I have a Baxi Barcelona boiler on primary loop to a Thermal Store.
In this configuration .. the store water contents are circulated around
the boiler (rather than just a transfer coil)

Primary loop has a pump, flow control valve and expansion vessel,
vessel charge is to 1 bar and static pressure on primary loop (via
filling loop ) is also 1 bar.
Had to change pressure vessel due to failure ...

Issue I have is that is I set static pressure to 1 bar cold ... then it
hits 2.5 bar hot (too high) ... this would suggest that there is air in
the system, expanding when hot.
There is an AAV on top of store which is working and if I manually
operate only water coming out .. (this was actually removed entirely
during filling)
There are air bleed screws on highest point of F & R pipes ... checked
and only water comes out of both.

Phoned system manufacturer he concurs it is air in system ... he
suggested releasing all static pressure, setting vessel to 2.5 bar and
then running pump (boiler off) and then refill system to 1 bar static
charge.
Done that .... same result.

Anybody any tips for getting air out ?
If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb







--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On Wed, 04 Jun 2014 15:58:41 +0100, Rick Hughes wrote:

Anybody any tips for getting air out ?
If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb

Is that drawing correct in regard of the relative vertical layout of
the bits?

If so the highest point is the filling loop, have you tried venting
there once the system is "full".

--
Cheers
Dave.

"Rick Hughes" wrote in message
...
I have a Baxi Barcelona boiler on primary loop to a Thermal Store.
In this configuration .. the store water contents are circulated around
the boiler (rather than just a transfer coil)

Primary loop has a pump, flow control valve and expansion vessel, vessel
charge is to 1 bar and static pressure on primary loop (via filling loop )
is also 1 bar.
Had to change pressure vessel due to failure ...

Issue I have is that is I set static pressure to 1 bar cold ... then it
hits 2.5 bar hot (too high) ... this would suggest that there is air in
the system, expanding when hot.
There is an AAV on top of store which is working and if I manually operate
only water coming out .. (this was actually removed entirely during
filling)
There are air bleed screws on highest point of F & R pipes ... checked and
only water comes out of both.

Phoned system manufacturer he concurs it is air in system ... he suggested
releasing all static pressure, setting vessel to 2.5 bar and then running
pump (boiler off) and then refill system to 1 bar static charge.
Done that .... same result.

Anybody any tips for getting air out ?
If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb


I would start by checking that there is in fact air in the expanson vessel.
The air in the expansion vessel is squeezed as temperature and pressure
rises in the system so stopping pressure from rising too much.
OR
The expansion vessel may be too small. You are going to need a big one.
If you have a stored water system, that is a huge amount of water compared
with a "normal" system.
You need to work out the water volume in the system, , temperature rise and
consult the P/Vessel manufacturer's data.

On 04/06/2014 15:58, Rick Hughes wrote:
I have a Baxi Barcelona boiler on primary loop to a Thermal Store.
In this configuration .. the store water contents are circulated around
the boiler (rather than just a transfer coil)

Primary loop has a pump, flow control valve and expansion vessel,
vessel charge is to 1 bar and static pressure on primary loop (via
filling loop ) is also 1 bar.
Had to change pressure vessel due to failure ...

ok so the thermal store itself is also pressurised by the sounds of it...

Issue I have is that is I set static pressure to 1 bar cold ... then it
hits 2.5 bar hot (too high) ... this would suggest that there is air in
the system, expanding when hot.

Not sure I concur with the train of logic. First if we assume that 2.5
bar is too high (and that is also questionable[1]) It sounds more like
you have either too little expansion room, or too high an expansion
charge pressure.

What pressure do you *expect* on a hot system?

Do you have an estimate of the actual water content of the primary side?

There is an AAV on top of store which is working and if I manually
operate only water coming out .. (this was actually removed entirely
during filling)
There are air bleed screws on highest point of F & R pipes ... checked
and only water comes out of both.

Phoned system manufacturer he concurs it is air in system ... he
suggested releasing all static pressure, setting vessel to 2.5 bar and
then running pump (boiler off) and then refill system to 1 bar static
charge.
Done that .... same result.

Anybody any tips for getting air out ?

It strikes me that air in the system would *reduce* the ultimate
pressure rise you observe - after all that is exactly what an expansion
vessel is - a bubble of (readily compressible) air waiting to be
squeezed but the incompressible water when it expands.

