Safety support requirements for air conditioners:
Tthis article explains and illustrates the need for safe, secure supports beneath window, through wall, and wall-mounted air conditioners and heat pumps.
Not only can an unsupported air conditioner fall from the building, risking injuring or killing someone below, but there is also a risk of simply dropping the entire unit out the window or down the wall during installation or removal - an annual project for some window and through-wall units.
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Safety Warnings About the Need for Proper Support for Wall-Mounted Exterior Air Conditioner / Heat Pump Compressor/Condenser Units or Window Air Conditioner Units
Watch out: inadequately-supported outdoor window air conditioners or inadequately-supported wall-mounted outdoor compressor/condenser units (referred to as the "inverter unit" in some literature) pose a potentially fatal hazard should one of these units fall from the building onto someone below.
Our through wall room air conditioner shown in our photo at left looks as if it is supported by the roof downspout - perhaps not the most reliable installation.
In 2012 the New York Times reported that that city has increased enforcement of proper exterior supports for air conditioners at public housing after air conditioning units fell out of two windows in a housing project on the upper East Side of New York City.
While those air conditioner falls, one onto a playground near children, luckily didn't hurt anyone a falling A/C unit (window air conditioners) or compressor/condenser unit (split system air conditioners with an outside wall-mounted compressor unit) are very dangerous.
The Times article noted that indeed, in 1988 a pedestrian was killed when an air conditioner fell from the seventh floor of a building in New York.
The window air conditioner unit shown at below left actually fell out of this window during installation (I was there - Ed.). It bounced down the lower roof, rolled over a few times, and fell another eight feet to the ground. Luckily no one was below at the time. Remarkably the unit survived and still worked after it was reinstalled in the window opening - you can see the smashed condensing coil fins on the rear of the unit - damage that occurred during the unit's fall to the ground below.
A through-wall air conditioner is supported by the friction of the air conditioner case against the wood frame of the opening.
At left you can see how a through-wall air conditioner looks from inside the building. If no safety bracket is installed on the exterior wall beneath this unit, and considering that most of the weight of the air conditioner is cantilevered outside the building (photos above), one can surmise that it is principally the friction between the 2x4 opening framed in the wall and the air conditioner's steel case that is holding this unit from falling out of the wall and to the ground below.
At below left the accordion-type expanding window-mounted air conditioner opening bracket upper edge, braced against the lower edge of the window sash, is the principal connection that keeps this unit from falling out of the window opening. Simply raising the window sash can result in the whole assembly falling off of the building.
Short screws, often sheet metal screws secure the expanding bracket and window-filler on the sides of the air conditioner to the window sash bottom edge near the left and right ends of the upper sliding metal bracket.
And two additional screws secure the accordion expanding fillers to the trim on either side of the window frame. These little screws are not structural and do not provide much additional security against losing the whole air conditioner out the window. The outside view of this type of window air conditionr makes clear that it has no other support.
Examples of Supported Window or Wall-Mounted Air Conditioner or Split System Compressors
Our photos below illustrates different types of exterior, wall-mounted split system air conditioner compressor/condenser units high on an apartment building in Buenos Aires. Our second photo of outdoor wall-mounted A/C compressor/condenser units (below right) illustrates the use of supporting brackets. A similar bracket is required beneath most window air conditioner units.
Examples of Support Brackets for Window Air Conditioners & Through-Wall Air Conditioners
The through-wall air conditioner at below right is supported by an owner-built plywood shelf and diagonal wood bracket - better than nothing, but a design exposed to risk of eventual collapse from rot and water damage. Steel brackets sold for supporting window or through-wall 9or wall-mounted equipment are in our OPINION a safer alternative. At below left, the Friedrich brand air conditioner is indeed supported by metal brackets (red arrows).
Below we illustrate an add-on wood-framed platform and brace below a window air conditioner at a resort in Olivera, New York. We notice that the air conditioer iteslf is quite tipped - perhaps someone noticed that it was about to fall out of the window opening. The adequacy of the wood platform and angled bracket and block as an air conditioner support depends on details we cannot see here: what was the type, size, and placement of the structural fasteners that secure the wood support platform for this air conditioner to the building?
Use exterior-use rated structural screws of adequate length to connect the supporting bracket to the wood frame of the structure. Don't just tack the wood brackets to the building siding or the whole assembly may still fall.
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