Combi boiler install doesn't seem quite right.

nub303 · Aug 12, 2023

I've just had a back boiler removed and combi boiler installed and have noticed that my radiators are heating up when using the hot water. I've been told this is due to the residual heat being moved around the system once the hot water is satisfied. But the radiators are heating up as soon as i start to use the hot water not afterwards unless i turn off the TRV's on the radiators. I've checked the position of the diverter valve via the boiler and it says it's in position 2 (DHW).

Any idea as to what's going on here, I'm i right in thinking that something isn't quite right with the install or is this normal?

much thanks for any advice.

ShaunCorbs · Aug 12, 2023

They do dump the heat into the rads after a hot water cycle but shouldn’t do it at the same time

What boiler do you have ?

nub303 · Aug 12, 2023

ShaunCorbs said:
They do dump the heat into the rads after a hot water cycle but shouldn’t do it at the same time

What boiler do you have ?

That's what i was thinking it shouldn't happen while the hot water is being used, found it kind of weird. It's a Viessmann Vitodens 050-W.

ShaunCorbs · Aug 12, 2023

Viessmann’s have had a few issues with the diverter valves best to phone them up for a warranty call

nub303 · Aug 12, 2023

ShaunCorbs said:
Viessmann’s have had a few issues with the diverter valves best to phone them up for a warranty call

I did initially suggest that to the engineer that installed it but he said it wouldn't be that. But this time i'll mention the fact that the radiators are heating up as the hot water is being used and not afterwards. Hopefully he'll take a closer look at it.

Thanks for your input.

John.g · Aug 12, 2023

Don't know if this will prove anything or not but think about it, with both CH and DHW off (boiler off) open a HW tap to give a small flow of say 1LPM but not high enough to fire the boiler, then switch on the CH and see if the water still runs cold.