Load Bank Testing in Data Centers (Robert Trefz)

Overview

Robert Trefz's article in the Spring 2024 issue of 7x24 Exchange Magazine (p. 33) describes how load banks are used to commission and maintain each part of a data centre power and cooling chain. The load bank type (resistive, inductive, resistive-inductive, portable, permanent, high voltage) is matched to the equipment under test. The equipment covered runs from generators and UPS to substations, PDUs, RPPs and busway.

The load type should match the circuit; motor-dominated circuits are tested with inductive load banks. For generators, resistive-only testing proves rated kW, while resistive-inductive testing applies out-of-phase current to test the full kVA capability. Loaded testing prevents diesel wet stacking caused by running gensets at insufficient load. Large sites often install permanent containerized resistive-inductive load banks outdoors for periodic generator tests, with automatic and transient test sequences archived.

UPS systems are usually tested with resistive load banks, discharging batteries per manufacturer specs. PDUs are typically 100-300 kVA and are tested with castor-mounted portable resistive load banks placed at each PDU. Each link in the chain is thus verified separately with a real load, which aims to reduce surprise findings carried over from commissioning into operation. This approach also makes it easier to document acceptance tests at every point in the chain.

The article also covers the cooling side: networked portable load banks placed through the hall simulate IT heat to verify HVAC performance and can create targeted hot spots. The record rests on the article's summary and key findings; specific site sizes or test durations are not included. NFPA 110 and ASHRAE Guideline 0 are the related references. The article's emphasis is on choosing the test type and load according to equipment type.

Key points

1. Load type should match the circuit: motor-dominated circuits are tested with inductive load banks.
2. Resistive-only testing proves rated kW; resistive-inductive testing applies out-of-phase current to test full generator kVA capability.
3. Loaded testing prevents diesel wet stacking caused by running gensets at insufficient load.
4. Large sites often install permanent containerized resistive-inductive load banks outdoors, with test sequences archived.
5. UPS systems are usually tested with resistive load banks, discharging batteries per manufacturer specs.
6. PDUs are typically 100-300 kVA and are tested with castor-mounted portable resistive load banks at each PDU.
7. Networked portable load banks through the hall simulate IT heat to verify HVAC and create targeted hot spots.
8. Related references: NFPA 110 and ASHRAE Guideline 0.

Using it in design

• Generate a commissioning test plan from the design: one load bank test entry per genset (resistive-inductive at rated kVA).
• Add resistive and battery-discharge tests for UPS, separate test entries for PDU/RPP/busway and a data hall heat test.
• Offer an optional permanent load bank connection point on generator switchgear for large sites.
• State the load type (resistive, inductive, resistive-inductive) separately for each item of equipment in the test plan.

Who should read it

Commissioning engineers, generator and UPS test teams and data centre operations managers.

Related standards

• NFPA 110
• ASHRAE Guideline 0

Publication details

Authors

Robert Trefz

Publisher

7x24 Exchange Magazine

Year

2024

Document number

Spring 2024 issue, p. 33

Document language

English

Source type

Industry body

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation