Gas Pipe Sizing

[bob the plumber]

I notice with a lot of jobs i go to that many engineers who have previously put new boilers in the premises have not installed the correct size gas pipe to the appliance, in particular the boiler e.g. worcester's generally require 22mm pipe from the mains.
What actually is the implication of this undersizing?? i know it could ultimatley affect performance but what else?

 

[SafeGasInstall]

gas rate it pal and wp at appliance !!! had fitted wb heat only 18kw to 15mm there was no other gas appliance, spoke to wb they say as long as is gas rated and if u dont get biger then 1mbar drop on wp you are OK

 

[AWheating]

Apart from the obvious implications of the incorrect operation of the appliance it would most likely void any warranty the manufacture has on the appliance. It probably also would indicate that there may be other problems with the installation. I have seen cookers go out when the hot water is turned on for example due to combi connected to exsisting pipework. it would also say to me that all the information on the benchmark book if it has been filled out was bull.

sadly its a very common problem.

 

[Billy Bob Bob]

I notice with a lot of jobs i go to that many engineers who have previously put new boilers in the premises have not installed the correct size gas pipe to the appliance, in particular the boiler e.g. worcester's generally require 22mm pipe from the mains.
What actually is the implication of this undersizing?? i know it could ultimatley affect performance but what else?

its ar and if affecting combustion/flame picture on a gas hob/cooker id

 

[AWheating]

I once did a quality control check on an install for a company i worked for, the tennant complained that the boiler kicking in took the gas fire out. On further investigation i found that the new 30kw combi was connected to a 1/2" steel pipe under the floor and the working pressure at the meter was only 11mb. The heating installer swore he had checked everything.... he was lucky that the company did quality checks and kept problems inhouse. In the end a new gas carcus was installed and the gas main was found to be almost completly blocked with carbon.

 

[mickie]

tennant is lucky they noticed the fire going out, someone could have died, ive never come accross it yet but a fast way of making sure everythings ok is if everything can be fired up at the same time without any difference in flame picture

 

[bobgarden]

How do you guys treat under sized pipes that still give a good gas rate but over the 1mb drop. NCS ?

 

[CMairiD]

Doing a recent quality control check, found a WB 28i Jr with 14mbar at the inlet to the appliance (3 year old install) & 20mbar at the meter. FGA was beautiful, no apparent effect on the performance (h/hw) and gas rate fine. Labelled as NCS.

 

[mfgs]

Doing a recent quality control check, found a WB 28i Jr with 14mbar at the inlet to the appliance (3 year old install) & 20mbar at the meter. FGA was beautiful, no apparent effect on the performance (h/hw) and gas rate fine. Labelled as NCS.

I would have At Risked it. Its below the required inlet pressure as stated in the MI's. If its more than 1mb drop between meter and appliance but meets the required input stated in the MI's then I NCS it.

 

[bobgarden]

I would have At Risked it. Its below the required inlet pressure as stated in the MI's. If its more than 1mb drop between meter and appliance but meets the required input stated in the MI's then I NCS it.

Thing is how to explain to the cutomer why you have AR the appliance thats been working for the last 3 years. Also has it been check for the last 2 years after its install?

 

[mfgs]

It doesn't matter how you explain it, if its wrong then it needs to be classified accordingly. They may not be happy about it, but you need to cover your own back in this line of work and not worry about the odd upset customer. 90% of back boilers I come across I have to AR due to the annular seal, pipes not sealed around etc etc and they have been in for up to 25 odd years and worked ok but that doesn't mean I am going to just NCS it to keep the customer happy.

 

[GrahamM]

I would have At Risked it. Its below the required inlet pressure as stated in the MI's. If its more than 1mb drop between meter and appliance but meets the required input stated in the MI's then I NCS it.

This is where you as an Engineer must use your individual judgment to make a decision.
The fact was in for 3 years and had no apparent effect on performance or safety, then as CMairiD I would have NCS'd it.
If was a recent install in past year I would have AR'd it.
I would be AR'ing probably 2 boilers a day if was to make that call for every install bellow the MI's stated inlet pressure.

