There are over 5.6 million commercial buildings in the U.S., comprising 87 billion square feet of floor space. Air moving, heating, and cooling systems account for the largest amount of electricity used in these buildings. The industry has made intensive efforts to improve the efficiency and productivity of motors and driven equipment. However, the belt drive connecting these components is critical to achieving maximum efficiencies. Two simple solutions for improved HVAC system performance are the use of energy efficient belts and proper drive installation.
The major belt energy loss during power transmission is caused by bending hysteresis and sliding friction. Belt hysteresis occurs as the belt rotates around the drive and undergoes cycles of both tension and flexing. These repetitive cycles cause energy loss by the production of heat. A raw edge cogged belt or a synchronous belt minimizes these factors and will result in increased energy efficiencies.
According to the Department of Energy (DOE), wrapped belts operate on average at a 93 percent efficiency rate, raw edge cog-belts operate at 95 percent, and synchronous belts at 98 percent.
RAW EDGE COG-BELTS
Raw edge cog-belts flex more easily around the sheave, generating less heat, which contributes to longer belt life. Raw edge side walls produce a higher coefficient of friction which keeps a tighter grip on the sheave and minimizes slippage — a key point of efficiency loss. Simply replacing old belts on existing drives can result in measureable energy savings.
When designing a new drive or replacing worn sheaves on an existing drive, consider a synchronous drive system. Synchronous belts operate on a “teeth in mesh” principle. The positive engagement between the belt and sprocket eliminates slippage and speed loss common to v-belts. Power transfer from the motor to the driven unit is 98 percent efficient.
OTHER DRIVE FACTORS
Correcting belt drive installation factors such as improper tension, poor alignment, and worn sheaves will also increase belt life, efficiency, and performance. Too little tension will result in slippage, causing rapid belt and sheave wear. Too much tension will result in excessive stress on belts, bearings, and shafts.
In addition to proper belt tensioning, care should be exercised regarding sheave groove wear and alignment. New belts should never be installed without a thorough inspection of the sheaves. Particular attention should be given to wobbling sheaves, a shiny groove bottom, and worn groove sidewalls. The cost of replacing a worn sheave can be recovered in longer belt life, reduced maintenance, and reduced downtime.
Timken Belts offers a free web app to calculate energy savings. PowerMiser™ (powermiser.driveengineer.com) is a powerful, but simple desktop and mobile-friendly app. Instantly see estimated annual energy costs, savings, and payback on drives upgraded with Carlisle® belts by Timken.
Using the right belt on a properly maintained HVAC drive will reduce downtime and maximize efficiency.