Diverter valve problem heat line vizo 24

[realmagic]

My daughter and son in law have the above boiler.
They have little of no heating, (luke warm radiators). I am a refrigeration and ac service engineer (not heating.

I have investigated the problem and discovered the boiler is running for a short while and switching off on temperature control. Further investigation revealed that the water is "short circuiting around the DHW heat exchanger. I ordered and fitted a diverter valve repair kit but this did not cure the problem.

I noticed that there is also a none return valve build into the diverter valve which appears not to be servicable. What is this none return valve's function? Is it a over pressure device to stop the pump dead heading or keep the flow through the primary heat exchanger?
I have order a complete new valve but I was wondering if there was any other possible causes?
The system is clean and run in plastic piping.

any ideas welcome

 

[diamondgas]

Possible causes other than dodgy diverter, as you suspect, are heating circuit blockage! If you have plenty hot water then most likely its the diverter valve stuck in hot water mode! I'm trying to picture a none return valve scenario as you see it . hmmmmmmm not sure that exists my friend? None the less i'd be interested to know if the replacement diverter does the trick 🙂

 

[realmagic]

Thanks Steve,
For your reply, I am begining to think that there may be an large air lock somewhere in the system the pipe work goes upstairs first then along the landing and drops down to the ground floor in 22mm plastic. The valve which is part of the diverter valve is next to and to the right of the diverter assembly as viewed from the front where the electric actuator is. When the actuator is removed the spindle assemby is on the left (which I have already replaced) and appeares to operate ok. Just to the left there is another black plastic cap which if removed reveals a valve seat which a white plastic ball which has a spring behind it and can be manually depressed. But there appears to be no way of dismantling this part of the valve. I am thinking if the system is blocked with air would the back pressure force this valve open effectively bypassing the spindle assembly part of the valve? The system is clean, completely run in plastic with new radiators. I've had the filter out clean and ok, the pump as been off and replaced there is no sign of dirt in the system.

Thanks again Mike.

 

[Jonwells]

The non return valve as you call it may be a boiler automatic bypass,
This needs to be closed in normal use, should only come into play if rads are all fitted with thermos,
Not sure if diverter valve is controlled by electric motor head on a flow switch or hydraulic controlled by Venturi.
In either case get hot water to circulate with hotbtap open full, if water is perfect, make sure hot water is not being dumped into the heating flow and return, when in hot water mode.
If h/w is good, then it will be circulation through heating circuit, caused by either diverter valve problem or blocked strainer, if its diverter valve, remove either electronic head motor or Venturi diaphragm, and work the diverter valve pin manually with a tool, the boiler will need to be in hot water mode with hot tap open. Then check flow and return to see how circulation is.
If boiler gets up to temp very quickly when in heating mode, see if the strainer filter on boiler return( if fitted) is blocked. Sorry about the rushed reply. Jon
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