Commissioning with Load Banks – False Load, Real Results
- Alex Mathers
- 1 day ago
- 10 min read
Alex Mathers P.E., CxA, NEBB CP
One major challenge of commissioning is proving system performance before full operations start. In an ideal world, building systems would always be commissioned under full, real operating load. In reality, during functional testing the building systems may be “ready for testing,” but with no loads. That is, no tenants, no occupants, no servers, or switches, no process equipment. Still, most owners want documented performance verification of the newly installed systems. This is where load bank testing becomes a valuable tool in a commissioning agent’s toolbox. While load banks may be temporary or “false,” the results are very real.
What Load Banks Do
Load banks are temporary, purpose-built resistor/reactor devices that safely convert electrical power into heat, allowing building and power systems to be exercised, measured, and validated under controlled conditions that closely match their intended design capacity. They are commonly used for:
Emergency and backup generators and paralleling switchgear
UPS systems and battery strings
Data centers (CRACs) and mission-critical facilities
Chillers, cooling towers, and heat rejection systems
By applying a controlled, measurable load or demand, the commissioning team can verify system performance, capacity, controls, and protection schemes before real loads ever arrive. At their core, load banks give CxA’s a way to put systems under conditions they were designed for when the building or facility can’t.
A load bank 'false' load refers to using a load bank to create an artificial, simulated, or dummy load for testing power sources like generators, UPS, or batteries, mimicking real-world operation without connecting to actual equipment, thereby revealing potential issues or confirming capacity. The "false" part emphasizes it's not the real operational load but a controlled, test-specific load.
Beyond Simple Startup
Startup focuses on verifying that each component functions installed in the field according to manufacturer specifications and safety standards. It typically includes inspections, calibration, and basic operational checks under no-load or minimal-load conditions. During startup, technicians verify things like proper wiring and piping, correct rotation, nameplate data, lubrication, safeties, basic controls, and manufacturer-required checks.
Functional performance testing is about proving that systems work together as designed under defined operating scenarios. It focuses on performance, sequences, and integration. Functional performance testing verifies control logic, setpoints, alarms, interlocks, failure modes, and responses to changing conditions.
The performance part of functional performance testing is key. Performance testing is where commissioning moves beyond checking boxes and into proving outcomes. It answers the question that startup and basic functional testing cannot: Can the system perform to what it was designed to deliver?
Unlike startup, which focuses on individual equipment operation, and functional testing, which verifies sequences and responses, performance testing validates capacity, stability, and endurance. It evaluates how systems behave when they are pushed toward design conditions and held there. This includes sustained operation at high load, response to step changes, recovery after disturbances, and operation near design limits where many problems first appear.
Performance testing provides measurable, defensible results. Instead of “the system ran,” the outcome becomes documented evidence of delivered kW, tons, airflow, temperature control, voltage stability, and response time. Trending data and test reports create baselines that operators can use long after turnover to understand what they should expect for their facility.
Most importantly, performance testing shifts failures to a time when they are manageable. Finding a capacity shortfall, control instability, or coordination issue during construction is inconvenient. Finding it after occupancy, during an outage, or under live production load is costly and disruptive.
Performance testing is often enabled by, and in some cases requires load banks. When owners ask whether a system is operating, load bank performance testing is the only part of commissioning that provides a confident, data-backed answer.
Load bank testing helps identify issues that may not be apparent during startup, such as overheating, voltage regulation problems, or insufficient response to load changes, ensuring the equipment will perform reliably once placed into service. This process validates the system’s performance, stability, and capacity to handle real-world operating demands.
I’ve seen installed equipment that has been called good after Startup fall apart the moment a real load shows up. Controls that had passed loop checks suddenly hunt. Unaccounted for air bypasses show up. Generators that ran all day at no load trip when pushed past 70%. None of that shows up during a startup checklist.
Why Waiting for a Real Load Rarely Works
Project schedules rarely align with ideal commissioning conditions. Common challenges include:
Tenants not yet occupying the building
Seasonal variables
IT or process equipment delivered after substantial completion
Phased occupancy or partial build-outs
Waiting for real loads often means deferring meaningful testing until after turnover, when access is limited and failures are far more disruptive and expensive.
Project schedules rarely align with ideal commissioning conditions. Waiting for real loads often pushes meaningful testing into occupancy, when access is limited and failures are far more disruptive. Load banks give the commissioning team a way to validate equipment performance at the right point in the project without waiting for perfect conditions that may never come.
