Boiler heating hot water every 10 min

[matz]

If it cuts off after 20 seconds and then comes on after 10mins, then you've a circuitory problem on Flow/Return or a partial blocked coil on cylinder. That's why its kettling on temp over 60c

The guy from the firm that installed the boiler originally 2 yrs ago stuck a wire coat hanger end up the out pipe at base of cylinder and told me it was blocked and I needed new cylinder. But this was after they had fitted new diverter valve (which never worked) Its a long story but they wired it wrong and I never trusted them.

2nd firm fitted new diverter valve and DHW has worked since then after a fashion certainly got hotter than it does now but this was in winter with CH on as well.

Now its DHW only, I'm getting the hassle. Maybe cyl is after all partially blocked. The water from boiler goes in to cyl too hot to hold pipe and comes out nearly as hot but there seems to be a 1 minute delay as the hot water works its way round the coil before bottom pipe gets really hot.

The only other thing is Valiant replaced main heat exchanger FOC I suspect it was partially blocked as boiler ran much better afterwards.

Again long story cut short, original install supposedly powerflushed as per warranty requirement but still alot of muck in system (alot caught by magnaflow which they fitted) In the end, I had all downstairs rads off the wall into garden and flushed them through then flushed through from each upstairs rad until clear water running from downstairs rad tails - loads of black residue etc. This excercise then blocked a couple of microbore bends with metal flakes downstairs. (15mm upstairs, micorbore downstairs) so I am wondering whether DHW exchanger is partially blocked?

Anyway will call the man out today and go from there....and will post back findings!

thanks for all the help here

 

[matz]

engineer has diagnosed obstruction in DHW circuit by listening to noise the boiler made when heating up also the rate at which the temp rose on the boiler. He seems to think its most likely the heating coil in the cylinder. Also saying still slight issue with heat exchanger which he will flush out. looking prob like a new cylinder as existing one is 15 to 20 yrs old. Interestingly he said he is seeing quite a few cases of Valiant Ecotecs playing up when fitted to existing systems which have not been properly cleaned out beforehand and that Worcester models fare better in this respect....