Combi boiler, CH comes on when running HW. Why?

[MagMrMax]

Hello.

I have a Semia Condens combi boiler.

It has started to heat the radiators when the HW is being run to fill the bath.

We have used the boiler for 8+ years and never noticed this issue until the last couple of weeks.

I have tried turning the controls to "summer" mode, and turning the radiator temperature all the way down. The wife insists we have the water temperature all the way up, otherwise the water isn't hot enough, apparently.

Any advice would be greatly appreciated.

Thank you.

 

[muggles]

Diverter valve is passing

 

[ianmcd]

As @muggles your diverter valve is passing, as a temp measure until you can get someone in, turn off all the radiator TRVs if you have them

 

[MagMrMax]

Thank you both for replying. Is this a definite job for a plumber, or could a competent amateur tackle it, in your opinions? I replaced the diaphragm on a previous boiler, for example, have done a number of wiring jobs around the house, removed a wired thermostat from this boiler, etc. Thank you

 

[ianmcd]

nothing to stop you doing it yourself legally, they can be a bit of a pain to get out sometimes, you need the complete valve not the diaphragm, on rare occasions it can be the plate heat exchanger that is blocked that causes the same symptom, so if it was me I would remove it and clean it when I had the diverter out

 

[Agile]

It is likely to be the lower part is somewhat jammed with system dirt.

Sometimes I have solved those by cleaning the boiler only with sulphonic acid. Sold as DS40.

But a replacement would be better however if that is done then cleaning the system would stop it reoccuring later.

 

[MagMrMax]

Hello. Thanks again for the replies.

Can anyone please advise exactly which replacement part constitutes the "diverter valve"? As you can see from the photos, there are apparently several different options.

Or would I need to open it up first to see first-hand which precise part is causing the problem?

I have also attached photos of the schematic and the front view into the boiler. It's a Saunier Duval F30 E.

Also, the term "diverter valve" doesn't appear in the manual. Is "hydraulic 3-way valve" the same thing?

Thank you.

 

[ianmcd]

yes Hydraulic 3 way valve the one in your first pic

 

[ianmcd]

@MagMrMax if doing it yourself crack open each nut, but dont unscrew till you have cracked open all the connections, or it will spin on you, leave them all connected until cracked then completely open them