View Full Version : Mutiple flues

Mike Schulz
05-24-2007, 12:41 PM
Does this setup look right to you. Elbow off the water heater then "t" into flue for two furnaces. Does the 12" rule apply off the heating unit like the water heater?
For my knowledge why does it have to be 12" straight off the draft hood before it makes a turn.


05-24-2007, 04:24 PM
Common vented natural draft water heater & induced draft furnaces.
Guaranteed to spill out the draft hood if the conditions are right.

Why they continue to allow this type of an installation I will never understand, don't guess there is a body count to justify banning it yet. :rolleyes:

Mike Schulz
05-24-2007, 04:40 PM
But what about the elbows right off the units?

05-24-2007, 05:04 PM
IMHO there are a lot worse things going on with that venting system than the elbow right on the inducer & draft hood.

imported_John Smith
05-24-2007, 05:05 PM
Man, I could spend hours in an attic that had that much room. An inspectors dream. Whats with the black ducting. All I ever see in Houston is the silver flex ducting.

Also, those flexible gas lines look like they have very sharp bends to them.

Mike Schulz
05-24-2007, 05:20 PM
This was a third floor attic area, stairs leading up to it. The flex duct is black plastic covered and common here (can't remember the name). The gas line had a sharp radius but wasn't kinked.

Should a wye connector be used at the furnace with the "T" connector? It seems a induced fan would push gasses in both directions of the "T" and into the other furnaces. Still haven't got a straight up answer on the elbows off the units?

Would you write this up and what would you say?

imported_John Smith
05-24-2007, 05:23 PM
Mike, I know your question wasnt about the gas lines, but I would write it up. There isnt enough radius to the line and its a potential problem.

Mike Schulz
05-24-2007, 05:45 PM
Thanks John for your input. I appreciate it. Would you know the max. radius?

Bob Harper
05-25-2007, 07:46 AM
A lot of work went into doing this wrong.

-all three do not have draft hood connectors. Improperly attached to the appliance.
-maintain 1" clearance off B-vent/ 6" off draft hoods
-how is that Armaflex/ foam attached to those water lines? Relying on the clamshell friction or is it adhered? Can it move or fall against hot things?
-support: each vent connector needs to be properly supported-none are. All those pretty boxed in drives do nothing except lateral spacing. The vents need to be secured as in wall bands, straps, etc.-something secured to the pipe that is then secured to the building. The vertical vent must be supported in three axis: vertical and two lateral.
-the code dictates vent connector sizing based upon horizontal offset and vent height and whether nat versus fan with min/max range.

-CSST bend radius per mfr. plus support. Should have used a black iron ell or two.

Are those supply ducts sealed? Any other combustion appliances in the home?

Manifolding is tricky and requires planning and checking in the charts for what's permitted by code. However, the proof in the pudding is testing to see if it works.