Potterton Puma 100 diverter valve??

[vmx1200]

Hi all

Read every thread about Potterton Puma diverter valves and still confused!

Puma 100 permanent pilot
CH working fine, fires up morning and evening and all rads start to warm within minutes.
Turn on DHW and can run as much as I want, completely filling a bath, turn off hot water and pilot light goes out, I guess due to over temp stat doing its job.
Noticed back in summer when heating was off if I ran hot water repeatedly for a few second at a time the boiler would lock out but not if run for a minute or two and then not used.
My thoughts are that the diverter valve is sticking in the hot water position so that the excess heat in the heat exchanger cannot be dissipated thought the central heating system .......... when the heating is off and I run hot water then turn it off although the pump is running the CH flow does not heat up (I am sure it used to).

So could it be the diverter valve and could I get away with just changing the wax capsule which looks easy and costs £20 or do I have to change the whole thing at 5X cost and much more hassle?

Thanks

 

[Dan Robinson]

Sounds more like a sluggish flow switch to me.

 

[vmx1200]

Hi Dan

Thanks for the rapid response!

I think you are correct in your diagnosis, when the DHW is turned off the red light on the control board and the burner were staying on for up to 5 to 10 seconds.

I have removed the micro switch and WD40 and 3in1'd the actuating rod (it is Sunday pm so I couldnt get a replacement), the burner is now switching off after 2 to 3 seconds, is this correct or should the micro switch respond instantly as it does when the hot tap is turned on? (Boiler not locking out)

I had an old flow switch which I replaced as it was leaking so I took it apart and there doesn't seen much to go wrong, just a diaphragm and an actuating pin.

So far in 10 years

I replacement boiler under warranty
2 pumps
1 fan
2 pressure relief valves
2 automatic air valves
1 water flow switch
Repaired the circuit board twice due to burnt out tracks
Unlocked the flexible hose to the expansion vessel twice

Time for it to go me thinks ..... any reliable combi's out their??

 

[Dan Robinson]

Not a bad record for a Potterton..


The burner should shut down almost immediately - 2 seconds is not too bad, but maybe give it another squirt later - and spray it while you are turning the tap on and off to make sure is get in there. You could strip down the fitting easily to give it a good clean.