Location of Sealed System Components
 

Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop valve
position.

Location of Sealed System Components
 

In article ,
Andy Hall writes:
Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop valve
position.

ISTR that when I was wading through lots of boiler installation
instructions when choosing a boiler, a number of them required
the expansion vessel in the return near the boiler. I doubt that's
a regulatory issue -- probably something more like ensuring there
was no momentary pressure drop in the boiler when pump started
that might otherwise trip a lockout due to low system pressure.

--
Andrew Gabriel

Location of Sealed System Components
 

Andy Hall wrote:
Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

When we had our Vaillant fitted a few years ago, I'm fairly sure the
installation instructions permitted/suggested the expansion vessel to be
sited near the boiler downstairs, as opposed to the tank upstairs (which
is where we wanted it, and where it went).

If you don't get a definitive answer here I'll have a root around and
see if I can dig them out.

David

Location of Sealed System Components
 

On Sat, 15 Jul 2006 01:59:01 +0100, Andrew Gabriel wrote
(in article ):

In article ,
Andy Hall writes:
Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

ISTR that when I was wading through lots of boiler installation
instructions when choosing a boiler, a number of them required
the expansion vessel in the return near the boiler. I doubt that's
a regulatory issue -- probably something more like ensuring there
was no momentary pressure drop in the boiler when pump started
that might otherwise trip a lockout due to low system pressure.



I looked as well and couldn't find anything. The items to make a system
are available separately.

The relief valve needs to have a suitable exit but I couldn't see a reason
that it needs to be next to the expansion vessel. I also couldn't see a
reason why the filling loop has to be near either apart from the point about
seeing the gauge when filling. Obviously the filling loop has to be a
proper one with check valve etc.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 10:30:15 +0100, Lobster wrote
(in article ):

Andy Hall wrote:
Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

When we had our Vaillant fitted a few years ago, I'm fairly sure the
installation instructions permitted/suggested the expansion vessel to be
sited near the boiler downstairs, as opposed to the tank upstairs (which
is where we wanted it, and where it went).

If you don't get a definitive answer here I'll have a root around and
see if I can dig them out.

David

Thanks David

I am pretty sure that that isn't' an issue, although note Andrew's point.

I was thinking about separation of the individual components such as the
expansion vessel, the filling point, the pressure gauge and the relief valve.
These often come as a kit, but I can't ind anything that says that they have
to be co-located. The components are available separately as well.

Location of Sealed System Components
 

"Andy Hall" wrote in message
...
On Sat, 15 Jul 2006 01:59:01 +0100, Andrew Gabriel wrote
(in article ):

In article ,
Andy Hall writes:
Is there any regulatory or other obvious reason to locate CH sealed
system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

ISTR that when I was wading through lots of boiler installation
instructions when choosing a boiler, a number of them required
the expansion vessel in the return near the boiler. I doubt that's
a regulatory issue -- probably something more like ensuring there
was no momentary pressure drop in the boiler when pump started
that might otherwise trip a lockout due to low system pressure.



I looked as well and couldn't find anything. The items to make a system
are available separately.

The relief valve needs to have a suitable exit but I couldn't see a reason
that it needs to be next to the expansion vessel. I also couldn't see a
reason why the filling loop has to be near either apart from the point
about
seeing the gauge when filling. Obviously the filling loop has to be a
proper one with check valve etc.

The source of expansion is the heat source, the boiler. The relief valve
has to be where the highest pressure point would be, the flow right on the
boiler. The expansion vessel has to be where the expansion would be
greatest, the boiler. Before system boilers came along, and all kit was
loose, the expansion was always on the flow. On the return, keeps it cooler
and Andrew hit on one the points it goes near the boiler. The expansion
vessel can add pressure when a negative pressure is around it. On the
suction side of the pump, when pressure drops compared to the pressure side,
it will expand back into the system equalising the pressure difference
around the pump somewhat. On an open vented system there may be sharp
differences in pressure from the highest to the lowest pressure around the
system as the expansion rise up the expansion pipe and nothing comes down to
compensate. The expansion vessel compensates to reduce negative pressure.

On an open vented system with a low head cavitation may occur in some pump
models. Having the charge pressure as high as possible in a sealed system
prevents pump cavitation (also this reduces as oxygen is eliminated from the
system), and also the higher pressure makes the boiler quieter as it raises
the boiling point. In some small capacity boilers there is local boiling of
the water in the heat exchanger giving the hiss sound. A higher pressure
prevents the boiler hissing.

Inhibitor can also cause system noise too. It may be wroth eliminating
inhibitor with a sealed system. The inhibitor swells joint seals and over
time causes leaks. In some Continental countries it is used infrequently.

Location of Sealed System Components
 

In article ,
Andy Hall writes:

The relief valve needs to have a suitable exit but I couldn't see a reason
that it needs to be next to the expansion vessel. I also couldn't see a

I don't think I've seen any such claim, but I would put
it close to the boiler exit (about 3" away in the case
of the one I fitted).

Whilst sitting at some traffic lights, I was looking at
the row of terraced houses along the road. On one, there
was the classic pattern of gas pipe, flue, and pressure
relief exit pipe indicative of a sealed system boiler
on the inside. However, what caused me to do a double-
take was that the pressure relief exit pipe was pushfit
plastic with a pushfit elbow and an extra 6" of pushfit
pipe pointing it downwards (and with no bracket holding
it in place). The house wall only about a foot back from
the pavement edge.

