On Wed, 14 Jan 2009 09:28:18 +0000, Private Enquirer wrote:

I was a little concerned about the gas pressure at my cooker hob so
decided to test exactly what was happening before deciding whether to
call a CORGI engineer or Transco/British Gas as I do not want to get
fobbed off by either as I like to understand what is happening first.

We had a new condensing boiler fitted about 4 years ago by British Gas -
a large one badged by BG but probably a Worcester Bosch 40 HE Plus with
a slightly higher heat output spec. They upgraded the gas supply pipes
to 28mm from the meter to allow for pressure drops while running. Our
gas cooker T's off this somewhere in 15mm I believe. All working fine!

Two years ago we had a new gas meter and regulator/governor fitted as
part of the gas mains upgrade in our road in plastic.

Last week during very cold weather I measured 22mBar static pressure
using a conventional water gauge at the gas meter test point. When the
boiler fires up the working pressure drops to anything between 16mBar
and 18mBar still at the gas meter depending on how large a flame is
being demanded
by the central heating system. I therefore detect about 5mb drop just
at the meter.

I called British gas this week when the temperature was very much warmer
and they came
within the hour. He showed me his water gauge readings (all at the gas
meter as before)
and they were totally different from mine last week. The static
pressure was 24mb and the
working pressure was 19mb when the boiler was running full. He got the
same sought of drop in pressure I had found (i.e about 5mb drop) but
from a much
higher static pressure.

No. You need to see the difference between the running pressure when the
smallest hob ring is on it's lowest setting. The standing pressure (24mb)
just tells you that there is at least 24mb in the service main.



He seemed a bit officious and said mine was his third similar visit that
day and he blamed CORGI engineers for taking wrong readings. He thought
my governor was the best brand new type available and should be correct.
He said if the working pressure was below 19mb he could adjust the
governor (I thought they were not supposed to do that).

No. You and I are not supposed to tamper with that but he may.



After he had gone I re-tested it myself and got very similar readings.
I found the static pressure was even up to 25mb today and I confirmed
his 19mb working pressure.

I think we were both right on the different days as I had measured it
low last week when the only thing that had changed was the ambient
temperature which was much colder then. Does the gas pressure change
much with weather temperature and overall demand in the street?

Quite probably, not all areas, not even most will have a problem. It's
far worse in Bulgaria ;-)


I cannot get them to do anything today so am stuck with what I have got
for the time being. Everything seems to be working OK.

What do others think.

What's happening at the hob. Can you see the flames alter? Do any of the
rings go out when on minimum?


--
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