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Can a HVAC be located in garage to feed house only?

J

jack ridley

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Jul 21, 2020
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Ran across something yesterday. Noticed they had a HVAC direct vent furnace in garage to feed a portion of a house. No takeoffs for garage from this system, however was curious if it can be mounted in a garage without being boxed in? My initaial thoughts are no because what if a car was running in the garage? Any thoughts if system should be boxed in? I am under irc code. Thanks!
 
Our house in virginia was built about 1995. Two systems, one for each floor. Heat pump in the attic for second floor. Gas furnace with a/c in the garage, supply and return ducts in the crawl space. Only combustion air sucked in from the garage.
 
I’ve seen hundreds of furnaces in a garage and never seen one suspended below a ceiling. That would come in handy if space is limited.
 
& * &

Does your manufacturer' installation instructions permit
this location ?........With the pvc intake & exhaust, it sounds
compliant.

& * &
 
R302.5.2 Duct penetration.
Ducts in the garage and ducts penetrating the walls or ceilings separating the dwelling from the garage shall be constructed of a minimum No. 26 gage (0.48 mm) sheet steel or other approved material and shall not have openings into the garage.
 
Could stretch this...

G2407.12 (304.12) Protection from fumes and gases.
Where corrosive or flammable process fumes or gases, other
than products of combustion, are present, means for the disposal
of such fumes or gases shall be provided. Such fumes or
gases include carbon monoxide, hydrogen sulfide, ammonia,
chlorine and halogenated hydrocarbons.
In barbershops, beauty shops and other facilities where
chemicals that generate corrosive or flammable products,
such as aerosol sprays, are routinely used, nondirect venttype
appliances shall be located in a mechanical room separated
or partitioned off from other areas with provisions for
combustion air and dilution air from the outdoors. Directvent
appliances shall be installed in accordance with the
appliance manufacturer’s instructions.
 
mtlogcabin said:
I do not see a code section that would prohibit the garage to be used to draw the combustion air from as long as the appliance is located within that garage
Click to expand...
Some manufacturers require that the vent and combustion air terminate in the same atmospheric pressure zone. When they first came on the market all manufacturers had that requirement. The installation instructions had drawings that explained what they meant by "same atmospheric pressure zone". I had that requirement not more than six months ago. There was no drawing so I had to explain that the two had to terinate on the same roof plane.
 
Last edited:
OP, is this what you are referring to? If so, this is about the only way we see it here in the Pacific NW. This would be a typical installation. Sometimes the HVAC unit is located at the rear wall of the garage, over a work bench or other area. Just make sure it is protected from impact by a bollard or is high enough to not be subject to impact.

1604332744748.png
(Stock google image)
 
I don't like it but the IRC commentary actually has a drawing in it with the furnace in the garage, showing that the duct all needs to be 26 gage minimum. Fortunately here with 90+ efficient furnaces we can fall back on they can't be in the garage to prevent the condensate and secondary heat exchanger from freezing.

As far as not being able to take combustion air from a garage, if you can't do that you can't put a hot dawg garage heater in the garage!
 
Could this be along the same lines of not allowing a sleeping room directly off a garage? If it is the CO poisoning in that scenario, then the same could be true of the direct vent unless the direct vent is hard piped to an exterior wall.
 
As long as you are not taking the return air from the garage the CO argument is unlikely...The combustion air is not discharged into the conditioned air....
 
The ductwork is probably airtight if it is sealed as required by code. My main concern would be access panels for filters, etc. IRC R315 requires CO detectors in houses which have fuel-fired appliances or an attached garage with a door to the house.
 
Follow up. I am torn on this and have never really settled it it my head. If a direct vent system is in a garage and all of the ducts supply the house in a code complaint fashion with 26g duct, without openings from the supply or return system in the garage we are good. BUT, cut a new duct into the supply plenum, that only feeds the garage. Are we still good? Now, enclose the whole system behind a partition and non-rated door. How 'bout now? What if the partition had a 20-min. door?

My thoughts are that any opening in the system from the garage breaches the system and would allow smoke and gases to circulate throughout the house. And, if it was behind a 20-min door and gyp wall to me it would no longer be in the garage, being provided with the same separation as the rest of the house. But the non-rated door, gives me heartburn. The gas codes say that for purposes of combustion air the rooms that are not part of the living space are considered in the garage. No such language for duct openings.
 
603.7 Rigid duct penetrations.
Duct system penetrations of walls, floors, ceilings and roofs and air transfer openings in such building components shall be protected as required by Section 607. Ducts in a private garage that penetrate a wall or ceiling that separates a dwelling from a private garage shall be continuous, shall be constructed of sheet steel having a thickness of not less than 0.0187 inch (0.4712 mm) (No. 26 gage) and shall not have openings into the garage. Fire and smoke dampers are not required in such ducts passing through the wall or ceiling separating a dwelling from a private garage except where required by Chapter 7 of the International Building Code.
 
Yes, but what is considered when determining "in the garage"? Its pretty clear that anything behind the 1/2" gyp wall and 20-min door is not "in the garage". My question is when it is in a closet in the garage, and that closet does not have the same level of separation as the house.
 
The intent is to maintain the separation between the dwelling and the garage, so everything on the garage side of that separation wall would have to be minimum 26 gage with no openings. A closet walled off on the garage side of the separation wall is still in the garage, so no openings.
 
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