Central heating system - hot water won’t switch off until whole system shuts down

[Matt Stroh]

Hi

I’ve got many fingers crossed in the hope that some of you good people can help me...

It’s an ‘S’ system traditional gas boiler with a hot water tank and radiators, with two 2-port valves to separate the HW and CH parts of the system. I can use the programmer no problem to fire up either or both, but the HW valve won’t close until both there’s no call for HW and the CH, that is it will only stop heating the water when there’s no programmer requirement for both.

I’ve taken the valve head off and the spindle appears to move freely. Could it be a Synchro motor fail or is it more likely to be deeper in the electrics?!

The programmer is a Drayton Wiser and I can hear a relay clicking when I ask for the HW to stop.

Help gratefully received. Thanks!

 

[CBW]

How do you know it’s still heating the hot water? How do you know that valve isn’t closing?

 

[Matt Stroh]

Thanks for the quick reply.

The sticky-out bit is staying in the open position and only goes back to rest when the power goes off for the CH. I can hear it close and the switch is loose until the CH powers down.

If I set just the HW (without the CH) to go on and then turn it off at the programmer, the valve closes as it should do. It seems to get confused when the CH has been on.

The hot water is getting very hot...

 

[ianmcd]

Sounds like it is wired wrong, the Hot water will only get as hot as the thermostat on the boiler is set to, but that is not the solution to your problem but turning it down will lower the HW temp

 

[Matt Stroh]

Thanks. There is a thermostat on the hot water tank and I meant to check whether that will limit the heating input to the water.

I feared that the culprit might be the mass of wires shoved into a junction box (not by me, I hasten to add!)

 

[ianmcd]

Thanks. There is a thermostat on the hot water tank and I meant to check whether that will limit the heating input to the water.

I feared that the culprit might be the mass of wires shoved into a junction box (not by me, I hasten to add!)

if the valve is not closing the cylinder thermostat is doing nothing

 

[Matt Stroh]

Ok... so a bit more fault finding. The water tank thermostat does cause the valve to close when it reaches the desired temperature which is a relief because it means that the water isn’t going to boil dry. It also means that the port valve must be working fine.

Now I need to spend a bit of time in the junction box working out why the call for heating is overriding the HW power from the programmer, but that can wait for a time other than a Saturday night methinks.

 

[ianmcd]

Im not experienced with the Drayton wiser, most programmers can be set to Gravity HW which brings the HW on everytime heating is selected, if the wiser has this check that it is set to fully pumped and not gravity HW , as said not sure if the wiser can be

 

[picasso]

There is a problem with s plans where the valves can latch on if the grey wires are not connected to a permanent live and instead the greys are connected to the browns (control wires from the stats).