If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb

[1] Many sealed primary systems will be designed to operate with say 1
bar cold pressure, and say 2.5 bar hot system pressure, with the PRV set
to operate at 3 or 3.5 bar.

Would a more plausible explanation be that previously the system did
have extra air in it, resulting in lower than expected hot pressures
while the expansion vessel was working. When it failed and swapped it
out, you bled out the extra air that was once there and are now
observing the expected pressure rise?



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 04/06/2014 17:28, Dave Liquorice wrote:
On Wed, 04 Jun 2014 15:58:41 +0100, Rick Hughes wrote:

Anybody any tips for getting air out ?
If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb

Is that drawing correct in regard of the relative vertical layout of
the bits?

If so the highest point is the filling loop, have you tried venting
there once the system is "full".



No highest point is the 2 vents screws on pipes ... and only water comes
out of these.


--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On 04/06/2014 17:48, harryagain wrote:

You need to work out the water volume in the system, , temperature rise and
consult the P/Vessel manufacturer's data.


The expansion vessel is correct one ... sized for system ... I bought
the whole lost as a 'package' and been in use for more than 10 years
..... just failed so replaced ... in fact replacement is 1L bigger as
they no longer make a 24L.




--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On 04/06/2014 18:27, John Rumm wrote:



I didn't come up with the 'air in system' idea, that was system
manufacturer. maybe its something else.

Checked air charge in pressure vessel .. set to 1.0 bar.

I removed AAV filled system slowly until store was full, refitted AAV
and continued to fill ... air was heard vesting from AAV.
Checked bleed vents - only water coming out.

Used filling loop to fill to 1.0 bar static pressure.

If I run system without boiler firing (i.e water being pumped in
loop/store) pressure drops a little but returns to 1 bar if I stop pump.

I start system and as temp increases in loop/store pressure goes up ...
reaching 2.5bar


System is a complete designed package ... and pressure vessel is
correctly sized.





--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

Rick Hughes wrote:
On 04/06/2014 18:27, John Rumm wrote:



I didn't come up with the 'air in system' idea, that was system
manufacturer. maybe its something else.

Checked air charge in pressure vessel .. set to 1.0 bar.

I removed AAV filled system slowly until store was full, refitted AAV and
continued to fill ... air was heard vesting from AAV.
Checked bleed vents - only water coming out.

Used filling loop to fill to 1.0 bar static pressure.

If I run system without boiler firing (i.e water being pumped in
loop/store) pressure drops a little but returns to 1 bar if I stop pump.

I start system and as temp increases in loop/store pressure goes up ... reaching 2.5bar


System is a complete designed package ... and pressure vessel is correctly sized.


Well, as John says, having air in the system would reduce the pressure rise
due to temperature rather than increase it. It is after all what your
expansion vessel should be filled with. Many pressurised tanks actually
have an air bubble in the tank for pressure control rather than an external
expansion vessel.

My first thought is that your new vessel is faulty.
Does water come out the air valve on the expansion vessel?

Tim

On 04/06/2014 18:54, Rick Hughes wrote:
On 04/06/2014 18:27, John Rumm wrote:



I didn't come up with the 'air in system' idea, that was system
manufacturer. maybe its something else.

Checked air charge in pressure vessel .. set to 1.0 bar.

I removed AAV filled system slowly until store was full, refitted AAV
and continued to fill ... air was heard vesting from AAV.
Checked bleed vents - only water coming out.

Used filling loop to fill to 1.0 bar static pressure.

If I run system without boiler firing (i.e water being pumped in
loop/store) pressure drops a little but returns to 1 bar if I stop pump.

I start system and as temp increases in loop/store pressure goes up ...
reaching 2.5bar

Which sounds pretty reasonable in the absence of any other information
like a manufacturers statement that the hot pressure should never excess
x etc.

System is a complete designed package ... and pressure vessel is
correctly sized.

Yup was not suggesting otherwise. In fact it sounds like its doing what
it should!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

I cannot see the pictures, but I do remember the antics of a neighbour with
similar air issues and in the end it seemed there was air in a point in the
pipework where it went up a bit, then down a bit again. I think in the end
they re routed the pipe to make it less of an issue.
I'm glad I don't have a boiler in this house one hears so many tortuous
incidents!

Brian

--
From the Sofa of Brian Gaff Reply address is active
"Dave Liquorice" wrote in message
ll.co.uk...
On Wed, 04 Jun 2014 15:58:41 +0100, Rick Hughes wrote:

Anybody any tips for getting air out ?
If you need a sketch due to my description being unclear ... :
http://tinyurl.com/npykyyb

Is that drawing correct in regard of the relative vertical layout of
the bits?

