C/H pump not working unless HW is switched off

[masonmjs]

At the moment, until rectified, you have a mid position valve, so any fault finding will/should apply with this type of installation. You should be able to follow this link fairly logically to identify your present problem.
When you say the CH pump doesn't run then if referring to the circulation pump, the boiler isn't firing either?

Y Plan central heating system (flameport.com)

Yes that is exactly what is happening, boiler switches off, pump stops, then all is good if I switch off the HW.

 

[John.g]

Yes, understood, but is there only one (or two) 2 port valves being installed, if only one, then the diverter valve must still operate IMO as normal but with the extra security of a normally closed two port valve.

 

[masonmjs]

Yes that is exactly what is happening, boiler switches off, pump stops, then all is good if I switch off the HW.

mistake, replied to my own post

 

[masonmjs]

Yes, understood, but is there only one (or two) 2 port valves being installed, if only one, then the diverter valve must still operate IMO as normal but with the extra security of a normally closed two port valve.

the original 3-port valve is still fitted, I intend to fit an additional 2-port valve and wire up in accordance with the Kingspan installation guide.

 

[EvilDrPorkChop]

the original 3-port valve is still fitted, I intend to fit an additional 2-port valve and wire up in accordance with the Kingspan installation guide.

Don't bother, save yourself some hassle and just fit two 2 port valves. You'll regret it in the long run if you don't

 

[plumbingdoctor]

Hi
Maybe your tempering valve doesn't work properly. this device can regulate the C/H of your hot water systems even with a multiple water supply