hi and thanks for your reply's I'm away from home at the moment,
since the replacement by the chap who wired it up incorrectly I had the boiler checked again by a gas safe engineer , who reset the gas ratios and said the boiler was fined after carrying out checks etc. and agreed it needed a automatic bypass valve and the boiler pump over run needed to be reinstated when this was fitted and rather than me taken the boiler case off to this a link was put in the wring centre to perm live and demand live to disable the pump over run , I recently drained down the system and fitted a automatic bypass valve after the pump but before the 2 zone valves and goes back to the return to the boiler and I also removed the link and the pump over run is now working fine the abv is set to about 0.3.5 bar and no more bangs from the boiler , I get back when I can remember the pump I think it was a grundfus 15/50 but had had a new interpart head insert thanks again
since the replacement by the chap who wired it up incorrectly I had the boiler checked again by a gas safe engineer , who reset the gas ratios and said the boiler was fined after carrying out checks etc. and agreed it needed a automatic bypass valve and the boiler pump over run needed to be reinstated when this was fitted and rather than me taken the boiler case off to this a link was put in the wring centre to perm live and demand live to disable the pump over run , I recently drained down the system and fitted a automatic bypass valve after the pump but before the 2 zone valves and goes back to the return to the boiler and I also removed the link and the pump over run is now working fine the abv is set to about 0.3.5 bar and no more bangs from the boiler , I get back when I can remember the pump I think it was a grundfus 15/50 but had had a new interpart head insert thanks again
