If you are installing an uncertified appliance, you should contact a qualified professional for details. When the flue gas path is straight, the system will produce stronger draft and will need less maintenance than if the assembly has elbows. The ideal flue pipe assembly rises straight from the appliance flue collar into the chimney. A straight single-wall flue pipe assembly needs an inspection wrap or telescopic section so it can be installed and removed without having to move the appliance. The wrap also allows some movement for expansion when the flue pipe gets hot.
Flue pipes carry the exhaust gases from the appliance flue collar to the base of the chimney.
As you will see from the list below, there is a number of rules for the safe installation of flue pipe assemblies. These rules apply to flue pipes connected to all wood-burning appliances, including central heating systems. Flue pipe assemblies should be as short and direct as possible between the appliance and the entrance to the chimney in order to maintain chimney draft. The ideal assembly is one that rises straight up from the appliance flue collar and directly into the chimney with no elbows. A straight flue pipe assembly offers the least restriction to gas flow and results in stronger draft.