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

--
Andrew Gabriel

Location of Sealed System Components
 

"Andrew Gabriel" wrote in message
...
In article ,
Andy Hall writes:

The relief valve needs to have a suitable exit but I couldn't see a
reason
that it needs to be next to the expansion vessel. I also couldn't see
a

I don't think I've seen any such claim, but I would put
it close to the boiler exit (about 3" away in the case
of the one I fitted).

Whilst sitting at some traffic lights, I was looking at
the row of terraced houses along the road. On one, there
was the classic pattern of gas pipe, flue, and pressure
relief exit pipe indicative of a sealed system boiler
on the inside. However, what caused me to do a double-
take was that the pressure relief exit pipe was pushfit
plastic with a pushfit elbow and an extra 6" of pushfit
pipe pointing it downwards (and with no bracket holding
it in place). The house wall only about a foot back from
the pavement edge.

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

It has to be metal, no need for sleeving through a wall, and terminate at
floor level with the pipe turned towards the wall (an elbow). It can
terminate at high level like at the eves when a boiler is fitted in the
loft, but must turn in on itself. and it must not be over a used pathway.
It can be terminated onto a flat roof too without turning into the wall.

The HSE should be called in to this house. If it blows it could scald
people in the street below.

Location of Sealed System Components
 

Well, I wouldn't normally respond, but since you mention me,
I'd better make it clear where I stand...

In article ews.net,
"Doctor Drivel" writes:

The source of expansion is the heat source, the boiler. The relief valve
has to be where the highest pressure point would be, the flow right on the
boiler. The expansion vessel has to be where the expansion would be
greatest, the boiler.

Oh dear -- every single statement incorrect.

Before system boilers came along, and all kit was
loose, the expansion was always on the flow. On the return, keeps it cooler
and Andrew hit on one the points it goes near the boiler. The expansion
vessel can add pressure when a negative pressure is around it. On the
suction side of the pump, when pressure drops compared to the pressure side,
it will expand back into the system equalising the pressure difference
around the pump somewhat.

The point was that in the initial fraction of a second when the
pump starts and there's not yet any flow, you will get a significant
momentary pressure drop (which in turn is responsible for starting
the flow round the system). This is not of any consequence as it lasts
only a fraction of a second, except it could trip an under pressure
sensor, and cause a lockout. The pressure vessel will significantly
reduce this pressure drop if there's a short path between it and
the pressure sensor. For this purpose, it's probably more important
to have it near the under-pressure sensore than the pump. You might
get similar effects as zone valves open/close when the pump is running.

On an open vented system there may be sharp
differences in pressure from the highest to the lowest pressure around the
system as the expansion rise up the expansion pipe and nothing comes down to
compensate. The expansion vessel compensates to reduce negative pressure.

That paragraph is rubbish, and there is no expansion vessel in
open vented systems (the header tank performs that function).

On an open vented system with a low head cavitation may occur in some pump
models. Having the charge pressure as high as possible in a sealed system
prevents pump cavitation

Gosh, that's actually right (but largely irrelevant).

(also this reduces as oxygen is eliminated from the
system), and also the higher pressure makes the boiler quieter as it raises
the boiling point. In some small capacity boilers there is local boiling of
the water in the heat exchanger giving the hiss sound. A higher pressure
prevents the boiler hissing.

Inhibitor can also cause system noise too. It may be wroth eliminating
inhibitor with a sealed system. The inhibitor swells joint seals and over
time causes leaks. In some Continental countries it is used infrequently.

This voids pretty well all boiler guarantees.

--
Andrew Gabriel

Location of Sealed System Components
 

On Sat, 15 Jul 2006 13:27:20 +0100, Doctor Drivel wrote
(in article ews.net):


"Andrew Gabriel" wrote in message
...
In article ,
Andy Hall writes:

The relief valve needs to have a suitable exit but I couldn't see a
reason
that it needs to be next to the expansion vessel. I also couldn't see
a

I don't think I've seen any such claim, but I would put
it close to the boiler exit (about 3" away in the case
of the one I fitted).

Whilst sitting at some traffic lights, I was looking at
the row of terraced houses along the road. On one, there
was the classic pattern of gas pipe, flue, and pressure
relief exit pipe indicative of a sealed system boiler
on the inside. However, what caused me to do a double-
take was that the pressure relief exit pipe was pushfit
plastic with a pushfit elbow and an extra 6" of pushfit
pipe pointing it downwards (and with no bracket holding
it in place). The house wall only about a foot back from
the pavement edge.

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

It has to be metal, no need for sleeving through a wall, and terminate at
floor level with the pipe turned towards the wall (an elbow). It can
terminate at high level like at the eves when a boiler is fitted in the
loft, but must turn in on itself. and it must not be over a used pathway.
It can be terminated onto a flat roof too without turning into the wall.

Do you have a reference?

Location of Sealed System Components
 

"Andy Hall" aka Matt wrote in message
...
On Sat, 15 Jul 2006 13:27:20 +0100, Doctor Drivel wrote
(in article ews.net):


"Andrew Gabriel" wrote in message
...
In article ,
Andy Hall aka Matt writes:

The relief valve needs to have a suitable exit but I couldn't see a
reason
that it needs to be next to the expansion vessel. I also couldn't
see
a

I don't think I've seen any such claim, but I would put
it close to the boiler exit (about 3" away in the case
of the one I fitted).

