Class Code 3643
Electric Power/Trans Equip Mfg; Electric Control Panel Mfg
Class Code 3643 applies to manufacturers that build electric power and transformer equipment and assemble electric control panels. This classification matters because it reflects specific exposure to electrical, mechanical and chemical hazards; the approved pure premium rate is $1.515 per $100 of payroll.
What Class Code 3643 Covers
This class covers shop-based manufacturing and assembly of electric power equipment such as distribution and power transformers, switchgear components, motor control centers, and industrial control panels. Included operations are coil winding and core assembly for transformers; sheet-metal fabrication and enclosure assembly for panels; internal wiring, terminaling, soldering and component mounting; and high-voltage or hipot testing and functional bench testing. It also includes related processes such as insulation application, varnish impregnation, oil filling and vacuum drying when performed as part of manufacturing. The classification applies to factory production work, not on-site installation or electrical contracting work performed at customer locations.
Who It Applies To
- Power and distribution transformer manufacturers and rewind shops
- Industrial control panel fabricators and OEM panel assemblers
- Switchgear and motor control center manufacturers
- Contract manufacturers that build electrical enclosures and wired assemblies
- Shops that perform coil winding, varnishing, and electrical testing
Common Job Duties
- Coil winding, core stacking and assembly of transformer components
- Sheet-metal cutting, bending, welding and assembly of enclosures
- Wiring, terminaling, soldering and routing of control wiring inside panels
- High-voltage/hipot testing, insulation resistance testing and functional bench testing
- Applying insulating varnish, oil filling/vacuum drying and related chemical handling
- Operating coil-winding machines, presses, drill presses and other powered equipment
- Material handling and rigging of heavy cores, tanks and enclosures
Common Injury Risks
Understanding the $1.515 Rate
The approved pure premium rate of $1.515 per $100 of payroll represents the expected loss cost assigned to this classification and is used by carriers as the baseline for calculating workers' compensation premiums. Actual employer premium will be that base rate multiplied by payroll, then adjusted for experience modification, policy-level rating plans, scheduled credits or debits, state assessments, and insurer expense loads or group program discounts.
Cal/OSHA Compliance Requirements
Cal/OSHA General Industry Safety Orders most relevant to Class 3643 include electrical safety standards, machine guarding, lockout/tagout for control of hazardous energy, hazard communication for solvents and varnishes, respiratory protection where airborne contaminants are present, and confined space entry procedures for tanks or large transformer housings. Employers should also follow NFPA 70E and established arc flash risk assessment practices when workers perform testing or maintenance on energized equipment.
How Key HR Helps Employers Under Class Code 3643
A PEO like Key HR helps manufacturers in this classification by consolidating payroll classification accuracy, administering workers' compensation programs, and implementing targeted safety and return-to-work programs that reduce claims severity. Key HR can provide training (NFPA 70E, LOTO, HAZCOM), OSHA recordkeeping, claims advocacy, and access to group purchasing power that can lower premiums and improve loss experience.
Get a QuoteFrequently Asked Questions
If my shop wires and tests control panels but my electricians also install them at customer sites, which class code applies?
Panel assembly and in-shop wiring/testing belong in Class 3643. Work performed by electricians who travel to customer sites to install, wire or connect panels is typically classified under an electrical contractor code, not 3643. Track payroll by task to ensure correct classification during audit.
What specific safety steps lower workers' comp exposure for transformer and control panel manufacturers?
Key measures include formal lockout/tagout and energized work procedures, arc flash risk assessments and PPE, machine guarding, mechanical lifting aids and rigging controls for heavy parts, solvent substitution and ventilation, mandatory training for high-voltage testing, and an early-return-to-work transitional duty program to reduce claim duration and experience modification impacts.
How is payroll allocated for employees who split time between bench assembly and clerical work?
Payroll should be allocated to the class that reflects the work performed. Time studies or percentage allocations are commonly used: hours spent on bench assembly go to Class 3643 while clerical hours are assigned to a clerical or office code. Accurate allocation reduces audit adjustments and misclassification penalties.
Quick Facts
- Class Code
- 3643
- Classification
- Electric Power/Trans Equip Mfg; Electric Control Panel Mfg
- Pure Premium Rate
- $1.515 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
Get a Quoteor call (800) 922-4133Ready to Simplify Workers' Comp for Class Code 3643?
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