Boiler running at 3 bar, is that normal?

[#1]

Long time no type, but on checking my boiler this morning I noticed that the dial on it says its running at 3 bar, is this normal? I'm no plumber but I don't think it's right. I do have an expansion chamber on it, so would it be wise to dump some of this pressure?

[#2]

Assuming you have maintained annually, why not ask your heating engineer?
Or perhaps on the Plumbfix forum.
https://community.screwfix.com/forums/plumbers-talk.2008/

[#3]

Thanks @Gel, It is maintained annually and the heating engineer is due to come in December so giving him a call wouldn't do any harm, but I'd still like to know if it's normal or not to run at this pressure so I know he's not feeding me a line or if I need to get him in earlier.

[#4]

@Mook  most modern boilers run at 1 - 3 bar   and if it goes over there should be a relief valve that opens

[#5]

Thanks @rongtw, that sounds promising, and now you mention the dump valve I recall having it replaced earlier this year and the old one the was left behind had a 3 bar marking on it.

[#6]

My combi boiler has a red zone at 3 and above. If it runs above I have to drain water manually.

As important it should sit just above one when not in use. It went way below that earlier this year (when I stopped using the heating in summer). Turns out one of the radiators had air in it - when this was drained the pressure came back up.

Brian

[#7]

3 Bar is fine for me on my baxi boiler... even if it does go into the red the pressure should blow off anyways 

[#8]

Thanks for the replies guys, I'm going to check the radiators to see if any need bleeding, but it would appear that 3 bar is acceptable so I'm happy with that.

[#9]

Hi Moor,

Operating at three bar is not good. Three bar is the pressure that the relief valve will activate at to limit the pressure.

Sealed heating systems have "pressure vessels" / "expansion vessels" to control the pressure.

A pressure vessel is simple a container which has a large air bubble/sack inside.

https://en.m.wikipedia.org/wiki/Expansion_tank

If you are reaching 3 bar then it is probable that the expansion vessel has lost it air.

With a failed expansion vessel the boiler pressure will drop when cold and exceed the normal high limit when hot.

Richard

[#10]

@RichardB, what you say is contrary to the other opinions, nothing wrong with that, but thinking about it 3 bar must be an acceptable pressure to operate at if the dump valve operates just on or above it, otherwise the value would have a lower pressure threshold.

I do have an expansion chamber on it and it was installed after my dump valve was replaced and that’s been in less than 2 years IIRC.

Anyone else have any thoughts to back up RichardB’s theory?

[#11]

We have a Worcester-Bosch boiler and the paperwork says the pressure "must not exceed 2.5 bar" and "The optimum pressure is between 1.5 and 1.7 bar" so that's where I keep it. No point taking chances.

[#12]

What's the pressure when everything is cold? If it rises a lot when the system heats up I'd guess that would be because of air in a radiator expanding.

[#13]

@Mook

A closed system is designed to replicate the head pressure that an open-vented system would run at in order to maintain prime at all the points in the system. One bar is about 33 feet of water head. Your boiler is running at over 100 feet of water head, which is equivalent to having a head tank in the loft of in one hell of a tall house! It's way too high. Ideally it should operate at no more that 1.5bar.

If you get a radiator or a joint springing a leak the fountain might reach the ceiling!

[#14]

Excellent @nozzer, thanks for that I'll check it again tomorrow and if it's sitting at over 2 bar I'll call the heating engineer in.

[#15]

@Mook

You were going to bleed some radiators? Try that first and let some water out. It's probably been set up with the system cold and risen because of the increase in water temp at the weather has got colder. A build up of air in the system will also have the same effect as others have suggested. Less space for the water to occupy.