pressure loss

[les2010]

Could anyone give a reason why the system is losing pressure.
It is an oil fired cooker which can either be used on sealed or open vented system as stated by m.i.
The system was originally open vented and is now converted to sealed.
There are 14 rads of various sizes 4 of which have new trv installed and 12 of the rads have aladdin auto bleed vents
There is a prv and aav on the highest point of the system
The ev is an 18lt and is precharged by factory to 1.5 bar
The filling loop is on the return line as well as the ev
The heating works fine except for the pressure loss
The pressure loss only seems to happen when the system is not on
So far i cannot see any leak on the system all connections are dry
If i pressurise the system to 1 or 1.5 bar after about 3 to 4 hrs it is reduced to .5 of a bar
The system has never worked as well as now all rads and cylinder are fully hot after about 1 hr
The reason the system was changed to sealed was that it was piped wrong and used to draw air in
The system has been completely flushed and an inhibitor added

 

[Biggles..]

Either prv is passing/opening or you have a leak.

Have you left a cup under or taped a bag round the discharge pipe to see if the prv is letting water escape

 

[les2010]

Thanks for reply.
prv not letting , aav closed , all aladdin air bleed vents on rads only open at 70 degrees no liquid coming out of them
All pipe work is accessible
The ev was just checked and is charged to m.i.
The only thing i can think of trying now is adding some cheap aftershave to try and sniff out where leak is
There is no water escaping even when system is cold so i presume it is only a micro leak

 

[heatserve]

My guess would be a perforated coil in the HWC. The fact that it settles down to 0.5 bar might correspond to the head of water provided by the CWC.

 

[Agile]

Thats a good technical description of the system. However it also identifies a possible cause of the problem.

The precharge in the EXV is stated to be 1.5 Bar. Firstly that should always be checked and readjusted. Secondly if the system pressure is to be 1.5 Bar the open system precharge should be about 0.9 Bar.

The PRV vent is stated not to be leaking. Whilst it may appear not to be leaking, it may be leaking at heat up. To check you need to put a bottle or condom over the PRV vent pipe and watch what happens over a 24 hr cycle.

There could always be some other leak but until the correct operating parameters are set it will not be possible to determine if there is any other fault.

Tony

 

[mysteryman]

You could be getting very minor leaks on the spindle glands at one or more of the old manual or lockshield valves. As stated above, it could also be a leaking coil or annular heat exchanger in an old cyl. Check by draining the CH and disconnecting the cylinder primaries. If it then drips continuously from the primary connections, the cyl is knackered.

 

[les2010]

I have pressure tested system with air upto 2.7bar over 12 hours and it has dropped by 1 bar in that time.
There is no water leaking from system at all and all rad valves are new and all joints have been tested with soapy water.
The boiler and hwc were both isolated from system when doing pressure test and that did'nt show any leak's .
I reconnected the boiler and hwc and pressure tested the whole of the system again for 12 hours and it is still showing a drop of about 1 bar.
I have even put a very smelly bottle of perfume into the system and still can't get any smell coming from the system and i had it pressurised to 2 bar on that test.
Any more thought's would be helpful as i'm running out of idea's.

 

[picasso]

The boiler and hwc were both isolated from system when doing pressure test and that did'nt show any leak's .
I reconnected the boiler and hwc and pressure tested the whole of the system again for 12 hours and it is still showing a drop of about 1 bar.

the way I read this your boiler or cylinder are leaking,try isolating just the cylinder and retest, heatserve got there first I do believe.

 

[Boilerman2]

As I see it Even your initial Pneumatic test failed as you lost 1-00bar over the test period - as has been said My money is on your Cylinder, as you are adamant that no water can be seen leaking from anywhere else, then the cylinder by deduction MUST be the prime suspect!! either that or the cooker is leaking in to the vermiculite insulation!

 

[les2010]

Got it sorted !!

There is a 312 connection on the flow of the cylinder that was leaking just enough for the air to escape but no water.

thank's

 

[Agile]

For anyone reading, 12 hours for an air pressure test is far too long!

Any significant leak will show up with air in 30 minutes.

Even this leak he found would probably have been inperceptable with water because it would evaporate as quickly as it came out.

Tony