Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


--
Tim Lamb

Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a cold
day. But even if you assumed 5 degrees to 85degrees you only get 1.5
litres so I'd reckon a 4l should be more than adequate unless I've done
my sums wrong.
hth
Bob

In message , Bob Minchin
writes
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a
cold day. But even if you assumed 5 degrees to 85degrees you only get
1.5 litres so I'd reckon a 4l should be more than adequate unless I've
done my sums wrong.
hth
Bob

Well the boiler has an internal expansion vessel of 8L I'm uncertain if
that is total volume (air plus water) or working range.

The flow and return piping about 14L

Heat exchange coil in the thermal store 5.5L

Extraneous pipework a few more say 3.0L

Do I actually need a separate vessel?

--
Tim Lamb

On 13/03/2018 11:17, Tim Lamb wrote:
In message , Bob Minchin
writes
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a
cold day. But even if you assumed 5 degrees to 85degrees you only get
1.5 litres so I'd reckon a 4l should be more than adequate unless I've
done my sums wrong.
hth
Bob

Well the boiler has an internal expansion vessel of 8L I'm uncertain if
that is total volume (air plus water) or working range.

The flow and return piping about 14L

Heat exchange coil in the thermal store 5.5L

Extraneous pipework a few more say 3.0L

Do I actually need a separate vessel?

Probably not...

I run 21 rads + cylinder (so probably 100 to 150L of primary water) on
the internal expansion vessel on my boiler, and with the initial
pressure set at 1 to 1.3 bar, it will never rise above 2 bar.


--
Cheers,

John.

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

On 13/03/2018 10:23, Bob Minchin wrote:
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a cold
day. But even if you assumed 5 degrees to 85degrees you only get 1.5
litres so I'd reckon a 4l should be more than adequate unless I've done
my sums wrong.
hth
Bob

Agreed. But just in case anyone interprets that to mean that a 4 litre
expansion vessel can accommodate 4 litres of expansion - it can't! Well,
not without the pressure going through the roof[1] when you squeeze its
air down to nothingness. In the case quoted, the air volume will reduce
from 4 litres to 2.5 litres - with the pressure rising from (say) 1 bar
to 1.6 bar - which is ok.

[1] And operating the pressure relief valve

--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 13/03/18 10:01, Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


I dont recall ANY expansion vessel on my UFH!

Other than what was in the boiler anyway

I think I had 600m+

I am sure a standard unit will cope - its a relatively easy thing to
retrofit more if needs be

Coefficient of expansion of water is 0.000214/deg C, so even if you max
out at 60 degrees (your house wont go below 10C internally) the worst
case expansion is 0.000214 x 50 x 85 litrs = 0.909 liters

That is something and in-boiler expansion vessel is well able to cope with.



--
Climate Change: Socialism wearing a lab coat.

On 13/03/18 11:17, Tim Lamb wrote:
In message , Bob Minchin
writes
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litresÂ* is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a
cold day. But even if you assumed 5 degrees to 85degrees you only get
1.5 litres so I'd reckon a 4l should be more than adequate unless I've
done my sums wrong.
hth
Bob

Well the boiler has an internal expansion vessel of 8L I'm uncertain if
that is total volume (air plus water) or working range.

The flow and return piping about 14L

Heat exchange coil in the thermal store 5.5L

Extraneous pipework a few more say 3.0L

Do I actually need a separate vessel?

No. Unless you start blowng the pressure relief valve.



--
€œit should be clear by now to everyone that activist environmentalism
(or environmental activism) is becoming a general ideology about humans,
about their freedom, about the relationship between the individual and
the state, and about the manipulation of people under the guise of a
'noble' idea. It is not an honest pursuit of 'sustainable development,'
a matter of elementary environmental protection, or a search for
rational mechanisms designed to achieve a healthy environment. Yet
things do occur that make you shake your head and remind yourself that
you live neither in Joseph Stalins Communist era, nor in the Orwellian
utopia of 1984.€�

Vaclav Klaus

In message , The Natural Philosopher
writes
On 13/03/18 10:01, Tim Lamb wrote:
Confused....
Either my known to be suspect mathematics is wrong or there is
something amiss with sites recommending pressure vessel sizes.
Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.
Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes
to 85L. A more agile brain may kindly care to check!
Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.
The underfloor heating systems suppliers suggest a 4L vessel is
adequate for 1000m of 16mm pipe yet most sites marketing PVs are
wildly in excess of this. Surely they know that the system is run at
a much lower temperature than 85C boiler output!
Any thoughts?

I dont recall ANY expansion vessel on my UFH!

Other than what was in the boiler anyway

I think I had 600m+

I am sure a standard unit will cope - its a relatively easy thing to
retrofit more if needs be

Coefficient of expansion of water is 0.000214/deg C, so even if you max
out at 60 degrees (your house wont go below 10C internally) the worst
case expansion is 0.000214 x 50 x 85 litrs = 0.909 liters

That is something and in-boiler expansion vessel is well able to cope with.