Whilst sitting at some traffic lights, I was looking at
the row of terraced houses along the road. On one, there
was the classic pattern of gas pipe, flue, and pressure
relief exit pipe indicative of a sealed system boiler
on the inside. However, what caused me to do a double-
take was that the pressure relief exit pipe was pushfit
plastic with a pushfit elbow and an extra 6" of pushfit
pipe pointing it downwards (and with no bracket holding
it in place). The house wall only about a foot back from
the pavement edge.

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

It has to be metal, no need for sleeving through a wall, and terminate at
floor level with the pipe turned towards the wall (an elbow). It can
terminate at high level like at the eves when a boiler is fitted in the
loft, but must turn in on itself. and it must not be over a used pathway.
It can be terminated onto a flat roof too without turning into the wall.

Do you have a reference?

Matt, look in Two-Jags site.

Location of Sealed System Components
 

wrote in message ...
On 15 Jul,
(Andrew Gabriel) wrote:

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

I thought the regulations were to have metal pipe within a metre of the
boiler, and similar for /all/ the releif valve piping.

Plastic pipe can go right to a boiler if it connects outside the casing.
See makers blurb. The relief pipe "has" to be metal and metal fittings.

Location of Sealed System Components
 

In article ews.net,
Doctor Drivel writes

Matt, look in Two-Jags site.

In other words, you don't have a reference.

--
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 14:45:04 +0100, Doctor Drivel wrote
(in article ews.net):


"Andy Hall" aka Matt wrote in message
...
On Sat, 15 Jul 2006 13:27:20 +0100, Doctor Drivel wrote
(in article ews.net):



It has to be metal, no need for sleeving through a wall, and terminate at
floor level with the pipe turned towards the wall (an elbow). It can
terminate at high level like at the eves when a boiler is fitted in the
loft, but must turn in on itself. and it must not be over a used pathway.
It can be terminated onto a flat roof too without turning into the wall.

Do you have a reference?

Matt, look in Two-Jags site.

That would be reasonable, and one might expect to find it in the Approved
Documents to the Building Regulations, ether in Part J or possibly Part G.

Presumably that's what you meant.

Part G3 appears to refer to pressurised stored hot water systems, where
indeed there is mention of discharge pipe arrangements, metal being required.
In section 3.9 it talks about different arrangements including terminating
the pipe below a grid in a gully. However, it does not mention elbows
pointed at the wall, only keeping the pipe less than 100mm from the external
surface but rather a guard where there is a possibility of children playing.

However...... there are specific exemptions if the storage vessel has a
capacity of 15 litres or less or the system is for space heating.

I can't see any reference to water discharge arrangements in part J at all -
it is about ventilation, flue arrangements and fuel storage.

Did you have the Building Regulations in mind, or something else?

This is not to say that it isn't sensible to make careful arrangements for
the discharge of water from a sealed primary circuit going faulty, but I
can't see where there is a regulatory requirement so to do.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 17:14:47 +0100, Doctor Drivel wrote
(in article ews.net):



Matt, look in Two-Jags site.

That would be reasonable, and one might expect to find it in the Approved
Documents to the Building Regulations, ether in Part J or possibly Part G.

Presumably that's what you meant.

Part G3 appears to refer to pressurised stored hot water systems,

Exactly that is what it covers, not boilers

where indeed there is mention of discharge pipe arrangements, metal being
required.
In section 3.9 it talks about different arrangements including terminating
the pipe below a grid in a gully. However, it does not mention elbows
pointed at the wall, only keeping the pipe less than 100mm from the
external
surface but rather a guard where there is a possibility of children
playing.

However...... there are specific exemptions if the storage vessel has a
capacity of 15 litres or less or the system is for space heating.

And if the vessel uses a plate heat exchanger then the G3 does not apply.
No approved unvented ticket installer or annual service required and only
one pressure relief valve is needed.

The W-B Highflow has an unvented pressurised vessel of over 15 litres yet
no BBA approval and annual service. It can be DIYed.

Because the vessel is on the primary circuit, presumably, and hence not
directly part of HW production....??

A Powermax has a
secondary water unvented pressurised cylinder and needs a BBA approved
installer. If the pressurised vessel has a coil inside (thermal store) it
comes under G3, use a plate, inside or outside the vessel, and it doesn't.
An unvented cylinder requires three mechanical safety stages while a
pressurised vessel of the same size using a plate needs only one.

I would put two pressure relief valves on, in case.

So, anyone can buy a cylinder, put on a plate for DHW, one relief valve,
have the boiler direct, the CH direct and have one ~24 litre pressure
expansion vessel for the lot. Or buy a pressurised Heat Bank complete and
do it yourself.

The W-B HIghFlow 440 clearly states what I stated in the manual, with a
little piccie too.

That's all nice, but wasn't really the question.



Try BS 6798. Installation of gas fired boilers.


Do you *know* that it's in this document?

Location of Sealed System Components
 

"Andy Hall" wrote in message
...
On Sat, 15 Jul 2006 17:14:47 +0100, Doctor Drivel wrote
(in article ews.net):



Matt, look in Two-Jags site.

That would be reasonable, and one might expect to find it in the
Approved
Documents to the Building Regulations, ether in Part J or possibly Part
G.

Presumably that's what you meant.

Part G3 appears to refer to pressurised stored hot water systems,

Exactly that is what it covers, not boilers

where indeed there is mention of discharge pipe arrangements, metal
being
required.
In section 3.9 it talks about different arrangements including
terminating
the pipe below a grid in a gully. However, it does not mention elbows
pointed at the wall, only keeping the pipe less than 100mm from the
external
surface but rather a guard where there is a possibility of children
playing.

