Acushnet Marine Electric EST. 2008 · MA #ME-12740
Plate P-04 Switchboard upgrades Last revised 2026-04-22

A new board, with the arc-flash labels to match.

A 1980s switchboard on a working scalloper has had forty years of vibration, salt, and patches. The breakers are not where the as-built drawings say they are. The bus is corroded behind the dead front. The selective coordination is gone or it never was. We replace these boards. We do the coordination study. We label them to NFPA 70E. We hand the captain a binder.

Voltages
120/240 V single-phase · 240 V Δ · 480/277 V wye
Switchgear we install
Eaton Magnum DS · Square D MasterPact · ABB Tmax
Standards
IEEE 45.1, NFPA 70E, 46 CFR Subch. J, ABYC E-11
Arc-flash analysis
SKM PowerTools · IEEE 1584-2018
A new 480 V switchboard installed on a 78-foot scalloper, with arc-flash labels visible on each section and breaker numbers stenciled in fuchsin pink.
Plate P-04.a · Main switchboard, F/V Providential, post-commissioning 2026-03

§ 01 · Scope of a board upgrade

The deliverable is a full replacement of the main switchboard, a re-coordination of the breakers downstream, an updated set of arc-flash labels for every panel on the boat, and an as-built binder. We do not "patch" boards — if a board is far enough gone to be on the upgrade list, the patch will fail in twelve months and we will be back. The replacement is the right answer.

What stays: the genset, the inverter, the load-sharing controllers if they are good, the field wiring on the load side of the panels (assuming it has been recently rewired or is in good condition), and the captain's preferences for breaker numbering — we keep the numbering scheme the captain has been using for thirty years, even if it is non-standard.

§ 02 · The selective-coordination study

Selective coordination is the arrangement of breakers in series such that a fault on a downstream branch opens the downstream breaker, not the upstream main. NEC 700.32 / 701.27 / 708.54 require it on certain emergency systems; on commercial vessels above the inspected threshold, USCG 46 CFR §111.10 requires it; on small vessels we apply it because losing the whole boat to a galley fault is not acceptable.[1]

The study is done in SKM PowerTools (the bench license lives at the yard). We model the genset, the bus, every breaker, every cable run, and we calculate the available fault current at every node. The output is a time-current chart that proves the coordination is selective for fault currents up to the genset's contribution.

The study is signed by Dom (master rate — see rates) and bound into the as-built binder.

§ 03 · Arc-flash labelling

NFPA 70E-2024 requires an arc-flash label on every panel that may be worked live, naming the incident energy at the working distance, the arc-flash boundary, the PPE category, and the date of the analysis.[2] We calculate per IEEE 1584-2018, label every panel, and provide the captain a copy of the analysis.

The label includes: working distance (typically 18 inches at the dead front), incident energy in cal/cm², arc-flash boundary in inches, the required PPE category (1 through 4), the analysis date, the analyst, and the available short-circuit current. The label is engraved phenolic, white-on-red, mounted with stainless rivets. It does not peel off.

§ 04 · Commissioning

The board is energized in stages. We pre-test every breaker on a Doble M4000 against the manufacturer's trip curves. We meg every cable run before we connect it. We Hi-Pot the bus before we land the conductors. We close the main with the load side empty and we measure phase rotation. Only when every reading agrees with the design does the load come on.

The first hour of running is on the load bank, not on the boat. Generator under load, board taking the load, every meter watched, every breaker thermography-imaged with a Fluke Ti200. Only after the thermography is clean does the boat take its own loads.

§ 05 · Cost & lead time

Switchboard upgrades are major projects. We slot two or three a year. The rough range:

Single-phase 240 V, 200 A$28k–$42k, 8–14 working days
240 V Δ 3-phase, 400 A$62k–$95k, 14–22 working days
480/277 V wye, 400–600 A$110k–$185k, 22–34 working days

The above includes the SKM coordination study, the IEEE 1584 arc-flash analysis, all engraved labels, and the bound as-built binder. It excludes any new field wiring (that is P-01) and any genset work (that is P-05).

A specific story

The 2026-03 board upgrade on F/V Providential ran 26 working days at the dock at Pier 3. The 1986 Eaton DS-206 was replaced with a new Eaton Magnum DS, the SKM study ran in three afternoons, and the arc-flash analysis came in at 4.7 cal/cm² at 18 inches at the main — PPE Category 2 with a 36-inch boundary. The labels were stenciled in fuchsin pink and white on phenolic; the binder lives in the chart-table drawer.

Cross-references: P-01 for upstream/downstream rewires, P-05 for genset rebuilds, P-07 for survey-prep walks of older boards.

Sources & further reading

  1. U.S. Coast Guard. 46 CFR Part 111 — Electric systems, general requirements. ↩
  2. National Fire Protection Association. NFPA 70E-2024: Standard for Electrical Safety in the Workplace. ↩
  3. IEEE Standards Association. IEEE 1584-2018 — IEEE Guide for Performing Arc-Flash Hazard Calculations.
  4. SKM Systems Analysis. PowerTools for Windows.
  5. Eaton. Magnum DS air circuit breakers.
  6. Schneider Electric. MasterPact MTZ.
  7. Doble Engineering. M4000 circuit-breaker test set.
  8. Fluke. Ti200 thermal imager.