Potterton diverter valve test

[bullvine]

Hi to all that can give me help in testing my Myson MSV 322/07 diverter valve.
over the years I have replaced certain parts on the flowsure 70/90 and had no real bother including the actuator head. This time I think the head could be at fault again or there is no signal to tell it to operate.
Reason, boiler getting up to temperature and the pump overrun thermostat is kicking in but the valve is not turning the 3 port valve to circulate the hot water to cool it's self down. I took off the head and watched it in the normal position ie dhw, when I called for CH it turned 90 degrees as it should, albeit it took some time and was not very strong.
when the pump overrun turns on SHOULD it also turn the 3 port valve by means of the diverter valve. i am sure this is the problem. if I do this manually it circulates the water through the heating system then the boiler cools down then I can get hot water.
So to conclude, should the diverter valve turn the 3 port valve when pump overrun in turn on, if not whats the best way to test it.
Once again thank you.

Bully

 

[45yearsagasman]

Pump over runs turn on the pump in a standard Y plan system,and have no further control of the 3 port valve.These valves always have an open port and cool down is achieved by water going through either port.

 

[bullvine]

Thank you for your reply 45yearsagasman, thats one thing less to worry about.
However what I have had to do for some time is open the PRV to take out the pressure then refill the system to cool it down enough to get the hot water from the boiler, otherwise the flow switch wont turn on the burner. could there be some sort of pressure build up in the boiler which will stop the hot water coming through.
As soon as i do this the boiler is back to normal, well until it feels like stop giving DHW. most parts have been replaced other time.
Any other adivce would be appreciated.

Regards
Bully

 

[oilhead]

Are you sure the problem isn't with the flow switch. Sounds as though the pump is not being switched on when there is a hot water demand. The valve should only turn when you have a heating demand. The actuator then switches on the pump for heating. Your hot water is controlled by the flow switch.

 

[bullvine]

The flow switch switches on the burner once the temperature is low enough so thats seems okay.
last night I had a poke about and the MCB on the comsumer board tripped off. I replaced the fuse on the main boiler switch and all is well again. what I did not mention is the original switch for off/timed and constant was replaced for a single switch for off and constant with a seperate switch for the timed part of it. so if I want timed I just push in the switch for timed.
It is a possibility that there is a loose wire, however the boiler today is working perfectly at the moment. temperature is 85 C and the pump overrun is coling it down. I will keep checking through the day to see if it will give me hot water when needed.
Cheers
Bully

 

[bullvine]

I will also check the pump once hot water is called for as well.
cheer's oilhead

Bully

 

[bullvine]

Okay oilhead
No hot water. checked the voltage on the flowswitch without calling for DHW 240 volts. once the tap is turned on, the voltage drop's off to only 14.9mv between the live and neutral mv. there is a distinct sound difference when the flow switch tells the pump to open and flow, when there is no DHW there is no sound so possibly the switch is not operating correctly. the pump has 240 volts when the taps are open to operate.
I can only get DHW when I let the pressure out using the PRV then refill, and all goes back to normal.

Volts needed please so I can check more
Bully

 

[bullvine]

Tested the pump overrun for volts when cooling down the system. 245 volts on the relay between 9 and 10. once stopped just under 2 volts.
also 240 volts between the brown and black terminals on the pump overrun thermostat.
Flow switch volts needed when not being used and when DHW is called for would be appreciated.

bully