Field reference for EV charging technicians. 7 entries, taken from the PlugWatt app.
Reference notes from PlugWatt, the offline field toolkit for electric vehicle charging installation and service technicians. It works with no cell signal, because the sites do not have any.
Get PlugWatt on the App StoreDC fast chargers carry up to 1000 V DC with high available fault current. DC arcs have no current zero crossing, so they sustain instead of self extinguishing.
An AC arc gets 120 chances a second to extinguish at a current zero. A DC arc gets none: once struck it burns until the circuit opens or the gap grows
Lower peak energy than a comparable AC event but longer duration; the exposure adds up
NFPA 70E requires an arc flash risk assessment and PPE for DC systems over 100 V
Available fault current at the DC bus is high; module outputs parallel onto the bus
The battery on the vehicle side is also a source: the cable can be fed from both ends during a session
NFPA 70E 130
NFPA 70E Annex D DC methods
Arc flash PPE for DC work comes from the site arc flash study, not from a field estimate. This app deliberately does not compute incident energy.
Use the site arc flash study and equipment labels for incident energy and PPE category
If a DC label is missing, stop and escalate; do not guess a category
DC incident energy methods exist in NFPA 70E Annex D, but they are engineering calculations with system data you do not have at the connector
Face shield and arc rated clothing per the study; Class 0 gloves handle the shock hazard, not the thermal hazard
NFPA 70E 130.5
NFPA 70E Annex D
Site arc flash study
Class 0 insulating gloves, arc rated face protection where the study requires it, and insulated DC rated tools are the working baseline for energized diagnostics.
Class 0 insulating gloves are rated for 1000 V maximum use, matching the DC fast charging voltage class
Leather protectors go over the rubber; the rubber is the insulation, the leather is its armor
Face shield rated for the arc exposure the study names
Insulated tools rated 1000 V for work near energized DC
Voltage rated meter leads and a meter rated CAT III or better for the environment
Standards: OSHA 1910.137 for the gloves program, ASTM D120 for the gloves, NFPA 70E for selection
OSHA 1910.137
ASTM D120
NFPA 70E 130.7
Insulating gloves live on a test clock. An expired or damaged glove is not PPE, it is a costume.
Electrical test every 6 months by an accredited lab; the stamp on the cuff carries the test date
Gloves issued for service must have been tested within the previous 12 months
Air test before each use: roll the cuff, listen and feel for leaks
Inspect for cuts, ozone cracking, swelling, and embedded debris before each use
Store gloves in their bag, out of sunlight, not folded, nothing on top
The glove log form in this app records certification dates, air tests, and issue history
OSHA 1910.137(c)
ASTM D120
ASTM F496
Personalized locks and tags on the disconnecting means, verification of absence of voltage, and respect for stored energy in DC link capacitors.
One lock, one tag, one person: everyone working applies their own lock
Identify all sources: the AC supply, and remember the vehicle battery feeds the cable during a session
Open the disconnecting means, apply lock and tag, then attempt normal restart to prove isolation
Verify absence of voltage with a meter proven on a known source before and after the check
DC link capacitors store real energy after isolation; respect the manufacturer discharge time before opening power compartments
Some cabinets have capacitor discharge indicators; absence of an indicator is not absence of charge
OSHA 1910.147
NFPA 70E 120
Manufacturer service manual
The DC bus capacitor bank holds lethal charge after every isolation. Discharge time is a manufacturer number, not a guess.
Bleed resistors take minutes, not seconds; the manual states the wait time
A failed bleed resistor means the bank may never self discharge: always verify with a meter
Measure DC bus voltage at the designated test points before touching bus work
Vehicle side: the battery holds its charge permanently; cable and connector work needs the vehicle disconnected
NFPA 70E 120.5(7)
Manufacturer service manual
Charging sites are live parking lots. Traffic, heat, weather, and awkward lifts injure more techs than arcs do.
Work near live traffic: cones, high visibility wear, and vehicle positioning as a barrier
Cabinets and cables run hot; liquid cooled cable skin temperatures surprise people
Power modules are heavy and awkward; use the extraction tooling and a second person
Outdoor cabinets host wasps, rodents, and their damage: look before reaching
Heat stress on black asphalt in summer is a real exposure; hydrate and shade
OSHA general duty
Site specific JHA
Reference notes from PlugWatt, the offline field toolkit for electric vehicle charging installation and service technicians. It works with no cell signal, because the sites do not have any.
Get PlugWatt on the App StoreThese notes are a field aid, not a substitute for the governing codes, the stamped drawings, the authority having jurisdiction, or manufacturer manuals. Verify against the current documentation for your installed equipment.