The problem with the condensate pipe freezing is down to an inadequate pipe size being used. When they first came out 22mm overflow pipe was used. This froze as the bore is too small. 32mm waste pipe is now to be used and it must discharge into a drain, either internal or external. Horizontal runs of the pipe are not allowed as this encourages the condensate liquid to lay in the pipe and thus be liable to freezing as well. As for boilers exploding due to this. Never. It won't happen. Too many safety systems on the boiler.