Inspecting and documenting bonding and protection

Harbourview's construction ran through the winter. By April the TRs had their racks, the riser had its backbone cables and the TBB, and the PBB in the entrance facility was full of green conductors. Daniel spent two days on site with Tomasz Wiercinski walking every telecommunications space with a checklist, a low-resistance ohmmeter and a camera. 'This is the part people skip,' Roz had told him. 'The design is only a promise. Inspection and documentation are how you find out whether the building keeps it, and how the next person knows what's there.'

This lesson covers the final stage: inspecting the installed bonding and protection system, testing it, labelling it, recording it and planning its maintenance. It ends with the Harbourview commissioning report and with what happened at the existing clinic building the following summer.

Inspect before it is hidden

Bonding conductors run through ceilings, shafts and walls that will be closed. Connections to building steel are often made before fireproofing is sprayed. The single most useful inspection habit is to look at work before it disappears. Daniel's construction schedule included hold points: the TBB in the riser before the shaft walls were closed, the connections to steel before fireproofing, and the PBB and protector field before the entrance facility backboard was crowded with equipment. At each hold point, Tomasz's crew called Daniel, who inspected, photographed and released the work.

Photographs are cheap and permanent. A photo of each connection to steel, each TBB tap and each busbar with its labels visible, filed by location, answers questions years later that no drawing can. Roz's office kept them with the project records and gave a copy to the owner.

The visual inspection checklist

A visual inspection checks that what was designed was installed, and installed properly. Daniel's checklist for each space followed the order of the bonding path, from the busbar out to the equipment.

In TR-3, the inspection found two problems. The cable ladder had been extended after the original installation to reach a new rack, and the new section had no bonding jumper. And one rack's bonding conductor had been landed on the SBB with a single-hole lug, because the installer had run out of two-hole lugs. Both were fixed the same day. On level 4, the TBB tap to the SBB had been made with a mechanical split-bolt connector instead of the specified irreversible compression tap. Tomasz had it replaced.

Testing the bonding network

Visual inspection finds missing and poorly made connections. Testing measures whether the connections that exist are good. Two kinds of test are used for ICT bonding networks.

The first is the two-point bonding test, sometimes called a continuity or bonding resistance test. A low-resistance ohmmeter, often a four-wire instrument that can measure in milliohms, is connected between two points that should be well bonded: an SBB and the PBB, a rack and its SBB, two sections of cable ladder. The reading shows the resistance of the bonding path between them. A good path gives a very low value; a poor or missing connection gives a high one. ANSI/TIA-607 discusses testing, and owners commonly set maximum values in their standards, for example a fraction of an ohm between any SBB and the PBB. The Harbourview specification set its limits in the owner's terms and required every SBB, every rack and every ladder run to be tested.

The test has a limitation: it measures resistance at DC or low frequency, not impedance at surge frequencies. A long, looping conductor can test perfectly and still perform poorly in a surge. That is why visual inspection of routing remains essential, and why the design rules for short, straight conductors matter even though no simple field test checks them.

The results show the pattern Daniel expected. SBB readings rise with distance from the PBB, because the TBB's resistance grows with its length, and all were well within the owner's limit. One rack in TR-3 failed at first: the single-hole lug found in the visual inspection had been left loose. After the lug was replaced and torqued, the rack tested at 9 milliohms. A test that finds nothing wrong is reassuring; a test that finds the fault an inspection already suspected confirms both methods.

The second kind of test is a ground resistance test of the building's grounding electrode system, which measures the resistance between the electrodes and remote earth, typically by the fall-of-potential method or with a clamp-on tester. That test belongs to the electrical system and is the electrical engineer's and electrical contractor's responsibility. The RCDD should obtain the result for the project records, because it explains how high the building will rise in a strike, but should not confuse it with the bonding tests.

