Engineering guide
Infrared thermography for UPS systems and battery rooms
An infrared scan photographs heat, so it finds the loose lug, the overloaded breaker or the failing battery connection before it fails. The 2023 edition of NFPA 70B makes thermography a scheduled task: every 12 months for equipment in condition 1 or 2, every 6 months in condition 3, unless the manufacturer's own instructions say otherwise.
Key facts
- Thermography, condition 1: Every 12 months, all equipment
- Thermography, condition 2: Every 12 months
- Thermography, condition 3: Every 6 months
- Condition decided by: The worst of physical condition, criticality and environment
- Manufacturer instructions: Take precedence over the standard's intervals
- CSA Z463 first published: November 2013
What a scan finds in a UPS room
Most electrical faults announce themselves as heat first. A bolted lug that has lost torque, a breaker carrying more than it should, a fuse clip with poor contact and a battery intercell connector with rising resistance all run hotter than their neighbours. On the scan they show as a hot spot compared with the same part on the other phases or the next block in the string.
Eaton's 93PS guide puts the same idea in maintenance terms: inspect periodically for components, wiring and connections showing evidence of overheating, with particular attention to bolted connections, which must be re-torqued periodically. Thermography is how that inspection is done while the equipment is carrying load.
The NFPA 70B interval
NFPA 70B moved in 2023 from a recommended practice to a standard with mandatory language. Its Chapter 9 sets intervals by an equipment condition assessment built from three inputs: physical condition, criticality and operating environment, and the worst of the three decides. For infrared thermography the table applies to all equipment:
| Equipment condition | Thermography interval |
|---|---|
| Condition 1 | 12 months |
| Condition 2 | 12 months |
| Condition 3 | 6 months |
The standard's intervals do not override the manufacturer: they apply when the manufacturer gives no other instruction. A UPS feeding a hospital or a data hall usually ranks high on criticality, which can push it into condition 3.
Where CSA Z463 fits in Canada
In Canada, CSA Z463 Maintenance of electrical systems covers the same ground. It was first published in November 2013 as a guideline and its clauses were converted from advisory to mandatory form when it became a standard. Many Canadian sites write their program against Z463 and use the NFPA 70B table as a reference for frequency; follow your own authority and insurer on which one governs.
How to scan a UPS and its batteries usefully
- Under load. A scan at 10% load hides problems that show at 60%. Schedule it when the UPS is near its normal peak, or during a load-bank test.
- Compare like with like. Phase against phase, block against block. The difference matters more than the absolute temperature.
- Battery strings. Scan the intercell connectors and terminals during a discharge or a battery test, when current flows.
- Record and trend. Keep the images with load and ambient temperature so next year's scan can be compared.
The scan is done by a qualified person with the PPE your arc flash assessment requires; covers are removed only where the procedure allows it. A preventive maintenance visit that includes a thermal scan gives you the images and the corrective list in one report.
What to do with a hot spot
A hot spot is a work order, not a curiosity. Connections are re-torqued or cleaned with the equipment de-energised or on maintenance bypass, overloaded circuits are redistributed, and a hot battery connector usually means the block behind it is next to be measured. If a string shows several warm blocks, plan the replacement before the next outage; a maintenance plan that tracks battery condition keeps the scan results and the battery history in one place. The three-phase UPS preventive maintenance guide covers the rest of the visit.
Related pages
Common questions
How often should a UPS get an infrared scan?
NFPA 70B (2023) sets infrared thermography every 12 months for equipment in condition 1 or 2 and every 6 months in condition 3, unless the manufacturer instructs otherwise.
What decides the equipment condition?
Three inputs: physical condition, criticality and operating environment. The worst of the three sets the interval.
Is NFPA 70B mandatory in Canada?
NFPA 70B is a US standard. Canadian programs usually follow CSA Z463 Maintenance of electrical systems; the authority having jurisdiction and your insurer decide what applies to your site.
Can thermography find bad UPS batteries?
It finds hot terminals and connectors, which often point to a high-resistance connection or a failing block. Scan during a discharge or a battery test so current is flowing.
Should the UPS be loaded during the scan?
Yes. Defects show under load, so scan near the normal peak or during a load-bank test.
Sources, checked October 4, 2026:
- Eaton white paper, Understanding 2023 NFPA 70B, Publication WP027024EN (March 2023), pp. 2, 4
- Eaton 91PS/93PS UPS 8-40 kW User's and Installation Guide, P-164000493 Rev 006, p. 110
- CSA Group, CSA Z463 Transforming from Guideline into Standard, p. web page
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