By enabling testing earlier in the project, load banks help compress risk into a controlled window when the full project team is still available to respond. Issues can be diagnosed, corrected, and retested before turnover, instead of becoming operational problems owned by facilities staff. That shift in timing often makes the difference between a documented commissioning success and a lingering reliability concern that follows the building into service.
Types of Load Banks
Not all load banks are the same. Electrical load banks are typically built from resistive elements, inductive elements, capacitive elements, or a combination of the three. Each behaves differently, and that matters depending on what you’re trying to prove.
Resistive loads are the most common. They turn electrical energy into heat and give generators and UPS systems a clean, predictable kW demand. That makes them ideal for verifying capacity, cooling, and basic control response. Here are some common form factors of resistive load banks:
Rack-mounted load banks (Server simulators) Designed to install directly into equipment racks, often used for UPS systems and data center testing. Built to mimic the electrical and thermal profile of IT equipment. These are common in data centers where airflow, heat output, and power density matter just as much as kW. They’re especially useful before real servers are installed.
Suitcase (portable) load banks Small, self-contained units that can be carried by one or two people. These are handy for panel-level testing, small generators, or targeted commissioning work where flexibility matters more than total capacity.
Trailer-mounted load banks Large, high-capacity units used for generators, central plants, and mission-critical facilities. They support full-load, multi-step testing and sustained runs. When you need to push a system hard and see how it behaves over time, this is usually the tool.
Inductive and capacitive load banks simulate reactive loads (motors, capacitors) to test power systems, unlike basic resistive banks (heaters) that only use real power, revealing performance issues like voltage drop or power factor problems by shifting current/voltage phases, crucial for generators, UPS, and power factor correction systems. Inductive banks use coils (lagging PF), while capacitive banks use capacitors (leading PF) to test different system conditions, often combined with resistive elements in RLC banks for comprehensive testing. Inductive and capacitive loads come into play when power factor, voltage regulation, or frequency response needs to be tested more realistically, especially for systems feeding motors, transformers, or sensitive electronic equipment.
It’s worth remembering that a load bank isn’t a perfect stand-in for every real load. A pure resistive bank can substitute for simple electrical demand, but it won’t fully mimic how motors ramp, how transformers magnetize, or how nonlinear loads behave. That’s fine, as long as the limitations are understood and the test is designed around them.
Used correctly, load banks don’t replace real-world operation. They give us a controlled way to stress systems, absorb power safely, and learn how equipment responds before real occupants, processes, or outages are on the line.
False Load, Real Findings
Calling it “false load” misses the point. The load may be artificial, but the system response is real. Load bank testing exposes things like:
CRAC, fan coil and mechanical system performance issues including faulty fan speed control (pressure or Delta T control), valve control (flow or Delta T), heat exchanger capacity and condensate pump capacity.
Rack system containment air leaks and short-circuiting airflow bypasses
Utility power quality issues including voltage instability, poor frequency control, harmonic distortion, and phase imbalance as load changes
Generator voltage and frequency instability during step loading
UPS under performance at sustained high load and shorter battery rundown time than planned
Chiller staging and control instability near design tons
Alarms, safeties, and failure modes that only show up under stress
Specific issues found during our load bank testing includes:
On one project, a generator passed every no-load and light-load test. During load bank testing, we found a generator exhaust and cooling issue that only appeared above 80% load. That fix cost a few days and some insulation changes. Finding it during an operational outage would’ve cost significantly more as potential overheating could have caused the backup system to fail.
On another project we deployed portable load banks to verify the fan coil cooling capacity and controls for a life science research lab planned to house heavy plug loads. It was discovered that the return air mixing with adjacent labs resulted in a lower airside Delta T and therefore reduced sensible capacity of the fan coil units.
During a recent data center commissioning project we employed rack mount load banks to verify the fan speed control and cooling capacity of both a high density rear door heat exchanger CRAC system and low density InRow cooling units with hot aisle containment. A few issues were identified and fixed including rack air pressure control, fan failures, power meter current transformer location, condensate pump issues and humidity control issues.
IR Thermal Scanning to identify hot spots
Electrical Testing: The Details Matter
Load bank testing is not only about proving that mechanical systems can carry the required load, it also provides a critical opportunity to evaluate electrical power quality and protective device coordination under real operating conditions.
