Furnace/Water Heater Shared Vent

[tvanwagner]

Hi All: I inspected a house today where the furnace and water heater were sharing the same vent. My concern is that the water heater is propane fired and the furnace is oil fired. I know that these units can't share a vent with a wood fired unit, but I'm not sure about mixing oil fired and LP gas fired.
Thanks in advance...

[Roy D. Cooke, Sr]

Originally Posted by tvanwagner

Hi All: I inspected a house today where the furnace and water heater were sharing the same vent. My concern is that the water heater is propane fired and the furnace is oil fired. I know that these units can't share a vent with a wood fired unit, but I'm not sure about mixing oil fired and LP gas fired.
Thanks in advance...

Not allowed in Canada . Two gas appliances are OK but not gas and another fuel . I expect it the same there not allowed .
Roy Cooke sr

[Vern Mitchinson, CMI]

I believe the reason is that different fuels require different vents, sizes and materials.

[Robert J. OConnor]

Modern U.S. model codes do allow common venting for gas and oil fired natural draft equipment to the same chimney (e.g. 2003 IRC G2427.5.6.2). But Vern is right that the venting requirements can be very different, so it does get tricky to do it right and get the proper draft. Also gas equipment can't just be connected to an exist unlined masonry chimney for oil equipment, as the gas equipment exhaust produces corrosive condensation ... sometimes excessive amounts, particularly with an oversized flue (cools too much before it exits).

JMO & 2-nickels ...