Switchgear and panel maintenance

Switchgear, switchboards and panels distribute power through a building and protect it when something goes wrong. Because they sit quietly for years, they are easy to ignore, but dust, heat, moisture and age all take a toll. A planned maintenance program keeps protective devices working as designed and finds problems before they become outages or fires.

Why maintenance matters

Distribution equipment has two jobs: carry current every day, and interrupt it safely when there is a fault. The first job can be checked during normal operation. The second cannot, because breakers may not operate for years. A breaker with dried-out lubricant or a failed trip unit may look fine until the day it needs to open, and then fail to clear the fault, letting it spread upstream or cause an arc flash with much higher energy than expected.

Common problems found during maintenance include:

• Loose or overheated connections and discoloured terminals
• Dust, debris and moisture inside enclosures
• Corrosion on bus, terminals and hardware
• Breakers that are slow to trip, stuck or out of calibration
• Damaged or deteriorated insulation
• Missing covers, filler plates and barriers
• Panel schedules that no longer match the circuits

Energized and de-energized tasks

Maintenance falls into two groups.

While energized

Some tasks can be done without an outage, from outside the equipment or by qualified workers using the right precautions:

• Visual inspection of the room and enclosures: access, housekeeping, signs of heat, water or pests
• Checking meters, indicating lights and alarms
• Listening and smelling for buzzing, arcing or burning
• Infrared thermography under load, described in our guide on infrared thermography for electrical systems
• Confirming labels, panel schedules and arc flash labels are present and readable

While de-energized

The tasks that prove the equipment will work need a planned shutdown, with the equipment locked out and verified dead:

• Cleaning enclosures, bus and insulators
• Inspecting and torquing connections to the manufacturer's values
• Insulation resistance testing of bus and cables
• Contact resistance testing on breakers and switches
• Exercising and lubricating breakers and switch mechanisms
• Trip testing breakers, by primary or secondary injection depending on the type
• Testing protective relays and ground fault protection
• Inspecting and testing draw-out mechanisms, interlocks and racking

How often

There is no single interval that suits every building. The right frequency depends on the equipment's condition, its importance, the environment and the manufacturer's instructions. CSA Z463, the Canadian guideline on maintenance of electrical systems, and industry maintenance standards describe a condition-based approach: equipment in good condition, in a clean environment, serving non-critical loads may be serviced less often than equipment in poor condition, in a dirty or damp space, or serving critical loads. Check the current edition of the guidance you follow.

As a practical matter, many owners do visual and infrared inspections at least annually and plan de-energized maintenance on a multi-year cycle, with critical equipment done more often. Insurers sometimes set their own expectations.

Planning the shutdown

Shutdowns are often the hardest part of electrical maintenance. Good planning reduces disruption and makes the most of the outage window:

1. Identify what loads each piece of equipment feeds, using up-to-date single-line diagrams and panel schedules.
2. Agree a time with building operations and tenants, and give notice.
3. Arrange temporary or standby power for critical loads, and confirm the generator and transfer switch are ready.
4. Prepare a written switching and lockout plan.
5. Have spare parts and the right test equipment on site.
6. After the work, re-energize in a controlled sequence and confirm loads are back.

Group work into one outage where possible: maintenance, repairs found during infrared scans and any upgrades.

Records

Keep test results, as-found and as-left conditions, and repairs for each piece of equipment. Trends in insulation resistance or contact resistance tell you more than a single reading. Up-to-date single-line diagrams and panel schedules are part of good records, and they make shutdown planning far easier. For overall planning, see our guide on building a maintenance schedule.

What the maintenance report should include

A report that just says "serviced" is not much use at the next outage. Ask the contractor for a report that covers, for each piece of equipment:

• Equipment identification matching the single-line diagram and labels
• As-found condition: cleanliness, signs of heat, moisture, damage, missing parts
• Test results with the test method, test values and acceptance criteria used
• Breaker trip test results compared with the settings and the manufacturer's curves
• Work done and parts replaced
• As-left condition and any settings changed
• Deficiencies still open, ranked by urgency, with recommended action

Keep the reports together by equipment. Over two or three cycles they show which items are deteriorating and help you decide whether to repair, retest sooner or replace.

A typical case

An older office building has a main switchboard that has not been serviced de-energized in many years. The annual infrared scan shows nothing alarming, so maintenance keeps being deferred. When the owner finally plans a weekend shutdown, the contractor finds dust packed on the bus supports, two feeder breakers whose mechanisms are stiff from dried lubricant, and one breaker that does not trip within its expected time during testing.

None of these faults would have shown on a thermal scan, because none of them makes heat under normal load. The stiff breakers are cleaned, lubricated and retested; the one that failed its trip test is replaced. The building now has a test record to compare against, and the owner sets a cycle for the next shutdown based on what was found rather than on how inconvenient the last one was.

Common mistakes

• Using the electrical room for storage. Boxes block access and working clearances, add fire load and get in the way in an emergency.
• Leaving filler plates out. Open knockouts and missing breaker blanks expose live parts and let in dust and pests.
• Torquing without the manufacturer's values. Over-tightening damages terminals as surely as under-tightening loosens them.
• Not updating drawings after changes. Out-of-date single-line diagrams make the next shutdown slower and less safe.

How ehZee can help

Our electrical system inspections review the condition of your switchgear, panels and electrical rooms, along with maintenance records and documentation. We report what we find, rank what to address first and can coordinate maintenance and repairs with your electrical contractor.

Common questions