Potterton Promax Ultra - Wiring

Picture taken from another post as my phone is a potato.

We have had a Potterton Promax Ultra 24 ErP Combi installed.
I am looking to install a Honeywell ST9100s clock. No roomstat is to be installed, just the clock. At the moment, I have a fused spur feeding the boiler. I have a 5 core coming back from the boiler to the clock. This is feeding the clock (spur to clock, neutral and earth connected in clock and lives joined through). I have removed the link from terminals 1 & 2 in the boiler. I have connected the cores so that the grey core feeds the clock from the '230v out' terminal in the boiler, and the black core is my switch wire for the heating.
On the clock (Honeywell ST9100s), i have wired my grey core to L to feed the clock and i have wired the black core to terminal 4 as per the diagram. This would not fire the boiler. I tried to put a link between L & 1 incase that was needed, but this just made the switch wire permanently live, which strangely still did not fire the boiler. Could anyone shed some light on how i can get this going? Currently put the link back in and just working the heating from the boiler buttons.

At end of day the boiler and clock need live, neutral and earth all the time, and the clock joins 1 and 4 to call for heating.
The boiler will either have potential free contacts or require 230v to fire.
So it looks as though the boiler end is ok and you want grey and black wires in 1 and 4 at the clock, with no link from L to 1 at the clock.
I can’t quite tell if you got the permanent supply to the clock correct from your post.

It’s not a great manual for that product but it looks as though 1 and 4 are for heating and 2 and 3 are for hot water.
Maybe post a photo of the clock end.

This is a link to the Honeywell ST9100. You will see there is a L & N, then 4 connections.
I currently have the N & E from the spur connected to N & E at the clock. My L from the spur is joined to the brown of the 5 core (not connected to the clock, just joined through. This brown, along with N & E, are connected into L N E at the boiler. My grey core is connected to '230v out'. This core is connected to L at the clock to feed it. My Black core is connected to the heating in the boiler. This goes back to the clock and is connected to 4. When I boost the clock, it does not fire the boiler. When I put a link from L to 1, it makes the switch wire permanently live. Strangley, this still does not fire the boiler. Is one of my connections wrong somewhere? Currently just removed the feed and switch wire and replaced it with a link just to get the heating working from the boiler buttons.

The link you removed must go through NV terminals on the ON CH of the time clock.
Hot water will switch ON via Boiler when required, opening of HW taps.
You can still use your existing T/C using the Heating option only
Hope I’ve understood this correctly

This should explain it a bit better

Strongly advise against not fitting a room 'stat of some kind. Without one, your boiler will cycle on and off, wasting fuel, when the house has reached the desired temperatures.

brianmoooore said:

Strongly advise against not fitting a room 'stat of some kind. Without one, your boiler will cycle on and off, wasting fuel, when the house has reached the desired temperatures.

Click to expand...

We don't use the heating for any more than an hour, and usually just over winter. I know what you are saying but it doesn't make sense for our kind of usage. We just boost the heating after tea for an hour then turn it off. We do that once a day. Might see if I've got one lying about the van.

LiamSpark said:

currently have the N & E from the spur connected to N & E at the clock. My L from the spur is joined to the brown of the 5 core (not connected to the clock, just joined through. This brown, along with N & E, are connected into L N E at the boiler. My grey core is connected to '230v out'. This core is connected to L at the clock to feed it. My Black core is connected to the heating in the boiler. This goes back to the clock and is connected to 4. When I boost the clock, it does not fire the boiler. When I put a link from L to 1, it makes the switch wire permanently live. Strangley, this still does not fire the boiler. Is one of my connections wrong somewhere?

Click to expand...

I would have used the brown to power the clock.
Then the link you removed gets extended with the grey and black wires to the clock and connects to 1 and 4 (load input and switched load output) at the clock.
See if the boiler fires with a wago on the grey and black the clock end of things.