Electrical Power

How to Choose a Company Switch: 8 Specs to Confirm Before You Buy

How to Choose a Company Switch: 8 Specs to Confirm Before You Buy

Aakash Kapoor

A company switch is the connection point where portable cam-lock cable feeds tie into a venue’s electrical system to power temporary equipment like touring sound, lighting, and broadcast gear. ESL Power Systems builds this equipment as the ShowSwitch™ line — 100A, 200A, and 400A standard cam-lock configurations, 60–100A pin & sleeve theatre outlets, and custom concert power distribution boards up to 1600A, all UL 891 Listed as theatrical switchboards. Choosing the wrong configuration usually shows up on load-in day, not before. The eight specs below apply to any company switch on the market; we’ve noted how the ShowSwitch line is built for each one.

Quick answer Before you specify or purchase a company switch, confirm: incoming wire size, 200% rated neutral, isolated ground, direct-wire lugs, digital ammeter, interior work light (standard on ShowSwitch), NEMA 1 vs. NEMA 3R/3RX enclosure, and mechanical vs. electrical interlock.

Jump to a spec:

What incoming wire size does a company switch need?

Short answer: Match the lugs to the conductor size, count, and material of the feed actually arriving at the install — not a spec sheet from a different job.

Undersized lugs can’t accept the conductors; oversized lugs leave a loose termination. Before ordering, confirm:

  1. Conductor size and count of the incoming feed
  2. Where conduit enters the enclosure (top, bottom, or side)
  3. Whether the feed is aluminum or copper — lug ratings differ

ESL’s ShowSwitch line sizes line terminals by amperage rather than using one lug kit across the board, so confirming the amperage and conductor size against the table below before ordering avoids a mismatched lug kit at load-in:

ModelAmperageLine TerminalsNeutralGround
3313-01100A#14 AWG – 3/0#6 AWG – 250 kcmil#6 AWG – 250 kcmil
3323-01200A3/0 – 350 kcmil#6 AWG – 250 kcmil#6 AWG – 250 kcmil
3343-01400A(2) 2/0 – 500 kcmil(2) #2 – 600 kcmil#6 AWG – 250 kcmil

Do you need a 200% rated neutral?

Short answer: Yes, if the load includes dimming systems, switch-mode power supplies, LED lighting, or other equipment that generates harmonic currents — standard neutrals sized to match the phase conductors aren’t enough for loads like these.

Neutral loading should be evaluated during system design. Keep in mind that triplen harmonics [180Hz] stack directly on top of each other at the neutral node.

Note: adding a second neutral can mean six cam-lock receptacles instead of five, so this affects the panel’s physical layout, not just its wiring. On the 400A ShowSwitch (3343-01), this is built in as dual #2–600 kcmil neutral terminals rather than a single lug — flag the load profile at time of order so the correct neutral configuration ships from the factory.

Is isolated ground required?

Short answer: Yes, any time the downstream load includes audio equipment sensitive to ground-loop hum or buzz.

An isolated grounding conductor provides a dedicated grounding path for sensitive electronic equipment, helping reduce electrical noise and ground-loop issues in audio systems.

ESL offers isolated ground as a factory option on ShowSwitch: an isolated ground bus, separated from the equipment ground bonded to the enclosure, can be specified at time of order for systems feeding sensitive audio gear. Flag this requirement up front — it changes the internal bussing rather than being a field modification.

Do you need direct-wire lugs?

Short answer: Yes, if any downstream equipment doesn’t have cam-lock connectors — direct-wire lugs let bare conductor ends terminate directly, no cam adapter needed.

Company switches are built around cam-lock connectors, but not every piece of connected equipment has them. Confirm this capability if any downstream gear lacks cam connectors.

On ShowSwitch, the direct-wire lug option uses mechanical lugs rated for #6 AWG to 250 MCM — useful for older house dimmer racks or fixed distro that predates cam-lock standardization. ESL also offers reverse-gender neutral and ground configurations and a POSI-LOK™ panel option for cam terminations where a different connection style is needed.

Do you need a digital ammeter?

Short answer: Yes, if you need a real-time read of current draw — to verify loads against rated capacity or track demand changes throughout an event.

A built-in digital ammeter provides a convenient way to monitor current draw in real time, helping venue managers identify potential overload conditions before protective devices trip. Without a built-in meter, operators may need to rely on external test equipment or system calculations to monitor loading.

