Thread: B-vent through HVAC duct?

I know this is wrong but need to reference codes on this. The B-vent is going through supply side of furnace. House was built in 2006. I was under the impression it was never acceptable for an exhaust flue to run through a duct. Sticker said it was a Simpson duravent

Am I correct?

//Rick

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There aren't enough codes to address stupidity.

That's not only stupid, that is called 'delayed assisted suicide' (or murder, depending on who dies first).

What does the big "Warning" label on the water heater say??

NFPA 54, National Fuel Gas Code, Section 12.4.5.1 Venting systems shall not extend into or pass through any fabricated air duct or furnace plenum.

The following code sections are out of the 2009 IFGC and 2009 IRC. This requirement has been in books for years.

503.3.5 Air ducts and furnace plenums.

Venting systems
shall not extend into or pass through any fabricated air duct

or furnace plenum.

G2427.3.4 (503.3.5) Air ducts and furnace plenums.

Venting systems

shall not extend into or pass through any

fabricated air duct or furnace plenum.

This is incredibly nuts. It looks like fairly new construction and I am blown away that a city/county inspector or even a close friend or even a painter on the job didn't ask WTH is going on?

Mike and Jim,

Thanks!

Followup - Somehow the bank found the HVAC company that did this and the owner contacted me. He explained that they sleeved the HVAC ducted before they ran the B-vent through it. The local building department blessed the installation and they then installed the visible collar to the duct. He suggested that in the future I should further evaluate before coming to an incorrect conclusion......my thought was "just smile and wave boys, just smile and wave..."

//Rick

It's crazy no matter how you slice it. Heck, if you can't find a viable way to vent the gas unit, just install an electric WH instead. Seems like that would be way less trouble.

Get that statement by the HVAC contractor in writing, complete with the names of the inspector and the manufacturer of that sleeve, which If I am not mistaken is not specified in any codes I know. If he balks at putting it in writing, then that might tell you something. At least somehow document what you were told to CYA.

Originally Posted by John Dirks Jr

It's crazy no matter how you slice it. Heck, if you can't find a viable way to vent the gas unit, just install an electric WH instead. Seems like that would be way less trouble.

I agree, it would be far less trouble.

However, (and you knew this was coming), if you are connected to the electrical grid, an electrical water heater installation may not meet the energy code. If your jurisdiction does not currently enforce the energy code, I suggest you keep fighting it at the municipal and state level.

CA is done. Stick a fork in us.

SMACNA does permit sleeving ducts around obstructions so if done properly I can understand how this got approval.

Originally Posted by Rod Butler

SMACNA does permit sleeving ducts around obstructions so if done properly I can understand how this got approval.

And I have seen this done around DWV piping, but ... I have never seen it done "properly".

The very basics is insulating the inside of the duct and making sure it is sealed and holds static pressure.

In the few times I've seen it, it was in a corridor in a high-rise and there was a fire damper door nearby, when I stuck a camera into the duct and took a photo of the insulated sleeve ... er ... I mean I took a photo of the sleeve which should have been insulated - because the sleeve was just too small of a diameter to properly insulate around, combine that with properly making up the seam and joints around the sleeve and none ever held static pressure without being all pokied up (coated with fiberglass mesh tape and mastic), and I would not want to use the word "properly" to describe how they were done.

Many years ago I did an install where the only path for the vent piping from a downstairs gas furnace was up through the air return chase of an upstairs system that was installed directly above. We had to get the City of Houston to approve a sleeved run of the vent pipe through the air return chase above because we just did not have any other viable alternative route.

We ended up using a single wall 8" diameter metal duct pipe (with a welded seam) inside of which we ran the 4" B-vent. This gave us a very effective way to isolate the B-vent run from the airstream of the system above. This is not something you will likely see very often but upon occasion you may run into an installation where the installer had to get creative and come up with an acceptable resolution using a seemingly unacceptable solution.

Strikes me a lot like running a sewer line through a spring or a well casing.

For starters, there is no way to inspect for the installation of the vent through the ceiling above the duct, which looking at this installation makes me nervous right there.

More generally, ya' gotta' wonder: "why did the HVAC contractor not just offset an appropriately sized duct to a reduction past the vent?"

However, perhaps the HVAC guy can demonstrate that the AHJ blessed this install... another example of why IMO in such cases it's best to report that you can not verify the installation is compliant, and recommend that the client have the sellers do so, in writing.