Power Quality for Sensitive Lab Gear: Brownouts, Harmonics, and Why Your Controller Resets Mid-Run

Process upsets get blamed on “operators” all the time: a batch that finishes late, a chiller that alarms overnight, a controller that mysteriously reboots, or a freezer that trips and takes hours to recover. In regulated environments, those events then cascade into deviations, root-cause investigations, and missed release windows.

The uncomfortable reality is that many of these issues aren’t training problems—they’re power quality lab equipment controller resets problems.

If you’ve ever heard “it ran fine at the seller” when commissioning used gear, power quality is one of the first suspects. A unit can be perfectly healthy mechanically, yet behave unpredictably when moved into a facility with overloaded panels, long feeder runs, noisy VFD loads, or marginal grounding.

This article breaks down what’s actually happening during brownouts, voltage sags, and harmonic distortion—and why sensitive lab gear responds with controller resets, alarm storms, compressor trips, and even inaccurate weighing. Then we’ll walk through a practical audit plan and commissioning checklist you can use to reduce downtime without major capex.

What “power quality” means in real operations (not in textbooks)

Most teams focus on “do we have the right voltage and an available outlet?” Power quality is about whether the power stays within tolerances over time and during real facility dynamics.

Common power quality events include:

• Voltage sags (dips): short reductions in RMS voltage, typically from faults, large motor starts, compressor inrush, or overloaded circuits. IEEE 1159 defines a sag as a drop to 0.1–0.9 per unit lasting from 0.5 cycles to 1 minute. (See Dranetz’s summary of IEEE 1159 definitions: https://www.dranetz.com/wp-content/uploads/2014/02/sags-and-swells.pdf)
• Brownouts / sustained undervoltage: longer periods of low voltage (utility-side or facility-side).
• Short interruptions: brief loss of voltage.
• Harmonics: waveform distortion (often from VFDs, switch-mode power supplies, and non-linear loads) that increases heating and can confuse sensitive electronics.
• Grounding and bonding issues: high impedance grounds, multiple ground references, neutral-ground problems, or shield terminations that inject noise into control circuits.

The key insight: you don’t need a full outage to lose a run. Many controllers and power supplies will reboot from a sag that lasts a fraction of a second.

Why controllers reset mid-run

Modern lab and manufacturing equipment is packed with:

• Microprocessor controllers
• Switching power supplies
• Data logging modules
• Network interfaces (Ethernet/RS-485)
• Alarms and remote monitoring

These subsystems often have limited ride-through capability. If input voltage drops below the power supply’s minimum for even tens to hundreds of milliseconds, the DC bus collapses and the controller reboots.

In power quality engineering, the ITIC curve is widely referenced to visualize how voltage magnitude and event duration affect equipment tolerance. Many classes of electronic equipment can misoperate during common sag depths and durations, especially if they lack adequate hold-up time. (Background: https://voltage-disturbance.com/voltage-quality/itic-curve/)

What this looks like on the floor:

• A rotary evaporator or vacuum oven controller restarts and loses the current recipe step.
• Your chiller comes back in a default mode (or in alarm).
• A freezer controller logs a power event and initiates protective logic.
• A SCADA node disconnects and backfills timestamps incorrectly.

The “operator” didn’t touch anything—your facility just had a 150–300 ms sag when a compressor started or a neighboring tenant’s load changed.

The failure modes you actually see: symptoms mapped to power quality

1) Alarm storms and “phantom” faults

Alarm storms often follow brief power disturbances:

• Multiple instruments simultaneously logging “power fail,” “communication error,” and “sensor fault.”
• Door alarms, high-temp alarms, and “motor overload” alarms appearing together.

The tell: alarms cluster around the same timestamp across unrelated equipment.

2) Compressor trips and long recovery times (especially in cold chain)

Compression systems are sensitive to undervoltage and power interruptions because compressors have high starting current (inrush), and many systems include protective relays.

A useful way to think about it:

• Undervoltage can increase current draw for certain loads, raise winding temperatures, and trigger protective trips.
• Repeated starts after brief interruptions can overheat components and shorten life.

For ultra-low temperature (ULT) freezers, even a short trip can mean a long climb back to setpoint—hours, not minutes—creating real product risk.

