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I live in a fairly warm and dry environment and due to HOA restrictions am unable to place a window A/C unit, outdoor unit, or a system on the roof. I understand that A/C shouldn't go in attics due to the heat.

However, I was wondering if an A/C unit could go into a garage that had an exhaust / intake fan cut into the side of the wall. This air flow could even be directed into a self contained box which the condenser portion is in.

Is such an installation feasible? If so, how do I calculate what amount of CFMs the fans will need to push to sufficiently cool the a/c unit?

Is it correct that a 1 ton A/C system passes about 400CFM per minute? If my garage is 5000 Cubic feet (25x25x8), then it would take about 12minutes to cycle through all the air. Thus I would need exhaust and intake fans that can push 400CFM?

Thanks.

  • Is this a single-family dwelling, or a condominium of some sort? Have you asked the HOA how they're expecting air conditioning to be provisioned, or if they are trying to forbid A/C altogether? – ThreePhaseEel Aug 7 '18 at 2:39
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    Also, 400CFM/ton is the indoor blower airflow rate, not the condenser fan airflow rate... – ThreePhaseEel Aug 7 '18 at 2:40
  • It is a condominium constructed in townhome fashion, with separate entrance. The HOA allows A/C for units that have patios or carports since those count as restricted area, neither of which I have. I simply have a garage. A/C is allowed at other units that have the features mentioned above, so they do not prohibit A/C. An old board also grandfathered in a unit that has a condenser in the common area but no longer allows this. – Arctic Aug 7 '18 at 2:43
  • How does one find the consender fan airflow rate? – Arctic Aug 7 '18 at 2:51
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    Do you have a neighbor within piping distance who has a "restricted space"? – Harper - Reinstate Monica Aug 7 '18 at 3:34
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According to this webpage, "the answer is an emphatic NO." The page goes on to say this is because the total volume of air in an enclosed space is insufficient, including a garage with an open door as the air isn't likely to circulate enough.

From this we can deduce:

  • There is nothing in most codes preventing you from doing it.
  • If you are planning to do this, you'll need to pay very close attention to where your intake and exhaust air are coming from.
  • If you don't design your ventilation perfectly, your system may not be able to cool your space
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I did it 10 years ago and it has worked well. It is only a room size unit but will work with larger sizes. It is not visible from outside except the 1/4" plastic drain hose sticking out of the garage wall. It is mounted close to the ceiling. I made a plenum with a 1/4 " fiberboard with a white plastic finish , so from in the garage you see a white box near the ceiling . The condenser draws air from in the garage, blows through the coils into the garage attic and eave. In the living space there is a normal room AC unit face ( projects from the wall about an inch.) except it is mounted a few inches below the ceiling. It is a window unit , essentially the 2 X 4 stud wall is the "window", I added no extra brackets. It has a remote control so being so high is no problem; actually gives excellent circulation . The only problem is that I forget to clean the air filters.

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I would say it would be simple if allowed to install 2 louvered vents on the outside of the home in the garrage wall. Encase the system in a box with the vents use a powered fan either temp controlled or if the unit has an aux contact on the motor contactor that can turn on the fan on. This would work you just need to move the air so the unit can heat or cool.

  • Why wouldn't the fan in the condensing unit be all that is needed to move the air? In the simplest setup the condensing unit is inside the garage and there is a short duct which butts to and seals against the case around the fan. The air inside the garage is drawn into the intake of the condensing unit and replaced by air moving into the garage through a vent elsewhere in the wall of the garage. – Jim Stewart Aug 8 '18 at 21:04
  • The condenser is supposed to be outside without some air forced through the box it will run very hot. – Ed Beal Aug 9 '18 at 18:56
  • I don't see the need for the condenser to be in a box--well, it would reduce the noise. But for the first try I would just have it on a bracket on the wall of the garage. I have not examined these minisplit units. Where are the input vents in the case for the cooling air? In some pictures there are no vents on one end so that would leave the back (which would be facing into the garage) and the other end (also facing into garage but close to the wall). The opening for air into the garage could be on the same wall say 5 ft to 10 ft away, the further the better. – Jim Stewart Aug 9 '18 at 21:21
  • Jim I have installed a few of these they require full flow air, the op wanted to put the unit in a box this would require forced venting, if the garage is closed as most are natural venting of even a small unit would have the garrage extremely hot in a very short time and the unit would not be able to cool. Of all the systems I have installed one entire side is the condensing coil – Ed Beal Aug 9 '18 at 21:34
  • I see pictures of these installed in Asia on the sides of multistory buildings and I have wondered how close the back side is to the building. In the US I have seen these units on the sides of high end mobile homes and on the sides of public school "portable" classrooms and wondered if those are special versions of the condensing unit or just the general version with a special installation kit. – Jim Stewart Aug 9 '18 at 22:29
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If you are anticipating making an opening in the wall of the garage so that the hot exhaust from the condensing unit would have an unobstructed path to the outside, then in theory your idea to have the condensing unit inside the garage could work.

You would need some sort of seal to prevent hot air from the condensing unit from flowing back into the garage. You could mount the condensing unit on brackets on the wall of the garage. The opening could have a decorative grill on it that would hide the fan.

Normally the fan side of the condensing unit faces outward from an exterior wall so this might not work in practice because having that face of the condensing unit close to the inside of the wall of the garage might impede access to diagnostic ports of the unit.

The input air to the condensing unit would be from the inside the garage and there would have to have an opening for air to be admitted to the garage to replace that being pumped out.

You would still have to get permission from the HOA board to do this and they might find grounds to withhold approval. Would the HOA allow you to cut an opening in the wall of the garage?

Finally, the noise of the condensing unit would be trapped in the garage and could be very disturbing. The condensing unit is meant to be outside where the sound disperses. But modern condensing units make much less noise than formerly.

*EDIT** You could get creative with ducting to get the hot air to the outside of the garage. The opening on the outside might be a rectangle 6 ft long by 0.5 ft high on the wall where it would not blow on passersby.

  • Yes, this is along the lines of what I was thinking. I will need to propose cutting the garage wall for this set-up and wanted to get my information before proceeding. I suspect this may be an easier approval than modifying the common area. With regards to the ducting, I was thinking of having the hot air exhaust at about 7 feet high, higher than anyone would walk past. – Arctic Aug 7 '18 at 20:05
  • Do you happen to know how to calculate how much air flow the condenser will need to stay cool and replace the air? – Arctic Aug 7 '18 at 20:15
  • No, I meant to suggest that it would be high on the wall, but my wording was confusing. – Jim Stewart Aug 8 '18 at 0:15

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