Without looking it up don't have a clue sorry , why new flue?
Although it's not leaking (tested it), the builders gaffer-taped the elbow joint, all screws were missing (which I replaced) - I just don't trust it. Plus Worcester said the blockage could be at the flue rather than condense trap so was gonna take the internal flue apart to inspect/clean and while I was at it replace the flue.