Flue Size

[Anonymous]

I believe I have to reline my 8″x8″ chimney because I’m planning on installing 2 natural gas heaters and 2 NG hot water heaters.
I’m going from oil to NG.

The heaters are 50K BTU each and the water hearters are 40K BTU ea.
The heater flue size is 4″ and the water size is 3″.

How do I calculate if my flue size is adequate?

Thanks

[hjParticipant]

A seven inch flue will have the combined area of those four smaller flues. Double wall pipe may not slide into the 8×8 tile, in which case you will have to have a stainless steel liner fabricated. The double wall will be better if it will fit.

[Art_xyzParticipant]

To determine if your chimney is the correct size you need a great deal of specific information. 1. Is chimney lined with clay tiles? 2. Chimney height. 3. Are the water heaters power vented or do they have draft hoods? 4. Are the heaters power vented or do they have draft hoods? 5. How far away from the chimney is the farthest piece of equipment? 6. How many connections will you have to the chimney (1,2,3,4)? 7. Will the vent piping be single wall or double wall? 8. Does the chimney go up inside or outside the house? 9. Does your gas co. or the city enforce the gas code? 10. What code are they using? Only after you have all these answers will you be able to get the correct answer.

[Author]

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