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Power venting duo?

Customer asked me to look at their "new" homes heating system.

Boiler is a Nat Gas Lennox GWEB8-1E... induced draft.

For some unknown reason they also added a Field swg-4L power venter to the venting...
They both run when calling for heat?
Any idea why?


  • lchmb
    lchmb Member Posts: 2,997
    edited January 2017
    This is a chimney vented boiler. In order to direct vent it must be with a power vent. The inducer is only to overcome the resistance of the boiler itself... I have the pdf file for the boiler if you'd like a copy..
  • kcopp
    kcopp Member Posts: 4,189
    Go figure..... seems pretty odd that that is the case but sure enough, you are correct.
  • lchmb
    lchmb Member Posts: 2,997
    I can tell you of at least 25 in my area that ran for years with no power vent. A lot of locals assumed since it had a motor it must be ok to direct vent it. Hard to explain to a customer that yes it worked, but it's not right and may be dangerous...even if it's been 15 years...
  • kcopp
    kcopp Member Posts: 4,189
    The whole thing is hooked into an old gravity hot water system.
    Its not piped into the system right and short cycles like mad. It just really needs to get through the winter and then it will be replaced w a proper condensing boiler.
  • Jack
    Jack Member Posts: 1,046
    Back in 92 when the efficiency standards changed all the furnace manuf made a single furnace that could be either Cat I or III. It was a catastrophe and quickly led to the introduction of Cat I & III specific appliances. All were draft induced. The difference was that while the Cat I appliances were induced the size of the inducer was really only sized to get the air/fuel mixture across the unit itself. From then on, you had to vent it correctly. They were high times, and holy smokes, 25 years ago. Anyway, just because it is induced, it is not "power vented"!
  • John Mills_5
    John Mills_5 Member Posts: 946
    Right. Induced draft sucks combustion air into the furnace or boiler. It's up to the draft of the flue to vent the combustion products. Some boiler manufacturers allow venting in stainless steel out the side wall on certain boilers, no forced air makers do. Single wall and b-vent leak so without the 2nd ventor fumes will leak into the house.