Eliminating Outdoor Air Recirculation

17th September 2020

Air recirculation can have a detrimental impact on the lifespan of your PTAC. Where outdoor air recirculation occurs the unit will need to work harder when operating, therefore increasing energy usage and in turn putting additional strain on components.

What Is Outdoor Air Recirculation?

Normal operation of a PTAC unit is to draw cool, fresh air into the outdoor side of the unit which gets pushed through the condensing coil. The refrigerant in the condensing coil transfers its heat to the air passing through it, turning the refrigerant back into a liquid state. This hot air is then expelled to the outdoor world where the air temperature is normalized by blending with the outdoor air.

Outdoor air recirculation is when air gets trapped in the wall sleeve instead of dissipating to the outdoor air. The trapped air then gets re-used by the condensing coil, causing the air temperatures to further increase. As this continues, the temperature of the air continuously circulates through the condenser until the point of the PTAC shutting itself down due to excessive condensing temperatures/pressures or failing.

Why Causes Outdoor Air Recirculation To Occur?

The PTAC must be pushed all the way back in the wall sleeve, so the seals at each end of the condensing coil make contact with the outdoor louver. This ensures that the air cannot get trapped within the sleeve and circulated through the condensing coil for a second time, third time and more.

The main reasons recirculation can occur is due to extended wall sleeves or obstructions outside the outdoor louver. The Applied Comfort PTAC units are designed to fit with the standard wall sleeve depth as determined by the original manufacturer.

What Damage Can Recirculation Cause?

Recirculation can greatly decrease the life of a PTAC unit as well as causing an unnecessary increase in energy consumption during operation. Recirculation causes the air passing through the coil to increase consistently, getting to extremely hot temperatures. The main concern with recirculation is the additional strain added to the sealed system due to the high pressures the compressor must work against to provide the cooling effect. This also steals cooling capacity and will seem like the unit is not cooling as effectively. Applied Comfort designs PTAC (Packaged terminal air conditioner) units with efficiency in mind, but if recirculation occurs then you will experience greatly reduced energy efficiency ratios.

A second issue which could occur is a failure with the fan blades. Like most other PTAC manufacturers, our fan blades are made of plastic with reinforcement in the blades to increase their life. If the air passing through the fan blades gets extremely hot from recirculated air, the integrity of the plastic may become weak and brittle, causing it to fail.

How Do You Stop Recirculation?

The easiest step is to look immediately outside of the outdoor louver. If there are obstructions, they should be removed to allow proper ventilation of the PTAC. If the sleeve is extended beyond standard depth, baffles need to be field fabricated and installed in the wall sleeve to ensure that air exiting the condenser coil is channelled and sealed right up against the rear louvers.