The idea of “divide and conquer” may have originally been created for ancient warfare, but that concept can also apply to your approach to energy efficiency. When you’re looking at the heating and cooling needs of your building, one of the best energy saving measures is to divide your building into as many zones as possible and conquer your energy costs by installing the right technology. This is especially true for buildings that have many individual rooms — like hotels, motels, assisted living facilities, hospitals and apartment buildings – which may not all be occupied at the same time or may be occupied by people with very different comfort levels. Using a technology that keeps each room at just the right temperature for its occupants means that you’re saving energy by not having to heat or cool the entire building to that level.
And that brings us to PTAC. PTAC is short for Packaged Terminal Air Conditioner, a self-contained, wall-mounted air conditioning and heating unit that offers greater energy efficiency and energy cost savings than traditional central air conditioning and heating. One of PTAC’s biggest advantages is that it doesn’t rely on ductwork to bring warm or cool air into the rooms where it’s needed, eliminating the cost of maintaining the ductwork and saving energy that would normally be lost as air passes through the ductwork. Instead, PTACs are designed to go through the walls they’re mounted on. This allows air that’s cooled by a refrigerant in the PTAC to be circulated inside the room while the heat and humidity that’s removed from the room can be vented outside.
Although PTACs are often thought of primarily for air conditioning – hence their name – they can be used for heating as well. PTACs will use either a heat pump or an electric heating element for this purpose, and the choice between them may come down to your local climate. Heat pumps will usually cost a little more upfront but are more energy efficient than electric heat, giving you greater energy savings in the long run. Heat pumps tend to work best in climates where winter temperatures don’t get too frigid, since they work by drawing out what heat there is in the outside air. If you’re in an area where you’re primarily using your PTAC for air conditioning, the heat pump is the better option. Electric heat is more powerful – and costlier over time – but is the better option for buildings in colder locations where the PTAC is the main source of heat in winter.
Choosing the PTAC unit with the right capacity for your needs is important for maximizing your energy savings as well as your comfort. Like most air conditioners, PTAC capacity is stated in British Thermal Units, or BTU, which is a measure of the amount of heat the air conditioner removes from the air. But there’s no one simple formula – like the square footage of the room – for calculating the right BTU capacity you’ll need for your PTAC. Instead, it’s important to consider several factors, like the age and condition of your building, the quality of its insulation, the amount of sunlight the room receives, the temperature range in your location and the comfort of the building’s occupants (for example, vacationers may enjoy a nice cold hotel room but senior citizens in an assisted living center like to keep their rooms warmer). Right-sizing your PTAC is important because a unit that’s too small will have to run more often than it should to reach the desired temperature, using more electricity and putting a greater strain on the equipment. On the other hand, a PTAC unit that’s too big will operate less efficiently because it will produce greater temperature swings that will cause it to cycle on and off more often than it should. The energy efficiency experts at Ecology Action can help you find the PTAC unit with exactly the right capacity for your specific needs.
Installing PTACs in buildings to control the temperature in individual rooms is part of an overall utility savings solution. But it takes one more step to make that solution complete: Integrating those PTACs with an energy management system, or EMS. The reason for combining a PTAC with an EMS is that PTACs alone are still subject to the whims of human behavior. For example, a hotel guest is likely to leave the air conditioning running when they leave the room to head for the pool, knowing that they’ll come back from their sunbathing to a nice cool room.
The most basic form of EMS for maximizing the energy efficiency of a PTAC unit is an occupancy sensor, which will signal the PTAC unit to reach the desired temperature when it detects that someone has entered the room and signal it to set the temperature back to a base level once the person in the room leaves. However, an occupancy sensor is not just a glorified on-off switch. The room’s temperature is kept at a base level while the room is unoccupied, allowing the PTAC to quickly bring it to the desired level moments after someone re-enters the room. The sensor can also be connected to the room’s lighting system to produce even more energy savings by coordinating both the room’s lighting and temperature levels with its occupancy.
There are more sophisticated sensors on the market which can not only tell if a room is occupied, but can determine how many people are actually in the room – and then adjust the PTAC’s thermostat accordingly to account for the amount of body heat. Other higher-end sensors will make thermostat adjustments based on the amount of time the room is unoccupied, setting the temperature back two degrees if the room is empty for half an hour; another two degrees if the room stays empty for a full hour; and four more degrees if two more hours go by without anyone entering the room. Perhaps the ultimate in EMSs is a web-based monitoring system that can wirelessly manage all the PTACs in a building through a single computer interface. The system provides detailed information on every PTAC unit, can control their settings remotely and can even notify the building owner if a unit needs maintenance.
By adding an EMS – and by installing PTACs with high energy efficiency ratios, or EERs – you may be eligible for government or utility rebate programs that recognize this equipment as qualifying energy efficiency measures. Ecology Action’s energy efficiency experts can advise you on the programs available and the equipment that may be eligible.
PTAC represents a smart, economical energy saving technology that has been installed in thousands of buildings across the country where individual temperature controls allow for greater personal comfort of guests and residents while controlling utility costs. Like the ancient armies who found a path to victory by splitting their enemies into smaller units, PTACs embody that concept of “divide and conquer”.