Boiler Pressure Keeps Falling to Zero

[joneng]

Worcester 28cdi

Pressure was on zero, not sure how long for.
Filled it with key but dial didn't rise.
Pressure slowly went up to 2.7
Vented nearest rad.
Pressure went down slowly to 1.5 over the next 2 hours then to 0.3 overnight.

I am right in assuming this is not normal and the pressure is leaking from somewhere?
I have limited knowledge and no manual or diagram of the boiler but a willing to give it a go and save £215 on the call out from Worcester.
Any help appreciated!
And where can I get a copy of the boiler manual from online?
Based in Christchurch Dorset if anyone can rreccomenda ccheapbut reliable engineer.

 

[holty]

first thing id look at. is to see if your blow off isnt leaking.thats the pipe that goes outside.

 

[joneng]

ok cheers. if it's the copper pipe I am thinking of, it maybe a problem, as it goes outside down the wall and straight into the ground...

if it is what should I do, if it isn't what should I do...?

 

[holty]

shouldnt be in the ground.your not mixing it up with the gas pipe are you.usually a blow off is just above ground or some installers elbow it to spray back on the wall.usually in 15mm.

 

[joneng]

ah could be will check again and let you know...thanks

 

[simond]

See

http://www.worcester-bosch.co.uk/in...e/28cdi-rsf-discontinued-june-2007-literature

You either have a leak from the radiator network - which is not covered by the Bosch one fix one fee - or the expansion vessel is mullered, which has been done to death on this forum.

 

[joneng]

Cheers for literature link Simon.
I will try to find the expansion vessel topics on the forum...

 

[holty]

Pressure went down slowly to 1.5 over the next 2 hours then to 0.3 overnight.

would go for leak first,wouldnt of thought it would be the EV. OP is it lossing pressure when cold.

 

[regsmyth]

Or your pressure gauge could be faulty.

 

[joneng]

yes losing pressure when cold. i did think it could be the gauge as it didn't move for at least 20 mins when i first filled. but does this explain the loss of pressure?

there doesn't seem to be any water leaking from the boiler...would I see water if it was the EV?!

 

[holty]

sounds like a mucky system prob due to corrsion, hence the leak and the dodgy pressure gauge.an EV would show up only when the system is hot.

 

[joneng]

how do I know if the system is mucky?
is there a way I can confirm the corrosion and know what parts will need to be replaced?

 

[DJS1]

If you've got a vented hot water tank and there's no sign of a leak, escape from PRV etc, then check out this thread

'0.5 bar/per hour pressure drop on system boiler'.

The pressure in my WB 30cdi boiler kept dropping to about 0.3-0.4 bar and it turned out to be a leak in the hot water coil. There's a few tips on this thread on how you can prove it's that. I replaced my cylinder and now all is fine.

HTH

DJS1