A plain-English overview of hazardous-location remote heads in Class I, Division 2 (C1D2)—what the listing covers, where to locate the power unit, acceptable wiring methods, and how to document your plan so it passes inspection.
Last updated: October 2025
What C1D2 means (and why it matters)
Class I, Division 2 areas are locations where flammable gases or vapors are present only under abnormal conditions (leaks, maintenance, failure). Hazardous-location remote heads installed in these spaces must be specifically listed for C1D2, including temperature code and enclosure type as applicable. General-purpose or only “wet-location” heads are not enough.
If you’re deciding when remote heads belong in a classified space (or comparing Div 1 vs Div 2), see Remote Heads in Hazardous Areas — When & How to Use, then return here for C1D2 listings, wiring, and inspection basics.
Quick takeaway: C1D2 isn’t automatically “explosion-proof” or Div 1 rated—only rely on what the nameplate states.
For broader code context and AHJ expectations, see the remote head code requirements overview.
- Area classification refresher: C1D2 (gas/vapor under abnormal conditions) vs C1D1 (present in normal operation) vs unclassified areas outside the boundary.
- Gas groups & T-codes: Select heads with the correct gas group and T-code; ensure max surface temperature is safe for the process/ambient.
Power unit location (best practice)
- Prefer unclassified (safe) areas: Mount the remote-capable battery/inverter where it isn’t exposed to the classified atmosphere—simplifies listings, wiring methods, and maintenance.
- If the host must be in C1D2: Use a unit and accessories that are listed for C1D2, with proper enclosure type. Coordinate labels and documents with your AHJ.
- Distance to heads: Keep runs short; long home-runs increase voltage drop and complicate conductor sizing.
- Boundary planning: If the host is outside, show boundary seals and routing on your one-line.
Wiring methods & voltage choices
Conductors & fittings: Follow classified-location methods (sealing fittings where required, approved conduit/hubs, bonding/grounding). Mark polarity at every termination. For long runs or many heads, step up supply voltage and size conductors to control drop.
Choosing supply: compare options in 12V vs 24V for remote heads, then use the wire-gauge & distance tables to pick AWG and confirm one-way distances within your drop limit (often ~5%).
Head selection & environment
- Listing first: Head must be C1D2-listed (and T-code appropriate to gas group and ambient).
- Nameplate checklist: Class I, Div 2 marking, gas group, T-code, ambient (Ta), voltage, and any NEMA/IP rating for washdown or corrosion.
- Environment: Many hazardous spaces are also wet, dusty, or corrosive. If exposed to weather or washdown, pair C1D2 with wet-location/IP/NEMA rating—see outdoor IP65 spacing & aiming for mounting/aiming details.
- Compatibility: Verify head voltage/load match the host. For mixed families, consult a remote head compatibility matrix before ordering.
- Optics & aiming: Reduce glare with off-axis aims and suitable beam angles; avoid hot spots on shiny equipment or thresholds.
Labeling & documentation
- One-line diagram: Show head count, watts/head, conductor gauge, run lengths, boundary seals, and host location (classified vs unclassified).
- Listings packet: Include spec sheets showing C1D2 listing, T-code, enclosure/hub details for heads and any in-space power equipment.
- Voltage-drop math: Keep calculations and assumptions (ambient, design buffer, drop target). Cross-check AWG with the wire-gauge tables above.
- Test records: Monthly quick checks and annual 90-minute logs retained per local policy.
Inspection checklist
- Correct listing: Heads (and any in-space equipment) marked for C1D2; T-code appropriate to hazard.
- Wiring method: Approved fittings/seals used; polarity/grounds correct.
- Voltage drop: Conductors sized per run length; far head remains bright at end-of-discharge. See the tables above.
- Coverage: Aim/overlap to avoid dark bands at doors and along the path. If outdoors, apply IP65 spacing/aiming practices referenced above.
- Documentation: One-line, listings, and test logs on file; see the code overview earlier for AHJ expectations.
Fire Code quick references
Useful baselines for hazardous-location egress equipment (confirm with your AHJ):
FAQ
Can a wet-location remote head be used in C1D2?
No—“wet-location” alone isn’t sufficient. The head needs a C1D2 listing appropriate to the gas group and T-code.
Where should I put the remote-capable battery/inverter?
Prefer unclassified areas just outside the boundary. If the host must be in C1D2, use equipment listed for the area and document enclosures, seals, and T-code.
Do I need 24 V for multi-landing risers?
Not always, but 24 V reduces current and helps manage drop on long vertical runs. Compare 12V vs 24V and select AWG from the wire-gauge tables.