OK

I am reassured:-)

--
Tim Lamb

In message , John
Rumm writes
On 13/03/2018 11:17, Tim Lamb wrote:
In message , Bob Minchin
writes
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a
cold day. But even if you assumed 5 degrees to 85degrees you only get
1.5 litres so I'd reckon a 4l should be more than adequate unless I've
done my sums wrong.
hth
Bob

Well the boiler has an internal expansion vessel of 8L I'm uncertain if
that is total volume (air plus water) or working range.

The flow and return piping about 14L

Heat exchange coil in the thermal store 5.5L

Extraneous pipework a few more say 3.0L

Do I actually need a separate vessel?

Probably not...

I run 21 rads + cylinder (so probably 100 to 150L of primary water) on
the internal expansion vessel on my boiler, and with the initial
pressure set at 1 to 1.3 bar, it will never rise above 2 bar.

OK. That's clear enough.



--
Tim Lamb

In message , Roger Mills
writes
On 13/03/2018 10:23, Bob Minchin wrote:
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a cold
day. But even if you assumed 5 degrees to 85degrees you only get 1.5
litres so I'd reckon a 4l should be more than adequate unless I've done
my sums wrong.
hth
Bob

Agreed. But just in case anyone interprets that to mean that a 4 litre
expansion vessel can accommodate 4 litres of expansion - it can't!
Well, not without the pressure going through the roof[1] when you
squeeze its air down to nothingness. In the case quoted, the air volume
will reduce from 4 litres to 2.5 litres - with the pressure rising from
(say) 1 bar to 1.6 bar - which is ok.

[1] And operating the pressure relief valve

Is one still allowed to run the relief valve to an outside wall?


--
Tim Lamb

In message , Bob Minchin
writes
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a
cold day. But even if you assumed 5 degrees to 85degrees you only get
1.5 litres so I'd reckon a 4l should be more than adequate unless I've
done my sums wrong.

Thanks Bob. Coincides with other posts but I still say there is
something awry with the PV sites.

--

On 13/03/18 14:31, Tim Lamb wrote:
Thanks Bob. Coincides with other posts but I still say there is
something awry with the PV sites.

remember PV is not about engineering its about marketing and profit


--
A lie can travel halfway around the world while the truth is putting on
its shoes.

Often found the wonders of undrfloor heating a bit odd.
I can recall many years ago a small flat for some relatives had it and it
looked to me limke the system was under a kind of mesh floor with heat sink
like vaned pipes underneath it on top of some lagging. Certainly a lot more
complex than has been discussed here.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Tim Lamb" wrote in message
...
In message , The Natural Philosopher
writes
On 13/03/18 10:01, Tim Lamb wrote:
Confused....
Either my known to be suspect mathematics is wrong or there is
something amiss with sites recommending pressure vessel sizes.
Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.
Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L comes to
85L. A more agile brain may kindly care to check!
Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.
The underfloor heating systems suppliers suggest a 4L vessel is
adequate for 1000m of 16mm pipe yet most sites marketing PVs are wildly
in excess of this. Surely they know that the system is run at a much
lower temperature than 85C boiler output!
Any thoughts?

I dont recall ANY expansion vessel on my UFH!

Other than what was in the boiler anyway

I think I had 600m+

I am sure a standard unit will cope - its a relatively easy thing to
retrofit more if needs be

Coefficient of expansion of water is 0.000214/deg C, so even if you max
out at 60 degrees (your house wont go below 10C internally) the worst
case expansion is 0.000214 x 50 x 85 litrs = 0.909 liters

That is something and in-boiler expansion vessel is well able to cope
with.

OK

I am reassured:-)

--
Tim Lamb

On 13/03/2018 10:01, Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is something
amiss with sites recommending pressure vessel sizes.
snip
Any thoughts?

Yes, Apart from physical space required, get a guestimate then go for
the next size up.
From my own experience the estimated size of expansion vessel based on
"at the time" UFH water volume was something like a litre more (or less)
than the closest size so I went to the next size up. Fortunately it
meant that when I re-fitted radiators in the bedrooms (not previously in
the system) I could fit bigger rads to work at UFH flow temperatures and
still have spare capacity.
Followed by previously un-planned front extension with another 300m or
so (3 zones on 4 circuits) of UFH pipework and still within capacity of
expansion vessel.
I still have another UFH zone to add in the bathroom so again this
wasn't originally factored into the volume calcs but will hopefully be
met with the existing vessel.

So bigger is better than being accurately calculated to meet "current"
system requirement.

On 13/03/2018 14:28, Tim Lamb wrote:
In message , Roger Mills
writes
On 13/03/2018 10:23, Bob Minchin wrote:
Tim Lamb wrote:
Confused....

