Free checklist
Power distribution unit annual maintenance checklist
The annual power distribution unit service is the deep pass: the measurements, cleanings and tests a quarterly round doesn't reach. This checklist keeps the full service on record with the photos that make it defensible later. Work is commonly verified against NFPA 70B, NEC (NFPA 70). Confirm the edition your authority having jurisdiction has adopted.
The checklist
Every item, and the photo evidence it needs
The photo count on each row is what RTI would require before the item can be submitted. Work the list here and watch the gate hold, or load it into RTI and let it enforce the real thing.
Outage coordination
Outage window agreed with the users of every fed load
Owner and the departments on each branch told the window, loads shut down in order or moved to an alternate source, and agreement recorded before the main opens.
No photoEvery source feeding the unit locked out and tested dead
Upstream feeder locked and tagged, the second input and any separate control supply too, then absence of voltage tested at input, transformer and output before covers open.
De-energized inspection
Terminations torqued and marked
Lugs and terminations torque-verified to the manufacturer's published values, re-torqued only where found loose, and torque-marked so the next tech sees they were done.
Bus, lugs and insulators inspected
No discoloration, pitting or heat tracking on bus joints, lugs and standoffs, connections clean and tight.
Interior vacuumed and cooling fans spun by hand
Dust vacuumed, not blown, from breaker, transformer and fan compartments, fans turning freely with no bearing drag, filters cleaned or replaced per the maintenance schedule.
Metering current transformers and sensor leads inspected
Current transformers seated around their conductors, sensor leads and harness plugs latched, branch sensors included where fitted, no cracked cases or loose wires.
Insulation resistance measured on output bus and feeders
Megohm readings on feeders and output bus, and transformer windings where fitted, recorded against last year's baseline, with electronic metering and surge devices isolated first.
Transformer section
Transformer connections and ventilation checked where fitted
Winding and tap connections tight, no heat discoloration, cooling openings clear and the section vacuumed clean.
No photo
Grounding and protection
Grounding and bonding verified back to the source
Ground and bonding connections tight and continuous, enclosure and neutral references confirmed as intended.
Breakers exercised while de-energized
Branch and main breakers operated through their travel, any that feel stiff or won't seat flagged for replacement.
Return to service
Interior cleared and every cover refastened before energizing
Tools, grounds and debris out, covers and dead-fronts refastened, and each lock and tag removed by the person who hung it before the feeder closes.
Display readings checked against a calibrated meter
After restart, voltage and current on each phase measured under the energized-work procedure and matched to the metering display, any drift noted for calibration.
Source transfer tested on dual-input units, owner warned first
Owner and the fed departments warned, load moved to the alternate source through the static transfer switch and back, no drop at the loads, events matching the log.
No photoTorque, megohm and metering results sent to the owner
Results compared with last year, open deficiencies listed, and the report kept against the unit as next year's baseline for the owner to accept.
No photo
What usually sends this back
The failures are almost always the evidence, not the work
- Terminations 'checked' by wiggling instead of torqued, so a creeping loose connection is never actually found.
- Transformer section skipped because it needs a shutdown, and its ventilation stays choked with dust year on year.
Verified against
Common questions
6 answers
- What does this power distribution unit annual checklist cover?
- 14 items across 5 sections, covering outage coordination, de-energized inspection, transformer section, grounding and protection, and more. Each item spells out what the person walking the job is actually looking for, not just a box to tick.
- Who should run this inspection?
- The electrician on the annual de-energized service, coordinated with a scheduled shutdown.
- When in the schedule should this walk happen?
- Once a year during a planned outage, since torqueing terminations and opening the transformer section means the unit has to come down.
- Why do these items ask for a photo?
- 10 of the 14 items call for photo evidence, 11 photos in all. A checklist answer without the photo is a claim; the photo is what makes the record worth something in a dispute and lets a reviewer approve work without re-walking the job.
- What most often fails a power distribution unit annual inspection?
- Terminations 'checked' by wiggling instead of torqued, so a creeping loose connection is never actually found. Transformer section skipped because it needs a shutdown, and its ventilation stays choked with dust year on year.
- Can I use this checklist in RTI?
- Yes. Start a free RTI workspace, build this list as a checklist, and the Photo Gate holds the submit button until every mandatory item is answered and its photos are attached. Approved inspections roll into a branded turnover package with a tamper evident audit trail.
Run it with the Photo Gate
A checklist nobody can submit half-finished
Load this list into RTI, stick a QR tag on the area it covers, and the submit button stays locked until every mandatory item is answered and the 11 required photos exist. Approved walks roll into a branded turnover package with a tamper evident record behind every line.
See all 508 checklists · 6741 items and 5984 photo requirements in total.