Gas furnace

[allen elliott]

Any Ideas on what caused the soot around the vent. The picture was taken from the bottom side of the flue. It is an upflow furnace located inside an interior closet. It is fueled by propane. Thanks for the input.

[Jim Luttrall]

Sorry, can't tell much from your picture, got any more? Bigger?
Soot is usually (if not always) caused by incomplete combustion.
Was there plenty of combustion and makeup air?
Did any other appliances or the return air of the furnace itself upset the apple cart with all the doors to the equipment closed?
Is the flue open and sized correctly?

[allen elliott]

I am leaning toward the vent. It did not meet the 2-3-10 rule. It was very short and next to a wall on the roof.

[Jerry Peck]

I am leaning toward the vent. It did not meet the 2-3-10 rule. It was very short and next to a wall on the roof.

"Vents" do not have to meet that rule.

By the way, it is also not 2-3-10, it is 3-2-10 for chimneys.

[Steve Lowery]

What does the 3 refer to?

[Jerry Peck]

For chimneys:

3 feet high minimum (on sloped roofs you measure the height on the high side of the slope).

2 feet minimum height above any part of any structure within 10 feet.