ShowSwitch offers a UL Listed 1/4 DIN volt-amp meter with a three-row, three-digit LED display, accurate to ±0.5% of full scale on voltage and ±2 digits on current, reading all three phases simultaneously by default. Every unit also carries door-mounted indicator lights that illuminate when each cam connector is mated and the breaker is on — a quick visual check before anyone touches a live connection.

Do you need an interior work light?

Short answer: Yes — it’s a low-cost option with an outsized effect on install speed and safety, since company switches are frequently accessed in dark venue environments: backstage, in trussing, under a stage.

An interior work light now ships as standard equipment on ShowSwitch, so this is one less option to track down separately — the chamber is lit as soon as the door opens, with no need to call it out as an add-on when specifying your unit.

Indoor or outdoor: NEMA 1, 3R, or 3RX enclosure?

Short answer: NEMA 1 for standard indoor/dry installs; NEMA 3R or 3RX if the unit will sit outside or in an exposed or corrosive location — it’s an enclosure-level construction difference, not a field retrofit.

Standard company switches ship NEMA Type 1. If the unit will sit outside or in an exposed location, specify NEMA 3R up front.

ShowSwitch’s standard NEMA Type 1 enclosure is 14-gauge steel with a powder-coated matte black finish. Full construction details are on the company switch specifications page. For outdoor work, ESL also offers a Type 3R enclosure (available in lighter colors) and a Type 3RX stainless steel enclosure for coastal air, washdown areas, or other corrosive environments where painted steel would degrade faster.

EnclosureEnvironmentTypical Use
NEMA Type 1Indoor, dry locationsStandard for most venues; ShowSwitch ships Type 1 by default
NEMA Type 3ROutdoor, exposed to rain/weatherFestivals, outdoor stages, exposed perimeters
NEMA Type 3RX (stainless)Outdoor, coastal/washdown, corrosive airLong-term outdoor installs where painted steel would corrode

Mechanical or electrical interlock?

Short answer: Most applications call for at least a mechanical interlock — it requires the intended sequence of operation without relying on a control circuit, so it still works during a control power failure. Add an electrical interlock only if the application needs the extra automation.

Interlocks help prevent unsafe operation by requiring equipment to be operated in the intended sequence. Depending on the application, interlocks may be mechanical, electrical, or a combination of both.

  • Mechanical interlock: Uses physical mechanisms to prevent certain actions or switch positions until specific conditions are met. Because it does not rely on a control circuit, it continues to function even during a control power failure.
  • Electrical interlock: Uses auxiliary contacts, relays, sensors, or control circuits to prevent unintended operation. Electrical interlocks can provide additional functionality and automation but depend on the proper operation of the associated control system.

ESL’s ShowSwitch ships with a mechanical, safety-interlocked door as standard. The interlock prevents making or breaking cam-lock connections under load by requiring the breaker to be opened before the door can be accessed. The operator handle is recessed so it does not protrude into narrow passageways, and the door can be padlocked for additional jobsite security. For applications requiring electrical interlocks or additional control functionality, consult ESL’s engineering team during the specification process.

FAQ: Company Switch Specification

What is a company switch used for? Connecting portable cam-lock power feeds from a venue’s electrical system to temporary equipment such as touring audio, lighting, and video gear.

Is a company switch the same as a transfer switch? No. A transfer switch selects between two power sources (such as utility and generator). A company switch distributes portable feeder cable to temporary equipment.

What amperage does ESL’s ShowSwitch line cover? 100A, 200A, and 400A in standard cam-lock configurations (models 3313-01, 3323-01, and 3343-01), 60–100A pin & sleeve theatre outlets, and custom concert power distribution boards up to 1600A.

Does ESL’s company switch carry a safety listing? Yes — ShowSwitch is UL Listed and labeled under the UL 891 standard for theatrical switchboards, which is typically required for code compliance and insurance in entertainment venues.

Does ShowSwitch include an interior work light? Yes — an interior work light is now standard equipment across the ShowSwitch line.

Final Takeaway

A company switch looks like a simple box with cam-lock connectors on it. The 8 specs above determine whether it fits the job: the wire coming in, the load going out, the environment it sits in, and how safely it fails.

ESL’s ShowSwitch line is built around these same 8 variables — model selection (3313-01, 3323-01, 3343-01, or a custom distribution board), lug and neutral sizing, grounding (including isolated ground), metering, enclosure rating, and interlock type are all confirmed before the unit leaves ESL’s Corona, CA factory, and an interior work light ships standard. Get these confirmed before you order, not during load-in.

