near-zero pressure on combi

[tonym911]

Worcester Greenstar CDi gas-fired condensing combi boiler, £2.5k job fitted brand new and on recommendation 2 yrs ago (just out of warranty).
Had my shower this morning no bother, the missis gets in and comes out pretty quick as the water is cold.
Pressure gauge on boiler reading zero, or close to it. Turning hot water tap on results in instant loss of whatever pressure was registering. Turn water off and needle slowly heaves itself off the zero stop by a couple of mills but as soon as you turn the tap on (or the washing machine takes in more water) it drops back down again to nowt.
Pressed reset, turned it on and off, done rain dance etc, no change. Sounds like the boiler is trying to kick itself into some sort of life but seems to give up almost immediately. Manual says 'in the unlikely event of a fault occurring (ha ha) the reset button will flash once per second, the mains indicator will flash, and the display (the bit with the numbers) will show a fault code'. None of these things have happened apart from a weird Klingon type symbol interposing itself between the display numbers (which are going up and down).
Bled most of the house rads last week before all this happened because two or three of them weren't warm above the bottom 3-4 inches, there was a fair bit of gas in those rads. Like I say though, that was last week. Bleeding seemed to work OK on those rads.
Now, after this morning's episode, I've just done the attic rad that I hadn't done on last week's exercise (forgot we had it). There was a lot of gas in there, bled all that out and went round all the rads again but of course there's next to no pressure in the system now.
All thoughts from the PH heating experts gratefully received.

[tonym911]

another pic

[TheD]

It would suggest to me that you have a leak somewhere in your system.

[Festive Ferg]

You bled radiators? Did you top the system back up with the filling loop?

The pressure is dropping when the pump fires, this isn't unusual. The pressure needs setting to around 1 Bar cold.

Edited by Festive Ferg on Sunday 12th December 12:08

[tonym911]

Could such a leak come from the bleed valves? I'm sure I did them all up ok.

[tonym911]

Festive Ferg said:

You bled radiators? Dis you top the system back up with the filling loop?

Er… what be that?

[tonym911]

I just let the air out till a tiny bit of fluid came out then retightened the bleed valves.

[Festive Ferg]

A braided stainless steel hose (normally) joining mains cold to the heating system. Normally, but not always, below the boiler.

[Festive Ferg]

Actually, you said it's a Greenstar didn't you!

They have an integral filling loop. Get the instructions out!

[tonym911]

What am I supposed to do with it Ferg?

[Festive Ferg]

http://www.youtube.com/watch?v=1Ea7czrQmsY

[tonym911]

Brilliant Ferg thanks, i'll give that a go

[Big Al.]

I did exactly the same as you when we first got our combi, bled rads and boiler not working.

Refill the system there should be a couple of taps on the underside of the boiler. opening one will recharge the system.

I can't be specific as to which tap will recharge yours but mine is the one at the front on the right, open tap gently and you will hear water starting to flow within the boiler and you will also see the pressure starting to rise as stated already turn off at about 1bar. It should only take about 10-15 seconds to recharge.

HTH.

[tonym911]

Thanks Al and Ferg, i've just had a look underneath, the bottom plate isn't there at all and the big white key that you can see in the pic will only turn about 45 degrees left from where it is before hitting the stop, no water comes in, no change to pressure. I'm wondering if the white nubby bit to the left of that is actually what the key should be connected to? That nubby bit will turn by finger pressure, and I tried pulling the key down to disconnect it from where it is to see if it goes onto the nubby bit, but it didn't seem that willing and I wasn't sure about either operation so I stopped.

[tonym911]

Just to say I've been right through the 'user instuctions' and it says nowt about refilling.

[Festive Ferg]

You need to turn that square knob to let the water in. The key should be clockwise looking from the bottom. As it is in your picture, in fact!

Edited by Festive Ferg on Sunday 12th December 12:51

[tonym911]

Think I've done it, the key needs to be moved from where it is (the locked position) to the unlocked position (45 deg anti-clock), then the nubbins on the left lets the water in. Got the pressure up to about 1.2 then stopped, is that enough would you say?

[Festive Ferg]

Yep, 1 Bar cold is sufficient.

I think pushing it in is what's required, the 'lock' and 'unlock' stops it from being pushed out by water pressure from memory.

Edited by Festive Ferg on Sunday 12th December 12:57

[SmokinV8]

Need to keep primimg mine as even the slighest weep from a joint will cause the pressure to drop. Just keep an eye on the pressure in future and prime when needed.

[tonym911]

Ferg, thanks a bunch for your advice, I'd send you a beer but it doesn't travel well on tintanet. Am liking your GTM btw.
Thanks to you also Al. Have great Christmases both.