However...... there are specific exemptions if the storage vessel has a
capacity of 15 litres or less or the system is for space heating.

And if the vessel uses a plate heat exchanger then the G3 does not apply.
No approved unvented ticket installer or annual service required and only
one pressure relief valve is needed.

The W-B Highflow has an unvented pressurised vessel of over 15 litres
yet
no BBA approval and annual service. It can be DIYed.

Because the vessel is on the primary circuit, presumably, and hence not
directly part of HW production....??

No. They wrote it before plate heat exchangers came along. A pressurised
thermal store with a coil is G3, one with a plate is not.

A Powermax has a
secondary water unvented pressurised cylinder and needs a BBA approved
installer. If the pressurised vessel has a coil inside (thermal store) it
comes under G3, use a plate, inside or outside the vessel, and it
doesn't.
An unvented cylinder requires three mechanical safety stages while a
pressurised vessel of the same size using a plate needs only one.

I would put two pressure relief valves on, in case.

So, anyone can buy a cylinder, put on a plate for DHW, one relief valve,
have the boiler direct, the CH direct and have one ~24 litre pressure
expansion vessel for the lot. Or buy a pressurised Heat Bank complete
and
do it yourself.

The W-B HIghFlow 440 clearly states what I stated in the manual, with a
little piccie too.

That's all nice, but wasn't really the question.

They have taken it from the BS.

Try BS 6798. Installation of gas fired boilers.

Do you *know* that it's in this document?

Last time I looked, the 200 vsn, I'm pretty sure. Available from the Corgi
Sharks for £88. Buy two.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 20:29:19 +0100, Doctor Drivel wrote
(in article ews.net):



Try BS 6798. Installation of gas fired boilers.

Do you *know* that it's in this document?

Last time I looked, the 200 vsn, I'm pretty sure. Available from the Corgi
Sharks for £88. Buy two.


Ar you on commission?

Location of Sealed System Components
 

"Andy Hall" wrote in message
...
On Sat, 15 Jul 2006 20:29:19 +0100, Doctor Drivel wrote
(in article ews.net):

Try BS 6798. Installation of gas fired boilers.

Do you *know* that it's in this document?

Last time I looked, the 200 vsn, I'm pretty sure. Available from the
Corgi
Sharks for £88. Buy two.

Ar you on commission?

I don't work for sharks.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 21:32:25 +0100, Doctor Drivel wrote
(in article ews.net):


"Andy Hall" wrote in message
...
On Sat, 15 Jul 2006 20:29:19 +0100, Doctor Drivel wrote
(in article ews.net):

Try BS 6798. Installation of gas fired boilers.

Do you *know* that it's in this document?

Last time I looked, the 200 vsn, I'm pretty sure. Available from the
Corgi
Sharks for £88. Buy two.

Ar you on commission?

I don't work for sharks.



I see. Who do you work for?

Location of Sealed System Components
 

"Andy Hall" aka Matt wrote in message
...
On Sat, 15 Jul 2006 21:32:25 +0100, Doctor Drivel wrote
(in article ews.net):


"Andy Hall" aka Matt wrote in message
...
On Sat, 15 Jul 2006 20:29:19 +0100, Doctor Drivel wrote
(in article ews.net):

Try BS 6798. Installation of gas fired boilers.

Do you *know* that it's in this document?

Last time I looked, the 200 vsn, I'm pretty sure. Available from the
Corgi
Sharks for £88. Buy two.

Ar you on commission?

I don't work for sharks.

I see. Who do you work for?

Matt, not sharks.

Location of Sealed System Components
 

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sun, 16 Jul 2006 00:08:35 +0100, Ed Sirett wrote
(in article .uk):

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.



Thanks Ed.

This is somewhat akin to Andrew's point, I think.

I have to drain my system to exchange a radiator for a different type in a
different place, so while doing so decided that some moving of these
components would be useful too. I can easily position the vessel
appropriately, but wanted to make the tee in for filling in a different
place. I can't see a reason why the two can't be separated, but thought
I'd ask in case there was a specific regulatory reason.

Location of Sealed System Components
 

On Sat, 15 Jul 2006 14:43:28 +0100, Doctor Drivel wrote:


"Andrew Gabriel" wrote in message
...
Well, I wouldn't normally respond, but since you mention me,
I'd better make it clear where I stand...

In article ews.net,
"Doctor Drivel" writes:

The source of expansion is the heat source, the boiler. The relief valve
has to be where the highest pressure point would be, the flow right on
the
boiler. The expansion vessel has to be where the expansion would be
greatest, the boiler.

Oh dear -- every single statement incorrect.

Unfortunately for you, every one right. Lets go into it again as you are bit
hard of thinking:

The source of expansion is the heat source, the boiler.

I usually let others take the load on the futile process of DD's education
in physical laws....

The expansion is not caused directly by the boiler (i.e. by the boiler
growing smaller say) but because the water in the primary circuit - all of
it - expands as it gets warmer.
As it says in the FAQ (which you claimed was so 'incomplete' you refused
to read it) the expansion is about 2.5% between 25C and 75C.

Obviously in some sense the boiler is the cause of the water getting
hotter and thus the expansion of the water. However, there is nothing
different about the expansion of the water in the boiler relative to that
in the pipework or radiators. Furthermore the bulk of the water is not in
the boiler.




