boiler trouble

[howler]

hi all
moved into my house in feb, central heating and hot water working fine until about 3 weeks ago, then it started playing up, the rads get warm when the hot waters on only, the hot water only stays on for about 30 mins then stops,if i put the cylinder stat up to 80 from 60 it stays on ok, i turned room stat down to 0 but rads still geting hot, iv recently had a new 3 port zone valve fitted by a local plumer cause that was the last problem i had, its a honeywell 3 port zone valve, honeywell L641A1039 cylinder stat, grunfos pump, with a potterton housewarmer back boiler. can anyone help please

 

[spudkey]

the hot water should only run for about 30mins once cylinder has reached 60 it will turn off, it will probably run constantly if you turn stat to 80 because the primary water isnt even this hot so it will never make 80.
the rads getting hot sounds like motorised valve is still at fault or maybe been wired incorectly.

 

[mickyg]

check lever on side of valve isn't left in manual position

 

[muggles]

Could be a dodgy zone valve, Honeywell seem to have had a bad batch I think - we've had a couple of brand new Honeywell 3-ports fail to operate out of the box in the last few weeks