 

[royston]

I had to id a back boiler the other week as it was spilling in loft and the flue liner wasnt connected to the spigot properly because it was cut at an angle, it looked ok from front but round the back you could push fingers through. Could see soot marks on wall round the back of it. But usual from customer.....Its been serviced for the past 20 years and never been a problem. Been bodged with fire cement thats why.

 

[mfgs]

This is where you as an Engineer must use your individual judgment to make a decision.
The fact was in for 3 years and had no apparent effect on performance or safety, then as CMairiD I would have NCS'd it.
If was a recent install in past year I would have AR'd it.
I would be AR'ing probably 2 boilers a day if was to make that call for every install bellow the MI's stated inlet pressure.

I understand what you are saying, but I personally would rather AR it and explain the risks to the customer. Remember they can refuse permission to turn off the appliance and carry on using it regardless at their own risk. Let them make the decision and cover yourself with the relevant paperwork.

 

[mfgs]

I had to id a back boiler the other week as it was spilling in loft and the flue liner wasnt connected to the spigot properly because it was cut at an angle, it looked ok from front but round the back you could push fingers through. Could see soot marks on wall round the back of it. But usual from customer.....Its been serviced for the past 20 years and never been a problem. Been bodged with fire cement thats why.

I had an old open flued boiler I serviced a couple weeks back, flue all boxed in and run up through the loft to a ridge tile. Did a smoke test, went up in the loft and loads of smoke coming up in the loft from the boxwork with the flue in. I obviously had to cap off the appliance, but the customer wasn't happy as no one in the past 17 years had been up in the loft to check before so thought I was trying to make work for myself.
You cant please everyone, but safety must come first.

 

[bobgarden]

It doesn't matter how you explain it, if its wrong then it needs to be classified accordingly. They may not be happy about it, but you need to cover your own back in this line of work and not worry about the odd upset customer. 90% of back boilers I come across I have to AR due to the annular seal, pipes not sealed around etc etc and they have been in for up to 25 odd years and worked ok but that doesn't mean I am going to just NCS it to keep the customer happy.

Yes i agree if the install is unsafe it should be classified accordingly but as the unsafe situations procedure states if the undersized pipework doesnt affect the safe operation of the appliance and the heatinput is ok then NCS is appropriate

 

[mfgs]

Yes i agree if the install is unsafe it should be classified accordingly but as the unsafe situations procedure states if the undersized pipework doesnt affect the safe operation of the appliance and the heatinput is ok then NCS is appropriate

I can see what you are saying, when its a situation like that I am normally overly cautious and personally would AR it. As Graham said earlier, its individual judgement at the time and life would be boring if we all agreed on everything.

 

[bobgarden]

As Graham said earlier, its individua
l judgement at the time and life would be boring if we all agreed on everything.

Agreed

 

[billybob150811]

if we all agreed there would only ever be one thread it should be borne in mind very few installs have a test point before the boiler testing on the gas valve has a lot of internal resistance its defo a good idea to cover yourself but i trust the FGA but i always include loads of comments to cover my back in paper

 

[tamz]

With older se's and band b's if you are getting the working pressure at the boiler it is NCS. Band A's with zpg's are totally different and maybe the regs need updating as far as the 1mb drop goes but in the mean time go with the mi's and check the working pressure at the boiler or gas valve, read the fga and make your own decision.

 

[bobgarden]

With older se's and band b's if you are getting the working pressure at the boiler it is NCS. Band A's with zpg's are totally different and maybe the regs need updating as far as the 1mb drop goes but in the mean time go with the mi's and check the working pressure at the boiler or gas valve, read the fga and make your own decision.

Why do you think they should update the regs with regards to zpg

 

[Billy Bob Bob]

Why do you think they should update the regs with regards to zpg

because theres more reliance on the correct air/gas ratio fit a duotec 40 kw on undersized pipework it makes a interesting noise bang,wooossh,etc