Chimney Liner Sizing

steve_173

Is there an online liner size calculator? I have gotten all sorts of liner sizes recommended. I plan to put in two boilers with a combined input of 301 MBH. There will be a water heater of up to 65 MBH. To be safe I am assuming I need 375 MBH liner capacity just for a little cushion. My chimney is 32 feet high (some say 35, I haven't measured).

Some say the smooth wall liners have 20% more capacity. Any validity?

Will I have any issues of the liner being oversized when just the hot water heater or one boiler is running? What are the efficiency penalties or condensing issued when oversized?

Matt_67

Liner

Is it oil, propane or natural gas? What is the make, model and input of each piece. How are the equipment laid out? What is the headroom in the location? AT what elevation are you? What is the real height of the chimney? Are there any offsets? Those are a few of the questions a professional needs to size a liner. This is also the reason there are no online sizing software: they don't want do-it-yoursel or non-qualified second guessing a pro. Your licensed installer should have the qualifications to size the common connector as well as the chimney liner. if he cannot, he should use a licensed chimney fabricator/installer.

FYI if natural gas or propane cat. 1:
if there is an ofset, chimney capacity is reduced by 20%
certified, corrugated metallic liners are aslo reduced by 20% any bends or ofsetswill further reduce the capacity

steve_173

Are smooth walled liners still reduced the 20%. I've been told the standard corrugated liners are derated due to the increased mass of the liner. If that is the case the smooth wall should still be derated, but perhaps by less than 20%

The pros that come to my house use very basic tables at best. The equipment is not installed so there is no known offsets, riser heights, etc.

What is the best material/product to line the chimney with? Gas will be used now, but there is the possibility of going back to oil/bio-oil/something similar in the future.

Is the chimney height from the point of connect in the basement to the top of the flue?

Matt_67

Liner

Are you in the US or Canada? I can forward you the applicable code sections and charts.