Can't get boiler commissioned (low gas pressure)

[Biggles..]

I am surprised that several RGIs here are not apparently understanding the requirements or their responsibilities.

The gas supplier should supply 21 mB =/- 2 mB atb the outlet of the meter on full load ( of the meter rather than the boiler fitted. )

We are taught and assessed on pipe sizing when taking the qualifications which we need to be registered so I would say he has no excuse!

Tony

Tut tut, are you sure your right Tony.

Have a read of BS6400.

21+-2 at the ECV could result 14WP at the boiler even when correctly sized.

 

[Steady]

The following seems to shed some light on things.

Look under:

'Minimum gas operating pressure for Greenstar boilers'

http://www.worcester-bosch.co.uk/installer/training/technical-training-bulletins

 

[Agile]

21+/- 2 at the ECV could result 14WP at the boiler even when correctly sized.

I said "should" supply 21 mB +/- 2 mB at the meter outlet.

What they should do and what they sometimes do is not always the same.

If they do what they should then the supply at the boiler with correctly sized pipework will not be less than 18 mB in the worst case.

In this particular case the installer has compounded the problem by undersizing his pipework, some would say seriously!

The gas shipper has then made the situation worse by adding a further length of undersized pipework!

I cannot understand how anyone can support the installer ( unless they advocate fitting undersized pipework ). But seeing how many installers do undersize pipework, that does not surprise me.

I always quote for installing the correct pipework size and advise the owner that if its not upgraded then it will still work but will not comply with the regulations.

Tony

 

[gassafeman]

The following seems to shed some light on things.

Look under:

'Minimum gas operating pressure for Greenstar boilers'

http://www.worcester-bosch.co.uk/installer/training/technical-training-bulletins[/QUOTE]

Ive known about that for sometime, but wasnt going to tell the OP about it. You would have thought the RGI would have known this.

 

[Meme21]

Very interesting today. I called out W Bosch to confirm that gas pressure and everything was now ok (front of boiler needed changing anyway because it wouldn't shut). Apparently I have much greater gas pressure than I need despite being told by the fitter that the pressure was border line. I have between 19 and 19.5mbar and the fitter said I had 16.5 at best even after changing all the mains pipework, meter etc.

All very strange. I could be that there never was a problem with gas pressure.

 

[Agile]

19 mB is the MINIMUM that is needed at the boiler ! You dont have "a much greater pressure than you need".

Many people dont seem to know how to measure the pressure loss in pipework.

I have seen a CORGI inspector who did not know how to do it properly. He has since retired.

Tony

 

[Agile]

Actually, 19 mB is not quite the minimum, its actually 18 mB if the pressure at the meter were at the bottom end of whats allowable.

The maximum pressure loss in the pipework should not exceed 1 mB to be within the regulations.

Some of the comments above relating to possible lower pressures relate to extreme supply demands where the pressure may fall lower but this should not happen for more than 5% of the time.

Of course during the very cold weather lately the gas supply network has been delivering greater than usual volumes of gas and the delivery pressures have in some cases been low. Any competent installer/tester would have measured at the meter and at the boiler to find out exactly whats going on.

Tony

 

[DP]

Onetap, read your reply with interest but am still in the dark on how, without ripping up the flooring to eyeball the pipe run, bore etc, one is going to 'calculate' gas pipe size prior to fitting a boiler. I am here to learn and will willing take on board any information that will assist me in gas related duties. By the way, gas carcase sizing to take place before boiler is fitted.

Route I would have taken is to connect the disconnected boiler, take inlet gas pressure with appliances running and take it from there. Good chance the old boiler was on 15mm branch, totally inadequate for just about any combi unless it was just about sitting on the gas meter.

I wonder why the OP did not get another GSI to check boiler spillage. Can BG guys disconnect appliance without permission?

 

[cross thread]

what a saga,bet you wish you had got good old british gas to do it

 

[onlyfitidealboilers]

Right then. when worcester say 16.5 is ok they mean this blr work down safely to 16.5 that does not mean this is ok to leave. you must issue a NTCS notice because it falls short of the minimum inlet working pressure at an appliance of 18mlb.

Just like when you fit a blr and have say 19mlb working at mtr, how
on earth will u get 20mlb at blr!!! impossible. national grid will refuse to upgrade the 19mlb because they say that is ok with them and stuff your 35kw blr so what does one do.......