Installing Evohome on Y-plan by DIY newbie

[kris_v]

Hello,

I'm fed off manually turning down TRV's, thus why decided to invest in Evohome. Investment will include:

- WiFi Controller
- Hot Water kit
- 12 x HR92 TRVs
- Wall Mount Pack

Currently wiring is based on 16-way junction box, and it looks like that:



Question 1:

Should I stick to existing junction box, or would it be better to change it for 10 way version ?

Question 2:

If I would use existing junction box, should it be connected like that:



Of course HTG BDR91 L -> mains live, N -> mains neutral, A -> mains live
DHW BDR91: L-> mains live, N -> mains neutral, A -> mains live

[Richard]

If you have Y Plan, take a look at page 47 of the evohome Installation Guide for the wiring diagram. I personally use Wago connectors in my own IP rated box rather than a 10 way, much easier!

[kris_v]

Hello,

I have looked at Page 47, but main problems are that it doesn't explain where to connect a Frost Protection Kit, and also boiler in that example has only 3 wires L, E, N, while ours has a 4th cable in yellow sleeve.

Will appreciate any help in this matters.

[Richard]

Frost protection 'switched live' brings on the heating, so should be wired to the B terminal of the HTG BDR91.

If you look at terminal 8 on page 47 this is attached to the pump and live of a boiler with no pump overrun but equally it can just be attached to the boiler switch live wire in cases where boilers have this facility.

[kris_v]

I found that Frost Protection Kit was wired incorrectly, it hasn't been wired to live mains but instead into ST9400C programmer

Boiler has indeed only 3 wires, but someone decided to replace original cable somewhere in middle, and it has been extended with 4-core cable. The didn't even follow cable colours, and extended live wire by using yellow core

I have connected everything together and followed your video with biding CS92 & BDR91's in Y-plan. For now works like a charm

Meanwhile 2 more questions:

1) How to take fixing plate (back plate) from CS92. I can not see any lip to open it.

2) How does the "Hot Water overrrun" in Stored Hot Water options work ? As default it is set to 0 minutes, if I will change it to e.g. 10 minutes, and there will be demand for CH, will 3-port valve go into position CH/DHW for 10 minutes, and after that time change just for CH ?

[Richard]

2x lugs dead center (behind) the batteries holds the front plate to the backplate of CS92A.

The overrun should be left as 0 minutes, but this should not be available unless you have a boiler demand relay? Is 'wireless relay box' still showing under boiler control in system devices menu? If you haven't got a boiler control relay (setup for Y plan as per my video) then it should be set to NONE.