diverter valve prolems

[ossie8743]

Hi
I am having a problem with my potterton performa 28i boiler.
Central heating works fine. Dhw giving cold water only.
When you open a hot tap, Dhw diaphragm opens and micro switch is made, boiler fires up and the temp sensor lights on the front panel go up from 30 deg up to 70 deg. but the diverter valve does not change position. No change in voltage on PCB [to move diverter]
I have tried different positions of taps to give different flow rates but still the same. Flow of water from taps is good
I have gone through the fault guide and tested and or changed the following items
Diverter valve works if you press down plunger manually and diverts water.
Dhw temp sensor 11 ohms cold 3 ohms very hot
Diverter head new
PCB tried 2 off brand new boards, not repaired.
Checked both microswitchs for continuity both ok
Both the pressure valve and the Dhw pressure differential valve are working fine and both microswitchs work ok.
I have removed microswitchs and manually operated them and still the same fault

[diamondgas]

Sounds like you know a lot about your boiler ossie8743, welcome to the forum

Could it be that the preheat diverter is stuck in preheat position? Deffo sounds like the water isn't getting through the plate hex.... Any temp rise at all on the hot water?

[Atouchofgas]

Are you sure the microswitch is operating? When you turn on the taps does the flow/return get hot, if so the diaphragm is your prob

[ossie8743]

Are you sure the microswitch is operating? When you turn on the taps does the flow/return get hot, if so the diaphragm is your prob

e

both of the micro switchs are working,have put meter across connections and they come on when boiler calls for dhw. both
the pressure diaphragm and diverter diaphragm operate. flow and return cold. boiler stays lit until water reaches 70 deg

[diamondgas]

e

both of the micro switchs are working,have put meter across connections and they come on when boiler calls for dhw. both
the pressure diaphragm and diverter diaphragm operate. flow and return cold. boiler stays lit until water reaches 70 deg

The diverter diaphragm can operate the microswitch but that doesn't say the diverter valve is moving from pre-heat to hot water position. Does the p-hex get hot when calling for h/w?

[ossie8743]

from cold with c/h t/stat turned to min so dhw only . open tap boiler fires up pri heat ex gets hot pipes from and to pri heat ex get hot diverter gets hot. but no dhw

[diamondgas]

Next stage is check flow rate at hot tap and temp diff hot/cold ... Check mi's for what you should be expecting ... If there is no significant diff between hot and cold I'd honestly think the water was being diverted away from the p-hex ... When you tried different flow rated did you crack the tap back as low as possible? Are you familiar with how the hydraulics work on this model boiler? Are you GSR?

[ossie8743]

many thanks for al l your help.
went back to basics and re checked everything
found that when dhw called for heat the diverter valve was heating the c/h side. and not the dhw side. i thing that the diverter main body is blocked and will fit a new one.

[SimonG]

Are you GSR?

That'll be a no then

[diamondgas]

many thanks for al l your help.
went back to basics and re checked everything
found that when dhw called for heat the diverter valve was heating the c/h side. and not the dhw side. i thing that the diverter main body is blocked and will fit a new one.

Thanks for letting us know ... It'd be interesting to know if that resolves the issue

[krafa]

Valve stems should have a gasket or packing material, usually adjusted for proper sealing without too much stiffness turning by tightening the cap or nut in front.

The valve stem can leak when turned to one direction and not leak when turned in another direction.

Could there be a hole in the diverter assembly? A hole that is in the channel going down to the spout? Plummer