Chimney Liner Size

Steve Garson_4

I am having a chimney liner installed in my 80-year old clay lined chimney. The chimney expert tells me I need an 8-inch liner. The length of the flue is 28-feet. The liner would be corrugated stainless 316-Ti with two bends to accomodate the flue passage above the fireplace.

To install the liner will require removal of the present clay tile lining, which will add to the cost and potentially require cutting a hole in our family room wall to access a bend in the flue that is behind a plasterboard wall.

The 8-inch size was based on the 7-inch vent pipe from my WM SGO-4 and the 3-inch vent from my Bradford-White Combicore 65,000BTU/hr water heater.

My boiler is under-fired at 1-GPH, so I was wondering if perhaps a 7-inch liner would be fine, instead of the 8-inch. This would be a total of 205,000 BTU/hour. This would allow the liner to be inserted without removing the tile lining.

I obviously want to do what's right, but wonder if the underfiring makes a difference.

Thanks!

Steve

Nick S

Why do you need a liner? If the current chimney is in good shape, fire your boiler and water heater where they should be and you should be fine. If the chimney is falling apart and you need a liner, put in the biggest one that will fit.

Steve Garson_4

The chimney needs a liner. The clay is deteriorating and some of the mortar has fallen. I also want to convert the boiler to gas. As it is today, the 65K BTU gas water heater is damaging the chimney.

bob young

fuel gas code

verify load capacity as per n.f.g.c. got a feeling you are well within limits with seven inch. chimney liner guys are not engineers. i could be wrong but it is worth researching.

Bob Harper

You need a Level II inspection of the chimney to ascertain if it needs a liner or not.

In this case, since you already know it has damage and you're venting higher efficiency equipment, you will need a liner. There is a lot of info. you need to size it you have not provided. However, as an example, if the boiler is rated at 84% steady state efficiency at 1.5 GPH with a 4 ft. lateral offset and 25ft. height, a 6 inch liner should do. Now, derate the liner for the offsets and still a 7 inch liner should do.

Get another chimney lining contractor's bid.

Bob

Unknown

Keep in mind that

liners have 20% less capacity than a type B gas vent when doing calculations.

Robert O'Brien

If

You're converting to gas anyway,use a mod/con and forget the chimney altogether!

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

allan_7

Spec Chart

Flex-L International 614-895-8948 Charted Values:

6" @ 25' Class B Connector Fan+Fan 270
Fan+Nat 221
Nat+Nat 198

Single Wall Connect Fan+Fan 262
Fan+Nat 214
Nat+Nat 192


6" @ 30' Class B 289 238 213
Single Wall 280 229 206

7" @ 25' Class B 409 341 268
Single Wall 398 332 261

7" @ 30' Class B 438 367 288
Single Wall 426 357 279

Tables reflect 20% de-rate from B-Vent Tables.

Most oem's recommend using the smallest liner possible, rather than oversizing (condensation, wet-time issues, etc.

Recommend Class B-1 double wall connectors for gas equipment.

Hope this helps....

allan_7

Spec Chart

Flex-L International 614-895-8948 Charted Values:

6" @ 25' Class B Connector Fan+Fan 270

Fan+Nat 221

Nat+Nat 198

Single Wall Connect Fan+Fan 262

Fan+Nat 214

Nat+Nat 192


6" @ 30' Class B 289 238 213
Single Wall 280 229 206


7" @ 25' Class B 409 341 268
Single Wall 398 332 261

7" @ 30' Class B 438 367 288
Single Wall 426 357 279

Tables reflect 20% de-rate from B-Vent Tables.

Most oem's recommend using the smallest liner possible, rather than oversizing (condensation, wet-time issues, etc.

Recommend Class B-1 double wall connectors for gas equipment.

Hope this helps....

allan_7

Spec Chart

Flex-L International 614-895-8948 Charted Values:

6" @ 25' Class B Connector

Fan+Fan 270

Fan+Nat 221

Nat+Nat 198

Single Wall Connect Fan+Fan 262

Fan+Nat 214

Nat+Nat 192


6" @ 30' Class B 289 238 213
Single Wall 280 229 206


7" @ 25' Class B 409 341 268
Single Wall 398 332 261

7" @ 30' Class B 438 367 288
Single Wall 426 357 279

Tables reflect 20% de-rate from B-Vent Tables.

Most oem's recommend using the smallest liner possible, rather than oversizing (condensation, wet-time issues, etc.

Recommend Class B-1 double wall connectors for gas equipment.

Hope this helps....

Rich Kontny_3

Why don't

You save that money and install a closed combustion boiler that vents out the side of your home? Size it for an indirect water heater and you have one gas fired heat source with no need for the chimney. This way you would have an updated heating system with energy saving capabilities.

If your liner is usable and safe I would not waste money on it if you plan to upgrade in he near future. Might even be some utility incentives $$$ call and find out. Don't rush into the chimney liner project (unless it is unsafe) until you have options and perhaps second opinions.

Rich K

Joe Brix

If you're getting a new boiler

I agree, just get an indirect HW heater. A smaller 5 or 6"
liner might be all you need for the single gas boiler.

Buzz G.

Lining old chimney

is expensive. I had this same problem and my chimney was not even clay lined. The solution chosen was Knight condensing boiler with IDHW (W-M) and using one 3 inch PVC for vent and one for combustion air -- and running those up chimney. It was a lot less costly than lining chimney and staying with gas HW heater and more efficient too. Have not looked back after making this choice.

Steve Garson_3

It's a steam system.

Paul Fredricks_3

I looked at a house the other day. It had a Smith boiler with a 7" flue connection. Someone at sometime had installed a 5" liner. Per the calculations, the 5" would work. But we called Smith and they said the smallest you can put on their units is 1" smaller than what it came with.

When in doubt, call the manufacturer.