Combi boiler keeps locking out

[Jbar871]

Hi everyone. I was hoping someone here might be able to help me with a problem I have.

After using our shower for around five minutes it seems to be causing the boiler to lock out.

It’s a thermostatic mixer shower running from a Worcester Greenstar 30si combi boiler.

Weirdly, this only seems to happen when we’re using the shower. Turning the taps on doesn’t appear to have the same effect and it only happens when we’re drawing hot water from the system, not while the central heating is on.

The flashing light sequence seems to indicate either a flue overheat, heat exchanger overheat or flue blockage.

We paid for a service just before Christmas when the problem first appeared and the engineer recommended the plate heat exchanger be replaced, which we had done in the new year. But this doesn’t appear to have cured the problem.

Before I get another engineer round, I was wondering if anyone here could give me some guidance on what this might be? The few people I’ve spoken to have all given the same answer: “probably the heat exchanger”, so I’m not really sure what to do next!

Thanks in advance.

 

[Deleted member 120897]

Possibly crossed pipes or cross flow. Isolate the cold feed under the boiler and run the shower for hot, if you’re still getting water out this could be your problem. Or possibly a blocked inlet filter.

 

[Billy Boiler]

The condensate pipe might be sharing the drain with the shower water. If this drain is blocked, it will smell and knock off the boiler