Boiler isolator switch

[BartC]

It's 24kW, and in fact the inlet is 22mm. But it turns out there is only 6/7 feet of 15mm pipe in the run to the boiler.

(The engineer is here now, but was not keen to do the work unless he also took care of some other stuff (to do with CH pipes and radiators, which, while needing to be done, would have been DIYable during the summer). He agrees the 'lead' pipe, which is actually copper, seems fine.

I let him go ahead, otherwise that would be the second engineer who'd declined to do the work because of not being happy to sign off a substandard, even if legal, installation.)

[John Rumm]

Assuming that is the heat input it gives a max gas rate of 24 / 38.5 x

3.6 = 2.24 m^3/hr

If that were being run in only 15mm then you would have a max effective length of a bit over 3m

(effective length counts a swept bend 0.3m, and an elbow as 0.5m)

So it unless very close to the meter and there is nothing else sharing the pipes, it would be more common to run 22mm for most of the way, and drop to 15mm for the last bit if it helps aesthetically.

Yup, given you are renting the place out, having the require paperwork is important. If he is happy to check and sign off everything without needing to demolish and rebuild the house, for a not too extortionate fee, then go for it.