Honeywell st6400c with Centaurstat 7 fault

[V2brett]

Hi everyone,

Weve just moved into a new house which has a conventional heating and hot water system with a tank controlled by the above.

The hot water slider on the 6400c doesn't fire the boiler unless the heating slider is on the 'cont' position.

Now this is fine as I understand when a centaurstat 7 is connected to the honeywell st6400c the heating slider is left in the 'cont' position and the centaurstat fully controls the heating.
Now problem is when i slide the heating slider on without the hot water and the centaurstat is not on the system makes hot water?

Is this looking like a wiring problem or a fault with the proggrammer?

Cheers

Brett

 

[stem]

There's not really a lot to go on in your post. It maybe that the plumbing system is old and does not have motorised valve/s to allow separate control of the hot water and heating. It will also depend upon how the various control components are wired together. To diagnose a wiring fault we would have to know what wires go where.

If you could provide additional details, then someone may be able to advise. But it may be necessary to have someone to physically check the wiring to see what goes where, and may not be possible to diagnose over a forum.

 

[V2brett]

Hi sorry for the delay in my reply what with moving in and working only over the christmas break have i managed to study the wiring and get to know the system.
The system compromises of a worcester greenstar ri boiler,horstmann z332 3 port valve, honeywell tank stat, honeywell st6400c programmer and of course a pump.
The system acts like a w plan system in that it prioritises hot water and shuts the heating off when hw is called for. And of course the main glitch which is the hw slider on the programmer does nothing, the ch slider has to be on to make hw and ch.

Upon studying my wiring i believe the hw on and ch on wire are crossed over in the 10 way junction box. My hw on wire black wire is in port 4 but should be 6 (note black tape on wire in programmer) and the ch on blue wire is in port 6 and should be port 4.

Ill attach some pics of the wiring.

I hope its enough for someone to help/confirm the problem.

Many thanks,

Brett.

Note the pump is not fed from the 10 way junction box

 

[V2brett]

Well just thought stuff it and swapped the brown wire black tape and blue wire over in the programmer and hey presto all is sorted.

I can only guess the previous home owner who was a technophobe and diy superstar switched back to this old programmer when moving out and got the wires crossed over some how.
Just need to wait a while now and see if the auto timer function works on the programmer.

Cheers.