If so the highest point is the filling loop, have you tried venting
there once the system is "full".

--
Cheers
Dave.

On Wednesday, June 4, 2014 5:48:33 PM UTC+1, harry wrote:
"Rick Hughes" wrote in message

...

I have a Baxi Barcelona boiler on primary loop to a Thermal Store.

In this configuration .. the store water contents are circulated around

the boiler (rather than just a transfer coil)



Primary loop has a pump, flow control valve and expansion vessel, vessel

charge is to 1 bar and static pressure on primary loop (via filling loop )

is also 1 bar.

Had to change pressure vessel due to failure ...



Issue I have is that is I set static pressure to 1 bar cold ... then it

hits 2.5 bar hot (too high) ... this would suggest that there is air in

the system, expanding when hot.

There is an AAV on top of store which is working and if I manually operate

only water coming out .. (this was actually removed entirely during

filling)

There are air bleed screws on highest point of F & R pipes ... checked and

only water comes out of both.



Phoned system manufacturer he concurs it is air in system ... he suggested

releasing all static pressure, setting vessel to 2.5 bar and then running

pump (boiler off) and then refill system to 1 bar static charge.

Done that .... same result.



Anybody any tips for getting air out ?

If you need a sketch due to my description being unclear ... :

http://tinyurl.com/npykyyb





I would start by checking that there is in fact air in the expanson vessel.

The air in the expansion vessel is squeezed as temperature and pressure

rises in the system so stopping pressure from rising too much.

OR

The expansion vessel may be too small. You are going to need a big one.

If you have a stored water system, that is a huge amount of water compared

with a "normal" system.

You need to work out the water volume in the system, , temperature rise and

consult the P/Vessel manufacturer's data.

Wot 'arry said.

Air charge in expansion vessel depleted or it's too small.

Phoned system manufacturer he concurs it is air in system ... he

suggested releasing all static pressure, setting vessel to 2.5 bar and

then running pump (boiler off) and then refill system to 1 bar static

charge.

I don't see it could be air in the system, but check and recharge the expansion vessel as they say.

The boat winch thing looks very impressive, I'd missed any updates.

On Wednesday, June 4, 2014 3:58:41 PM UTC+1, Rick Hughes wrote:

PS Good practice is to have an air bottle on the air vents,
i.e. a tee with an upright dead-leg with the vent on the end of it.
The idea is to trap a few cubic inches of gas before
the tee fills up and the bubbles just go round and round the circuit.

On Wednesday, June 4, 2014 3:58:41 PM UTC+1, Rick Hughes wrote:

PPS Also good practice to have the pump pumping away from the expansion vessel.

Google "pumping away".

The point of connection of the expansion vessel is the point of no pressure change,
pressure there is the static head.

Pressure drops, due to frictional losses, as you go around the circuit to the pump inlet. The flow control (regulating) valve will be a big pressure loss.
Pressure at pump inlet is lowest and pumps do not like low inlet pressures.
See NPSH.

PPPS Also suspect a duff pressure gaug until you've confirmed its accuracy.
Some are very cheap and nasty.

On 05/06/2014 13:07, Onetap wrote:
On Wednesday, June 4, 2014 5:48:33 PM UTC+1, harry wrote:
..

I don't see it could be air in the system, but check and recharge the expansion vessel as they say.

Released all pressure and refilled ... set static pressure to 1 bar ...
again run pump without firing boiler ... get some air pushed out via AAV
... keep topping up until 1 bar steady.

Put boiler onto heat .. and as it gets hot pressure rises to between 2
and 2.5 bar


Called system supplier again this morning ... pressure vessel is
definitely the right size for supplied thermal store.
They are suggesting that pressure increase could in fact be acceptable
as water heats up ....
Seems a big change to me, and didn't do it previously.



The boat winch thing looks very impressive, I'd missed any updates.



Boat winch works a treat ... now just watch and press button on remote
control ... been in use for almost 18 months now.



--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On 04/06/2014 20:44, John Rumm wrote:
On 04/06/2014 18:54, Rick Hughes wrote:
On 04/06/2014 18:27, John Rumm wrote:



I didn't come up with the 'air in system' idea, that was system
manufacturer. maybe its something else.

Checked air charge in pressure vessel .. set to 1.0 bar.

