supply pipe to new combi boiler with 15mm inlet gas connection
Anonymous user 28/02/2024 - 3.05 PM
Hi,
I recently had a glow worm ultimate 30c combi boiler fitted by a gas safe registered fitter. I want to enquire whether it has been fitted correctly regarding the gas supply as per building regulations and other legal requirements. The gas inlet connection on boiler is 15mm but I understand that as per building regulations it should be fitted to a 22mm gas pipe within one meter of the boiler.
Originally the fitter said a 22mm gas pipe would have to be fitted from the meter through the kitchen to the cupboard in the lounge where the boiler is sited.
But when he installed the boiler he said that wasn't now necessary.
I live in a flat and the existing supply goes into the concrete floor at the meter in the hall as 22mm and emerges from the concrete floor in the cupboard as 15mm to which the boiler is now connected about a meter away via 15mm pipe, as was the old blow air boiler. There is no way of knowing whereabouts the pipe changes from 22 to 15mm as it is buried in the concrete.
Please can you tell me whether this is acceptable, and whether performance of boiler maybe compromised as I can't see any guidance in the installation guide, as I'm not sure whether the fitter has taken a shortcut by not fitting the 22mm pipe as he previously advised.
Presumably he checked the gas flow rate and found it to be satisfactory even connected to 15mm pipe.
The boiler appears to work okay with enough hot water.
Many thanks,
Simon
Are you a tradesperson and able to answer this question?
Personally i would ask him for his gas safe number and phone gas safe and ask that one of their inspectors come out and do a free check on you're installation. They will tell you whether or not it is acceptable and sort things out for you. It does not sound like a very satisfactory set upto me and i would suspect you're gas appliance is under rated because of this and should not be operating like this.
I know by experience that a 15mm gas pipe supply is under sized for your new boiler.
Your installer should of carried out two gas rate tests, the first being in hot water mode at full rate and the second your central heating, again at full rate. This procedure is part of the manufacturers Benchmark, these important tests, amongst others determine if the boiler is operating correctly as it is designed to do! If you have more than one gas appliance in your property, for example a gas cooker and your cooker is running at full rate i.e. oven and gas rings all running and your boiler is also running at full rate i.e. the boiler will be starved of gas causing 'incomplete combustion'.
I would now challenge the installer to prove he has first carried out a gas pipe sizing exercise to prove the gas supply pipework to the boiler is of sufficient size, which also will take in to account any other gas appliances you have in your home and also he has properly gas rated the boiler as previously mentioned both in heating & hot water mode. If he tries to be evasive or just simply pays you lip service ask another gas safe engineer to double check!
The most appropriate way to actually tell if the Boiler is under gassed is by working pressures at the boiler and meter. You are only allowed a 1mb drop. So if the working pressure at the meter is 21mb, the working pressure at the appliance should be 20mb. You also do this test with anything else on the Gas Supply. So same test but just turn on hob, observe the readings, as if hob on at the same time as the Boiler, the drop is more than 1mb, there will be a starvation on the appliances of Gas. (Incomplete Combustion.) Gas Rate just checks the Boiler is consuming the right amount of Gas. The working pressure is more appropriate for sizing pipework. . .
