Bosch Worcester 28cdi rsf DWH Combi issue

[wrighar]

I've had a Bosch Worcester 28CDi RSF for 10 years now, (with only circulating pump issues...).

Last week the Domestic Hot Water flow volume dropped to almost nothing and the boiler over temps. Turn the hot tap on and water flows, the boiler fires, and after a few seconds the flow drops to a trickle and the boiler cuts out with an overtemp.

2 Plumbers have been and can't see any issues, the 2nd has said the water to water exchanger was blocked, but when he removed it it was fine.

He also says water flow to the boiler is fine.

Does anyone have any ideas why this sudden flow rate drop? Cold water flow is fine (as is central heating).

If it's of any interest, we did have a big water main fail 1 week before the boiler stopped behaving.

Thanks
Andrew

 

[Homesafe]

filter/flow restricter blocked. but you say it's been checked .

 

[nickso]

He also says water flow to the boiler is fine.

i would agree with newgas.

what did the guy do to confirm the filter is clear? if he did anything. the filter is not all that easy to get to.