From the Alpha combi boiler instructions:

"Note: If the mains is fitted with water meter, check valves or loose
jumper stop cock, then a DHW expansion device must be fitted."

and there's a similar note in the W-B Si instructions, but not in, for
instance the Glow-worm equivalents. I can see that there is a risk of
trapping a quantity of water in a length of pipe, which then gets
warmer, but doesn't this apply to all cold water systems?

Does anyone fit these devices in real life?


--
Kevin Poole
**Use current month and year to reply (e.g. )***

Autolycus wrote:
From the Alpha combi boiler instructions:

"Note: If the mains is fitted with water meter, check valves or loose
jumper stop cock, then a DHW expansion device must be fitted."

and there's a similar note in the W-B Si instructions, but not in, for
instance the Glow-worm equivalents. I can see that there is a risk of
trapping a quantity of water in a length of pipe, which then gets
warmer, but doesn't this apply to all cold water systems?

Does anyone fit these devices in real life?


Yes.

On Thu, 22 Nov 2007 21:29:01 +0000, Autolycus wrote:

From the Alpha combi boiler instructions:

"Note: If the mains is fitted with water meter, check valves or loose
jumper stop cock, then a DHW expansion device must be fitted."

and there's a similar note in the W-B Si instructions, but not in, for
instance the Glow-worm equivalents. I can see that there is a risk of
trapping a quantity of water in a length of pipe, which then gets
warmer, but doesn't this apply to all cold water systems?

Does anyone fit these devices in real life?

Quite a few boilers will have a very small expansion vessel T'd into the
incoming cold connection.




--
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

"Ed Sirett" wrote in message
...
snip

Quite a few boilers will have a very small expansion vessel T'd into
the
incoming cold connection.

Do you mean they are an integral part of some boilers?

Would you, Ed, fit an external one to, say, a W-B Si? They're not at
item I've often seen listed.


--
Kevin Poole
**Use current month and year to reply (e.g. )***

On Thu, 22 Nov 2007 21:29:01 +0000, Autolycus wrote:

From the Alpha combi boiler instructions:

"Note: If the mains is fitted with water meter, check valves or loose
jumper stop cock, then a DHW expansion device must be fitted."

and there's a similar note in the W-B Si instructions, but not in, for
instance the Glow-worm equivalents. I can see that there is a risk of
trapping a quantity of water in a length of pipe, which then gets
warmer, but doesn't this apply to all cold water systems?

Only boilers with gas-to-DHW heat exchangers (rather than gas-to-primary
and primary-to-DHW). The old W-B (non-Greenstar) iJunior was another
example, as I think were some Ferrolis.


Does anyone fit these devices in real life?

On the Juniors I fitted I didn't have water meters or loose jumpers on the
stopcocks. I'd guess/hope that in any real-world installation a WC cistern
valve would provide a pressure-relief path. However to be safe you can get
little potable expansion vessels cheaply enough (e.g. from Toolstation)


--
John Stumbles

Things don't like being anthropomorphised.

On Fri, 23 Nov 2007 22:45:27 +0000, Autolycus wrote:

"Ed Sirett" wrote in message
... snip

Quite a few boilers will have a very small expansion vessel T'd into
the
incoming cold connection.

Do you mean they are an integral part of some boilers?

Yes.


Would you, Ed, fit an external one to, say, a W-B Si? They're not at
item I've often seen listed.

To fit externally is very unusual but they are available they are called
shock arrestors, are more or less spherical and would fit into a 100mm
cube. Nevertheless that the same as any other expansion vessel, you need
a blue one for use on potable water.

I suppose I would look at the instructions carefully before fitting one
to see if I really had to. Also I might change the main stop valve for a
1/4 turn full bore level valve (WRC approved) this latter being, usually,
already in available in the van.

--
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