Thread: Proper venting of high efficency furnace

I had this home a few days ago. The furnace is located in the garage and has the exhaust coming out the side of the home (see photo). There is an openable window within 2-3' of the vent. I called it out that "Flue venting should terminate a minimum of 4' below or to side or 1' above window or door." The seller had a furnace repair person out and they stated that because it is a 90% unit this does not apply. I can't find the installation manual for this furnace (Goodman,
GMPN060-3 REV B) to verify one way or the other.

Any help is much appreciated.

Reis


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Reis,

According to my Code Check, forced or induced vent requires 1 foot clearance to windows. However, this might be overridden by the manufacturer's installation instructions.

for years 4 foot was the rule..
last week i looked it up because one was close,
1 foot was ok per the manual
i checked the newest fuel gas code book and 1 foot is ok
stuffs allways changin

The four foot rule used to be my basis but there are manufacturer specs that allow for much less. Unless you can get your hands on those specs you're not going to know for sure. If a contractor says you can have less than 4 feet simply because it's a H.E. system then he's condemned himself to BubbaStatus - a fate that any self-respecting H.I. would want avoid at all cost.

Originally Posted by Richard Pultar

for years 4 foot was the rule..
last week i looked it up because one was close,
1 foot was ok per the manual
i checked the newest fuel gas code book and 1 foot is ok
stuffs allways changin

What year is the newest?

books at work ...guessing 2006. it is the adopted code for NJ at this time
I think the water heater discharge can be more of a nuisance since it will operate in the warm weather when the window might be open

Is that the 90+ vent coming out at/inside the gutter, that green flat 90 contraption?
- Is that some homemade thing or what, never seen anything like it and doubt it is approved. Looks like it would count as at least 2-3 regular 90's; How many 90's in the overall run; does the total count exceed allowed???
- Forgive my ignorance but ... doesn't it freeze around Seattle? If it does I can see the gutter ice forming around that thing and eventually blocking the opening. Remember the condensation coming out of the pipe will contribute to buildup. I've seen it many times.

I happen to have a set of installation instructions for a GMH95/GCH9 Goodman Gas-Fired Warm Air Furnace. The revision date of my manual is 04/2008. On page 13 of the manual you will find several clearance requirements. For the application in your picture there is a 4'-0" clearance requirement for a "Non-Direct" Vent Termination or a 1'-0" clearance requirement for a "Direct" Vent Termination.

I hope you find this information helpful.
Shawn

Shawn:

That's the goofy thing. I've never understood why direct vent makes a difference on the distance requirement. Perhaps someone thinks that the combustion gas with DV is less of a hazard. Maybe if you place a DV near an open window then air should somehow not enter the window.

I'm sure that greater minds than mine know something that I don't.

With direct venting, the rationale seems to be that some of the exhaust gas is drawn back in to the combustion chamber, due to the proximity of the interior and exterior vents. This does create the question of duration of operation though. If i direct vented unit operates continually for an extended period of time, will the exterior (intake) vent material reach a temperature at which nearby combustibles are ignited? Perhaps this winter, we will have a few cases that will give us more data on that. As for the contractor's explanation; if my client is willing to accept such a foolish response, I suggest to them to get it in writing, with a signature. The contractor never is willing, and it quickly becomes apparent who knows what.

Originally Posted by Randy Aldering

With direct venting, the rationale seems to be that some of the exhaust gas is drawn back in to the combustion chamber, due to the proximity of the interior and exterior vents.

Another goofy thing - combustion gases are quite corrosive. Pulling them back into the furnace through concentric vents seems like a bad idea.

I bet some really bright intelligent well paid person is behind some of these ideas. Ever notice how really bright intelligent well paid people lack common sense? Kinda like the stupid 2x4 tests for O.H. door openers that some wizard dreamed up. But then I don't imagine they get released into the field very much or lead any form of life that resembles reality.

Originally Posted by Eric Barker

That's the goofy thing. I've never understood why direct vent makes a difference on the distance requirement. Perhaps someone thinks that the combustion gas with DV is less of a hazard.

Because of the secondary heat exchanger in a 90+ furnace the flue gas is cooler to the touch, you can put your hand in front of it to see. There is no concern with the temperature of the flue gas. Now the CO is still a concern, I never installed a direct in indirect vent under a window and followed the 4' rule. The vents are to be extended 12" out from the house, that gets the flue gas out away from the intake on a direct vent application to reduce the recirculation of flue gas problem.