Main combi 24 he hot water issue

[armyash]

Hi

Went to look at a main combi 24 he boiler. The issue was hot water would only work with the heating on.

We had a look and from cold, ran the hot tap at the sink and it was going down the flow pipe. We changed the diverter and now the boiler would come on with a hw demand as normal but the water would be hot/cold. Cleaned the plate and everything was fine.

No issues for about 10 days, got a call to go back as hw not working again. Pin not coming out when demand put on. Checked filter all clear.

Manually operated micro switch and ran hot tap and its going down the flow again.

Ch works fine.

Any advice what next. Don't want to throw parts at it.

Thanks

 

[Allgoode]

Might have to tweak the microswitch if you have fitted a refurbishment kit as some of the pins seem to be of slightly different lengths thus when demand is put in it does not fully make the switch,
Cheers,
Andy

 

[firemant]

Might have to tweak the microswitch if you have fitted a refurbishment kit as some of the pins seem to be of slightly different lengths thus when demand is put in it does not fully make the switch,
Cheers,
Andy

I think he changed the complete DV?

Hydraulic venturi broken to bits?

 

[AMGasServices]

Is it the one with the smaller dhw diaphragm at the back of the boiler or is it a big diaphragm at the front?

 

[armyash]

It's the big diaphragm at the front, small at the back.

Haven't looked at the hydraulic venturi.

 

[AMGasServices]

It's the big diaphragm at the front, small at the back.

Haven't looked at the hydraulic venturi.

When you remove the dhw diagram. You’ll see the diverter valve (similar thing at a ideal logic) drain the boiler down. Undo the big nut at the front of the diverter remove the inners and clean them make sure there pristine. check the quality of the water too if it’s full of crap advice for a system flush and magnaclean to be installed.

I’d check the dhw diaphragm too. And grease it all up.

 

[armyash]

When you remove the dhw diagram. You’ll see the diverter valve (similar thing at a ideal logic) drain the boiler down. Undo the big nut at the front of the diverter remove the inners and clean them make sure there pristine. check the quality of the water too if it’s full of crap advice for a system flush and magnaclean to be installed.

I’d check the dhw diaphragm too. And grease it all up.

Thanks the diverter is brand new though. If the venturi is playing up would that make the hot water go down the flow?

 

[AMGasServices]

Thanks the diverter is brand new though. If the venturi is playing up would that make the hot water go down the flow?

The Venturi is a part fan proving safety device.

Sounds like you’ve got a blocked plate to plate or crap in the diverter I understand it’s been replaced (if there is crap in the system it’s going to block the inners).

If the pin isn’t coming out enough to make the micro switch I’d check the dhw diaphragm.

What’s the pump proving switch doing?

 

[armyash]

Yeah only thing I can think is more muck has been caught somewhere. Ch works fine.

Inlet filter OK.

Cleaned the plate also.

Was wondering if pcb but I've had to concede defeat. I can't throw any more time/parts at it. Had to be honest with the customer that from a business point of view she is better off getting manufacturer out. Otherwise where do I stop. Not fair on customer to keep returning and I can't spend all day swapping parts.

The fact it worked spot on for a while then started doing the same thing didn't help.

Customer happy with that, I've been honest and not trying to rip them off.

 

[Ollieg]

There is a venturi for the DHW diaphragm in the right hand brass block. Its the nut below the 2 small copper pipes. The nut is 24mm i think and needs ring spanner to remove. If the venturi fails the microswitch will not make and the diverter will stay in ch mode. This explains all your issues. (as long as the DV is new)