Hot water supply often runs cold

[smaug]

We have moved into a house with a Worcester Bosch R40 HE plus. The hot taps and shower sometimes run hot then go cold.

Heating Engineer has so far fitted a new plate heat exchanger and a new hot water thermistor without resolving the problem. So I am £500 worse off and still have the problem.

Have any of you out there any suggestions on what the cause and solution might be before I spend more replacing components which just "may" resolve the problem?

Thanks

smaug

 

[just pumps]

Replace the heating engineer if he is just throwing parts at it

 

[CBW]

I’d be suspecting failed check valves if fitted. I’m guessing it’s a Combi boiler with a plate being fitted?

 

[smaug]

Thanks Chris.

Yes it is a combi - the first time we have had one. Any advice on best way to check your suggested cause.

Just pumps may be right but we have used a well regarded firm though as we are new to the area we had no direct experience of them

 

[CBW]

It’s fairly simple, if you’re able to, isolate the cold under the boiler (this isolates the hot water from the boiler), open a hot tap and if water runs, you have a passing check valve somewhere.

 

[smaug]

Thanks but with the cold supply off there is no flow from the hot taps.


Any further suggestions

 

[CBW]

Wait until system is cold, run the hot tap and feel the flow pipe (usually the 1st pipe on the left under the boiler) and let me know if it heats up.

 

[smaug]

Each time I have tried this the pipe heats up but the hot taps haven't run cold at that time (but have later).

Thanks for your help but as the Heating Engineer says he has spoken to Bosch and they cannot suggest any other action except to replace the boiler I have given up and will live with the problem.

 

[HERTS P&D]

'You can lead a horse to water but you can't make him drink'

Andy

 

[CBW]

Each time I have tried this the pipe heats up but the hot taps haven't run cold at that time (but have later).

So the pipe I mentioned heated up each time? Suggests a diversion issue to me.