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Andrew Smith
Andrew Smith, Home Appliance Technician
Category: Appliance
Satisfied Customers: 3768
Experience:  Gas cooker specialist
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hi i have a potterton performa 28 The central heating runs

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i have a potterton performa 28
The central heating runs contiously even when the selector switch is calling for hot water only.
I have replaced the PCB but no change.
***** ***** : It sounds like the hot water is firing continously - does your model ahve a hot water flow switch or divertor valve?
***** ***** : Do you have the GC number?
***** ***** : I take it that it shuts down if you turn the boiler off at the selector switch?

The GC Number is ***** 393 07


The GC Nr47 393 07 it has a diverter valve and I am using the selector switch to turn the boiler off.

***** ***** : Are you able to take the case off and observe the divertor valve and tell me iff the pin rises and fall when the tap is run?


***** ***** : Are you able to look inside the boiler?

Hi the diverter valve works fine for the water.the problem is that when the boiler is switched on it call for heating even thogh the programmer is off and the selector switch is set to hot water only

***** ***** : yes
***** ***** : The hot water is on all the time
***** ***** : This means that there is power to the divertor valve switch at all times
***** ***** : This can fire the boiler
***** ***** : If the pin is not out making the contact then the contact is faulty
***** ***** : Your boiler thinks the hot tap is running all the time
***** ***** : This is why I needed to make sure it still switched off when the selector was set to off

Andrew there are two valves with pins, one for the hot water, which i have changed the diafram in a couple of years ago, the pin only comes out when the tap is running, the pin on the heating valve comes out without callling for heating and stays out until the power is switched off.

***** ***** : ok,
***** ***** : one for the hot water
***** ***** : and one for the heating when the pump comes on
***** ***** : Are you able to disconnect the wiring for the hot water flow switch from the pcb by disconnecting the plug
***** ***** : Let me know if the boiler shuts off

I took off the two connections at the flow switch, nothing worked (all off) then i took the plug out of the PCB same result.

***** ***** : So this points to a faulty switch as it has stopped the boiler firing
***** ***** : The GC no. you gave me is for a Performa with a hw flow switch mounted on the top of the divertor valve?
***** ***** :

Yes I also switched the boiler to heating and took one of the connections off the flow switch and it switched the boiler off !

***** ***** : 2 or 3 wires in the connector block?



I think you have sorted it with the hot water switch disconnected I am able to switch the heating on and off with the programmer, is it a case of replacing the switch ?

***** ***** : That is where i would start, are you able to take the pcb back?

I bought it on line and it is a new version with an earth lead pre fitted so I had to cut the original lead to get it out, so will keep the old one as a spare. Im still confused I thought the micro switch on the front of the hot water valve should only work when activated by running the tap, but when it is connected it brings on the heating, without the taps running ? what does the switch on top of the heating valve do ? and should I replace it ?

***** ***** : Do you have the version of the boiler the same as the link I sent you?
***** ***** : It is like the old Potterton Puma with the hot water flow switch mounted on the front of the divertor valve on the left hand side at the bottom new
***** ***** : near the front


***** ***** : When in hot water mode (heating off) then this microswitch on the front fires the boiler
***** ***** : This is the one you disconnected?


***** ***** : ok you should change this part

Andrew Many thanks, ***** ***** I had used this service last week, could of saved myself a few quid !!

***** ***** : No problem
***** ***** : At least you have a spare PCB now......

If you get another customer who needs one give me a shout !!! What is the proceedure do I change the switch and give you a rating after (assuming it works) or leave a rating now and contact you with the result ?

***** ***** : You can leave feedback now and then jump back on to the question once you have swapped it



Many thanks


Regards Mick

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