The relief valve has to be where the highest
pressure point would be, the flow right on the
boiler.

The pressure in the primary circuit is affected by three things
1) The current pressure in the expansion vessel.
2) The height of any part of the circuit relative to the vessel.
(increases c. 0.1 bar /metre of height difference).
3) The differential pressure introduced by the circulating pump.

It would be unhelpful to place the relief valve at a great height
difference to the boiler. The manufacturers instructions are the final
arbiter in the matter, anyway.



The expansion vessel has to be
where the expansion would be
greatest, the boiler.

It has to.

There that is better you.

As mentioned before the expansion is a property of all the primary water
not just of that in the boiler.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sat, 15 Jul 2006 19:57:15 +0100, Andy Hall wrote:

On Sat, 15 Jul 2006 17:14:47 +0100, Doctor Drivel wrote
(in article ews.net):



Matt, look in Two-Jags site.

That would be reasonable, and one might expect to find it in the Approved
Documents to the Building Regulations, ether in Part J or possibly Part G.

Presumably that's what you meant.

Part G3 appears to refer to pressurised stored hot water systems,

Exactly that is what it covers, not boilers

where indeed there is mention of discharge pipe arrangements, metal being
required.
In section 3.9 it talks about different arrangements including terminating
the pipe below a grid in a gully. However, it does not mention elbows
pointed at the wall, only keeping the pipe less than 100mm from the
external
surface but rather a guard where there is a possibility of children
playing.

However...... there are specific exemptions if the storage vessel has a
capacity of 15 litres or less or the system is for space heating.

And if the vessel uses a plate heat exchanger then the G3 does not apply.
No approved unvented ticket installer or annual service required and only
one pressure relief valve is needed.

The W-B Highflow has an unvented pressurised vessel of over 15 litres yet
no BBA approval and annual service. It can be DIYed.

Because the vessel is on the primary circuit, presumably, and hence not
directly part of HW production....??

A Powermax has a
secondary water unvented pressurised cylinder and needs a BBA approved
installer. If the pressurised vessel has a coil inside (thermal store) it
comes under G3, use a plate, inside or outside the vessel, and it doesn't.
An unvented cylinder requires three mechanical safety stages while a
pressurised vessel of the same size using a plate needs only one.

I would put two pressure relief valves on, in case.

So, anyone can buy a cylinder, put on a plate for DHW, one relief valve,
have the boiler direct, the CH direct and have one ~24 litre pressure
expansion vessel for the lot. Or buy a pressurised Heat Bank complete and
do it yourself.

The W-B HIghFlow 440 clearly states what I stated in the manual, with a
little piccie too.

That's all nice, but wasn't really the question.



Try BS 6798. Installation of gas fired boilers.


Do you *know* that it's in this document?

It's in the links below.
Section 5.4.3 contains the answers to this thread unless the manufacturers
say otherwise.


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sat, 15 Jul 2006 14:21:06 +0100, me9 wrote:

On 15 Jul,
(Andrew Gabriel) wrote:

Then I got to thinking. I suppose there's no point in a
metal pressure relief pipe if the system itself is all
pushfit indoors, although I don't think I've ever seen
a plastic pressure relief pipe before.

I thought the regulations were to have metal pipe within a metre of the
boiler, and similar for /all/ the releif valve piping.

That is only the instructions on some models.
Other models say other things.

HTH

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sat, 15 Jul 2006 11:08:48 +0100, Andy Hall wrote:

On Sat, 15 Jul 2006 10:30:15 +0100, Lobster wrote
(in article ):

Andy Hall wrote:
Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

When we had our Vaillant fitted a few years ago, I'm fairly sure the
installation instructions permitted/suggested the expansion vessel to be
sited near the boiler downstairs, as opposed to the tank upstairs (which
is where we wanted it, and where it went).

If you don't get a definitive answer here I'll have a root around and
see if I can dig them out.

David

Thanks David

I am pretty sure that that isn't' an issue, although note Andrew's point.

I was thinking about separation of the individual components such as the
expansion vessel, the filling point, the pressure gauge and the relief valve.
These often come as a kit, but I can't ind anything that says that they have
to be co-located. The components are available separately as well.

It certainly is often convenient to put the expansion vessel in the
loft when "rolling you own" sealed system.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

"Ed Sirett" wrote in message
n.co.uk...
On Sat, 15 Jul 2006 14:43:28 +0100, Doctor Drivel wrote:


"Andrew Gabriel" wrote in message
...
Well, I wouldn't normally respond, but since you mention me,
I'd better make it clear where I stand...

In article ews.net,
"Doctor Drivel" writes:

The source of expansion is the heat source, the boiler. The relief
valve
has to be where the highest pressure point would be, the flow right on
the
boiler. The expansion vessel has to be where the expansion would be
greatest, the boiler.

Oh dear -- every single statement incorrect.

Unfortunately for you, every one right. Lets go into it again as you are
bit
hard of thinking:

The source of expansion is the
heat source, the boiler.

I usually let others take the load
on the futile process of DD's education
in physical laws....

Are you serious? The source of the expansion is not the boiler? What is it
then. Some old man with foot pump?

The expansion is not caused directly
by the boiler (i.e. by the boiler
growing smaller say) but because the
water in the primary circuit - all of
it - expands as it gets warmer.

The source of the heat and the place were it is hottest is....the boiler?
You must be in a different world to me if you think otherwise.

