Boiler pressure question

danlightbulb

danlightbulb

danlightbulb

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Joined
14 Jul 2005
Posts
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Location
Birmingham
Hi all,

My boiler pressure gauge was broken so I had it repaired. Installer left it at 2 bar cold, about halfway in the green zone which would seem to be perfect.

However when the heating came on the pressure went up to 3.5 bar, well into the red zone which starts at 3 bar.

Should I be worried about this, do I need to let some pressure out?
 
When cold it should be 1 to 1.5 bar for the majority of boilers, that should be the lower end of the green zone on the gauge, and it should stay within the green zone when hot then. But the pressure is most important when it's hot.
 
andy_mk3 said:
When cold it should be 1 to 1.5 bar for the majority of boilers, that should be the lower end of the green zone on the gauge, and it should stay within the green zone when hot then. But the pressure is most important when it's hot.
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Ok I'll let some out but it went from 1.5 to 3.5 which is s 2 bar increase so if I set it to the lowest green area which is 1 bar and I get a 2 bar increase that will be 3 bar hot which is still on the red.
 
You need to let it fully cool down then drop the pressure down to 1 bar. If the pressure is still going too high then the expansion vessel is too small and you might need to add another one in to the system. But try it first.
 
SpellowHouse said:
You need to let it fully cool down then drop the pressure down to 1 bar. If the pressure is still going too high then the expansion vessel is too small and you might need to add another one in to the system. But try it first.
Click to expand...

Dangerous Dave said:
I’d check the air pressure in your expansion tank as it shouldn’t be going up 2bar when the system is hot.
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Ok. It's a Worcester Bosch combi boiler so don't know if air pressure is adjustable or maybe I need the engineer back in?

I've let some pressure out it's now running at 2.5 bar. Will see what it reads in the morning when it's cooled down completely.
 
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The charge of air in the expansion vessel needs topping up. This can only be done with the boiler empty of water and the drain point left open while being recharged. Once the vessel is pumped back up (usually 1 bar air) then the drain can be closed, and the boiler refilled.
This will keep the pressure stable when the radiators are heated. And this issue is quite common at this time of year ;)
 
FlyingFish said:
The charge of air in the expansion vessel needs topping up. This can only be done with the boiler empty of water and the drain point left open while being recharged. Once the vessel is pumped back up (usually 1 bar air) then the drain can be closed, and the boiler refilled.
This will keep the pressure stable when the radiators are heated. And this issue is quite common at this time of year ;)
Click to expand...

Technically I'm not allowed to do this myself am I. I've watched some YouTube vids though and it doesn't seem difficult. Slightly annoyed the installer didn't check this after replacing the gauge. Yet another tradesperson I've lost confidence in after just one job. It was only serviced in March by previous homeowner.

1 bar this morning system cold. Turned on the heating, boiler setting 2 on the temperature, gauge went up to just under 2.5 bar after about 20 minutes then I had to turn it off. So 1.5 bar rise in 20 minutes.
 
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Technically, (as I understand it, although don't recommend it) you can do what you want under your OWN roof, as long as what you do doesn't result in harm to others, or a risk to others. But don't quote me on that.

With certain WB boilers you can recharge the vessel without even taking the casing off. Draining the heating from a drain point on the radiators, and accessing the Schroeder valve at the top back of the boiler, without even using any tools apart from the pump itself.

Any work we do on a combi boiler, always involves checking/recharging the vessel, even on an annual service. It's just good practice.
 
FlyingFish said:
work we do on a combi boiler, always involves checking/recharging the vessel, even on an annual service. It's just good practice
Click to expand...

I could take enough pressure off to get the gauge to zero probably by draining some off the kitchen rad, and yes I believe the Schrader valve on this model is at the top behind the flue.

I agree with you it's definitely something I would expect to be checked on a service.
 
Went through the full boiler installation manual and user guide this morning - no mention of procedure to top up expansion vessel, and no fault finding guidance on it at all. All it says is how to replace one, and that it comes precharged to 0.75 bar.
 
I accessed the schreader valve on the expansion vessel, pressed it, and its immediately flowing water out.

That means expansion vessel gone I believe.

Extremely annoyed about it. Boiler serviced back in March, documentation supplied as part of house purchase. Get in the house, pressure gauge broken. I get the installer who serviced the boiler back in, pressure gauge replaced, installer didn't check vessel. Is this incompetence? It sounds like it to me. It can't be a coincidence that both these items have broken in the 6 months between the boiler being serviced and me buying the place.

So what now. Do I call the installer and confront him, give him chance to resolve? Or do I write off that guy and go somewhere else.

Thanks.
 
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