Want to see these options on an actual unit? Watch ESL’s ShowSwitch company switch feature video, review the standard specifications and features pages at eslpwr.com, or contact ESL Power Systems at 1-800-922-4188 or info@eslpwr.com to talk through the right configuration for your venue.

Benefits of Well Written Specifications

Erika Thorson

Why Well-Written Specifications Are Essential to Project Success 

Whether you’re an engineer, facility owner, contractor, manufacturer, or distributor, one challenge remains constant: making sure everyone is working toward the same goal. 

When project specifications are vague, incomplete, or open to interpretation, problems quickly follow. One supplier may quote a basic solution, another may quote a premium solution, and neither may align with what the customer actually needs. The result is confusion, inconsistent bids, change orders, project delays, and unnecessary costs. 

Well-written specifications help eliminate these issues by providing a clear roadmap for everyone involved. 

1. Clearly Defines Project Scope and Expectations 

A comprehensive specification establishes exactly what the project requires, including performance expectations, safety requirements, installation considerations, environmental conditions, and quality standards. 

Good specifications: 

  • Clearly communicate design intent and project objectives 
  • Align expectations among owners, engineers, contractors, and suppliers 
  • Reduce assumptions and misunderstandings 
  • Provide important details that may not be fully captured in drawings 

When everyone understands the requirements from the beginning, projects move forward more efficiently and with fewer surprises. 

2. Saves Time and Reduces Project Costs 

Creating detailed specifications requires effort upfront, but that investment typically pays for itself many times over during procurement and execution. 

Well-written specifications help: 

  • Generate comparable “apples-to-apples” bids 
  • Reduce contractor contingency costs associated with uncertainty 
  • Minimize requests for clarification during bidding 
  • Reduce change orders and project rework 
  • Accelerate project execution by eliminating ambiguity 

In short, clear specifications lower project risk—and lower risk often translates directly into lower project costs. 

3. Improves Quality and Compliance 

Specifications serve as more than a design document. They become an important tool for quality control throughout the project lifecycle. 

Detailed specifications: 

  • Establish measurable performance and safety requirements 
  • Help identify non-compliant bids before equipment is purchased 
  • Create accountability among project stakeholders 
  • Provide a documented reference when questions or disputes arise 
  • Support consistent project execution across multiple sites 

A strong specification helps ensure that the equipment delivered matches the equipment that was intended. 

Why Technical Expertise Matters 

The most effective specifications are typically written by people with deep technical knowledge and real-world application experience. They understand not only how equipment should perform, but also how it will be installed, operated, maintained, and serviced throughout its lifecycle. 

This expertise is particularly important for specialized electrical equipment where safety, reliability, code compliance, and operational uptime are critical. 

The Bottom Line 

Specifications are often viewed as a project requirement. In reality, they are a risk-management tool. 

A well-written specification creates alignment, improves bid quality, reduces project costs, supports compliance, and increases the likelihood of a successful outcome for everyone involved. 

The time invested in developing clear, detailed specifications upfront can prevent significant costs and headaches later. 

At ESL Power Systems, we regularly partner with engineers, consultants, contractors, facility owners, and end users to develop detailed specifications for safety-critical electrical power distribution applications. From the earliest planning stages through final installation, clear and complete specifications help ensure that equipment is properly selected, code-compliant, application-specific, and aligned with long-term operational needs. 

Whether your project involves emergency power connections, shore power systems, reefer power, entertainment power distribution, wayside power, or a fully custom-engineered solution, strong specifications are one of the most important foundations for project success. They reduce ambiguity, support smoother bidding and approval processes, help avoid costly changes, and give project teams greater confidence that the final system will perform safely and reliably in the field. 

To support your upcoming projects, ESL Power Systems offers a variety of downloadable Standard Specifications that can be incorporated into your project documents and adapted to your specific application requirements. Explore the resources below to find specification language for common power distribution applications: 

Reefer Outlets 
Shore Power 
Commercial Ship-to-Shore Power 
Emergency Power Resources 
Company Switch 
Wayside Power

Adapted from 3 Benefits of Well Written Specifications | July 23, 2012

Specifying Hospital Emergency Power Interfaces: A Safety-First, Code-Compliant Q & A Guide for Engineers

Erika Thorson

Safer, code-compliant power interfaces engineered to your site for critical facilities.