There are industry discussions noting that a voltage sag can push a ULT freezer into a compensation mode and add stress to the compressor if the low voltage persists. (Example discussion: https://www.stellarscientific.com/blog/is-your-ult-freezer-marching-to-a-silent-death-a-voltage-alarm-would-have-helped/)

3) Inaccurate weighing and intermittent checkweigher rejects

High-accuracy weighing systems can be affected indirectly:

• Electrical noise couples into analog signal paths.
• Poor grounding causes ground loops that shift reference potentials.
• Harmonics and switching noise degrade power supply stability.

You may see:

• Random drift or unstable readings
• Intermittent “out of tolerance” rejects
• Calibration that won’t “stick” between shifts

Even when the scale itself is fine, the environment can be noisy.

4) Network dropouts and data integrity risks

If your controllers reset, your data capture is at risk:

• Missing run segments
• Timestamps that jump
• Partial files
• Lost audit trails

This becomes a compliance and QA headache even if the batch is salvageable.

The hidden culprit: harmonics and VFD noise

Harmonics are common in facilities that run:

• VFD-driven HVAC fans
• Pumps
• Large refrigeration racks
• Modern LED lighting drivers

Harmonics can cause overheating in conductors and transformers and contribute to nuisance tripping. Many guidance documents and technical overviews note these effects and recommend mitigation (filters, proper sizing, and monitoring). (One technical overview referencing nuisance tripping/overheating from harmonics: https://www.precision-elec.com/wp-content/uploads/2025/09/AC-Motors-with-VFDs_-A-Comprehensive-Technical-Overview.pdf)

In practice, harmonics can:

• Stress power supplies inside controllers
• Increase neutral currents
• Cause protective devices to behave unpredictably
• Add “hash” onto reference signals

If you’ve ever seen equipment that behaves perfectly on a clean bench circuit but glitches in its installed location, harmonics and grounding are prime suspects.

A practical power-quality audit plan (do this before blaming people)

You don’t need a full engineering study to get actionable answers. You need targeted measurements, a short timeline, and a plan to act on what you find.

Step 1: Confirm nameplate requirements and circuit reality

Start with the basics:

• Confirm the equipment’s rated voltage, frequency, phase, and amperage.
• Identify whether the unit has a high inrush (compressors, heaters).
• Verify whether the circuit is dedicated or shared.

Then inspect:

• Breaker size and type
• Wire gauge and run length
• Panel schedule and what else is on that panel

Real-world issue: equipment is often installed on a circuit that is “available,” not one that is appropriate.

Step 2: Log voltage and current where the equipment actually plugs in

Measure at the receptacle or disconnect feeding the equipment—not at the main.

What to capture:

• RMS voltage over time
• Event waveform snapshots if possible
• Current draw and peaks (inrush)
• Frequency (especially if generator transfer is involved)

Timeline that works:

• Minimum: 72 hours of logging
• Better: 7–14 days, especially if your load profile changes by shift or day

What you’re looking for:

• Repeated sags at the same times (start events)
• Voltage trending low during peak facility load
• Current peaks correlated with controller resets

If you see the controller reboot at 2:03 AM every day, you want a log that shows what the voltage did at 2:03 AM.

Step 3: Check circuit loading and “nuisance sharing”

Common facility-side root causes:

• Two compressors on one branch circuit
• ULT freezer sharing a circuit with a vacuum pump or oven
• Long extension cords or undersized feeders

A rough rule of thumb operationally: sensitive gear does best on dedicated circuits with headroom, especially if it has compressors, heaters, or high starting loads.

Step 4: Verify grounding and bonding integrity

Power quality isn’t only voltage—it’s reference stability.

Actions:

• Verify proper equipment grounding conductor continuity.
• Check for neutral-ground issues in subpanels.
• Identify ground loops created by multiple bonding points.
• Confirm shield terminations follow manufacturer guidance.

When grounding is poor, control electronics may “see” noise as signal, or communication ports become unstable.

Step 5: Deploy UPS and surge protection strategically (not everywhere)

UPS systems are often misapplied. The goal is not to run everything for hours—it’s to prevent controller resets and preserve alarms + data through sags and short interruptions.

Prioritize UPS coverage for:

• Controllers and HMI panels
• Remote alarms and notification gateways
• Data capture (PCs, mini PCs, network switches)
• Critical comms (routers, modems)

A key point: You generally do not size a UPS to carry the compressor load of a large freezer. Instead, you size it to keep the control brain alive and keep alarms/data intact while power stabilizes or a generator transfers.