As it says in the FAQ (which you
claimed was so 'incomplete' you refused
to read it) the expansion is about 2.5%
between 25C and 75C.

Gosh some figures. The FAQ is fine if it is 1986..but I looked at the
calendar and it wasn't. You have no idea of what way the industry is going,
what people are buying and what is available. It may be around your street
but is around elsewhere.

Like those in the south who say microbore doesn't work while in the north of
the country it is the norm.

Obviously in some sense the boiler
is the cause of the water getting
hotter

You don't say!!!!!!!!! Wow!!! The boiler!!!! Gosh.

and thus the expansion of the water.
However, there is nothing
different about the expansion
of the water in the boiler relative to that
in the pipework or radiators.
Furthermore the bulk of the water is not in
the boiler.

The greatest expansion and the expansion starts there.

The relief valve has to be where the highest
pressure point would be, the flow right on the
boiler.

The pressure in the primary circuit
is affected by three things
1) The current pressure in the expansion vessel.
2) The height of any part of the circuit relative to the vessel.
(increases c. 0.1 bar /metre of height difference).
3) The differential pressure introduced by
the circulating pump.

It would be unhelpful to place the relief
valve at a great height difference to the
boiler. The manufacturers instructions are the final
arbiter in the matter, anyway.

They always put it right on the boiler. Get it quick at its source.

The expansion vessel has to be
where the expansion would be
greatest, the boiler.

It has to.

There that is better for you.

As mentioned before the expansion
is a property of all the primary water
not just of that in the boiler.

The expansion is greatest around the boiler. Even a sealed system has
different pressure around it. Put the expansion vessel where the greatest
expansion would be - the boiler.

I've actually seen an expansion vessel before and after the boiler. On a
small commercial system. It looked like someone screwed up somewhere so they
spit it. It worked.

Location of Sealed System Components
 

On Sun, 16 Jul 2006 00:25:59 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 00:08:35 +0100, Ed Sirett wrote
(in article .uk):

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.



Thanks Ed.

This is somewhat akin to Andrew's point, I think.

I have to drain my system to exchange a radiator for a different type in a
different place, so while doing so decided that some moving of these
components would be useful too. I can easily position the vessel
appropriately, but wanted to make the tee in for filling in a different
place. I can't see a reason why the two can't be separated, but thought
I'd ask in case there was a specific regulatory reason.

Looks like BS 6798 is not worried about the location of the filling loop.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sun, 16 Jul 2006 08:17:52 +0100, Ed Sirett wrote
(in article .uk):

On Sun, 16 Jul 2006 00:25:59 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 00:08:35 +0100, Ed Sirett wrote
(in article .uk):

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed
system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.



Thanks Ed.

This is somewhat akin to Andrew's point, I think.

I have to drain my system to exchange a radiator for a different type in a
different place, so while doing so decided that some moving of these
components would be useful too. I can easily position the vessel
appropriately, but wanted to make the tee in for filling in a different
place. I can't see a reason why the two can't be separated, but thought
I'd ask in case there was a specific regulatory reason.

Looks like BS 6798 is not worried about the location of the filling loop.

Good. Thanks for that, Ed. I couldn't see a reason that it would matter.

I am now seriously concerned about the vessel location. I think I'd
better remove one of the kitchen cupboards so that I can fit it high on the
wall next to the boiler flow within a few cm of the boiler itself. Do you
know if Plumbcenter offer expansion vessels in Farrow and Ball colours? ;-)

Location of Sealed System Components
 

In article ews.net,
"Doctor Drivel" writes:

"Ed Sirett" wrote in message
n.co.uk...
In article ews.net,
"Doctor Drivel" writes:

Unfortunately for you, every one right. Lets go into it again as you are
bit hard of thinking:

The source of expansion is the
heat source, the boiler.

I usually let others take the load
on the futile process of DD's education
in physical laws....

Are you serious? The source of the expansion is not the boiler? What is it
then. Some old man with foot pump?

All the water in the system, which is mostly in the radiators and
pipework. It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

The expansion is not caused directly
by the boiler (i.e. by the boiler
growing smaller say) but because the
water in the primary circuit - all of
it - expands as it gets warmer.

The source of the heat and the place were it is hottest is....the boiler?

No.

You must be in a different world to me if you think otherwise.

Oh, most definately. I live in the world governed by the laws
of physics.

--
Andrew Gabriel

Location of Sealed System Components
 

In article ,
Andy Hall writes:

I am now seriously concerned about the vessel location. I think I'd
better remove one of the kitchen cupboards so that I can fit it high on the
wall next to the boiler flow within a few cm of the boiler itself. Do you

Is that shortly before the pump (external I presume)?

know if Plumbcenter offer expansion vessels in Farrow and Ball colours? ;-)

What about fitting it inside one of the cupboards?

Also, if my hypothsis is correct, then it would appear your
boiler has not been affected by low pressure lockout, in
which case moving it would not seem to be required in your
case. Another option would be to leave it where it is, and
add a small one in the pipework at the desired location
(which would use up even less cupboard space).

--
Andrew Gabriel

Location of Sealed System Components
 

Andrew Gabriel wrote:
In article ews.net,
"Doctor Drivel" writes:

"Ed Sirett" wrote in message
mon.co.uk...

In article ews.net,
"Doctor Drivel" writes:


Unfortunately for you, every one right. Lets go into it again as you are
bit hard of thinking:

The source of expansion is the
heat source, the boiler.

I usually let others take the load
on the futile process of DD's education
in physical laws....

