3 port valve motor permantly on!

[ktilbury16]

Help!

Pulling our hair out!

Have a Worchester Bossch Boiler, Honeywell Programmer, thermostate, hot water thermostate.

The 3 port MPV is is always hot to touch and the motor is always on even when the valve is closed and hotnwater/heating is off.

The programmer, thermostate and MPV have all been replaced and the wiring checked in the wiring centre but still the problem persists.

Any ideas or trouble shooting suggestions greatfully received.
Thanks

 

[terryplumb]

Does the boiler fire up when there is no demand from programmer ?

 

[Madrab]

That's the way they can work, hence why they can and do burn out really quickly. They can still be powered up when the boiler's off. Have a quick read through this

How the 3-port Valve Works - Julian Rogers - Practical Projects

This page describes how the 3-port central heating valve works in detail.

www.newmrr.co.uk

 

[ktilbury16]

Does the boiler fire up when there is no demand from programmer ?

Yes when on continueous it fires up as and when thermostate drops below temperature.

Even in middle of night when no heating and no hot water on the MPV can still feel motor of MPV vibrating and its very hot.

Thanks for help!

 

[ktilbury16]

That's the way they can work, hence why they can and do burn out really quickly. They can still be powered up when the boiler's off. Have a quick read through this

How the 3-port Valve Works - Julian Rogers - Practical Projects

This page describes how the 3-port central heating valve works in detail.

www.newmrr.co.uk

Thanks

Will have a read. I was wondering if that was the case as cannot actually find a fault!

 

[CBW]

Try turning off and back on again after say 5 minutes

 

[Johntheo5]

Above should work if power switched off at the supply.

Or as a temporary measure before retiring for the night, switch both HW & CH off. then switch HW only back on, turn the cylinder stat right up for 10 secs or so then return it to its original setting, valve is now unpowered, you can then just return the programmer as set up for the morning. I think I saw some method of getting it to default to do this somewhere, will have a look or google it maybe.

 

[Johntheo5]

Here you are.
That should work IMO, with that NO relay, every time the CH is switched off or the roomstat is satisfied then the relay will open and the valve, now unpowered , will spring return to the HW position

Motorised Valves - DIYWiki

wiki.diyfaq.org.uk