connect everything and the wires literally sprung out on me. There are 5 cables coming up from the floor with barely any slack and varying numbers of cores ranging from 3 - 5. I have not way of tracing the cables as they're all under hard floor or behind plastered walls.

Anyway... I'm hoping most the cables are control cables and are therefore irrelevant. If i were to remove the legacy systems wiring altogether i'd be left with something similar to the attached drawing (apologies in advance for the ms-paint effort). I think the wiring diagram on page 47 ( Y Plan: Three-port Mid position valve with a wired boiler If a wireless boiler relay is used the Orange wire and feed to pump and boiler are not required.) Is most relevant to me but i'm still a bit confused about as to how everything is wired. Which cable(s) is the "Feed to pump" cable in the diagram? I had expected to have a receiver in the the garage next to the boiler (HTG) a receiver in the airing cupboard next to the wireless CS92A (DWH) and then power between all three and their corresponding devices.

Appreciate any advise.

Thanks
Andrew

[Richard]

Hi Andrew,

The 'basic' Y Plan wiring diagram is on page 47 of the evohome Installation Guide (http://www.honeywelluk.com/Documents/Al ... lation.pdf).

If you look at the Worcester Installation Guide for your boiler (https://www.worcester-bosch.co.uk/suppo ... 6720815723) page 27 details the wires you need to get off the boiler and you will see that the boiler actually powers the wiring centre and has provision to power the pump from the boiler.

The two BDR91 wireless relay boxes are the same as the two channels of a normal programmer. But install the BDR91's and CS92A wireless tank thermostat with caution as they need to be spaced apart, as detailed here - http://theevohomeshopforum.co.uk/viewto ... ?f=15&t=30

Worcester also have a handy wiring guide for your boiler (https://www.worcester-bosch.co.uk/suppo ... oad/WGCDIR).

That should be all you need. If you are unsure of anything, please contact a local heating installer to do the work for you.

Thanks,

Richard

[quinla01]

Thanks,

Starting to make a bit more sense although i'm wondering if I'm a BDR91 short (The kit came with 2) given my setup? Do i need 3 in total?

1 x BDR91 for Mid position zone valve HTG
1 x BDR91 for Mid position zone valve DHW
1 x BDR91 for Boiler Relay.

Alternatively, I can get away with two

1 x BDR91 for Mid position zone valve DHW
1 x BDR91 for Boiler Relay & HTG

But i'd have to somehow get a cable between the BDR91 connected to the boiler (in garage) & the HTG zone valve in an airing cupboard on 1st floor?

Thanks

[Richard]

If you want to control the boiler with a dedicated wireless relay, then yes you are a relay short. Traditional Y Plan normally switches the boiler on with a switched live wire as shown on page 47...