I have a 15mm bypass (with valve) and a 22mm loop to a towel rail fitted to the Potterton Netaheat 16/22. I'm looking to replace the towel rail with one with 15mm fittings. Could this be a problem? Does the boiler need both loops or will one or other be sufficient to prevent overheating?

John More, January 2007

It will be fine... Are you 'S'-Plan or 'Y'-Plan as with the 'Y' you don't necessarily need it; with the 'S' a 15mm auto by-pass will be sufficient.

GasAid.co.uk, January 2007