Resolving Electrical Issues After Energy‑Efficiency Upgrades

Cutting energy costs with variable‑frequency drives (VFDs) and lighting retrofits is common, but the upgrades can introduce new electrical challenges.

Understanding that the energy‑efficient devices themselves can be the root cause is the first step. Modern VFDs, electronic ballasts, and other high‑efficiency electronics perform flawlessly on contemporary distribution systems, yet older plants may struggle with the non‑linear loads they create.

Electrical problems that arise after an energy‑upgrade typically fall into three categories:

• Application
• Installation (including startup)
• Maintenance

VFD Mismatches

VFDs are the most popular energy‑saving device for centrifugal pumps, fans, and blowers. By varying motor speed, they maintain flow and temperature more efficiently than throttling valves. However, problems arise when:

• The VFD is not properly sized or selected.
• The drive and motor installation did not anticipate a VFD.
• Parameters were mis‑configured at startup.
• Harmonic currents were not considered in design or maintenance.

Non‑Linear Loads and Harmonics

VFDs, ballasts, and many control systems are non‑linear loads. They draw current in pulses, creating notches in the sine wave and generating harmonic currents that feed back into the distribution system at multiples of 60 Hz. The third harmonic (180 Hz) can overheat neutrals and transformers; the fifth harmonic (300 Hz) can cause motor overheating, noise, and inefficiency.

Bottom line: Every electronic device introduces harmonics and voltage distortion.

Other non‑linear loads added during upgrades—computers, PLCs, building automation components—also contribute. Always use a true‑RMS meter when measuring these loads; see Fluke’s true‑RMS guide.

Sensitive Controls

Control systems are often sensitive to power quality. The very equipment installed to save energy can, paradoxically, cause inefficiencies and hidden maintenance costs.

Fortunately, many issues are resolved with quick checks and standard troubleshooting.

VFD Troubleshooting Examples

Typical symptoms: poor motor speed control or nuisance trips. Likely culprits include:

• Three‑phase voltage unbalance.
• Harmonics flowing back into the distribution system.

For instance, a chiller with a VFD may mis‑control temperature if the harmonic‑induced voltage distortion affects PLCs and temperature controllers.

Incorrect tachometer wiring can also mislead the VFD. Solution: Use shielded cables for low‑voltage signals and ground only one end. Keep these cables away from power conductors to avoid electromagnetic interference.

Installation Checks

Verify that the drive, motor, and accessories were correctly selected. Walk the installation to confirm proper cable types, environmental suitability, enclosure cleanliness, and ventilation.

Drive Parameter Checks

Review the programmed parameters. They should match the motor nameplate and be set for the intended operation (e.g., variable torque for pumps). Mis‑settings or accidental resets often cause performance issues.

Quick Measurement Checks

Measure VFD input voltage with a true‑RMS multimeter to confirm voltage unbalance is within the manufacturer’s specification. Use a power‑quality clamp meter or analyzer to assess harmonic levels at the VFD inlet and at the feeder serving other loads.

Solution: If unbalance is the issue, redistribute single‑phase loads. If harmonics dominate, consult the drive manufacturer or a harmonic‑filter supplier to select a properly tuned filter.

Lighting Retrofit Issues

Lighting upgrades often lead to flicker, non‑operation, or nuisance breaker trips. These symptoms usually stem from harmonics. An IEEE study found that fluorescent lighting comprising 25% or more of a facility’s load can trigger significant harmonic problems.

Electronic ballasts can overload shared neutrals in older plants, causing overheating of neutrals, panelboards, and transformers. Tip: Add dedicated neutral conductors per phase as needed and use infrared thermography to detect early overheating.

Dimmer Controls

Dimming T‑8 lamps with electronic ballasts or switching to CFLs saves energy. Matching the dimmer type to the ballast and lamp is essential; mismatches can damage components.

Zero‑to‑10 V control wiring should be kept short and away from power conductors to prevent erratic lighting control.

Automated lighting systems that start or stop erratically after retrofit should be checked for sensor operation. Many photo‑sensors allow deadband adjustments to fine‑tune the on/off timing.

Overheating Motors

Switching lighting banks for energy savings can create phase unbalances that damage three‑phase motors. Tip: Monitor motor voltage during all plant operations; keep voltage unbalance below 1% and avoid exceeding 5% to prevent damage.

Conclusion

A skilled, well‑equipped maintenance team is the best defense against post‑upgrade issues. Understanding the energy‑saving system, reviewing design, installation, and startup procedures, and applying systematic troubleshooting with the right tools will preserve savings and extend equipment life.

Refer to Figure 1 for common post‑upgrade problems and a quick‑check guide.

For more information, visit the Fluke Corporation website at www.fluke.com.

Figure 1. Typical problems reported after energy upgrades and quick checks to resolve them.

Figure 2. Preserve your energy upgrade savings by troubleshooting and repairing issues in-house.