5" Flexible Chimney Liner On A Unit That Requires 6"

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ender760

New Member
Dec 11, 2023
1
Maritimes
Hello All,

New to the forum. However, in searching around I know similar questions have been asked in the past so please be patient with me.

I have a 100 year old house with a 28' chimney (7 feet straight, then 1 foot 30 degree turn before continuing 21 more feet straight) coming up from a solid brick and mortar fireplace. An opportunity has come up to purchase a 30' stainless steel insulated 5" flexible liner and a Spartherm 600 (max 45,000BTU) fireplace insert unit from a friend. In reading the manual insert it requires that the insert be installed with a 6" liner, not a 5" like my friend has been using with apparently no issue.

Looking for real-world experience or insight into how you would imagine the unit would perform. I understand the issues regarding insurance already, so thanks in advance, but I'm really just wondering how the unit would hypothetically perform given my set-up and any real/apparent danger I would be putting myself in.

Thanks in advance,
Ender