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Old 05-07-2012, 10:12 AM   #1
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I live in Missouri where it is very hot and humid in the summer. I have found that my central AC unit runs constantly to maintain 74 degrees in the house when the outside temp is around 88-90. I noticed there is an air duct going to my garage. Is it possible the air vent to the garage is reducing the AC units ability to lower the house temperature?


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Old 05-07-2012, 12:46 PM   #2
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It's a possible contribution, especially if it was an additional duct run after the fact.

What's your supply air temperature at the nearest to the unit's supply register and what's the return air temperature at the return air grill?


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Old 05-07-2012, 04:07 PM   #3
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Ideally, you should extend the vent outside. For best efficiency make sure your heat/cooling coils are clean and not crushed for maximum airflow and/or heat transfer. This should be done at least once a year. If there is a filter somewhere make sure it gets cleaned/replaced as needed.
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Old 05-07-2012, 05:04 PM   #4
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Seal off the vent to the garage. it is a code violation, an a risk to your health and life.
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Old 05-07-2012, 05:38 PM   #5
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As already stated get rid of the air vent in the garage. That's a fine way for high levels of carbon monoxide to get inside the house,hence the reason for a code violation.

One vent is not going to make a difference in your cooling though. Is the furnace in the basement or attic? A few duct joints leaking in an attic can HUGE impact on the cooling ability. If the ducts are sealed,indoor and outdoor coils clean and the filter clean then it probably is low on refrigerant due to a leak. Check the easy stuff,including insulation in the attic, and if that gets you nowhere it's time to call a pro.
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Doc Holliday (05-07-2012)
Old 05-07-2012, 05:44 PM   #6
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Sometimes AC ducts are run to garages to keep any rooms above them heated in winter. Sometimes they are run to keep the garage cool.

Either way they are a violation (as beenthere notes), because they provide a connection between a garage and its car exhaust (and any other fumes in the garage) to the main living space.

You might want to go up in the attic and cap off that vent close to the air handler, to eliminate most of the run to the garage, and make sure it's well sealed.

Then you should remove the vent from the garage wall and drywall the hole, tape it, and seal it closed with drywall compound. Your garage should be totally sealed off from the house, meaning your drywall should be intact and sealed up with two coats of joint compound.


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