Worcester 24i over flow pipe dripping has high pressure.

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Hi.

Please can some one assist me.
Our worcester cd24i boiler has developed a problem.
The over flow pipe is constantly dripping & the pressure gauge is above 2
I have drained the system to the correct pressure but it creeps up again when hot tap switched on.
I thought it could have been a faulty valve on the cold side mains water top up so replaced the ball valve but after that the pressure still creeps up
Im not a complete idiot & am pretty confident I can repair it providing it doesn't involve working on the gas supply which I know can only be worked on by corgi registered person.
I have a feeling it may be a problem with the diverter valve but would appreciate some input from some one in the know.

Chris.
 
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Hi.
I have just drained pressure down to 1.2 bar & turned water completely off.
I do not have the heating on at all.

As I said I have replaced the tap that you use to allow cold mains water in to repressurise the system.
The pressure guage was steady at 1.2 after 10 mins I ran a hot tap & preaure went up to 3 so I know its not water getting in from the top up valve.

chris.
 
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Hi.

Ok have done the following tests.
turned off mains water supply set gauge to 1.2 bar no heating on pressure stayed constant 1.2 bar.
Left mains water off called for heating at room stat. After 10 mins pressure rose to 1.5 bar.
Kept heating on turned back on mains cold water supply but did not run any hot taps & over the next 10 mins pressure rose to 2.4 bar.
I have turned room stat right down to stop the heating & have turned off mains water will allow to cool to see if pressure drops down.
does this give you any ideas what happening with my boiler.

Chris.
 
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Firstly ensure that the mains cold water is disconnected from the heating side. If the pressure still rises the chances are that the secondary heat exchanger has failed and is allowing mains pressure water into the heating side via this exchanger, hence the pressure increasing significantly when you draw off hot water.

Under the boiler isolate the cold feed into it with the 1/4 turn tap. This should isolate your hot water but also prevent the pressure rising. This should test the theory for you.
 
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Hi Jonjb.

I replaced the 1/4 turn valve earlier today with a new one as I thought this may be leaking when in the closed position & allow cold mains water in to the system & cause the pressure to rise.

You mentioned the secondary exchanger is it possible for this to take on water from the house cold supply with no hot taps running & only central heating on ?

This is difficult to write with out it sounding crazy.
Basically what im saying is with 1/4 turn valve closed so no mains cold water can enter the central heating system to pressurize is it possible that when I call for heating that water from the hot water side is leaking in to the central heating side or even vise versa.
Im 100 percent certain that no mains water is getting in through the 1/4 turn valve I have replaced.

If you want to talk over land line email me at ***Removed***

Regards Chris..
 
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If the secondary heat exchanged is holed then mains cold water can still enter the heating side of the system as this is not isolated via the 1/4 turn valve that you fill the system with.

As i posted previously, to test this you will need to isolate the cold water feed to the boiler. This is located at the rear of the boiler and will isolate the hot water. To ensure it is closed properly open a hot tap then close this valve down. Water should stop coming from the tap.

If the pressure increase now stops, chances are that the secondary heat exchanger has failed.
 
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