Disconnects: code-required, operationally essential.
NEC 430.102 requires disconnect within sight of motor for maintenance safety. Proper sizing, placement, and lockout/tagout compatibility matter for both code compliance and worker protection.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Machinery disconnect requirements per NEC 430: disconnect must be within sight of motor (≤50 feet, unobstructed view), sized at minimum 115% of motor FLA, capable of being locked in open position for OSHA lockout/tagout compliance. Common forms: heavy-duty safety switch (most common, fusible or non-fusible), motor circuit protector (combination disconnect + overcurrent), molded-case switch in MCC bucket. Wrong sizing or improper placement creates both code violation and safety risk — workers cannot reliably de-energize machinery during maintenance.
01Why disconnect placement matters more than people expect.
OSHA lockout/tagout (LOTO) regulations require that energy sources be physically isolated and locked out during machinery maintenance to prevent unexpected startup. The disconnect within sight requirement supports this: the worker performing maintenance must be able to verify their lock is on the disconnect from the work location, and other workers must be able to see the locked-out condition before re-energizing.
Common installation failures we encounter in older Marin facilities: disconnects located in distant electrical rooms (not within sight of machine), disconnects without lockout provisions (older switches without locking holes or pins), shared disconnects serving multiple machines (lockout of one machine de-energizes others creating production disruption that incentivizes bypassing LOTO). Modernizing these installations is straightforward but often gets deferred until inspection or incident forces the issue.
02Disconnect specification basics.
Sizing
Heavy-duty safety switch rated at least 115% of motor FLA. For 30 HP 480V motor at 40A FLA: minimum 46A switch — typically 60A standard size. Common sizes: 30A, 60A, 100A, 200A, 400A. Fusible versions accept time-delay fuses; non-fusible versions rely on upstream overcurrent protection.
Placement
Within sight of motor (≤50 feet) per NEC 430.102. Mounting height 4'-6.5' to operating handle per NEC 404.8 (accessible without ladder). Working clearance 36 inches in front per NEC 110.26. Often mounted on machine frame or adjacent wall.
Lockout compatibility
All modern heavy-duty safety switches include lockout provisions (hasp accepts padlock when handle in OFF position). Older equipment may need retrofit lockout devices ($30-$150 per switch) or replacement. OSHA expects multiple-employee lockout capability (multiple locks on single switch) for jobs involving multiple workers.
03Common Marin installations.
Single-machine disconnect installation: $400-$1,800 depending on size, location accessibility, conduit run length. Includes the disconnect, mounting, conduit and connections, lockout devices. Multi-machine facility upgrades to add proper disconnects often combine with other code corrections during planned shutdowns: typical scope $5,000-$25,000 for facility-wide disconnect retrofitting.
Recent projects include Marin food processing facility (15+ machine disconnects updated to current code with proper lockout provisions during planned annual shutdown), local prototype shop (new CNC machine disconnects installed during shop expansion), and various commercial HVAC equipment disconnects for mechanical contractor partner projects.
Common questions.
Can the breaker in the main panel serve as the disconnect?
Sometimes, if located within sight of motor and meeting NEC 430 requirements. In small commercial buildings where main panel is in same room as small motor (like exhaust fan), main panel breaker can serve as disconnect. For typical industrial layouts where panel is in electrical room and motors are scattered in production area, separate motor disconnects are required (panel isn't within sight).
What about emergency stop vs disconnect?
Different functions. Emergency stop (E-stop) is a control device that signals the machine controller to safely stop machine motion — it doesn't necessarily disconnect power. Disconnect physically isolates power supply. OSHA LOTO requires power isolation (disconnect), not just control stop (E-stop). Many machines have both: E-stop for normal operational stops, disconnect for maintenance lockout.
Do battery-powered or low-voltage machines need disconnects?
NEC 430 motor disconnect requirements apply to motors served from electrical supply system. Battery-powered or self-contained low-voltage equipment has different requirements. OSHA LOTO still applies — energy isolation point exists somewhere (battery disconnect, fuel cutoff) and must be lockable. For typical industrial machinery on building electrical system, NEC 430 disconnect applies.
How often should disconnects be tested?
NFPA 70B (Maintenance of Electrical Equipment) recommends annual operational test of motor disconnects: physically operating the switch under load to verify proper operation, inspecting for arcing damage, verifying lockout function. Most Marin industrial facilities incorporate disconnect testing into annual electrical maintenance program — we provide this as scheduled service for clients on maintenance contracts.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
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Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.