On 18/12/2020 20:28, Chris French wrote:
So, fitted the new gas valve to the boiler and the house is warming up nicely
now.

I set the output pressure on gas valave (abiout 12 mbar), and while I was at it
checked the supply pressure on the valve as well.

It was about 14-15 mbar. So somewhat low..

I checked the pressure at the meter, it was fine, 21 mb.

ISTR from that a quick look at the manual the other day, the input
pressure latitude was quite generous on that boiler. Probably helped by
not being fanned flue with forced combustion etc. So although likely
well out of spec it will probably work fine.

The bigger worry would be could the boiler firing momentarily extinguish
a burner on the hob? If so, does that have flame failure detection?

Now this doesn't entirely surprise me. We have lived here since 2004, there is
the boiler and the gas hob on the same pipe (they are on oppsite sides of a
wall), if the hob was on full, you would notice a change in the burner sound
when the boiler fired up. So I suspect it maybe has been like it for a long
time (we've never had aplumber in, it's never been checked). Everythign wroked
ok, and doing anythign about the supply would be a PITA until we rdid the
kitchen and utility room area. so I let well alone .

A ssume this is down to the pipe run, most of it runs under the floor, the
total run is probbaly about 25m, the first 4m or so is 1inch OD steel pipe,
somewhere between there and the boiler/hob it tunrns into 15mm copper, there
are probably 4-5 bends on the way.

The boilers rated gas consumption (it's a basic open flued, on/off boiler) is
4m^3/hr.

so given that it has worked in this fashion for presumably some years I am
minded to carry on, we hopefully will get round to a full kitchen refit in the
next few years.

what are the implications of that sort of low pressure?

As above, plus possibly lower than expected boiler output (although at
35kW+ you may not notice!)

You could always run through the calcs to see what the setup ought to be:

http://wiki.diyfaq.org.uk/index.php/Gas_pipe_sizing


--
Cheers,

John.

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