Last summer, the electric bill was especially high (even compared to the previous hot summer). The facility manager hired an HVAC firm to thoroughly examine the system. The firm found and repaired many problems, including ductwork leaks. But this firm normally subcontracts the electrical work because it doesn’t have an electrical engineer or licensed electrician on staff. The firm’s mechanical engineer overseeing the project said the problems would account for some of the increase, but there “has to be something wrong electrically.”
To find this “money leak,” where should you look?
As with many electrical tests, anomalies may not show up at partial load. Chillers are especially heavy loads, so conduct testing with all chillers running.
Measure phase-to-phase voltages. Look not just for low voltage, but also for voltage imbalance. This greatly reduces motor efficiency as well as motor life. The maximum deviation between phases should be 2%. Wherever you have more than 2%, look there first for single-phase loads and rebalance them. Loads at 1% or higher may also be worth rebalancing. Lighting is a common culprit.
Calculate power factor. If it’s severe, either put the motors on power-factor corrected drives or add PF capacitors at the motors. Do not confuse these with the starting capacitors (different purpose).
Test alignment and vibration. These problems are energy hogs but easy to fix.
Send a motor or two out for complete testing. A motor shop may find problems that decrease the efficiency of the motor. Often, they can repair these.
