hot water won't turn off

[Bradley31]

Hi All
We have an oil fired Boiler, Tank in the loft and Hot Water tank in the airing cupboard with a Honeywell ST9400A control and HCW80 and HC60NG remote thermostat.
For a while the Hot Water was not coming on. We had to fire up the Heating if we needed Hot Water.
I swapped the motorised head of the valve from the Heating to the Hot Water and it worked fine, so i thought i would buy a new synchron motor. I have just fitted the new motor but now the Hot Water won't switch off. When the power is on the MV activates and closes the switch which then switches the Hot Water on even though all of the controls and HC60NG are off. When i turn the power off the valve does close (and when i have turned it by hand i can feel the valve moving inside) so i don't think it is ceased open. Is it a wiring issue? or the Tank Thermostat? (i have turned the thermostat on the tank down but it has no effect. I can hear the click at over 70 degrees even though its only set to 55)
I am at a loss of what to try next. Should I keep it turned off for now?
Any help is much appreciated.
thanks

 

[Bradley31]

I have taken the fronts off all the controls but the Lee is still 240v on the orange and the grey cables and when I turn the far right switch on or off this turns the hot water on and off without any controls. Is there a wire I need to move etc?? I have tried it with the MV head from the heating valve and re wired it but it does exactly the same thing so can’t be the head as the Heating head works fine when it’s on the Heating.

 

[John.g]

Have you checked the wiring at the ST9400A controller in case there is a extra permanent live connected by mistake to the "HW Off" which is used for a Y plan configuration or something along those lines.

 

[ShaunCorbs]

You have a bad port valve or one permanently calling do you have any voltage on the browns on the port valve wires ?

 

[Bradley31]

Need to test no point in throwing parts at it

i have taken the program unit and the HG60 module off. The power is on. you should make out the numbers behind the wires. with the black wire on the tester in space 3, I have 240v in lines 1, 7, 8 and 0. The HW is on and won’t switch off. Even though the controls are removed.

 

[Bradley31]

Have you checked the wiring at the ST9400A controller in case there is a extra permanent live connected by mistake to the "HW Off" which is used for a Y plan configuration or something along those lines.

I notice that this is not how it says it should be wired on the back of the program box

 

[ShaunCorbs]

240v on either 6 or 8?

 

[ShaunCorbs]

It’s s plan so programmer is correct

 

[Bradley31]

240v on either 6 or 8?

Yes, always On 8

 

[ShaunCorbs]

Turn the fused spur off and remove the grey wire and make safe (when you turn power back on this might be live)

 

[Bradley31]

Turn the fused spur off and remove the grey wire and make safe (when you turn power back on this might be live)

Ok, done that. Now there is only 240v to 1 and 7. The HW didn’t come and the MV didn’t move

 

[ShaunCorbs]

Now try your heating and hot water systems eg one at a time does everything work eg boiler come on pump etc

 

[Bradley31]

Turn the fused spur off and remove the grey wire and make safe (when you turn power back on this might be live)

I have just realised that we have had some underfloor heating out in downstairs in an extension and they wired it in next to the boiler. Could they have wired something in wrong there? We had noticed that our water all winter was really hot and we had been using a lot of oil. I think I have only noticed this issue when the heating finally went off. Maybe this has been happening since the new bit of wiring went in!

 

[moonlight]

Thats sounds like a possibility.

 

[ShaunCorbs]

Yep maybe do you have an extra port valve by the manifold?

 

[Bradley31]

Yep maybe do you have an extra port valve by the manifold?

I think the grey wire I have disconnected upstairs is the one in the frost stat in the screw without a number to the right of slot 4