Why the need for larger gas pipes for Condensing Boilers?

Chris asks what reason is there for the change in Gas Safe regs reducing the allowable pressure drop between meter and boiler?

It now seems to be between 1 and 3mbars the pressure at the governor is 19-21mbar and the required pressure at the boiler is now 18mbar – even when the manufacture (Vaillant) writes that the boiler needs only 16mbar. This often leads to a requirement to rip out the existing 22mm pipework installed for the same 24kw boiler (1 bed flats) installed less than 10 years ago and replace with 28mm pipework to deliver 18mbar at the boiler.

The existing pipework provides 16mbar at the boiler. This work can easily cost 1/3 or more of the cost of the new boiler, and my gas engineer says it’s happening all over. This is a mad waste of the country’s treasure unless there is a good case for it: what is the case?

The 2003 regs appear to have been content with 12.5mbar at the boiler! Has anybody done a whole-life cost of condensing boilers? I have been undertaking planned replacement of older boilers, but I am seriously considering changing to the IIABDFI policy (If it ain’t broke, don’t fix it). I am seriously considering service boilers and separate point of use electric water heaters.

I’d also like a boiler that didn’t need mains electricity as I don’t trust any of our politicians to make decisions in time to safeguard either supply. Best alternative is solar tubes and a pv pump, with a Honda 4.5kw generator in the shed, but it doesn’t work for flats!

On a parallel issue with the Gas:

When we bought the block of flats we lived in (12 years ago) because the landlord, a retired Barclays director, had let the property get into such a bad state we were the only buyers, we amalgamated two 1 bed-flats to make our own living space.

10 years later when we moved out to another wreck to live in and refurbish, both Gas & Electricity said we needed new supplies for the street. When they installed the new gas pipe, in a trench from the other side of the street, I suggested they put in a larger pipe, as we have permission to convert the basement and will need a new supply for the as well.

All it needed was a slightly larger pipe, if at all. The price for the new connection was £290 – standard price. To put a 3mm larger diameter pipe (28 vs 25mm) in an already dug trench put the price up to £2100. When we do the conversion they will come back, dig a new trench and make a new connection, again for £290 (plus inflation).

Funny economics?