venting

eric_29

Can you vent 2 80% warm air furnaces that are fan assisted flus and 2 nat draft hot water heaters into 1 b-vent as long as it is sized accordingly?

Brad White_130

I would not mix

induced and natural draft on the same flue no matter how sized. You can force combustion products out into the space or prevent natural draft appliances from working properly.

Induced draft appliances can be combined if they use a common inducer downstream of both appliances; however this wastes energy drawing through the non-operating appliance.

Q: Why are there both? If one works with natural draft, why not all?

And natural draft is like, so 20th century...

Tim_33

No pressurized exhaust

in B-vents. B-vent is only for negatively pressurized (i.e. gravity vent or natural draft), non-condensing flues.

eric_29

the furnaces that are 80% efficiency do not have a powervent just the fan on the furnace this is a condo project which we are trying to limit the number of roof penetrations by common venting 2 units (1 hot water heater and 1 warm air furnace each unit) into 1 b- vent with a total of 2 furnaces and 2 hot water heaters

Joannie_11

Categories Matter

The National Fuel Gas Code allows Category I natural draft and Category I fan-assisted products to be vented into a common b-vent, as long as the vent system is designed properly.

As Tim stated, natural draft is not allowed to be vented with positive pressure unit (Categories III or IV).

Jim Davis_7

Venting these together is totally legal but the headaches in may cause down the road may not be worth the savings. Pilots outages are common when 80% furnaces and water heaters are vented together. The furnace can vent out the water heater and never shut down.. The flues can be plugged and neither will shut down. I have seen thousands of these installations over the years that don't work and get hundreds of calls every year on what to do to correct them.