I have to line my old chimney flue before installing a new boiler. I plan to have an stainless liner installed. Flue dimensions are roughly 10 3/4" x 12".

The boiler will most likely be a Buderus G215 which has a 6" vent connection. The flue length is 30', and will not be shared with anything else.

2 questions:

What diameter liner for this boiler and a 30' flue?

Any recommendations against a standard stainless steel liner (like Z Flex)?

Regards, NH Homesteader