Are you serious? The source of the expansion is not the boiler? What is it
then. Some old man with foot pump?


All the water in the system, which is mostly in the radiators and
pipework. It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

Hang on a mo. If there is a massive, rapid expansion (explosion?) at
the boiler, it will indeed take time (albeit small) for that pressure
increase to be transmitted down the pipework to the HW cylinder, won't
it? I'd have thought that the pressure relief valve would indeed be
best sited near the boiler in this instance.

Having said that, how likely is an exploding boiler? Isn't it more
probable that a thermostat or valve could fail, causing a gradual,
simultaneous pressure build-up across the whole system? Under those
circumstances it is the cylinder which is the main source of danger
because of its relatively massive volume, as shown by the video clip of
one exploding which Drivel likes to post from time to time.

David

Location of Sealed System Components
 

"Andrew Gabriel" wrote in message
...
In article ews.net,
"Doctor Drivel" writes:

"Ed Sirett" wrote in message
n.co.uk...
In article ews.net,
"Doctor Drivel" writes:

Unfortunately for you, every one right. Lets go into it again as you
are
bit hard of thinking:

The source of expansion is the
heat source, the boiler.

I usually let others take the load
on the futile process of DD's education
in physical laws....

Are you serious? The source of
the expansion is not the boiler? What is it
then. Some old man with foot pump?

All the water in the system, which is
mostly in the radiators and pipework.

The source of the expansion is not the water in the rads, it is the boiler,
the heat it emits. Did you get that?

It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

18 to 28C is very different from 18C to 82C in very short time.

The expansion is not caused directly
by the boiler (i.e. by the boiler
growing smaller say) but because the
water in the primary circuit - all of
it - expands as it gets warmer.

The source of the heat and the
place were it is hottest is....the boiler?

No.

He says the souce of the heat is not the boiler. Mabe someone has sneaked in
a nuclear device, if it is not the boiler. He says it is not hottest around
the boiler. Maybe it is hotter around some nuclear device in the loft?
Mmmmmm

snip idiotic drivel

Not going on any further. Maybe he has been admitted to Richard Cranium's
institution.

Location of Sealed System Components
 

In article ews.net,
Doctor Drivel writes

Do your own looking.

In other words, you don't have a reference and are making it up as
usual.

--
(\__/)
(='.'=) This is Bunny. Copy and paste bunny into your
(")_(") signature to help him gain world domination.

Location of Sealed System Components
 

"Lobster" wrote in message
...
Andrew Gabriel wrote:
In article ews.net,
"Doctor Drivel" writes:

"Ed Sirett" wrote in message
emon.co.uk...

In article ews.net,
"Doctor Drivel" writes:


Unfortunately for you, every one right. Lets go into it again as you
are bit hard of thinking:

The source of expansion is the
heat source, the boiler.

I usually let others take the load
on the futile process of DD's education
in physical laws....

Are you serious? The source of the expansion is not the boiler? What is
it then. Some old man with foot pump?


All the water in the system, which is mostly in the radiators and
pipework. It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

Hang on a mo. If there is a massive, rapid expansion (explosion?) at the
boiler, it will indeed take time (albeit small) for that pressure increase
to be transmitted down the pipework to the HW cylinder, won't it? I'd
have thought that the pressure relief valve would indeed be best sited
near the boiler in this instance.

You got it.

Having said that, how likely is an exploding boiler? Isn't it more
probable that a thermostat or valve could fail, causing a gradual,
simultaneous pressure build-up across the whole system? Under those
circumstances it is the cylinder which is the main source of danger
because of its relatively massive volume, as shown by the video clip of
one exploding which Drivel likes to post from time to time.

David

Location of Sealed System Components
 

On Sun, 16 Jul 2006 08:32:17 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 08:17:52 +0100, Ed Sirett wrote
(in article .uk):

On Sun, 16 Jul 2006 00:25:59 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 00:08:35 +0100, Ed Sirett wrote
(in article .uk):

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed
system
components physically close together as is achieved with a sealed system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.



Thanks Ed.

This is somewhat akin to Andrew's point, I think.

I have to drain my system to exchange a radiator for a different type in a
different place, so while doing so decided that some moving of these
components would be useful too. I can easily position the vessel
appropriately, but wanted to make the tee in for filling in a different
place. I can't see a reason why the two can't be separated, but thought
I'd ask in case there was a specific regulatory reason.

Looks like BS 6798 is not worried about the location of the filling loop.

Good. Thanks for that, Ed. I couldn't see a reason that it would matter.

I am now seriously concerned about the vessel location. I think I'd
better remove one of the kitchen cupboards so that I can fit it high on the
wall next to the boiler flow within a few cm of the boiler itself. Do you
know if Plumbcenter offer expansion vessels in Farrow and Ball colours? ;-)

Does the boiler instructions say anything about where the vessel should go?
If so they 'trump' any requirements of BS 6798.

If the system pressure is reasonable (1-1.5 bar) then even if the pump
came before the vessel then the reduction in circuit pressure would not be
that significant.