Labels

ANSI/TIA-606, the administration standard, defines identifiers for telecommunications infrastructure, including bonding parts. Each busbar gets an identifier tied to its space; each bonding conductor gets an identifier showing what it connects. Labels must be durable, legible and placed where they can be seen without disturbing the installation. The TBC and the TBB are labelled at each end with a warning that the conductor must not be disconnected without contacting the person responsible for the telecommunications infrastructure.

At Harbourview the PBB was labelled with its identifier, the date of installation and a small plaque explaining what it was, because the facilities staff were not ICT specialists. Every conductor on the PBB carried a label at the busbar end showing its far end: 'TBB to TR-1, TR-2, TR-3, TR-4, rooftop', 'TBC to MDP ground bus', 'Protector, provider copper'. Tomasz's crew used printed wrap-around labels rated for the environment.

Records

The records for the bonding and protection system are part of the building's telecommunications documentation. They should include as-built drawings showing every busbar, conductor and connection to steel; the busbar schedule with the conductors on each busbar; the protector and SPD inventory with locations, makes and models; the test results; the photographs; the written answers from the AHJ; and the maintenance plan. ANSI/TIA-606 describes records and reports in general terms, and owner standards often set the format.

Roz insisted that the records be handed over in a form the owner could actually use: drawings in the owner's CAD standard, a spreadsheet of busbars and conductors keyed to the labels, and a single summary document that a new facilities manager could read in twenty minutes. The test reports went in an appendix.

Maintenance

A bonding and protection system needs care. Connections loosen with vibration and temperature cycles, corrosion builds in damp spaces, protector units wear out after surges, SPDs degrade, and renovations add racks and ladder sections without bonding them. Daniel's maintenance plan for Harbourview set out an annual inspection of every busbar and a sample of rack bonds, retesting of SBB-to-PBB resistance every few years, inspection of protectors and SPD status indicators after every major storm and at least yearly, and a requirement that any change to a telecommunications space include bonding of new racks and pathways, tested and recorded.

The plan also named a person. Bonding systems fail through neglect when nobody is responsible for them. The clinic group appointed its IT infrastructure manager as the owner of the telecommunications bonding system, with the facilities manager responsible for the electrical side, and both names went on the PBB plaque.

Renovations deserve their own rule. Most bonding failures in older buildings were not design errors but changes made years later by people who did not know the system existed: a rack added and never bonded, a ladder extended, a TBB cut during a ceiling replacement. Daniel added a one-page bonding requirement to the clinic group's standard for tenant and renovation work, so that every future project touching a telecommunications space would bond, test and record its changes.

Commissioning the whole system

Commissioning tests the system as a whole. For bonding and protection, that meant confirming the inspections and tests above, verifying that SPD status contacts reported to the building management system and, with Priya, running a planned power test: the utility supply to the building was opened during a weekend window, the UPS systems carried the data room and TRs, the generator started and the transfer switches moved the loads. Every switch and server was monitored for resets. None occurred. The generator ran under load for an hour, the utility was restored and the loads transferred back.

Daniel wrote the commissioning summary for the bonding and protection system in two pages: what was installed, what was found and fixed, the test results, the open items (none) and the maintenance plan. Roz reviewed it, signed it as the responsible RCDD, and, for the first time on a project, added Daniel's name beside hers as the designer.

The following summer

In July, a storm stronger than the one that had started the project crossed the lake. The existing clinic building had been retrofitted the previous autumn using the lessons of this course: a new PBB beside its service with a proper TBC, a short protector bond, an SBB and TBB to the second-floor TR, individual rack bonding conductors and all-dielectric fibre on the campus link. Harbourview was open and running.

On Monday morning, the facilities manager called Roz. Nothing had failed in either building. The SPD monitoring at Harbourview showed that the Type 1 device at the main switchboard had operated several times during the night and that two of the outdoor camera SPDs had registered surges. The switches had logged nothing unusual. The nurse call system had not rebooted. 'That,' Roz told Daniel, 'is what a good bonding design looks like from the outside. Nothing happens.'