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Amana PTAC Units: The DigiSmart System -- Real Energy Reduction?

PTACs are typically installed in hospitality industry environments: hotels, hospitals, managed care facilities, etc. And while the owner of a building full of ptacs is very concerned with energy efficiency, the typical guest usually isn't too concerned about saving energy. You know the drill. It's a hot summer day and you arrive in your hotel room and just before you throw yourself on the bed you crank up the a/c. Then later, you get hungry so you head out to the nearest restaurant. But did you remember to turn off the PTAC before you left?

Amana's DigiSmart System
The DigiSmart system links all of the ptacs in a building to a central computer. From there all of the ptacs can be controlled. Each ptac can be programmed to only heat or cool up to a certain temperature setting. These limits save energy and extend the life of the unit. Rooms can also be pre-cooled or pre-heated via the front desk before the guest arrives. Occupancy sensors in the room can determine if the guests are in the room or not.

Wireless connections...
All Amana ptac units can "talk" to the central computer wirelessly if the ptac is equipped with the DigiSmart wireless antenna. The antenna simply snaps in to the inside of the unit. Once installed, the ptac can then communicate with other wireless devices in the room, like wireless thermostats and occupancy sensors; and can also communicate with the central computer in another part of the building.

How does it reduce energy usage?
Amana claims a 35% reduction in energy usage when the DigiSmart system is in use. The bulk of the energy savings is in the occupancy sensor: the unit can shut down, or "set-back" the temperature at pre-determined intervals when no one is in the room. This is really where the rubber meets the road. The ability to cut energy consumption of selected ptac units while guests are not in the room is a welcome advance.

Increased complexity?
Amana claims that 45,000 rooms have wireless installed since 2005, and an additional 120,000 wireless devices have been deployed. These numbers are intended to reassure the ptac purchaser that this system is ready for primetime. Typical HVAC engineers on the other hand fear increased complexity. It's difficult enough keeping several hundred ptacs operating smoothly without adding wireless networking and computer software to the picture. Suddenly it isn't just electrical components, but software bugs, etc., that must be considered--another unwelcome link in the failure chain.

The bottom line...
The DigiSmart system, especially the occupancy sensor's ability to shut down ptacs in unoccupied rooms is a winner. But move forward cautiously. Maybe start with one or two units, and if they work well for a year, then go from there.

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