Advise needed wrt gas pipe size.

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I'm looking for some advise from any gas fitters out there.

We had a new boiler fittted last month (Veissmann 100 compact 19kW) along with a replacement gas pipe.

No problems with the boiler looks and works fine.

Bit concerned with the sizing of the gas pipe though.

It was installed by a Gas Safe Registered fitter but having done a few calcs of my own I think the pipe is undersized.

Any chance someone can check over my calcs before I call him back :?:

Pipe details are as follows :-

From the meter.
9.3 Meters of 22mm copper with 6 x 90° bends
reducing to 4.2 meters of 15mm also with 6 x 90° bends to the boiler

No other gas appliances are in the house.

Allowing an extra 0.3m for each 90° bend gives an effective length of 11.1 (22mm) and 6 meters (15mm).

19kW needs flow of 1.78 m³/hour

Gives pressure drop of 0.37mbar through the 22mm and 1 mbar through the 15mm - Total 1.37mbar pressure drop.

I think this is out of spec as I thought 1 mbar was the max.

Any help gratefully received - Thanks.
 
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Seems like you are right!! call Gas Safe register and ask for a free work inspection - unless your RGI is a good friend of course!! ;)
 
When commissioning the boiler he should have checked all the gas pressures. Inlet pressure, working pressures, burner pressures, gas rates, etc.

If they are all okay, your gas pipe sizing is fine. Did he fill out the benchmark (in the back of your MI)?
 
Yerinho - The only paperwork I have are a Gas Safety Inspection sheet and the comissioning checklist.

No pressures are filled in on either - only the gas rate of 1.86m³/hr.

Also on the Central Heating Mode - measure and record box he has a Central heating Flow Temp of 20°C and a Return temp of 60°C which makes me wonder why I need the boiler :rolleyes: !!
 
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The general rule of thumb was no more than 1m of 15mm including bends.

But that was for combi's and yours is just heat only,
If the boiler is working ok whats the problem.
 
You are correct, apart from each elbow is 0.5m, pulled bends are 0.3m.

Assuming you have elbows fitted, the pressure drop for the 22mm section is 0.41 mbar and the 15mm section 1.2 mbar, so in total you have a drop across the carcass of 1.61mbar.

You need 22mm all the way, except the last 1m can be in 15mm and still be well within the theoretical pressure drop.
 
CompHeat - Thanks for that - Should have mentioned, not a combi - Heat only boiler on a Y-Plan system.
 
apon commissioning of the boiler the inlet pressure should have been checked if this is a 1milibar drop from meter to appliance then every thing is fine bearing in mind gas rates check out etc, 20 - 60c lol not sure how that was recorded lol , but you are looking for a a return drop of not less than 10c i.e 70 flow 60 return.
 
I suspect your installer may have cooked the books i suspect he has copied the gas consumption straight from the boiler manual and not actually measured it through the gas meter :rolleyes:
 
I think you may be overworrying about this. Just ask Agile or many others to comment on some of the standards of work from jobs seen. Some are shocking and downright dangerous.

Most modern boilers allow a bigger tolerance of gas pressure even if they state otherwise. Some installations where you cannot replace the gas pipe will work okay down to 15mbar. He must have checked the working pressure at the boiler.

Its your choice to call gas safe for an inspection but personally I think there are more important things to worry about in life than hauling him over the coals for 0.5 mbar. :confused:
 
Some modern boilers work down to pressures like 14mb (ideal isar 35) which is impossible to ever achieve with a 1mb drop on the pipework

21mb +/- 2mb working pressure at meter = 19mb
19mb - 1mb = 18mb (theoretical lowest poss value at boiler)
BUT YOU KNEW THIS

As long as the gas rate is fine and the gas pressure is within the MI's the pressure drop can be more than 1mb (as long as it doesnt affect other gas appliances (which you dont have) why did you bother hiring a gas safe reg plumber when you could obviously do a much better job!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
 
As long as the gas rate is fine and the gas pressure is within the MI's the pressure drop can be more than 1mb (as long as it doesnt affect other gas appliances (which you dont have) why did you bother hiring a gas safe reg plumber when you could obviously do a much better job!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Where in the regs does it say this?

I have spent the last ten mins looking trough my books and its no where to be seen.

Excess pressure drop on an existing installation would be classed as NTC as long as all is working fine, however on a new installation i would be tempted to slap an AR sticker on it or phone the Manufacturer and get a notice off them to say its running fine with the measurements achieved.
 
just going off isars MI you can install that 35kw wioth in there words 20m of 15mm you wont ever get the gas rate with that pipework
 

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