Strange Heating Issue

[Marty25]

We have a problem with our Y plan heating, the programmer is a Honeywell ST699, running a Main 24 Heat ERP boiler.
The 3 port valve which had been sticking was replaced spring 2025 with a ESI 3 port Zone.

The heating will work by itself as will the hot water.
But using the 2 timer period the heating and water only work on an evening.
In the morning once the water is up to temperature it will turn the heating off even though it has not reached the thermostat set point.

I was going to change the ST699 for a ST9400C and after watching a tutorial I checked my wiring and I have an extra wire on connection 7 on the ST699.
As I understand to upgrade to the ST9400C I would make the connections as follows.

ST699 Connection 1 Live goes to Live on the ST9400C
Connection 2 Neutral goes to Neutral on the ST9400C
Connection 3 Heating On goes to 4 on the ST9400C
Connection 6 Hot water On goes to 3 on the ST9400c
But I also have a wire on 7 on the ST699, where does this go?

Any comments or suggestions would be appreciated.

 

[CountryFan]

But I also have a wire on 7 on the ST699, where does this go?

It’s the Hot water off connection, iirc terminal 1on the Honeywell. It’s required for the correct operation of the 3 port valve

 

[Marty25]

Many thanks, Will get this setup, did not want to guess and cause further problems.