PTAC Units: How They Work and How They are Installed
Packaged terminal air conditioner, or PTACs are self-contained heating and air conditioning systems that are commonly used in apartments, hotels, schools, offices, nursing homes, and hospitals. Most of them are designed to go through a masonry wall and have vents and heat sinks indoors and outdoors. Most of them are 42 inches wide, though they do come in a few other sizes.
Typically, PTACs are used for heating or cooling a single space using electricity, with resistive heating. There are cooling-only PTACs, plus PTACs with natural gas heating. In terms of heating or cooling capacity, values generally go from 5000 BTU/hr to 20,000 BTU/hr. With PTAC units, there is no drain piping necessary. The condensate water pulled from the air by the evaporator is directed by the condenser fan to the surface of the condenser coil, where it evaporates. Installation requires, in addition to the unit itself, a metal sleeve, louver, and heating coil. The room it's used in should be one that can be closed off from the rest of the building.
Installation is fairly straightforward, assuming that there is already a properly-sized hole cut in the wall. Here are a few of the main points of installation: For the condensate water to drain correctly, the sleeve has to be level from left to right, and it needs to pitch slightly downward from the indoor to the outdoor side. For direction of air flow for proper operation, an outside grill has to be installed. This also protects the outdoor coil. The grill must be in place before installation of the chassis.
Installing the chassis involves removing the cabinet front from the chassis and inserting the chassis into the sleeve until the flanges on the chassis meet the front edge of the wall sleeve.
Once you secure the chassis to the wall sleeve and ensure a proper seal between the two, you can put the cabinet front back on. If it's a 265-volt unit, it has to be hard wired rather than using cord connection to a wall socket.
Once the unit is installed, check both the inside and outside grills for anything that could obstruct air flow. This includes curtains or furniture, trees, and shrubbery. Obstructed air flow can cause the air conditioner compressor to cycle rapidly, possibly damaging the compressor.
Newer PTAC systems sometimes use a desiccant wheel to improve energy efficiency and promote better indoor air quality. When these have been tested against traditional PTAC systems, with weather conditions factored in, cost savings up to 35% have been produced. There is also a reduction in thermal cooling power by up to 52%. While desiccant systems are generally more expensive up front, a return on investment will take place in approximately 5 years.