Worchester Greenstat 24i poltergeist syndrome

[diynob]

Hi all. First post, prolific diy-er, just not that prolific when it comes to plumbing and electrical wiring.

Have a Greenstar 24i boiler which, for the past few days has been throwing out a lot of water via the airing valve (the one outside, might be named differently). So I top it up to 1 bar (at the gauge), next heating cycle pressure goes to 3 - 3something BARs and the cycle repeats itself. Today I came home to a zero gauge indication on the boiler, told myself to experiment (you know like non believers usually do) and crank up the heating (to start the cycle). To my surprise heating started just fine, no weird sounds, left it like that for 2 minutes then stopped it. Pressure stopped at 0.5BARs on the gauge. The boiler is inherited, last year i was having 4 bars or pressure at times with no sounds/gurgles (unlike my car at 90Mph plus).

Is is the gauge? I remember last year the plumber that helped with the bathroom do-over charged the expansion vessel to 0.8bars (via a pump).. he also said the expansion vessel needs changing, but it worked a treat, so obviously did not need changing.

So basically the boiler is working fine with zero pressure... Will look forward to the next heating cycle to see how high the pressure goes, but am i right to suspect the gauge is gone or posessed at least?

Some advice or reassuring would be really appreciated.

 

[terryplumb]

Your Expansion vessel isn't functioning as it should.

 

[kidgreen61]

It's quite likely that your expansion vessel needs recharging, it may be leaking through the Shraeder valve, or it's possible that the membrane has split inside it, meaning it needs replacing.
Your boiler has a pressure relief valve inside which is supposed to open at 3 Bar to relieve excess pressure, that it the water you can see coming from copper pipe outside.

 

[diynob]

Thank you for the replies. Attached a picture 10 minutes into a heating cycle. The previous picture is just from before the cycle started, had zero pressure. I did not add any water in the system, left it at zero. Is the expansion vessel easy to change? Wouldn't do it myself, but just wondering generally. Is there a way to tell if the membrane is slit inside or whether it's the valve (which I assume is easy to replace?). Thinking it's just weird for the heating cycle to start with zero pressure and then go up and up, which made me suspect the gauge ..

 

[terryplumb]

With heating on ,water expands and increases system pressure.
Your boiler will fire up ,some don't, when pressure is very low . Better to have the system pressurised as it should be.
EV replacement ,if indeed required,is best left to an engineer.

 

[kidgreen61]

If the membrane is split, water will gush from Shraeder valve when pressed, assuming there's enough water pressure in the system.
Occasionally, the valves just leak air, giving rise to your problem.
I believe there's a FAQ page on this site telling you how to to recharge your expv properly.

 

[ianmcd]

you have an expansion problem, nothing to do with the guage

 

[CBW]

Is the expansion vessel easy to change? Wouldn't do it myself, but just wondering generally.

On these, quite often the boiler will need to be removed to change the vessel. As advised you have an expansion issue, might not be the vessel itself, could be the communication pipe. Get yourself a gas safe registered engineer or contact Worcester Bosch for a fixed price repair.

 

[diynob]

Thank you all for the replies.

From reading online I understand the easiest method to check whether the vessel is blown (or punctured/ruptured) is to release air via the valve on the upper side (on this model) and see whether water comes out. If water comes out it's punctured, therefore needs changing.

The overall repressuring of the vessel is easy-ish from the FAQ, so will try that bit if (fingers crossed) the vessel is not punctured. Last year I had roughly the same issues, plus the release valve was changed and vessel repressured, so am hopeful it's the same thing (repressuring).

The heating cycle ended, no issues, radiators are hot as should be, pressure stopped at 2.5 - 3BARs as the highest pressure point during the heating cycle.

 

[diynob]

UPDATE Drained the system (took too long) and repressurised the expansion vessel. It had 0.4 BARs according to my reader(for a car). Bumped that to 0.75BARs as per the manual, then added inhibitor and filled the system, started the heating. 15 minutes into the cycle pressure went from 1BAR to almost 1.5BARs, which is good I suppose (previously went from zero to 1,5BARs).

Before I emptied the system I've let some air out of the expansion vessel to check for water, none cane out, so fingers crossed.

Will come back with an update later in the evening after a full heating cycle (when the thermostat reaches the temp).

 

[ianmcd]

UPDATE Drained the system (took too long) and repressurised the expansion vessel. It had 0.4 BARs according to my reader(for a car). Bumped that to 0.75BARs as per the manual, then added inhibitor and filled the system, started the heating. 15 minutes into the cycle pressure went from 1BAR to almost 1.5BARs, which is good I suppose (previously went from zero to 1,5BARs).

Before I emptied the system I've let some air out of the expansion vessel to check for water, none cane out, so fingers crossed.

Will come back with an update later in the evening after a full heating cycle (when the thermostat reaches the temp).

Why did you drain the system ? you dont have to do that

 

[diynob]

This was my understanding for repressuring the expansion vessel. I think there were air pockets in the system as well, because air kept coning out of the rads (from the 2 tower rads, highest point), so when I refilled it i left all rads open until water started coming out without hissing sounds..

If there is an easier option I am definitely open to it... My dyi self could not comprehend why the pressure was on zero, yet the heating was working as normal, minus water being spewed out of the air valve outside. This lead me to believe there were air pockets in the system, somewhere in the piping. I might be getting this wrong.

Yesterday after I did this the pressure was at 1 spot on, now, when the heating is not working it's a bit below one, raises to 1,5BARs throughout the heating cycle. Water works fine, heating works fine, no weird sounds and no water coming out outside.

Thanks.

 

[ianmcd]

This was my understanding for repressuring the expansion vessel. I think there were air pockets in the system as well, because air kept coning out of the rads (from the 2 tower rads, highest point), so when I refilled it i left all rads open until water started coming out without hissing sounds..

If there is an easier option I am definitely open to it... My dyi self could not comprehend why the pressure was on zero, yet the heating was working as normal, minus water being spewed out of the air valve outside. This lead me to believe there were air pockets in the system, somewhere in the piping. I might be getting this wrong.

Yesterday after I did this the pressure was at 1 spot on, now, when the heating is not working it's a bit below one, raises to 1,5BARs throughout the heating cycle. Water works fine, heating works fine, no weird sounds and no water coming out outside.

Thanks.

that is within expected range so you have sorted it, but as said you need to de-pressurise the boiler and leave a drain point open when charging the vessel, no need to drain the system , glad you have it sorted, and draining the system and adding fresh inhibitor wont have damaged anything and can sometimes be good for the system water