In message 6w8Rn.42970$4w7.20324@hurricane, John
writes
I am about to have a new Combi fitted (Worcester Bosch 30cdi). The installer
and I cannot see the existing gas pipe to the current Worcester Highflow
Heatslave so are not sure if it is 22mm or smaller. (obviously we will see
it when the boiler is removed)

A neighbour in the same type of house found when his Heatslave was replaced
that the pipe was only 15mm and had to have a new (ugly external) 22 pipe
run installed. This neighbour never had much success with his Heatslave -
but mine has always performed well and has been inspected every year by B
Gas.

I told the installer I was concerned that the pipe could be 15mm so he
offered to perform some sort of drop check. He took a reading at the meter
with a manometer with the gas cooker and boiler running - he then repeated
the test at the boiler and phoned Worcester Bosch. They confirmed that the
pressure was acceptable. I think the drop was 2 milli-bar. (from 21 down to
19)

I realise there is some risk and uncertainly and that I may have to run a
new 22mm pipe - but what do you think. Does the 'evidence' point to the
hidden pipe being 22mm - or is this irrelevant because the pressure is okay?

Do you think the installers approach is reasonable?

What do you want, a magic answer?

If the installer has taken readings which WB consider to be acceptable,
then either go with professional advice or don't

Nobody else can make your decision for you


--
geoff