Any boilers that can still use 15mm gas supply?

[Timmy D]

This may be a basic question for many of you, but I do need good advice. I want to replace my 16 year old 15kw heat only boiler with a more powerful one since we are building an extension onto our small 30yr old house. With the extension completed we will then have 17 small rads, plus the existing hot water cylinder and gas hob. The existing gas feed into the boiler is 15mm. What size boiler can I go up to please?

Is your boiler more than a couple of meters away from your meter? If so, you’re already undersized.

 

[Knappers]

Just to make it really clear.
I'm not a jobsworth and am happy to push the limits when appropriate but...
A 1mb drop is the maximum drop allowed, there's no tolerance and no exceptions!
Even if boiler manufacturer permits it (and they dont) there's a world of difference between safe operation and the requirement for a new install to be compliant.

 

[Riley]

You would mark undersized pipework on a landlords check you cannot install a boiler not to requirements. If it’s that close I’d either insist on upgrade or walk away