First of all, thanks to all respondents for useful comment


"John Stumbles" wrote

22mm copper, not 3/4" outside diameter steel, right? The latter is 1/2"
bore.


Yes original 22mm copper in 1970s build.


Ahem! you say 22mm pipe, suggesting copper rather than steel. Now you say
concrete floors. Errr, it _is_ adequately protected where it's laid in the
concrete, isn't it?


Again the installation is original.
Haven't had need to expose the gas, but the heating pipes are wrapped in
hession type stuff, laid in a sand filled channel and concreted over.
Does this constitute adequate protection?


If you replaced accessible lengths with 28mm and/or 22mm elbow bends with
swept bends you could reduce the effective length by perhaps a few metres.


Unfortunately, nearly all is buried.


Final question - if the gas supply pressure as measured is high, can I
take this into account in calculation?

No. It has to be 1mBar drop in the pipework. (If the meter regulator is
high when you install the appliance and subsequently gets re-set correctly
are you going to shut down the appliance because the pressure is now below
spec?)

In practice one sees a lot of installations in which the drop is
1mBar. If I came across one I wouldn't be worried as long as the pressure
is still reasonable, and far enough above the boiler's required burner
pressure not to affect operation. However in installing an appliance one
can't take such an accomodating attitude but should do it by the book.



From the various responses and Treloar, I believe that the installation
should be OK.
Will put the onus on the installer to confirm and check pressures though.

Thanks for the comprehensive response

Phil