Does a data centre thermography survey at night or at the weekend see enough load?

Usually, yes. In most data centres the IT load changes little between day and night, so the UPS, busbar and PDUs carry much the same current at 2am as at 2pm. What does change out of hours is office and landlord load and, in cool weather, the cooling plant. Check the site’s power trend before booking, and record the load against every finding.

Why the critical power path holds its load

A data hall doesn’t go home at five. Servers, storage and network equipment run around the clock, so the current through the UPS output, busbar runs, tap-offs, floor PDUs and rack PDUs is often close to flat across the day. That makes an out-of-hours survey of the critical power path a sound choice for many sites, and it often fits the site’s change windows and escort rota better (see change freezes and maintenance windows).

Not every site behaves this way. Enterprise sites with batch work, sites with heavy daytime office use and halls that are still filling up can all show a pattern. That is why the trend is checked first rather than assumed.

What does change out of hours

Cooling plant. Chillers, pumps and CRAH or CRAC units follow the heat they have to reject. On a cool night with free cooling running, mechanical plant can be lightly loaded, so a connection that would show on a hot afternoon may not show at night (see what load a survey needs).
Office and landlord supplies. Lighting, small power, kitchens and the office side of the building drop away in the evening and at weekends.
Generators and changeover panels. These only carry current on a test or a real transfer, day or night. Time them to the site’s on-load test.

How to check before booking

Ask the site’s operations team for the power trend from the EPMS, BMS or UPS displays over a normal week. If the IT load is flat, out of hours works for the critical path. If cooling load drops sharply at night, survey the mechanical plant boards in the day, or on a warm day, and keep the night slot for the halls and UPS rooms. Large sites are often split this way anyway, hall by hall or system by system.

What has to be in place at night

Panels are still opened by the site’s authorised electrician under the site’s own permit, so the night shift needs someone who can do that, not just an escort (see who opens the panels). Agree access cards, photography rules and any out-of-bounds racks in the method statement before the day (see preparing a live data centre). Avoid nights when load has been moved across for maintenance, because a path with its load transferred away tells you little.

What the report should record

Every finding is located by equipment reference, with the measured temperature, where on the component it was taken, the difference in °C from a matching reference and the load at the time where the equipment displays it. If load was low on any system, the report says so plainly. Ti Thermal Imaging issues the report the same day. Ti inspects and reports; the operator’s maintenance contractor investigates findings and carries out any work.

Why load is the whole point

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. They showed because the busbar was carrying current. On a live site the same rule applies at any hour: survey each system when it is carrying its normal load.

Frequently asked questions

Is a weekend survey as good as a weekday one?

For the IT power path, often yes, if the load trend is flat. For office supplies and some cooling plant, a weekday is usually better.

Should a survey be done during a load bank test instead?

At commissioning, yes. On a live site the real IT load is what matters (see busbar thermography at commissioning).

Does a night survey cost more?

Out-of-hours working is one of the factors in the price, along with item count and access (see what affects the cost).