Also consider:

• Appropriately rated surge protective devices (SPDs) at the panel and/or point-of-use
• Line reactors or harmonic filtering where VFD noise is severe

Step 6: Re-test and “prove the fix”

After changes:

• Repeat logging for another 72 hours.
• Confirm the absence (or reduction) of the triggering event.
• Document the before/after in your maintenance records.

This turns “we think it helped” into evidence.

Commissioning used equipment: why “it ran fine at the seller” isn’t proof

When used equipment changes sites, three things change immediately:

1) The supply impedance and circuit design2) The neighboring loads (VFDs, compressors, welders, etc.)3) The grounding/bonding environment

So yes—it may have run flawlessly at the seller on a dedicated circuit in a quiet facility, and then it becomes unstable in your building.

A commissioning best practice is to include a facility readiness assessment that covers:

• Electrical: circuit capacity, voltage stability, grounding
• HVAC: heat rejection and ambient temp
• Space: clearance, access for service
• Safety: disconnects, emergency power plans

This is one of the highest ROI steps you can take because it prevents weeks of “troubleshooting the equipment” when the root cause is upstream.

Why this matters specifically for ULT storage

ULT upright freezers are unforgiving:

• They are continuous-duty assets.
• Recovery from trips is slow.
• Alarm reliability is mission-critical.

If you run -80°C storage, your power quality strategy should include:

• Dedicated circuit and correct breaker sizing
• Verified grounding
• Alarm path resiliency (battery backup, UPS for comms)
• Clear SOPs for power events (what to check, when to escalate)

Product plug (Urth & Fyre listing)

If you’re expanding cold-chain capacity or replacing an unreliable unit, consider the Ai RapidChill 26 CF -86°C Ultra-Low Temp Upright Freezer (UL, 120V).

Recommended gear: https://www.urthandfyre.com/equipment-listings/ai-rapidchill-26-cf--86degc-ultra-low-temp-upright-freezer-ul-120v---low-temp-freezer

From an operations standpoint, the key is not just getting a freezer—it’s commissioning it with the right electrical protections so you don’t end up chasing power quality lab equipment controller resets that look like freezer “problems.”

Implementation framework: 7-day power quality sprint

If you want a simple, ops-friendly approach, run a one-week sprint:

Day 1: Baseline + scoping

• List critical loads (freezers, chillers, ovens, packaging/weighing, analytics)
• Pull last 30–90 days of alarm logs and downtime notes
• Identify “repeat time-of-day” events

Day 2–3: Instrumentation

• Install a power quality logger on the worst offender circuit
• Add a second logger at the panel if possible
• Start capturing current + voltage

Day 4: Facility checks

• Verify circuit loading and shared loads
• Confirm breaker sizing and conductor gauge
• Inspect grounding/bonding points

Day 5: Mitigation trial

• Add UPS to controllers/alarms/data capture
• Add SPD at appropriate location
• Move equipment to a dedicated circuit if feasible

Day 6–7: Verify + document

• Confirm event reduction
• Document changes as part of a commissioning record
• Update SOPs: response to controller reset, alarm storm, and power events

SOP checklist: what to do when a controller resets

To avoid chaotic responses, define a short SOP:

• Confirm whether other equipment reset at the same time (power event vs. local failure)
• Check the controller event log for “power fail” or undervoltage indicators
• Capture time of event for correlation to logger
• Verify setpoints and critical safety states after reboot
• If repeated: escalate to facilities to check circuit loading and grounding

This prevents repetitive blame cycles and speeds up root-cause resolution.

Urth & Fyre angle: reduce downtime without major capex

Most facilities don’t need a massive electrical retrofit to improve reliability. They need:

• Commissioning checklists that include power quality, not just “plug it in.”
• Facility readiness assessments before moving in used equipment.
• Guidance on where UPS/SPD protection actually matters.
• Practical rewiring recommendations (dedicated circuits, load balancing, grounding verification).

Those steps are often cheaper than a single lost production week—or a single freezer temperature excursion.

Next steps

If you’re seeing random resets, alarm storms, compressor trips, or unexplained weighing instability, treat it as a power quality problem until proven otherwise. Measure first, correlate events, then apply targeted protections.

Explore equipment listings and learn more about commissioning support and consulting at https://www.urthandfyre.com.