Can overhead busbar and tap-off units be thermally imaged in a live data hall?

Yes. Overhead busbar trunking and its tap-off units can be imaged live in a working data hall, with nothing switched off. Each joint, tap-off unit and outgoing cable is imaged from the floor or an approved access platform, the load on each run is recorded, and the report locates every reading by run and tap-off number.

Why overhead busbar needs a place on the live survey

In many halls the rack supply no longer comes from floor-standing PDUs but from busbar runs above the aisles, with a tap-off unit dropping to each rack or pair of racks. Tap-offs are added, moved and re-plugged as the hall fills and customers change. Every one of those changes is a connection made in a live room, and the runs carry more load each year than they did at handover.

Commissioning thermography checks the busbar once, under load bank test. See busbar thermography at commissioning. The live survey checks it again under real IT load, after the hall has been worked on.

What gets imaged

The feed unit or end feed where the run is supplied from the switchboard or PDU
Each joint along the run
Each tap-off unit body and its plug-in point on the busbar
The outgoing flexible cable, glands and connectors down to the rack
Any tap-off fitted since the last survey, which is listed separately so it can be tracked

Busbar trunking is imaged as installed. Its joints are enclosed, so the image shows the surface of the joint cover or housing, and the report says so. Where a tap-off has an inspection point or cover that the site’s authorised electrician opens, the connections inside are imaged as well.

Working overhead in a live hall

Much of a run can be imaged from the floor where there is a clear line of sight. Where cable trays, containment roofs or lighting are in the way, a podium or other access platform is used, only under the site’s own permit and access rules. Nothing touches the busbar, and nothing is unplugged or switched for the survey.

Hot aisle containment needs planning. Exhaust air from the racks warms everything above the hot aisle, including the busbar housing, so readings in a hot aisle are compared with other points in the same aisle, not with a run above a cold aisle.

Load: comparing like with like

Two tap-offs on the same run can carry very different currents, depending on what the rack below is doing. A cool tap-off on a near-empty rack tells you little about its connections. So the load on each run, and on each tap-off where the site’s monitoring shows it, is recorded with the image, and tap-offs are compared with others at a similar load. See what load a survey needs and enough load in a 2N data centre.

Traps a good thermographer avoids

Reflections. Busbar housings are often smooth painted or bare aluminium and reflect light fittings and warm surfaces nearby. Readings are taken from more than one angle where needed, and any limitation is noted.
Emissivity. Painted housings and bare metal give very different readings at the same temperature. Measurements are taken on suitable surfaces, and any reading on bare metal is treated with caution and noted in the report.
Warm air, not a warm joint. Housing temperature follows the air around it. A joint is judged against similar joints in the same air, at a similar load.

What the numbers look like

On a London data centre build, commissioning thermography by our team found 16 busbar sections reading above 80 °C under test load, the highest 103.5 °C at a tap-off unit. Each was located and imaged before handover. A live survey gives the same located, measured record under the load the hall actually runs.

Ti inspects and reports. Any finding is investigated and put right by the site’s electrical team or contractor.

Frequently asked questions

Do the busbar joint covers need to be removed?

No. The busbar is imaged as installed, and the report records that readings were taken on the housing surface.

How often should overhead busbar in a live hall be surveyed?

With the rest of the critical power chain, usually at least once a year, and again after a significant load increase. See how often a live data centre should be surveyed.

Can the survey use our commissioning images as a baseline?

Yes. If the runs and tap-offs are referenced the same way, the live survey can be compared point by point with the commissioning record, with the load noted for both.