central heating won't turn off

[ianmcd]

what make was the origional valve and what make are you replacing it with they are not all the same

 

[D_Hailsham]

what make was the origional valve and what make are you replacing it with they are not all the same

The OP says, in his first post, that he has a Drayton valve.

It doesn't matter what make valve he previously had or what he has now, the boiler should not be lighting when CH has been satisfied.

 

[ianmcd]

The OP says, in his first post, that he has a Drayton valve.

It doesn't matter what make valve he previously had or what he has now, the boiler should not be lighting when CH has been satisfied.

if the origional valve was an early Sunvic it does matter as the wiring is different, he may have replaced a motor open /motor close with a sspring return valve so the question was relevant

 

[D_Hailsham]

if the origional valve was an early Sunvic it does matter as the wiring is different, he may have replaced a motor open /motor close with a sspring return valve so the question was relevant

The only Sunvic momo valves I know of are wired exactly the same as a spring return.

 

[ianmcd]

The only Sunvic momo valves I know of are wired exactly the same as a spring return.

well you need to look again , any mo Mo that is wired the same as a spring return ????

 

[D_Hailsham]

well you need to look again , any mo Mo that is wired the same as a spring return ????

You need to read Sunvic's pdf, which is attached.

 

[macwales]

Update

Solution found!!

I now have the CH working.

First what was not causing the problem of CH not switching off when CH only required

Boiler
Programmer
HW Thermostat
Room Stat

I had fitted new, all of the above without curing the fault and the boiler is 4 years old.

Wiring

Boiler wiring for pump overun in the garage beside the boiler was not as per the boiler fitting instructions. it seemed to have been rigged to save wire so I rewired it correctly but this did not cure the fault. I then put in a new airing cupboard junction box to replace the cramped rats nest installed by the house builders 20 years ago. To do this and to ensure separate and direct wiring to the pump, I used a wiring diagram provided via an e mail by the Drayton Help Desk. ( Make sure that you get the diagram that includes boiler pump overun.) See attachment

This diagram was very helpful and very clear

After all this I did not cure the problem. So I ordered and obtained another Drayton 3 port valve actuator and valve from a different source.

This second new actuator is now fitted and the system is working normally so PROBLEM CURED.

So

if you have a Drayton 3 Port Valve and your central heating will not switch off when either of, or both, your programmer and room stat are off then the actuator on the valve may be faulty and require replacing.

In my case I can only summise that the micro switch in the new actuator bought 6 weeks ago that supplied power to the orange wire was sticking in the on position and this kept the boiler firing up. I am not taking it apart to confirm this as its going back for a refund tomorrow.

Thank you all who contributed to this thread it greatly assisted in building up my knowledge.