Either my known to be suspect mathematics is wrong or there is
something
amiss with sites recommending pressure vessel sizes.

Under my new floors I have carefully:-) laid 820m of 16mm pex-al-pex
piping.

Sadly absent from the mainly American sites offering pipe volume
calculations. My vernier gives a bore of 11.5mm and Pi x r2 x L
comes to
85L. A more agile brain may kindly care to check!

Could that length of pipe bore conceivably squash into an 18 gallon
container? Probably.

The underfloor heating systems suppliers suggest a 4L vessel is
adequate
for 1000m of 16mm pipe yet most sites marketing PVs are wildly in
excess
of this. Surely they know that the system is run at a much lower
temperature than 85C boiler output!

Any thoughts?


Coefficient of expansion of water is 0.000214/degree c or for your 85
litres is 18ml per degree c
I'd allow for a max temperature assuming your mixing valve had failed
and a minimum of + a few degree assuming the system was filled on a cold
day. But even if you assumed 5 degrees to 85degrees you only get 1.5
litres so I'd reckon a 4l should be more than adequate unless I've done
my sums wrong.
hth
Bob

Agreed. But just in case anyone interprets that to mean that a 4 litre
expansion vessel can accommodate 4 litres of expansion - it can't!
Well, not without the pressure going through the roof[1] when you
squeeze its air down to nothingness. In the case quoted, the air
volume will reduce from 4 litres to 2.5 litres - with the pressure
rising from (say) 1 bar to 1.6 bar - which is ok.

[1] And operating the pressure relief valve

Is one still allowed to run the relief valve to an outside wall?

Not only allowed, but required usually. (and positioned / angled in such
a way as there is a low rick of injuring a bystander should it let go).
So normally a pipe taken down to "low ish" on the outside of the wall,
and then turned back to point at the wall a bit (or it could discharge
into a gully)


--
Cheers,

John.

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

On 13/03/2018 16:03, Brian Gaff wrote:
Often found the wonders of undrfloor heating a bit odd.
I can recall many years ago a small flat for some relatives had it and it
looked to me limke the system was under a kind of mesh floor with heat sink
like vaned pipes underneath it on top of some lagging. Certainly a lot more
complex than has been discussed here.

UFH for suspended floors is a tad more complicated that those buried in
a screed.


--
Cheers,

John.

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

On 13/03/2018 11:40, John Rumm wrote:
On 13/03/2018 11:17, Tim Lamb wrote:


Do I actually need a separate vessel?

Probably not...


Until the internal vessel fails. Then you will probably be glad. I had
to put in an external vessel about 20 years ago when the internal one
failed after five years. I've just replaced the external one. (But I am
on my third boiler now).

In message , John
Rumm writes
On 13/03/2018 14:28, Tim Lamb wrote:
Agreed. But just in case anyone interprets that to mean that a 4 litre
expansion vessel can accommodate 4 litres of expansion - it can't!
Well, not without the pressure going through the roof[1] when you
squeeze its air down to nothingness. In the case quoted, the air
volume will reduce from 4 litres to 2.5 litres - with the pressure
rising from (say) 1 bar to 1.6 bar - which is ok.

[1] And operating the pressure relief valve

Is one still allowed to run the relief valve to an outside wall?

Not only allowed, but required usually. (and positioned / angled in
such a way as there is a low rick of injuring a bystander should it let
go). So normally a pipe taken down to "low ish" on the outside of the
wall, and then turned back to point at the wall a bit (or it could
discharge into a gully)
OK. I was thinking a discharge under the worktop via some tundish
arrangement might not be noticed.



--
Tim Lamb

On 13/03/2018 20:52, Tim Lamb wrote:
In message , John
Rumm writes
On 13/03/2018 14:28, Tim Lamb wrote:
Agreed. But just in case anyone interprets that to mean that a 4 litre
expansion vessel can accommodate 4 litres of expansion - it can't!
Well, not without the pressure going through the roof[1] when you
squeeze its air down to nothingness. In the case quoted, the air
volume will reduce from 4 litres to 2.5 litres - with the pressure
rising from (say) 1 bar to 1.6 bar - which is ok.

[1] And operating the pressure relief valve

Is one still allowed to run the relief valve to an outside wall?

Not only allowed, but required usually. (and positioned / angled in
such a way as there is a low rick of injuring a bystander should it
let go). So normally a pipe taken down to "low ish" on the outside of
the wall, and then turned back to point at the wall a bit (or it could
discharge into a gully)

OK. I was thinking a discharge under the worktop via some tundish
arrangement might not be noticed.

For the boiler primary circuit relief valve there is no actual
requirement for a tundish (there is no mains water contamination risk),
and you also have other indications that the system has lost water (i.e.
a loss of sealed system pressure)


--
Cheers,

John.

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