WB Highflow 3.5 circa 94 problems with DHW going cold

[BriscsWK]

My Aunty has an old WB Highflow 3.5 circa 94 and after about 5 minutes the DHW runs cold/tepid. This problem is only apparent when the heating is on. She has had WB service engineers out who have replaced the tank and heat exchanger etc. within last couple of years but problem still exists even though she did mention it to them.

Can anyone shed light on probable cause and/or solution as she is talking of changing the boiler for a new condensing WB Highflow and I am not certain that is necessary or wise?

If she were to change what sort of % savings would be likely?

And yes she does turn it to DHW only mode when she remembers and wants a longer shower but it is not really a long term solution

 

[BriscsWK]

Anyone have any thoughts/suggestions?

Many thks

PS She is talking of replacing with a WB Highflow and I mentioned the new 440 & 550 - anyone experience of these new models and can they be recommended?

 

[Agile]

I am sorry that no one has replied.

This is probably because there is no obvious answer to what is causing the problem.

In front of the boiler the cause may well be quite obvious after doing a few simple tests.

Its now 15 years old and they were never terribly good boilers.

A similar style replacement would save about 12% if it were operated in the most efficient settings.

Tony

 

[BriscsWK]

Tks v much Tony - I'll pass the info' on and I suspect in time she may well go for a new boiler.