Today’s inspection had a 90k BTU furnace in the basement that direct-vented through the basemet wall. I’ve never seen a furnace setup like this. I was under the impression the Category I vent needed to go up above the roofline. It’s a Goodman gas furnace built in '06 and is not an Annual Fuel Utilization Efficiency (AFUE) unit. The exterior vent appears to be a standard direct-vent, however, I’ve not been able to find any documentation on it. Has anyone else encountered anything like this?
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Grab the model number and check the install manual. That is the best way to know for sure and also back up your narrative. That said, it is likely an improper installation method.
Hey Ryan, I did. It was a bit vague.
Category I Venting is venting at a non-positive pressure. A
furnace vented as Category I is considered a fan-assisted
appliance and the vent system does not have to be “gas
tight.” NOTE: Single stage gas furnaces with induced draft
blowers draw products of combustion through a heat exchanger allowing, in some instances, common venting with
natural draft appliances (i.e. water heaters). All installations
must be vented in accordance with National Fuel Gas Code NFPA 54/ANSI Z223.1 - latest edition. In Canada, the furnaces must be vented in accordance with the National Standard of Canada, CAN/CSA B149.1 and CAN/CSA B149.2 -
latest editions and amendments.
NOTE: The vertical height of the Category I venting system
must be at least as great as the horizontal length of the
venting system
Can you post the model number or pic of the data tag?
Did you take a photo of the model #?
This is from the MES80 / CES80 install manual. I am a little confused as this callout is only listed in furnaces installed in the horizontal position. Which this one is not.
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Looks like cat 1 flue pipe. Good call.
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Page 10 of the manual…
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Thanks for the info, Ryan! Where’d you find the manual? I’ve been through several different websites and they’re all very generic.
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I just googled the brand and model number. Link in my last post to the install manual. Keep in mind, the manufacturers use the same manual for a broad range of model numbers. If you can find a manual that matches pretty close, you are on the right track.
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Got it. Thanks Ryan and everyone else for the input. I love learning here!
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Look it up. I would expect you to know what horizontal venting means.
I am not the one misinterpreting the situation!
Wrong
Yes, you are!
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I would say it’s Vertical since the horizontal distance is less than 75% of the vertical distance.
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Correct!
Also noting that the first 75% is vertical before turning horizontal, which is necessary for draft velocity to build!
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I had to Google to understand why it was an issue. Here’s what I found for those who might wonder.
Category I furnaces, designed for natural draft venting, are generally not approved for horizontal venting because they rely on gravity and the chimney effect, which is not as effective in horizontal applications, and can lead to safety issues like backdrafting.
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