Data centre cleaning schedule

Why is there no standard cleaning frequency?

Because rooms differ too much. ASHRAE's contamination white paper gives the target, ISO 14644-1 Class 8, and the filtration that usually reaches it, but it leaves the frequency to the site. It does point to the best everyday indicator: the quantity of dust can normally be judged by visual inspection of the IT equipment and by how often the filters need replacing.

That makes filter life the clock to watch. A room whose filters load up quickly is a room that needs cleaning more often, and a change in that rate, after a fit-out or a change in outdoor air, is the signal to look again. The UPS filters are a good place to read it, because Eaton already asks for them to be checked every month.

What does a typical schedule look like?

What should be checked every month?

The UPS air filters, first. Eaton asks for them to be inspected every month because dust can block them and shut the UPS down on overheating. A monthly look takes minutes, and the state of the filter tells you as much about the room as about the UPS.

• UPS air filters: inspected, with the condition noted so the loading rate can be compared month to month.
• Fan intakes and grilles: clear of dust build-up and of anything stored against them.
• Room humidity: below about 60%, the level ASHRAE gives for keeping settled dust dry.
• Packaging and paper: none left in the room, since ASHRAE warns that fibrous dust from cardboard and paper fouls heat sinks.

These checks need no tools, and most can be read remotely; humidity is part of server room monitoring.

What happens at each UPS maintenance visit?

The parts of the UPS that cleaning crews should not touch. Battery cleaning is one: EnerSys asks for the battery to be observed for cleanliness at regular intervals, and its standard cleaning procedure begins with disconnecting the battery, then wiping dust off the cell covers with a cloth dampened in clean water. It forbids oil, solvents, detergents and ammonia on the jars and covers, because they cause permanent damage and void the warranty.

Mild terminal corrosion is cleaned with a bicarbonate of soda solution, which EnerSys mixes as 1 gallon (4l) of water with 1 lb (500g) of bicarbonate. It also warns that if routine cleaning of the bolted connections has been neglected, heavy post corrosion may occur, which means unbolting the connectors and re-torquing them to the installation values. This is why battery terminals belong in the UPS maintenance schedule, with the battery isolated, and not in a general room clean.

What gets replaced every year?

The UPS air filters, according to Eaton's paper on ageing three-phase UPS units, which gives a recommended replacement timeframe of 1 year for air filters. The same table gives 7 years for fans, which is when a monthly look at a dusty fan intake starts to pay off: a fan that has spent years pulling dirty air is a fan that wears sooner.

Replacement filters only help in a clean room. Fitting new filters into a room full of settled dust means they load up again within weeks, so a room clean planned just before the UPS and cooling filter changes gets more life from both. The audits and planning section covers how replacement dates are tracked across the whole UPS.

When does the room need a deep clean?

When something has changed, rather than on a date. Common triggers are:

• After building work: Eaton notes that vibration from local construction can affect UPS internal connections, and the same work fills the room with dust.
• After zinc whiskers are found: ASHRAE's remediation is to replace the affected tiles and have professionals clean the data centre.
• When filters load faster than usual: the indicator ASHRAE points to.
• When a particle count misses Class 8: the target ASHRAE recommends.
• Before a major UPS or cooling change: so new equipment starts in a clean room.

A deep clean covers the raised-floor void, the tiles, the cable trays and the outside of the equipment; the live-room cleaning guide explains how that is done with everything still running.

How do you know the schedule is working?

By measuring, at intervals that suit the site. ASHRAE's tools are simple: a particle count against Class 8 for dust, and copper and silver coupons exposed in the room for 30 days for corrosive gases. Its paper also describes collecting dust from easily accessible equipment surfaces in clean plastic bags and sending it to a laboratory to find the humidity at which it turns corrosive.

Keep the results with the UPS maintenance records. Filter condition, humidity, particle counts and battery terminal condition tell one story, and an auditor or a new UPS designer will ask for all of it.

Who should be in the room during cleaning?

Someone who knows the UPS. Uptime Institute notes that accidental EPO activation is a recurring cause of downtime, and an emergency power-off button is exactly the kind of thing a cleaning cart or a mop handle can reach. Cleaning is delivered through specialist partners, and the site's own staff or the UPS service team should know when a visit is on, which areas it covers and where the EPO buttons are.

For the UPS side of the schedule, the UPS preventive maintenance guide explains what each visit covers.

Related pages

• Dust and contamination in the data centreCorrosive dust, zinc whiskers, gases, and the filters that stop them.
• What a live-room cleaning visit involvesBefore, during and after a clean, with the UPS on load.
• Data-centre audits and planningTier claims, capacity, end of life and the report.
• Data centre cleaningDust and contamination, schedule, and live-room visits.