System drained, expansion vessel showing 1.5bar?

[Evostance]

We had a new boiler fitted in a new location a few months ago, and we're currently in the process of fitting new valves and TRV's to the radiators as they're dripping slightly, and we want some new TRVs anyway.

When the plumbers came, they fit an expansion vessel in the loft, to replace the old hot water header tank - same placement within the system.

We've drained the system by opening the drain off valves downstairs, and opening the bleed valves upstairs and have since replaced the TRV's and valves.

I've gone into the loft to refill the system to 1.5bar cold, and the expansion vessel still shows 1.5 bar.

Has anyone got any ideas what could be causing this? The vessel and pressure gauge are only a few months old, and unfortunately I cannot fill the system back up without knowing the pressure in it. As a result, the system is empty and we have no heating.

Any help would be appreciated.

 

[walterwhite]

The guage in your pic is for the system pressure and not the expansion vessel. The guage might be faulty or there could be a blockage or they might have put an iso valve in the pipe to the vessel & guage (dangerous). Is there a guage on the boiler?

 

[Simon F]

the valve will tell the pressure in the system,
the vessel would be tested with a schrader valve.
is there an isolation valve somewhere?
more pictures??

 

[Evostance]

What do you think the chances of the gauge being broken are? I don't get how there can be pressure when everything is drained and the bleed valves are open.

There are 2 valves before the expansion tank to fill the system up, and I think there is an isolation valve in the airing cupboard, but this is open.

 

[Best]

The gauge could be stuck or a bit of dirt blocking the gauge. Simply check if any good pressure is at rads.
Unless some idiot has put an isolating valve on the pipe that connects into system from there & it's turned off. The expansion vessel should ideally be close to boiler and the pressure relief valve (one with red cap) really needs to be at boiler - or a second one fitted at boiler. If those pipes froze in the loft, the system has no expansion and perhaps no relief valve operating.

 

[Evostance]

Apologies, this is what I was referring to.

The only valves I can find are:

2 valves before the expansion vessel that connect to the mains water (off the same pipe as what fills the main header tank)

There is a valve in the airing cupboard too which is fully open.

There is no pressure gauge on the boiler

 

[bigads28]

Open the red handle blow off, it will reseat ok. If nothing comes out the gauge is blocked, just unscrew it and clear the magnatite out and you be fine. If it won't clear just get another, they aren't expensive.

 

[AWheating]

Prob blockage at gauge. Fix or replace and fit a magnetic filter if it is a blockage to help you boiler last a few years.

 

[jtsplumbing]

Just wondering if you have had a new boiler fitted, I am assuming that they have converted your old system to a sealed one, again assuming that they have fitted a system boiler , why have they fitted another expansion vessel in the loft ? could you put some information on here about what type of new boiler was fitted.

 

[Evostance]

The boiler they fitted was a Vaillant ecoTec 428 which is not a system boiler. The reason is because they fitted the expansion tank afterwards as they made a huge cockup (cut through the water pipes) so they fitted the expansion tank to remove the airlock and as compensation..

 

[jtsplumbing]

If they left you the installation book, have a look at where the expansion tank should be connected to the system, and what size is required,

 

[Evostance]

I can't quite make much sense of it, however I read something about the expansion vessel being higher than the boiler and must have an active feed.

It met that requirement

 

[IDCHAPPY]

I presume that's an open vent boiler? seems strange to make it a sealed system when the boiler is open vent.

 

[jtsplumbing]

I presume that's an open vent boiler? seems strange to make it a sealed system when the boiler is open vent.

Yes its an open vent heat only boiler, have a look at post 10, installer made some sot of cock up cutting out some pipes, so put expansion vessel in loft, think its connected in wrong place, think OP needs to get someone in to check it out

 

[Evostance]

Yes its an open vent heat only boiler, have a look at post 10, installer made some sot of cock up cutting out some pipes, so put expansion vessel in loft, think its connected in wrong place, think OP needs to get someone in to check it out

Got a plumber coming to take a look. I don't understand it well enough myself.

All I know is that the expansion vessel has been plumbed into the same place as where the original open vented header tank was