When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

VAG_dude wrote in news:bd4932e4-0e04-473a-a550-
:

When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?


It does not matter if the drain cock is open or closed when pressurising
the expansion vessel as long as there is zero pressure
in the system whilst this operation is carried out.

--- news://freenews.netfront.net/ - complaints: ---

On 20 Aug, 19:33, Heliotrope Smith wrote:
VAG_dude wrote in news:bd4932e4-0e04-473a-a550-
:

When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

It does not matter if the drain cock is open or closed when pressurising *
the expansion vessel as long as there is zero pressure
in the system whilst this operation is carried out.

--- news://freenews.netfront.net/ - complaints: ---

Cheers, turns out I had read a rather confusing guide!

"VAG_dude" wrote in message
...
On 20 Aug, 19:33, Heliotrope Smith wrote:
VAG_dude wrote in news:bd4932e4-0e04-473a-a550-
:

When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

It does not matter if the drain cock is open or closed when pressurising
the expansion vessel as long as there is zero pressure
in the system whilst this operation is carried out.

--- news://freenews.netfront.net/ - complaints: ---

Cheers, turns out I had read a rather confusing guide!

Sorry but it does matter.
When you pressurise the expansion cylinder you want to leave it empty of
water, if you pressurise it while full of water there will be no room for
expansion afterwards.

That is if the system is full of water but at zero pressure the expansion
vessel may still be full of water (there is nowhere for it to go), when you
start to pump in air the pressure will go up but still leave no space for
expansion.

You do need to ensure there is somewhere for the water that may be in the
expansion vessel to go and that is the drain.

On Fri, 20 Aug 2010 20:32:11 +0100, dennis@home wrote:

"VAG_dude" wrote in message
...
On 20 Aug, 19:33, Heliotrope Smith wrote:
VAG_dude wrote in news:bd4932e4-0e04-473a-a550-
:

When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

It does not matter if the drain cock is open or closed when pressurising
the expansion vessel as long as there is zero pressure
in the system whilst this operation is carried out.

--- news://freenews.netfront.net/ - complaints: ---

Cheers, turns out I had read a rather confusing guide!

Sorry but it does matter.
When you pressurise the expansion cylinder you want to leave it empty of
water, if you pressurise it while full of water there will be no room for
expansion afterwards.

That is if the system is full of water but at zero pressure the expansion
vessel may still be full of water (there is nowhere for it to go), when you
start to pump in air the pressure will go up but still leave no space for
expansion.

You do need to ensure there is somewhere for the water that may be in the
expansion vessel to go and that is the drain.

Yes, that's what I wondered, otherwise one is trying to compress water!
--
Peter.
The gods will stay away
whilst religions hold sway

On Fri, 20 Aug 2010 09:34:52 -0700 (PDT), VAG_dude wrote:

When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

By inference, on my Vaillant, with it open; i.e. it doesn't say close it.

"Release the pressure from the boiler as described in Section 7.1.4"
"Check that the internal pressure is... If the pressure is lower than this
the vessel should be repressurised ..."
Refit the valve cap"
"Repressurise boiler and heating system if necessary"

So, no explicit instruction to close the drain point.

I did mine a couple of days ago and it was 12psi with the drain open so no
action necessary, but it'd be interesting to see if it did make a
difference. I suppose that it depends on how much of the volume outside the
inflated part is occupied by air/water.

Had to search for a gauge - the one that I use nowadays starts at 50psi!
--
Peter.
The gods will stay away
whilst religions hold sway

On 20 Aug, 19:43, PeterC wrote:
On Fri, 20 Aug 2010 09:34:52 -0700 (PDT), VAG_dude wrote:
When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

By inference, on my Vaillant, with it open; i.e. it doesn't say close it.

"Release the pressure from the boiler as described in Section 7.1.4"
"Check that the internal pressure is... If the pressure is lower than this
the vessel should be repressurised ..."
Refit the valve cap"
"Repressurise boiler and heating system if necessary"

So, no explicit instruction to close the drain point.

I did mine a couple of days ago and it was 12psi with the drain open so no
action necessary, but it'd be interesting to see if it did make a
difference. I suppose that it depends on how much of the volume outside the
inflated part is occupied by air/water.

Had to search for a gauge - the one that I use nowadays starts at 50psi!
--
Peter.
The gods will stay away
whilst religions hold sway

This boiler is a Vaillant Turbomax and I have just re-pressurised the
EV and now it appears the diverter valve is not working as it should
occasionally getting stuck in mid-position! Is this to be expected for
a boiler that is 9 years old?

On Fri, 20 Aug 2010 11:53:10 -0700 (PDT), VAG_dude wrote:

On 20 Aug, 19:43, PeterC wrote:
On Fri, 20 Aug 2010 09:34:52 -0700 (PDT), VAG_dude wrote:
When you re-pressurise an expansion vessel in a boiler are you
supposed to leave the drain cock open once you have got the pressure
to 0 bar ?

By inference, on my Vaillant, with it open; i.e. it doesn't say close it.

"Release the pressure from the boiler as described in Section 7.1.4"
"Check that the internal pressure is... If the pressure is lower than this
the vessel should be repressurised ..."
Refit the valve cap"
"Repressurise boiler and heating system if necessary"

So, no explicit instruction to close the drain point.

I did mine a couple of days ago and it was 12psi with the drain open so no
action necessary, but it'd be interesting to see if it did make a
difference. I suppose that it depends on how much of the volume outside the
inflated part is occupied by air/water.

Had to search for a gauge - the one that I use nowadays starts at 50psi!
--
Peter.
The gods will stay away
whilst religions hold sway

This boiler is a Vaillant Turbomax and I have just re-pressurised the
EV and now it appears the diverter valve is not working as it should
occasionally getting stuck in mid-position! Is this to be expected for
a boiler that is 9 years old?

Sorry, don't know. Mine is 10 - 11 yo and, touch wood...
--
Peter.
The gods will stay away
whilst religions hold sway