New boiler needed - but do we need new pipe work too?

[Virginiaplain1]

Our 12 year old boiler started playing up before Christmas - kept locking out/switching itself off. Heating engineer came out and, after a couple of attempts, managed to get it going again, but has issued an 'at risk' notice and says it should be replaced. This in itself is not a problem, but the engineer says that new regulations mean that we need new 28mm(?) pipework from the meter at the front of the house, to the boiler, to replace the current 15mm(?) pipe. Unless we want to dig up the concrete floors (which we don't), this is going to mean running an unsightly gas pipe around the outside of the house.
Is this really the case? It seems very odd that anyone wanting a new boiler is going to have to go through this disruption. We intend to get a second (and probably a third) opinion on the job in the New Year, but I'd appreciate some independent advice on this, if anyone can give it. Thanks.

Yes old 15mm pipe must be replaced with 22mm/28mm ( depending on the distance of your boiler from the gas meter and if you have other gas appliances and where they come off the gas supply) if fitting a new boiler.

Modern boilers (especially combis) are usually more powerful than old models, so they need a greater gas supply, so the pressure does not drop too much when the boiler is firing. As well as preventing the boiler working correctly, a drop in pressure could prevent other appliances (such as a gas cooker or fire) working correctly.

The gas pipe must be able to deliver enough gas to the boiler, and a long, narrow pipe is likely to prevent this.

Thanks. When did these regulations come into force? Our current boiler was installed 12 years ago, when we had a new extension built - would the wider pipes have been used at that time?

Sorry, we have a Megaflow type system, with a hot water cylinder, so I assume this wouldn't be a combi boiler.

it would depend on the power of the boiler (modern ones are often around 30kW, which is quite a lot), and the length of the pipe run. A short pipe impedes the gas flow less than a long one. It's the distance from the meter that matters.

If your current boiler is 12 years old, I'd expect it to have a gas pipe that is adequate for its power.

A qualified gasman may be able to describe it better.

Yes you can only drop a millibar between the meter and boiler with all appliances running. For a basic Combi you would need 22mm pipe if it's more than a couple of metres, and if it's getting on for 10 metres and a powerful Combi especially shared with a hob or fire you'd need a 28mm pipe.
You can ask for calculations from the engineer if you're unsure of the exact specifics.

Ps an existing boiler with too much drop would be Not to Current Standard, it would only be At Risk if it was affecting other appliances.