Manufacturers or gas regs?

[TFGplumbing]

Went to price a job, gas pipe 22mm 17.5 meters roughly without elbows only supplying a boiler, roughly 8-12 elbows so lets say around 22.5 meters in total - I estimate this to provide somewhere between 2.90 & 2.50 m3/hr of ng. The boilers that I have priced for will require a minimum of 3.2 m3/hour. If I connected the new boiler to that gas the existing gas supply there would be approx a 1.5mbar drop in pressure over the system by my calculations. Worcester said the boiler in question will work on as low as 18 mbar I think it was.. so that would be a 3mbar drop..

Whos right? do manufacturers have the whip hand on the gas regs?

I wont be installing it without an upgrade of the gas line as I like to stick to the book religiously.

 

[tamz]

This is what worcester say and it is in line with the regs 1mb drop to inlet.


Btw you wouldn't believe how low it will work.

 

[TFGplumbing]

well I would actually tamz haha!, they reckon that the CDi 30 LP works at 29mbar. As I went out to one the other day that had 32mbar; with hob on. they said that was fine apparently

 

[TBServices]

Ideal logics across the range will work at 14 mb.

 

[tamz]

I fired a 30 si up last year and had it running a good half hour before i tested the wp. 3ft from the meter.
It was running fine on 7mb including the hot water and fga spot on ¿.
It was water in the service.

 

[TFGplumbing]

So if I got 21mbar at the meter and 16.5 at the inlet test point on the boiler, but would that be a 4.5mbar drop? and your only allowed a 1mbar drop

 

[tamz]

So if I got 21mbar at the meter and 16.5 at the inlet test point on the boiler, but would that be a 4.5mbar drop? and your only allowed a 1mbar drop

You need a bigger pipe or a horse :smile:

 

[TFGplumbing]

But Worcester say thats acceptable and the boiler will work safely etc etc. Is it something you would write a ticket out for? can you see what I'am trying to get at?

 

[tamz]

It would be NCS if someone could be bothered to check it at the meter.
You can't fit it as NCS

 

[lame plumber]

if you look at tamz diagrams properly you see that if the meter is 19 at boiler 18 then 16.5 at the gas valve is acceptable, and ooooh it meets the regs 1mb drop allowance. its not saying 23 at meter meaning you can have 19 at boiler inlet.!!!

 

[TFGplumbing]

I know it would be ncs and I wouldn't fit it as such.

I was thing more along the lines of worc say it will work safely on 4.5mbar drop no problem and gas reg's say 1mbar bar drop. Who the hell do I listen too. If you know what I mean Tamz

 

[TFGplumbing]

if you look at tamz diagrams properly you see that if the meter is 19 at boiler 18 then 16.5 at the gas valve is acceptable, and ooooh it meets the regs 1mb drop allowance. its not saying 23 at meter meaning you can have 19 at boiler inlet.!!!

hang on the only place on Worcesters to test the inlet is on the gas valve, to my recollection.

So I'am working on Worcesters assumptions?

 

[tamz]

The regs state 1mb drop on the pipework.
The other 1.5mb worcester (and most other manu's) allow is for the drop through the internal pipework and valve. That is their built in allowance.
Everyone knows that is a bit of a cop out and extra allowance as if your run is quite short you can have less than 1mb between the meter and the valve test point.
If you were so inclined you could cut a test piece in before it connects to the boiler to confirm your pipework drop.

 

[zeebeedee]

Ideal allow a 2.5 mb drop. 1 mb standard drop and 1.5 across there valve. Id fit a test point before the boiler if its more than 1mb drop there upgrade a few meters to 28.

 

[DirksPlumbing]

Ideal allow a 2.5 mb drop. 1 mb standard drop and 1.5 across there valve. Id fit a test point before the boiler if its more than 1mb drop there upgrade a few meters to 28.

Lets formulate it so: If you check your WP and it is 16.5mbar and above on the built in test nipple then everything is ok. No NCS detectable.

If you now fit a test nipple in the line and find a drop of 1.5mbar it is NCS and requires upgrade.

The amount of effort is entirely up to you as long as it is within regulations.
You should at least make the customer aware of potential work being required to upgrade the pipework.

The pressure loss you experience in practice does broadly vary. I found for example that I get away with much longer runs in 22 if I carefully deburr the pipes. And use a pipe cutter instead of a pipe slice to keep the internal diameter as big as possible.

Forgetting it often means that you will even exceed the calculated pressure loss. The type of fitting will have influence as well.

 

[Mike Jackson]

This is what worcester say and it is in line with the regs 1mb drop to inlet.
View attachment 12366

Btw you wouldn't believe how low it will work.

I've had a 24 CDi conventional working on 2 mbar inlet. Meter governer was goosed. Knew there was a problem when customers gas fire went out when we fired the boiler.

 

[villa_tom]

Ideal allow a 2.5 mb drop. 1 mb standard drop and 1.5 across there valve. Id fit a test point before the boiler if its more than 1mb drop there upgrade a few meters to 28.

This is what I would be inclined to do and have done in the past.

To be honest though, if you upgrade the gas pipework as you plan to then your pressures should be ok anyway

 

[AWheating]

this is why its important to pipe size correctly, you must only have a 1mb drop on your pipework simple

manufacturer instruction only cover the appliance, not the installation pipework so they cant over ride anything in that respect anyway.

i think its about time manufacturers where forced to fit a test point at the iso valve, problem is its not there problem really is it?

it was mentioned on the last worcester course i did that they were considering putting one in, probably due the the high number of boilers they attend that have very low gas pressures/poor installation pipework.

 

[DirksPlumbing]

this is why its important to pipe size correctly, you must only have a 1mb drop on your pipework simple

manufacturer instruction only cover the appliance, not the installation pipework so they cant over ride anything in that respect anyway.

i think its about time manufacturers where forced to fit a test point at the iso valve, problem is its not there problem really is it?

it was mentioned on the last worcester course i did that they were considering putting one in, probably due the the high number of boilers they attend that have very low gas pressures/poor installation pipework.

Agree with you. But. What effect has it to have one test point more if I can find on half the commissioning sheets I come across the same numbers over and over and mostly not correlating to my readings at all? Or worse.
I had an oil boiler where the commissioning sheet stated a smoke number of 20+.

The reason for checking the inlet pressure on a modern appliance is rather not to protect the appliance as these might simply draw what ever it needs but to protect the rest of the installation from negative impacts.

Mind the mentioned case where the fire went off when the boiler kicked in? This could have been an older fire with pilot light or a cooker without FSD.

Roast on the plate and no salt. Nip out to the shops, boiler kicks in, fire/cooker goes off, boiler switches off, gas escapes, homeowner returns with salt and puts the light on --> boooom, roast ready but not spiced

 

[Mike Jackson]

The fire had a fsd but the hob didn't so it would have been classified as ID and the meter capped but the easy option was to call in SGN and get a new governer fitted to the meter.