We have a Glow worm Flexicom 18 sx condenser boiler which is efficient except for the coldest days of the year 2009 and 2010 when the outside pipe froze up with the expelled water from the boiler and shut it down until you go out with a kettle of water and thaw the pipe out. Last year as a temporary solution an interior drain pipe was fitted which we drained into a jug in the kitchen and emptied daily. This appears to be a very common problem if you search on aam. So if you get one make sure to discuss this first, the solutions we have now been offered are to have the pipe permanently inside and liked to the waste from the sink, or a thermal wire fitted to the tube to prevent freezing. So be warned!