Very few manufacturers will say that on installation their boilers MUST be checked with a FGA. I would be very surprised if Vaillant really say its a must. In any case hardly 1 in 10 installers even own an FGA. Even those who do rarely use them and many dont even know confidently how to interpret the reading they obtain.
The boiler will happily work with your gas supply but the fact remains that it does not comply with the British Standard for pipe sizing. A complaint to CORGI would result in a defects notice being served on the installer to upgrade the pipe at his cost!
We would charge about £135 to upgrade the pipe in your garage to 28 mm ( with us retaining the 22 mm ! ). That would probably result in the presure at the inlet to the boile being about right with a loss of 1 mB in the pipework from meter to boiler.
The problem with those Vaillant boilers is that they have an inlet pressure test point on the gas valve but a restricted convoluted pipe which loses a few mB extra. That can cause some installers difficulties with their CORGI inspectors who dont really understand the situation. At least one has had to fit a test point on the inlet to the boiler to show the inspector that its adequate at that point.
Tony Glazier
The boiler will happily work with your gas supply but the fact remains that it does not comply with the British Standard for pipe sizing. A complaint to CORGI would result in a defects notice being served on the installer to upgrade the pipe at his cost!
We would charge about £135 to upgrade the pipe in your garage to 28 mm ( with us retaining the 22 mm ! ). That would probably result in the presure at the inlet to the boile being about right with a loss of 1 mB in the pipework from meter to boiler.
The problem with those Vaillant boilers is that they have an inlet pressure test point on the gas valve but a restricted convoluted pipe which loses a few mB extra. That can cause some installers difficulties with their CORGI inspectors who dont really understand the situation. At least one has had to fit a test point on the inlet to the boiler to show the inspector that its adequate at that point.
Tony Glazier