Minimum legal gas pressure to my boiler


Postby hairbymaurice » Tue Apr 01, 2008 7:09 pm

Hello a Corgi man has just switched off my gas supply to my boiler saying it is too low. Last year when they tested it it was 19 Bar and this year it is down to 9.

The solution is about 4 days work replacing all the pipes, pulling up the floor boards etc

My question how can this have happened over a year does this not mean that there may be a pressure problem at source rather than with the pipe work? Should i be speaking to british gas before undertaking the work in the flat?
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Postby htg engineer » Wed Apr 02, 2008 10:30 am

The working pressure should have been checked, this should be 21+/-2mbar, then at the appliance this should be no more than 1mbar drop across the system. So if it's 20mbar at meter the minimum it can be at boiler is 19mbar.

If the drop across the system is greater then you need to upgrade the pipe sizing.

If the working pressure is low - then the gas board need to reset the meter governor.

If it is 9mbar at the boiler - then that's a pressure drop of 9+ mbar. I would get someone else to check this, as the boiler would struggle to heat the central heating and water and the flame picture would be noticeably different and should have been picked up during other services.

I'm not saying he is wrong - but he may have made a mistake. What options did he give you ? did he offer to upgrade the pipes ? or did he offer any advice ?
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Postby hairbymaurice » Wed Apr 02, 2008 6:59 pm

thanks for the help so far

There was never any problem with the heating or the gas to the hob they always burned well. So i am unsure whats going on.

So the guy has changed some pipes and has got pressure up to 14bar, he still wants to change the pipes going to the appliances, but i cannot see the point yet. The way i see it is this is not going to solve anything as the pressure is too low at the source so that is where he should be looking.

Do you agree?
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Postby htg engineer » Wed Apr 02, 2008 9:17 pm

I would expect him - as a CORGI registered gas installer to have checked the pressures at the meter.

If changing part of the pipwork has reduced the pressure loss - then upgrading the rest should bring it up to standard.
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Postby gasmasters » Thu May 29, 2008 10:48 pm

[quote="htg engineer"]I would expect him - as a CORGI registered gas installer to have checked the pressures at the meter.

If changing part of the pipwork has reduced the pressure loss - then upgrading the rest should bring it up to standard.[/quote]

if the system was checked properly last year and the pressure at the appliance was correct it would be highly unlikley that you need to upgrade any pipe work!!

however if the last engineer was right he then needs to investigate what has gone wrong ie. was the engineer that reported a pressure of 19mm compitent.

have you had any other gas appliances fitted since your last gas saftey check?



i would most def get a second oppinion
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Postby MrKleenezeMan » Fri Mar 30, 2012 9:45 pm

Please Please Please can you try to be accurate with what you are asking/typing.

The pressure in your system is most definitely NOT 9 bar
If it were 9 bar (as opposed to 9mbar - 9 THOUSANDTHS of a bar) you would have an almighty gas leak in your house and you would be dead, as would probably half of your street from the size of the gas explosion there would have been.

9 mbar (0.009 bar) is a very small pressure indeed when you consider that the atmospheric pressure is around 1000 mbar.

My first question to the engineer would be "when was the last time you had your incredibly sensitive pressure measuring instrument (probably a Druck) CALIBRATED?"

You have to understand that the zero setting for the instrument is actually 1013 mbar (absolute) and if it was calibrated during a high pressure weather system it could easily be calibrated wrongly by 10mbar or more.

Ask to see it checked on the day that they test your pressure. They need to show you that when it is NOT connected to your gas supply it reads ZERO. Then you can believe the readings that they give you.

At best the instrument is reading low due to ignorance/incompetence. At worst it has been deliberately zeroed during a high pressure weather system to generate unnecessary repairs and you've been the victim of a con man (corgi registered or not).
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