Flues, sizes and adaptors

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allfunkedup

New Member
Sep 25, 2024
1
Devon
Hi,
I have a medieval cottage in Devon with an inglenook fireplace.
I have just removed a Franklin Stove which was old and juicy on the wood and am replacing with a new wood burner. The Franklin used an 8" flue, stove pipe to the register plate, then approx 18' flexible straight up to the top.
The new stove has a 5" flue.
My questions are as follows: should I
a) join a piece of 5" stove pipe from the new stove using an adaptor to the existing 8" flexible flue at the register plate
or
b) drop a new flexible 5" flue down the 8" and connect the two 5"
is 5" increasing to 8" too much of a increase? Will it compromise the stove operation/ performance?
Does a smaller flue give a better draw?
If I go with option b) will one flue within another cause any problems?
Thanks in anticipation
Robert