Grounding investigation in commercial buildings: path, not a slogan
Commercial grounding conversations collapse three different jobs into one word: a connection to earth, a fault-current return that opens a breaker, and equipotential bonding that keeps exposed metal near the same potential. Those jobs share hardware and they do not share tests. A ground rod reading copied from a commissioning sheet does not tell you whether a receptacle ground is continuous to the panel, or whether two “grounds” in a telecom closet are actually two systems fighting through a data cable shield.
How the investigation is actually run
Begin outdoors at the electrode and the water-bond, then walk inward to the first disconnect, then to the panels that actually serve the complaint. Do not start in the telecom closet; that closet is usually a symptom of a building-level bonding story. Use a test current that will show a painted conduit joint as a joint, not a continuity beep from a dry-cell meter. Clamp residual current on feeders that should be near zero and on data risers that should not be carrying power-frequency current at all.
If two “isolated grounds” exist, measure the voltage between them under load and during a nearby motor start. That number, even without a dramatic decimal, tells you whether signal cables are being asked to equalize the building. Write whether the equipment grounding conductor is continuous, whether an extra electrode is unbonded, and whether a neutral-ground bond is in the wrong place. Those three sentences are the report. Anything else is atmosphere.
Revisit after a renovation punch: kitchens, tenant fit-outs and generator additions are where bonding is most often cut and “made good” with a green screw into paint. The investigation is finished when a competent electrician could find the joint from the text alone.
The studio’s grounding work is investigation of low-voltage building systems: continuity, impedance of the return path, stray currents, and whether the drawing’s electrode system still exists after renovations. It is not a claim to design utility earthing networks.
Symptoms
Tingle on cases, repeated residual-current trips, unexplained current on cable shields, and IT equipment that “needs a dedicated ground” because someone lifted the equipment grounding conductor. Noise on analog controls and Ethernet that tracks motor starts often belongs here and in EMI, SNR and communications — electrical environment first, protocol second.
Causes
Broken or omitted equipment grounding conductors after fit-outs. Isolated ground receptacles used as a folklore fix. Multiple electrodes that are not bonded, so lightning or fault current chooses a signal cable. Neutral-ground bonds in the wrong place creating circulating current. High-frequency noise from drives returning on unintended paths because the intended bond is a long steel conduit full of paint.
Investigation
Start with the one-line and the as-built bonding sketch, then walk: electrode, water pipe, structural steel, telecommunications grounding busbar, and every “isolated” bar someone added. Measure continuity of equipment grounding conductors under a test current that actually stresses the joint. Clamp residual current on feeders and on data risers. If you inject, say so and stay within a method that does not energize other people’s systems. Electrical diagnostics covers the intermittent cases; power quality covers the voltage you see between “grounds.”
A conclusion names the missing or high-impedance joint, the unintended parallel, or the extra bond that should not exist. It does not quote a magic earth-resistance number as proof the building is safe. Related: when the network problem is electrical.