--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://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
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he http://www.makewrite.demon.co.uk/GasFittingStandards

Location of Sealed System Components
 

On Sun, 16 Jul 2006 12:17:47 +0100, Ed Sirett wrote
(in article . uk):

On Sun, 16 Jul 2006 08:32:17 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 08:17:52 +0100, Ed Sirett wrote
(in article .uk):

On Sun, 16 Jul 2006 00:25:59 +0100, Andy Hall wrote:

On Sun, 16 Jul 2006 00:08:35 +0100, Ed Sirett wrote
(in article .uk):

On Fri, 14 Jul 2006 23:43:49 +0100, Andy Hall wrote:

Is there any regulatory or other obvious reason to locate CH sealed
system
components physically close together as is achieved with a sealed
system
kit,
or is it acceptable to separate them?

e.g. expansion vessel located remotely from other components.

Obviously the pressure gauge ought to be visible from the filling loop
valve
position.

There is I beleive a BS for this. I suppose it might be useful to obtain
a
copy someday. However most boiler installation instructions are somewhat
schematic in this area, many favour putting the vessel on the return
(probably because the pump is on the return in the boiler.

The Potty Suprima wants the components on the flow before the external
pump.

My guess is that th expansion vessel before the pump makes sure that the
pump operation increases rather than decreases internal pressure in the
circuit.



Thanks Ed.

This is somewhat akin to Andrew's point, I think.

I have to drain my system to exchange a radiator for a different type in
a
different place, so while doing so decided that some moving of these
components would be useful too. I can easily position the vessel
appropriately, but wanted to make the tee in for filling in a different
place. I can't see a reason why the two can't be separated, but
thought
I'd ask in case there was a specific regulatory reason.

Looks like BS 6798 is not worried about the location of the filling loop.

Good. Thanks for that, Ed. I couldn't see a reason that it would matter.

I am now seriously concerned about the vessel location. I think I'd
better remove one of the kitchen cupboards so that I can fit it high on the
wall next to the boiler flow within a few cm of the boiler itself. Do
you
know if Plumbcenter offer expansion vessels in Farrow and Ball colours? ;-)

Does the boiler instructions say anything about where the vessel should go?
If so they 'trump' any requirements of BS 6798.


The boiler has one internally already. However, it isn't quite large enough
for the system capacity, so an additional one is needed.



If the system pressure is reasonable (1-1.5 bar) then even if the pump
came before the vessel then the reduction in circuit pressure would not be
that significant.

Nothing bad seems to happen.

Location of Sealed System Components
 

On Sun, 16 Jul 2006 10:50:22 +0100, Lobster wrote
(in article ):

Andrew Gabriel wrote:
In article ews.net,
"Doctor Drivel" writes:

All the water in the system, which is mostly in the radiators and
pipework. It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

Hang on a mo. If there is a massive, rapid expansion (explosion?) at
the boiler, it will indeed take time (albeit small) for that pressure
increase to be transmitted down the pipework to the HW cylinder, won't
it? I'd have thought that the pressure relief valve would indeed be
best sited near the boiler in this instance.

Think about an open vented system. The relief vent is generally two floors
at least away from the boiler. This doesn't cause a problem.




Having said that, how likely is an exploding boiler? Isn't it more
probable that a thermostat or valve could fail, causing a gradual,
simultaneous pressure build-up across the whole system? Under those
circumstances it is the cylinder which is the main source of danger
because of its relatively massive volume, as shown by the video clip of
one exploding which Drivel likes to post from time to time.


Not quite.

That example is of a sealed pressurised water cylinder where the bulk water
in the cylinder is the DHW - in the video heated electrically.

The nearest to this would be a similar arrangement, possibly with immersion,
but also a coil heated by water in the primary circuit of the boiler. Part
G of the Building Regulations applies.
If you look at the installation guide for the UK of a typical pressurised
cylinder, (e.g. Albion), it shows an expansion valve on the cold feed and a
pressure and temperature relief valve on the hot side.


However, in the case of a loft tank fed storage cylinder, the cylinder
contents are not at mains pressure. The coil is at sealed system pressure.
If a problem happens with that such that the pressure relief valve blows,
water will be discharged from the primary circuit and not replaced. This is
not likely to result in the cylinder exploding.

The same would be true of a heatbank or thermal store. The bulk water in
the cylinder may be heated by the boiler directly or indirectly, but is open
vented

Location of Sealed System Components
 

"Andy Hall" wrote in message
...
On Sun, 16 Jul 2006 10:50:22 +0100, Lobster wrote
(in article ):

Andrew Gabriel wrote:
In article ews.net,
"Doctor Drivel" writes:

All the water in the system, which is mostly in the radiators and
pipework. It happens even when the boiler isn't on, e.g. if the
house temperature climbs from say 18C to 28C on a hot day, the
water expands proportionally and is taken up by the pressure
vessel.

Hang on a mo. If there is a massive, rapid expansion (explosion?) at
the boiler, it will indeed take time (albeit small) for that pressure
increase to be transmitted down the pipework to the HW cylinder, won't
it? I'd have thought that the pressure relief valve would indeed be
best sited near the boiler in this instance.

Think about an open vented system. The relief vent is generally two
floors
at least away from the boiler. This doesn't cause a problem.

It does. The water in an open vented system is constantly rising up and
down. It boils over at 100C. In a pressurised system the boiling point is
higher, when it does go it is over 100C. Also there may be a weak point in
the system. This weak point might blow inside the house casuing serious
injury before the remote relief valve opens. You have the relief valve "on
the boiler" or within a few feet of it.

Location of Sealed System Components
 

"Mike Tomlinson" wrote in message
...
In article ews.net,
Doctor Drivel writes

Do your own looking.

In other words,

You are a lazy sod aren't you. It is a nice day, get down to the beach at
New Brighton. You need to.