hi there i have just purchased a central heating kit from Band Q the usual 7 radiators plus combi boiler valves flue etc .
on the boiler it has the gas inlet at 15 mm, i have been told by a lay man that it has to be 22 mm to feed the gas i am not doing the gas side of things but was wondering if this is true to have 22mm does this have to go all the way back to the meter . any info would be appreciated

Your fitter will know how to pipe size.

"Paul Barker" wrote in message
...

pickled_magpie Wrote:
hi there i have just purchased a central heating kit from Band Q the
usual 7 radiators plus combi boiler valves flue etc .
on the boiler it has the gas inlet at 15 mm, i have been told by a lay
man that it has to be 22 mm to feed the gas i am not doing the gas side
of things but was wondering if this is true to have 22mm does this have
to go all the way back to the meter . any info would be appreciated

The rule of thumb is 22mm pipe to within 1 metre of the combi, then use 15mm
to connect up.
This is purported to be a practical rule of thumb for the average combi. If
you have a really powerful model I expect you might need to go to 28mm. It
also depends on the length of gas pipe you are running, there is more to the
rule-of-thumb than I have mentioned, in that you can only have up to a
certain length of 22mm, and you have to take into account any right-angle
copper fittings as subtracting a certain amount from the max allowed length
etc. Can't remember what the specifics are, you'll have to google for it or
look in the u.k.d-i-y archives. I can tell you my 28kW boiler is fed by 22mm
pipe to within a metre of the inlet, that the 22mm pipe is about 20 feet
long with 2 right angle joints ( gentle curves don't count ) and ISTR that
that was within the allowed rule, and the pressure at the boiler measured OK
when operational, so that was a good reality check. DYOR.

Andy.

andrewpreece wrote:

The rule of thumb is 22mm pipe to within 1 metre of the combi, then use 15mm
to connect up.
This is purported to be a practical rule of thumb for the average combi. If
you have a really powerful model I expect you might need to go to 28mm. It
also depends on the length of gas pipe you are running, there is more to the
rule-of-thumb than I have mentioned, in that you can only have up to a
certain length of 22mm, and you have to take into account any right-angle
copper fittings as subtracting a certain amount from the max allowed length
etc. Can't remember what the specifics are, you'll have to google for it or

Chapter and verse he-

http://www.cda.org.uk/megab2/build/p...0Tube%20Sizing

long with 2 right angle joints ( gentle curves don't count ) and ISTR that

Depends on whay you mean by gentle... a "swept" bend does count, just
less than an elbow (i.e. adds 0.3m rather than 0.5m to the effective
length of the pipe for the purposes of calculation)



--
Cheers,

John.

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On Mon, 24 Jan 2005 19:07:27 +0000, pickled_magpie wrote:


hi there i have just purchased a central heating kit from Band Q the
usual 7 radiators plus combi boiler valves flue etc .
on the boiler it has the gas inlet at 15 mm, i have been told by a lay
man that it has to be 22 mm to feed the gas i am not doing the gas side
of things but was wondering if this is true to have 22mm does this have
to go all the way back to the meter . any info would be appreciated

See the Gas Fitting FAQ.
--
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