Connecting on to existing gas run.

[dazpara]

Question for you guys, blokes at work with me doing refurbs, back boilers out, combi's in, baxi 28he, some bungelows you've got 22mm gas from meter, then reduces down to 15mm under floor. Where it comes back up in 15mm, the blokes are connecting back on in 22mm and running to boiler, my argument is that surely its the same situation as with water, that once youve reduced down youre only going to get that flow rate of the lesser diameter pipe, thing is tho the working pressure at the boiler is within the min and max pressures, but is more than 1mbar drop from the meter, i argue that this would be unsafe, but their argument is that the boiler working pressure is within its working parameters and works fine. Whats your views?

 

[SafeGasInstall]

"Blokes at work" ??? gas safe -competent people?
i personally would not bother argue as it's more then 1 mbar drop ,end off conversation !
i would not put my name on that certificate!
working pressure is fine but what happens when there is high demand of gas in the pick hours!
to safe all that lift up few floor boards and see if you can pick from the 22 mm,
you say is working fine within the parameters at maximum settings with hot water on?

 

[GreenArmy]

The 'Blokes in work' need to be sent back to put their work right.

 

[dazpara]

No Fga's get used, parameters meaning it modulates between the min and max pressures with hot water on full, i agree with you tho, the blokes are gas safe registered within the last 18 months and have argued that one of their 'tutors' said this was okay as long as you get the correct pressures at the boiler, i havent checked, but surely the mi's say 22mm must be used? So what would you class this installation as? Tbh the blokes are put under a lot of pressure to get these refurbs done in a day and are potentially not commissioning the installations as they should be! I even heard last year an old sweat (who should know better) suggesting that doing a tightness test, then starting up the boiler and just checking that water warms and heating warms would safice!

 

[GrahamM]

Firstly, any more than 1 mbar drop across the pipework, the installer is incompetent.
Secondly, as far as I am aware most of the Baxi HE MI's state "Do not use smaller than 22mm in gas supply". Maybe you can check the exact models MI's.

 

[dazpara]

100% agree, my question is then if you went to service one of these appliances what would you classify it as in unsafe procedures and why? Even if the appliance was operating correctly, the mi's are clearly not being adhered to.

 

[ferret]

These installs are NCS but as you cannot have NCS on a new install they would be shut off as AR , 20mb wp at boiler is required for complete combustion any less is AR end of!

 

[GrahamM]

As ferret mentioned these installs are AR.
Apart from the gas supply issue, you cannot commission a HE condensing boiler without the use of a FGA.
There are a number of major issues you have mentioned. How many are you not aware of?
These guys should be reported.

 

[tamz]

Firstly. Gas does not behave like water for reasons it is too late to start explaining why.
Secondly. They are leaving the work not commisioned properly ie over 1mb pressure drop so the pipe obviously needs upgrading. Every man and their dog knows these boilers will work safely on much less than is specified (they have to as potentially they may only get 12.5mb supply at gas valve (another long explanation) and have to function ok) but the regs as they stand say no more than 1mb drop so it is wrong.
As it stands as a new install it would be AR BUT if you work on it next month it would be ncs as it is not technically a new install.
Thirdly. Very few boiler manu's insist an HE boiler is commisioned using an analyser. That is why CPA1 has been introduced and tied in with CEN1. So that in the future it will be a requirement.

I blame the companies just as much as the fitters.

 

[Toddyplumb]

I would like to know what the gas rate is on these boilers through a 15mm restriction . Should be 3.1m3.