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It’s summer, which is always a test for data center operators and data center design and preparedness.
With the arrival of the “dog days of summer” occasionally comes an unexpected and potentially dangerous byproduct of the weather. The problem can show up as water dripping out of electrical conduits, right into critical data center “grey space” or “white space” equipment, that is clearly not designed to handle water. This most likely is not a plumbing problem, rather a characteristic of the “changeable states” of water.
It is not an uncommon occurrence for metal electrical conduits that run through “well air conditioned spaces” within a building to develop condensation on the inside of the conduit. This may be very dangerous (depending on what the water dribbles into).
This phenomenon is usually accompanied by an air pressure difference between the origination point of the conduit and the conduit’s terminus. Moist air at one end of the conduit is drawn into the conduit by an air pressure differential. The water vapor within the air condenses when the moist air passes through the conduit and is lowered to dew point, whereupon liquid water continues traveling down the conduit.
The problem may be the result of unanticipated changes within a building that temporarily alter the building’s “air balance”. While NEC 300.7 requires “sealing” of conduits subject to different temperatures, the conditions necessary to apply 300.7 may not have been present or anticipated when the data center or other improvements within the building were originally built.
Assuming that it is not possible or desirable to insulate the conduits from their surroundings or raise the operating temperatures in the “offending spaces” within the building or data center; an inexpensive and effective fix is to stop the movement of air through the conduit.
With no air movement in the conduit there should be no new condensation.
A product commonly used by electricians on low voltage systems (under 600 volts) to inhibit the movement of air/moisture in runs of conduit is “Electrician’s Duct Seal”. This (typically) grey moldable putty is a product sold by many manufacturers. The compound is a non-conductive, moldable, non-setting putty that is manually pressed into the open end of a conduit, closing off the air space around the entering (or exiting) conductors.
While it’s a good idea to investigate which end of the conduit is in the “typically moist area” and seal only that end, leaving the other open to dry out, no air movement generally equates to no condensation.
