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08-19-2008, 07:22 PM #1
Two gas appliances on separate floors.
Came across a one family dwelling (house) today that was built in 1990. The furnace was located in the crawlspace and the water heater on the first floor. The 2003 International Residential Code book clearly states that two gas appliances cannot be installed in a common natural daft venting system when those two gas appliances are on separate floors. I came across a house that was built in 1990 where the 80 plus gas furnace is located in the crawlspace and the standard 40 gal. water heater is located on the first floor. The house was clearly built this way so I'm wondering if this code existed when the house was built. Again, I am referencing the 2003 IRC M1801.11.
Another question. If the type of venting noted above is not allowed, why not. What is the difference if the water heater and furnace are both vented on the first floor or on different floors. I've been told in the past the reason is in case of back drafts. But if the unit is going to back draft, I don't see the difference if the water heater back drafts with the furnace on the same floor or on a lower floor than the water heater.