I removed AAV filled system slowly until store was full, refitted AAV
and continued to fill ... air was heard vesting from AAV.
Checked bleed vents - only water coming out.

Used filling loop to fill to 1.0 bar static pressure.

If I run system without boiler firing (i.e water being pumped in
loop/store) pressure drops a little but returns to 1 bar if I stop pump.

I start system and as temp increases in loop/store pressure goes up ...
reaching 2.5bar

Which sounds pretty reasonable in the absence of any other information
like a manufacturers statement that the hot pressure should never excess
x etc.

System is a complete designed package ... and pressure vessel is
correctly sized.

Yup was not suggesting otherwise. In fact it sounds like its doing what
it should!




It has 'reduced a bit' ...
Now with a 1bar static pressure when cold ... it gets to 1.5 - 1.7 bar
when hot.
Maybe that is what should happen ... just that now I have an accurate
0-2.5bar 100mm pressure gauge I can read it accurately ... whereas
previously I only had the 30mm 0-10 bar gauge built into pressure
vessel valve.







--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

On 05/06/2014 13:11, Onetap wrote:
On Wednesday, June 4, 2014 3:58:41 PM UTC+1, Rick Hughes wrote:

PS Good practice is to have an air bottle on the air vents,
i.e. a tee with an upright dead-leg with the vent on the end of it.
The idea is to trap a few cubic inches of gas before
the tee fills up and the bubbles just go round and round the circuit.



With hindsight should have soldered in short 15mm upstands on bleeds -
instead of just putting the bleeds direct on 28x15x28 Tee.
However there is a 150mm upstand on top of the thermal store to which is
fixed the AAV.

So any air being 'pumped around' should find its way to this upstand.

--
UK SelfBuild: http://uk.groups.yahoo.com/group/UK_Selfbuild/

"Rick Hughes" wrote in message

Maybe that is what should happen ... just that now I have an accurate
0-2.5bar 100mm pressure gauge I can read it accurately ... whereas
previously I only had the 30mm 0-10 bar gauge built into pressure vessel
valve.

There's yer answer, your using a different gauge to before, and to make it
'worse' the new gauge has a totally different pressure range to the old un.

So basically, don't worry about it, the old gauge was cheap and inaccurate,
the new gauge is just showing what the system has been doing all along, and
what all hot water systems do as they heat up.

On Friday, June 6, 2014 12:36:30 PM UTC+1, Gazz wrote:
"Rick Hughes" wrote in message



Maybe that is what should happen ... just that now I have an accurate

0-2.5bar 100mm pressure gauge I can read it accurately ... whereas

previously I only had the 30mm 0-10 bar gauge built into pressure vessel

valve.



There's yer answer, your using a different gauge to before, and to make it

'worse' the new gauge has a totally different pressure range to the old un.

On Friday, June 6, 2014 1:35:58 PM UTC+1, Onetap wrote:
On Friday, June 6, 2014 12:36:30 PM UTC+1, Gazz wrote:

Are there expansion vessels & pressure relief valves on both secondary circuits? Might a leaking heat exchanger be involved?

On 05/06/2014 16:19, Rick Hughes wrote:
On 05/06/2014 13:07, Onetap wrote:
On Wednesday, June 4, 2014 5:48:33 PM UTC+1, harry wrote:
.

I don't see it could be air in the system, but check and recharge
the expansion vessel as they say.

Released all pressure and refilled ... set static pressure to 1 bar ...
again run pump without firing boiler ... get some air pushed out via AAV
.. keep topping up until 1 bar steady.

Put boiler onto heat .. and as it gets hot pressure rises to between 2
and 2.5 bar


Called system supplier again this morning ... pressure vessel is
definitely the right size for supplied thermal store.
They are suggesting that pressure increase could in fact be acceptable
as water heats up ....
Seems a big change to me, and didn't do it previously.

To me that seems like a reasonable pressure rise for the amount of
expansion capacity available and (my estimate) of the water content. (by
way of comparison, my system boiler with a large primary circuit (21
rads) shows a similar rise as it heats to full temperature (although due
to the weather compensation it rarely needs to get that hot)

My guess would be you are seeing a combination of two things:
previously it had not been bled as well, so there was an additional air
pocket in the system somewhere that was lowering the pressure rise
observed. Also a better pressure gauge is showing you more detail than
was available before.

Ultimately, if the store is rated to take the pressure, and the PRV
valve is set correctly, then you have nothing to worry about.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/