really unusual potterton lynx 2 problem

[antd]

Hi

I have a really bizzare potterton lynx 2 problem.

pressurize the system.
It leaks a little from the system pressure relief pipe until the system gets warm then holds the pressure all day.
Then when the system is turned off at night it losses all the system pressure.

OK I hear you all say its the pressure relief valve...

I changed it last night (bloody expensive at £25)
pressurised the system it didn't leak via the pressure relief pipe. ran system all evening. WooHoo I thought.

Got up this morning
All the pressure gone again.......

Anyone got any ideas???

By the way..
Other than this fault the system seems fine.
All the rads heat properly.. So circulation problems would seem unlikely...

 

[baxpoti]

You would have been better off asking on here before spending money!
Try checking the expansion vessel.

 

[antd]

Hi thanks for the reply

I seem to remember there being 2 pressure vessels a small one on the main flow pipe and a much larger one high up in the unit.

Any idea how to check which one is at fault??

 

[baxpoti]

Any idea how to check which one is at fault??

Locate the schrader valve on the large vessel, with no water pressure, showing on the boiler guage, put a tyre type pressure guage on the schrader valve and record the reading.

 

[Agile]

I would recommend that you follow the full procedure shown in the FAQ but ignore the bit about 10 litres.

Just repressurising can fail to identify some faults and may not always sort out the problem.

I am going to post a revised instruction of this topic on the FAQ shortly.

Tony

 

[antd]

Thanks for the replys

I look forward to seeing the ammended guide on pressure vessels.

I have just printed a copy out for reference tonight.

I hope the vessel isn't knackered... I seem to remember that it is pretty inaccessible...

 

[Agile]

Should I try pressing the pin, before I drop the pressure, to make sure no water come out??

Exactly!

Before you repressurise the boiler let ALL the air out of the air valve. If a few drops of water come out then although not ideal will usually mean its still serviceable.

Tony

 

[namsag]

So it losing its pressure overnight.
Is boiler on or off when this happens
does the gauge go anywhere near 3 bar
do you have any pipework under concrete or suspended floors downstairs

 

[antd]

So it losing its pressure overnight.
Is boiler on or off when this happens
does the gauge go anywhere near 3 bar
do you have any pipework under concrete or suspended floors downstairs

It is off when we go to bed...
The gauge doesn't go near 3 bar but I haven't checked it when I turn it off at night..
Non of the pipework is enclosed in concrete
But it does run under the 1st floor flooring..
I am convinced that it isn't a leak because the fault has been running for a while and I would have expected to see something if It had been leaking.

The pressure vessel seems the most likely at the moment