During load bank testing, power quality measurements such as voltage, current, frequency, power factor, harmonics (THD), and phase balance are monitored at generators, UPS outputs, PDUs, and critical distribution points. As load is applied in steps and held at sustained levels, issues such as voltage distortion, frequency instability, excessive neutral currents, or poor power factor often become apparent. These conditions can stress sensitive IT equipment, reduce equipment life, and indicate problems with generator regulation, UPS inverter performance, or nonlinear load interactions.
Breaker trip setting verification is equally important. Load bank testing allows circuit breakers to be exercised near their actual operating points without risking production equipment. By confirming long-time, short-time, and instantaneous trip settings against design documents and coordination studies, teams can verify that breakers will trip when required, and only when required. Common findings include mismatched settings, incorrect breaker types installed in the field, or coordination gaps that could result in nuisance trips or failure to clear faults.
Testing also validates system response during abnormal conditions. Load steps and simulated overloads can reveal whether protective devices operate as intended, whether alarms are generated at appropriate thresholds, and whether upstream and downstream devices coordinate correctly. This is especially critical in data centers and mission-critical facilities where a single misconfigured breaker can cascade into a widespread outage.
By incorporating power quality testing and breaker trip verification into load bank testing, owners gain confidence that their electrical infrastructure is not only capable of carrying the load, but is also stable, coordinated, and resilient under real-world operating conditions.
Where Load Bank Testing Goes Wrong
Like any meaningful commissioning activity, load bank testing lives or dies on planning and coordination. Load banks are heavy, generate significant heat, and affect multiple trades at once, which makes them unforgiving of poor communication. The most common failures are predictable: unclear test objectives, rushed schedules, and weak coordination between vendors, the general contractor, and the electrical contractor. Just as often, the test technically happens, but the data is never fully reviewed, or trending was never set up to begin with.
The load bank test plan must include defined goals, clear acceptance criteria, and ensure proper data collection and trending to turn a temporary setup into lasting documentation. The test plan must be reviewed and signed off months prior by all stakeholders – the GC, EC, MC, owner among other. It is also highly recommended to physically walk through the test plan onsite with all trades to ensure full coordination.
Lasting Value from a Temporary Setup
Load banks may create a “false” load, but they deliver real results: confidence, reliability, and proof of performance. The best load bank tests result in documented proof of the systems performance during full load operation including trend logs, issues logs and reports which explain how the system behaves at high load and how it recovers. Testing allows for operators get to see their plant stressed in a controlled way, not during an emergency. Load bank testing takes uncertainty out of the early life of a building and replaces it with evidence. When done well, load bank testing doesn’t just prove systems work; it proves they’re ready.
References and Further Reading:
ASHRAE. ASHRAE Handbook – HVAC Applications, Data Processing and Data Centers Chapter. American Society of Heating, Refrigerating and Air-Conditioning Engineers.
ASHRAE. Thermal Guidelines for Data Processing Environments. Latest Edition.
ASHRAE Guideline 0. The Commissioning Process. American Society of Heating, Refrigerating and Air-Conditioning Engineers.
ASHRAE Guideline 1.1. HVAC&R Technical Requirements for the Commissioning Process.
Uptime Institute. Tier Standard: Topology and Tier Standard: Operational Sustainability.
IEEE Std 3007 Series (formerly IEEE 399). Recommended Practice for Industrial and Commercial Power Systems Analysis.
IEEE Std 519. Recommended Practice and Requirements for Harmonic Control in Electric Power Systems.
IEEE Std 242 (Buff Book). Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems.
U.S. Department of Energy. Advanced Energy Design Guide for Data Centers.
Building Commissioning Association (BCxA). Best Practices in Commissioning Mission Critical Facilities.
Schneider Electric. White Papers on Data Center Load Testing, Power Quality, and Cooling Validation.
Cummins Power Generation. Generator Set Load Testing and Commissioning Guidelines.
Caterpillar. Generator Load Bank Testing Application and Installation Guide.
NETA ATS & MTS. Standard for Acceptance Testing Specifications and Maintenance Testing Specifications for Electrical Power Equipment and Systems.
Trane Technologies. Data Center Cooling Design and Commissioning Application Guides.
Siemens. Protective Device Coordination and Arc Flash Analysis Technical Notes.
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