"Andy Dingley" wrote in message
...

Another fix is one of those foul drain air admittance valves, with the
flappy plastic bag valves, on the outfall from the condensate drain.
If you can stop air whistling up the pipe, you've solved most of the
freezing problem.

Yes. A HepVo trap near the end of the condensate pipe run that stops -0C air
running up the pipe, and heavily insulate the condensate pipe and trap.
Replacing a condensing boiler was far too drastic. Appears the boilers
makers knowledge doesn't stretch to pragmatic installations.

Also 32mm pipe must be used where there is a possibility of freezing, or run
outside.