105 he instant Hot water not up to scratch - advice please

[redmonp]

Gents, I am so greatful for previous advice on my boiler. I recently posted problems with my 105 he instant (diverter v/v change) which cured that particular problem. However, i think now i have a DHW heat ex problem? Hot water is hot instantly but i have to throttle the flow to keep some temperature in the water, its hot but not hot enough like it used to be.

I have been underneath the boiler with the hot tap on and the bypass from the diverter v/v is too hot to touch, and the CH return pipe is warm but no apparent flow through it.

Is this bypassing a normal occurence by design? Could it be a blocked/restricted heat exchanger?

Any advice greatly appreciated, cheers.

 

[stem]

It could be the long spell of sub zero temperature, which causes the incomming mains water to be colder so it's not as hot when it comes out of the boiler. The mains water supply can be much colder according to the weather.

Saunier Duval quote these figures for their combi:
Summer- typical mains temp 15˚C, hot water temp 50˚C
Winter – typical mains temp 4˚C, hot water temp 39˚C

I would wait a week or so after the weather has warmed up a bit and see if normal service is resumed.