Pumping air into combi expansion vessel - how many PSI?
 

I checked the air pressure in my Britony 80 combi boiler's expansion
vessel the other day; that's after I lowered the water pressure to
about 0.8 bar. There was no air pressure at all - as I suspected.

I now need to know how many psi of air to pump into it when the water
presure is, say, about 0.8 bar. I'm asking for a psi figure because my
air pressure guage only has psi reading no bar reading.

The expension vessel was originally pre-charged to 0.7 bar according
to the manual.

Thank you

Dave L

In an earlier contribution to this discussion,
Dave£ wrote:

I checked the air pressure in my Britony 80 combi boiler's expansion
vessel the other day; that's after I lowered the water pressure to
about 0.8 bar. There was no air pressure at all - as I suspected.

I now need to know how many psi of air to pump into it when the water
presure is, say, about 0.8 bar. I'm asking for a psi figure because my
air pressure guage only has psi reading no bar reading.

The expension vessel was originally pre-charged to 0.7 bar according
to the manual.

Thank you

Dave L

1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
be exact - but I doubt whether your pressure gauge measures fractions of a
psi]

--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
Dave£ wrote:

I checked the air pressure in my Britony 80 combi boiler's expansion
vessel the other day; that's after I lowered the water pressure to
about 0.8 bar. There was no air pressure at all - as I suspected.

I now need to know how many psi of air to pump into it when the water
presure is, say, about 0.8 bar. I'm asking for a psi figure because my
air pressure guage only has psi reading no bar reading.

The expension vessel was originally pre-charged to 0.7 bar according
to the manual.

Thank you

Dave L

1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
be exact - but I doubt whether your pressure gauge measures fractions of a
psi]

SS, Thank you for your help again. One thing I'm not clear about: At
what pressure should the heating system water be when I pump the
expansion vessel to 10psi? And, should the boiler be tuned on or off
during this operation?

Dave L

In an earlier contribution to this discussion,
Dave£ wrote:

On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square"
wrote:

1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi
[10.15 to be exact - but I doubt whether your pressure gauge
measures fractions of a psi]


SS, Thank you for your help again. One thing I'm not clear about: At
what pressure should the heating system water be when I pump the
expansion vessel to 10psi? And, should the boiler be tuned on or off
during this operation?

Dave L

You must pump up the pressure vessel with the heating system cold and
un-pressurised. At this point, the pressure vessel will be completely filled
with air at 0.7 bar. *Then* use the filling loop to pressurise the system to
around 1 bar, cold. *Some* water will enter the pressure vessel (on the wet
side of the diaphragm), and will compress the air a bit more - but still
leave plenty of expansion potential. When the system is hot, it shouldn't
get to much more than 2 bar if everything is working correctly.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Mon, 25 Oct 2004 09:30:47 +0000, Dave£ wrote:

On Sun, 24 Oct 2004 19:54:11 +0100, "Set Square"
wrote:

In an earlier contribution to this discussion,
Dave£ wrote:

I checked the air pressure in my Britony 80 combi boiler's expansion
vessel the other day; that's after I lowered the water pressure to
about 0.8 bar. There was no air pressure at all - as I suspected.

I now need to know how many psi of air to pump into it when the water
presure is, say, about 0.8 bar. I'm asking for a psi figure because my
air pressure guage only has psi reading no bar reading.

The expension vessel was originally pre-charged to 0.7 bar according
to the manual.

Thank you

Dave L

1 bar = 14.5 psi - so, for 0.7 bar, you'll need just over 10 psi [10.15 to
be exact - but I doubt whether your pressure gauge measures fractions of a
psi]

SS, Thank you for your help again. One thing I'm not clear about: At
what pressure should the heating system water be when I pump the
expansion vessel to 10psi? And, should the boiler be tuned on or off
during this operation?


The FAQ may help (if it's read).


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html