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PEI IMA Grade 9 study materials
PEI IMA Grade 9 study resources

PEI IMA Grade 9: Electrical and Control Systems

PEI IMA Grade 9 · Work through your exam, one topic at a time.

All guide sections

Electrical and Control Systems

Electrical and Control Systems (Domain 3) tests hazardous-area classification, wiring methods, bonding and grounding, and the control chain from the tank monitor to the dispenser. The recurring theme is that a spark in the wrong place ignites vapor, and the code rules exist to keep sparks out of that place.

Classified areas (NEC Article 514)

  • Gasoline vapor is Class I, Group D. The area within 20 ft of a dispenser from grade to 18 in above grade is Division 1, as are the interiors of sumps, pits and tanks and any place where vapor can accumulate.
  • Beyond the Division 1 envelope the area is Division 2 or unclassified depending on layout; the approved classification drawing governs the site, and state or local amendments can tighten it.
  • Sump interiors are Division 1 regardless of how tidy they look.

Wiring methods

  • Threaded rigid metal conduit, explosion-proof boxes and listed fittings. No EMT, no wire nuts, no cord grips in classified areas.
  • Seal-offs are required where conduit leaves a classified area, within 18 in (450 mm) of the boundary, and at dispenser and sump entries, to stop vapor migrating through the conduit.
  • Flexible connectors at the dispenser and STP are for vibration and removal only and must be listed for the location.
  • Bonding: tank, piping, dispenser frames and all metallic components are electrically continuous; the grounding electrode system and bonding jumpers are part of the inspection.

Controls

  • The STP control relay, dispenser controller, ATG console, sump sensors and emergency stop form one chain.
  • The emergency stop must de-energize all dispensers, not just the nearest one, and must be reachable without walking into a fire.

Worked example

Dispenser 3 will not dispense; the others work. Isolate in order: (1) does the dispenser display have power? (2) is the STP for that product running, checked by sound or amp clamp? (3) has the line leak detector tripped, or has the ATG put the product into alarm or shutdown? (4) is the emergency stop latched? (5) breaker? Working from the dispenser back to the tank top finds the fault without opening a junction box in a classified area.

Traps

  • Substituting duct seal for a seal-off.
  • Ignoring the 18 in seal location when a conduit run is re-routed.
  • Mounting a single emergency stop inside the sales building only.
  • Installing non-listed sensors or junction boxes inside a sump.