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.

 

[Billy Bob Bob]

15mm to the inlet?????????????????they should lose their licence COWBOYS

 

[plumbster3456]

I have been to fix a few boilers over the years that bri***** gas have installed namely worcester with a 22mm gas valve on the outlet to boiler they had run the 22mm pipe out of valve and round out of site and connected it to the old 15mm pipe that was going to the old boiler.
Is bri***** gas not supposed to do things right ? or are the just the same as all these other cowboys who think this is ok to do

 

[kirkgas]

I have been to fix a few boilers over the years that bri***** gas have installed namely worcester with a 22mm gas valve on the outlet to boiler they had run the 22mm pipe out of valve and round out of site and connected it to the old 15mm pipe that was going to the old boiler.
Is bri***** gas not supposed to do things right ? or are the just the same as all these other cowboys who think this is ok to do

any registered gas company is just the same as the rest, doesnt matter how big or small they are, they are all guided by the same regs and MI's so every engineer should do the job properly,

 

[dazpara]

Expected to get shot with this one here, i agree totally with everything you guys are saying, tamz i wasnt comparing gas to water mate just stating that if you reduce down then back up a pipe size you'll only get the flow of the lower diameter pipe. I asked this question because i know its wrong what these guys are doing, and i can guarentee you that its not the standard i work to, however i have just past acs withing the last month and am awaiting my GSR number, now, i've been at this company for about 3 years and the guys that are doing these AR installs have been here a lot longer and have had their gas quals 18 months plus. If you were genuinly in my position of being basically a novice then what would you do or say to these guys. Put yourself in my place when considering this and not in yours, cheers.

 

[tamz]

Quick explanation.
Gas is different to water in that gas is compressible and water isn't.
Once the water flows through a smaller pipe then back to a bigger one, all you can get is the smaller volume.
With gas as it passes through the smaller pipe it compresses and expands again once in the bigger size.
Try it some time if you have a bit spare time. Cut a bit half inch into a 3/4" run and check the difference in flow/pressure. Not much.

With the 12.5mb thing.
The inlet pressure can be as low as 19mb, there could be a 4mb drop across the meter at high flow rates, a 1mb drop on the pipework and 1.5mb through the boiler inlet to the test point on the valve. Now the problem then becomes compounded if there is say a 2mb pipework drop then we are down to 11.5 and so on.
Btw the transporter only legally has to supply 14mb!! Do the sums on that one!

So far as what do you do.
Well as there is more than a 1mb drop obviously they are not doing it to standards. So pull them on it. They are doing it wrong. Don't worry about them being older or "more experienced" than you. A lot of experienced guys fk things up and think they know better.
Educate them

 

[wnjswozo]

1 m/bar drop on on pipework.gas rate the applaince,round off with fga,easy

 

[Blackcatgas]

you can lose 1.5 mb across the inlet of the boiler, Worcester Bosch had a technical artical out about it a few years ago basicly saying that the restriction through the isolating valve and pipe work to the gas valve was 1.5mb.

 

[Reg Man]

You hit the nail on the head, first discription. No way is this allowable. Another lazy installation. 22mm alll the way as long as its not to long a run. Have you tried to drink a McDonalds thick milkshake through a thin party straw? So how is the boiler going to operate within the requirements?

 

[smillsey]

why dont you just open up the esg on pipework discrimination, is it not in there?

 

[Billy Bob Bob]

pipework discrimination,?????????? never heard that one "is it because i is copper?" LOL

 

[smillsey]

Well i call it discrimination, as in 22mm to 15mm going down in size.

Not, 22mm down to 15mm up to 22mm etc.

 

[smillsey]

I didnt mean anything to do with dissimilar metals lol, just saying you cant go down from 22 to 15 then go back up. Well, technically you can. But ofcoarse not if the appliance actually requires 22!