Is there any way of stopping overflow dripping, it's a Vokera excell 80 sp?

very rare for cold mains to go thro secondary heat exchanger bit it is possible, more probable is the expansion vessle has lost its charge. or something more simple like your filling loop passing water when in off position

higgs
May 2010

....but first recharge your expansion vessel. Is the pressure so high when the heating is cold?. If the pressure shoots up when the central heating warms up, and drops when it is off you need to recharge your expansion vessel, a fairly easy DIY job. No domestic hot water could be a holed diaphragm or a bust microswitch.

c
May 2010

Yes, have someone fit a new heat exchanger,your high pressure indicates cold water supply leaking thro' into the c/h cct and venting off thro' your safety valve its not an overflow valve this valve open to dump the water at 3.5 bar so your 3 bar is virtually there and it will continue to be there with this leak present.

Guytawe
May 2010