Ask the Engineer: What Are the Issues When Putting in Ductless Air-Conditioners | Co-op & Rental Boards | Habitat Journal

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THE ENGINEERS ANSWER: Ductless air-conditioners encompass an air-cooled condenser unit, sometimes put in outdoors the constructing, and an inside evaporator or air handler unit that cools the inside area. As a substitute of utilizing a packaged system of ducted air, the ductless air-conditioning system makes use of refrigerant-filled tubing that connects the outside and inside items.

As a result of the condenser and evaporator are separate items, ductless air-conditioners are generally known as cut up methods. In a standard cut up air-conditioning system, one condenser unit offers cooling for only one inside unit. In a multi-split system, one exterior unit powers a number of inside items that may be individually managed for a selected room or area. Some methods could be configured to offer each cooling and heating.

Cut up air-conditioning methods have develop into more and more common in residential buildings due to their low-profile design and ease of set up. Nevertheless, the location of out of doors items and the refrigerant tubing that connects the outside and inside items can pose potential issues for boards as a result of the tubing can intrude on the constructing’s frequent areas.

Roof Set up

Roofs are a typical location for putting in the outside condenser items as a result of the items don’t take up a lot area and it (normally) locations them out of the best way and out of sight. Lighter items are sometimes positioned on pads so that they don’t harm the roofing membrane, whereas bigger items might require metal dunnage. Another choice when roof area is restricted is to mount the unit on a bulkhead wall.

The principle concern for boards is the trail of the refrigerant tubing because it runs from the rooftop unit to the air handler/evaporator unit within the residence. For aesthetic causes, most boards won’t permit the tubing to run alongside the skin of street-facing façades. Equally, buildings positioned in designated New York Metropolis historic districts are prohibited by the Landmarks Preservation Fee from working tubing that’s seen from the road. As well as, boards will generally declare stairwells, hallways, lobbies, and different frequent areas off limits for the tubing.

Many boards will, nevertheless, give residents the choice of working the tubing on a aspect or rear façade, however they could cost the resident to be used of roof area for placement of the condenser. Another choice is working the tubing by a chase or conduit if one is offered.

For residences straight beneath the roof, it could be doable to run the refrigerant tubing by the roof itself. In such instances, the penetrations must be waterproofed and firestopped. However some boards might object to permitting penetrations by the roof out of worry that leakage issues may end result.

One other issue to contemplate is that for optimum efficiency, the outside unit and indoor unit should be positioned inside a sure distance of one another, relying on the kind of cut up system. For residences far beneath the roof, that distance must be considered.

Given your residence’s location two tales beneath the roof, working the tubing alongside a rear or aspect façade could also be the best choice for you. However once more, it’s going to require your board’s approval and can also require paying a rental price to your condominium to be used of the roof. Remember the fact that cut up air-conditioning methods run on electrical energy, so you’d additionally must run wiring out of your residence to the skin unit.

Inside Models

There are a variety of choices in your indoor evaporator/air-handler items. The within items, that are sometimes wall- or ceiling-mounted, are available in varied designs and kinds appropriate for the actual room being cooled. Models could be recessed to scale back their profile, and a few residents conceal the items with custom-made millwork. Other than mounting, the items require a plumbing connection for condensate drainage. Some items could be piped into an current oblique drain, corresponding to one utilized by a washer, for instance. Different setups require a devoted funnel drain fitted with a tool generally known as a entice primer to redirect the condensate.


Upkeep of cut up air-conditioners is much like most cooling methods. Sometimes, upkeep includes cleansing the filter and condenser coils, reviewing the system cost, checking fan operation, repairing or changing tubing and insulation, and checking electrical connections.

Prior to installing a cut up air-conditioning system, your board would require a plan evaluation to ensure the set up doesn’t adversely have an effect on the constructing as an entire, and it’ll determine if it’s going to require you to pay a month-to-month rental cost for placement of the outside condensers. The set up can even require {that a} licensed engineer file plans with the New York Metropolis Division of Buildings.

Cut up air-conditioning methods are a handy possibility for cooling your residence. Simply make sure you work along with your board to handle any set up considerations and keep away from potential issues.


Stephen A. Varone, AIA, & Peter E. Varsalona, PE, are principals in RAND Engineering & Structure.

Photograph credit score: Sashkin/Shutterstock


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