Horstmann 425 Diadem to Wiser Kit 2 installation

[Williaz]

Upgrading from Horstmann 425 Diadem (no thermostat connected) on an oil boiler (Myson) to Drayton Wiser kit 2.

I'm just trying to confirm exact wire placement for the new plate. There are a few loops from the old system which I suspect are done internally/switching system with the wiser 2.

Horstmann 425 diagrams and pictures

Wiser 2 diagrams

Oil boiler

Horstmann 425 wires
1
2
3
4
5
6
7
8
9

Drayton Wiser 2 Wiring setup

Back panel plate
1
2
3
4
5
6

 

[ericmark]

Yes links not required so what was 1 will be 3 on new, and what was 4 will be 4 on new.

 

[Williaz]

Thanks

Does that mean 6 on the new wiser plate is empty?

Horstmann >wiser
1 > 3
2 > 1
3 > 2
4 > 4
5 > ignore
6 > empty
7 > 5
8 > empty
9 > empty

 

[ericmark]

There is no 6 it only goes to 4. It goes N, L, 1, 2, 3, 4, and an earth tether. The 1 and 2 are often not used, 1 is used with Y Plan but very little else. It seems not used with yours so just N, L, 3, 4 are used plus earth tether.

 

[Williaz]

Thanks for the feedback Eric.

I ended up with the wiring as below.

Connected the wiser hub via app. Main issue is HW fires up the oil boiler (showing hot water light green on hubR) but heating doesn't come on when heating light green on hubR.

Hot water light on - boiler fires up
Heating light on - boiler doesn't fire up - can feel the water pump beside it starting though
Heating and Hotwater lights on - boiler fires up

The wireless thermostat shows a flame to indicate it is on, but boiler not doing anything despite heating light on the HubR.

It seems to be something simple such as no independent water heating and it should be all or nothing ie heating/hot water on at same time, would that mean switching 3 and 4 around would solve the problem as current setup doesn't allow use of wireless thermostat.

 

[CBW]

Did you previously have to have both on for heating, or were they separate?

 

[RandomGrinch]

May we have a look at the front of your Horstmann 425 Diadem?

I have a sneaking suspicion that it is set to gravity mode - and heating will only come on with hot water.
I'm afraid Wiser may not be compatible with a gravity system...

https://wiser.draytoncontrols.co.uk/blog/wiser-common-domestic-boiler-systems-explained#:~:text=Wiser%20is%20not%20compatible%20with,Wiser%20needs%20to%20work%20effectively.

 

[Williaz]

 

[RandomGrinch]

I believe it has been interlocked for a gravity system

 

[Williaz]

Thanks for the feedback. Would the nest gen 3 work with this setup or any other wireless suggestions?

 

[RandomGrinch]

Thanks for the feedback. Would the nest gen 3 work with this setup or any other wireless suggestions?

A Hive could be a replacement, it has a built in gravity mode option.

The Nest could also be used, but it needs some clever wiring...

Nest Thermostat and Gravity Fed System

Hi, can anyone help? I had a Hive system running my Heating and Hot Water, just been given a Nest and thought I would give it a try. I have an old system which is Gravity Fed and with the Hive I simply held a button down and it went into 'Gravity Mode'. Don't seem to have that with Nest unless...

www.diynot.com

Alternatively, it's not out of the question to change your system away from gravity, with the addition of some zone valves for an S-Plan, or a mid position valve for a Y-Plan.