How to determine flue pipe size?

[Roger Smith]

Can anyone tell me where to find information on sizing a flue pipe for oil fired furnace. Inspected one today where a fire started right where the 8" pipe was reduced to 6".

[H.G. Watson, Sr.]

Please don't double post.Beyond the scope of HI.If you find evidence of malfunction or fire should be referred to a pro.Your terms are ??? and descriptions ?'able.If you're DIY or HO, post in that area.Gotta know the specs.Annual evaulation, service, maintenance by a professional.Dampers, adjustments, maintenance, combustion analysis.Sizing and chimney/flue evaluation is for specialized trained & qualified solid fuel, etc. chimney professional.

[Roger Smith]

First time I used this, not sure how it got double posted. Professionals are looking at the furnace, just wanted to get a little knowledge on the subject. Thanks for the reply.

[H.G. Watson, Sr.]

For starters
NFPA 31, Standard for the Installation of Oil Burning Equipment; and

NFPA 211, Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances

Both can be viewed via

List of NFPA codes & standards (http://www.nfpa.org/AboutTheCodes/List_of_codes_and_Standards.asp?cookie%5Ftest=1)

So you're a Home Owner, Home Buyer, DIYer or what?

[Bob Harper]

Flue and connector sizing is not simple and beyond the scope of this forum. If there was a fire loss and a claim filed then let the pros do their jobs.

You can click on the F.I.R.E. service banner below to get certified in the subject. There can be many codes, standards, and manufacturer's instructions that come into play for sizing. As for a fire loss, there can be issues with the appliance itself and how its firing in addtion to the chimney connector and venting.

[Roger Smith]

I am involved in inspections and claims for the insurance industry. I let the professionals handle the complicated issues. Just trying to learn as much as possible about this one.

[Tom Thompson]

Let's say there was no fire, what some are saying is let a pro handle this. Home inspectors must have some knowledge in this area, easies method is to insure flues are never smaller than the appliance connector they terminate as sized or larger through the roof. Flue can be interconnected with others, but must increase a minimum of one pipe size of the largest appliance connector. If you notice areas of excessive darkening of the vent or surrounding area this indicates overheating, advise the customer and shut the appliance down let a pro take it from there.