Hospitals rely on uninterrupted power to sustain life-support systems, surgical environments, and critical infrastructure. Even a momentary loss of power can compromise patient safety, making system reliability and fail-safe operation non-negotiable.

Emergency power systems are specifically designed to protect life and property during outages by providing an independent power source when normal utility power fails.

Healthcare environments face stricter requirements than most industries because power loss directly impacts patient outcomes and safety

What Specifying Engineers Need to Get Right in Hospital Emergency Power Systems

Hospital emergency power systems are not just infrastructure; they are life safety systems. For specifying engineers, the responsibility goes beyond meeting code. It includes ensuring:

  • Safe operation under real-world conditions
  • Elimination of human-error risk
  • Reliable performance during critical events

Q: What is the engineer’s primary responsibility when specifying EPSS equipment?

A: To ensure the system is not only code-compliant, but also safe, operable, and aligned with the facility’s real-world conditions.

What Codes Directly Impact Emergency Power Specifications?

Healthcare power systems are governed by multiple overlapping standards:

  • NEC Article 517 (NFPA 70) – Defines Essential Electrical Systems (EES)
  • NFPA 110 – Performance requirements for emergency power supply systems
  • NFPA 99 – Risk categories and healthcare facility requirements
  • NFPA 101 – Life safety considerations

Q: Why is code compliance not enough?

A: Codes define minimum requirements, but they do not address all operational risks, especially those related to human interaction and system misuse.

Where Standard Specifications Fall Short in Healthcare Applications

Many emergency power specifications rely on generic or legacy language, which can introduce risk.

Q: What risks are commonly overlooked in standard specs?

A:

  • Operator error during switching
  • Unsafe or unintended backfeeding
  • Misaligned connectors or configurations
  • Lack of clarity in operating procedures

Key Insight:

👉 Most failures don’t happen in equipment; they happen at interaction points.

Designing for Human Error Prevention in Critical Power Systems

In hospital environments, manual interaction is unavoidable and that’s where risk concentrates.

Q: Where do the highest risks occur?

A:

  • Temporary generator connections
  • Switching between power sources
  • Maintenance and testing procedures

Q: How should engineers address this risk?

A: By specifying systems that:

  • Physically prevent unsafe actions
  • Guide correct operation
  • Reduce reliance on procedural controls

👉 This is the foundation of safety-first design.

What Are Safety-Interlocked Power Interfaces?

Safety-interlocked systems are designed to mechanically or electrically prevent unsafe conditions.

Q: What does a safety interlock do?

A: It prevents:

  • Parallel connection of normal and emergency sources
  • Switching under unsafe conditions
  • Incorrect sequencing of operations

Why It Matters for Engineers:

  • Reduces liability
  • Improves AHJ acceptance
  • Simplifies safe operation

Standard vs Custom-Engineered Power Interfaces

CriteriaStandard EquipmentCustom-Engineered (ESL)
Code ComplianceMeets minimumFully aligned + optimized
Site FitAssumedEngineered to facility
SafetyProceduralBuilt-in interlocks
Operator RiskHigherReduced
FlexibilityLimitedHigh

Q: When should engineers specify custom solutions?

A: When:

  • Facility layouts are complex
  • Load requirements vary
  • Safety risks cannot be mitigated through standard equipment

How to Write a Safer Emergency Power Specification

Specifying engineers can directly reduce system risk through clear, intentional specification language.

Sample Specification Language:

Provide safety-interlocked emergency power connection systems designed to prevent parallel connection of normal and emergency sources. Equipment shall be UL Listed and labeled under the UL 1008 standard and meet all applicable NEC standards.

Download ESL Specifications:

Q: What should every emergency power spec include?

A:

  • Code compliance requirements
  • Interlocking or safety mechanisms
  • Site-specific configuration requirements
  • Clear operational intent

Submittals and AHJ Approval: What Engineers Should Expect

Approval authorities (AHJs) and reviewers focus on clarity, safety, and compliance.

Q: What do reviewers look for in submittals?

A:

  • Defined interlocking methods
  • Accurate load ratings
  • Clear labeling and operation
  • Documentation of compliance

Q: What causes delays or rejections?

A:

  • Ambiguous specifications
  • Lack of safety mechanisms
  • Poor alignment with code intent

ESL Power Systems: Supporting Engineers from Specification to Implementation

ESL Power Systems works with engineers to ensure specifications translate into safe, compliant, real-world solutions.

Q: How does ESL support specifying engineers?

A:

  • Application-specific engineering guidance
  • Custom design aligned to drawings and site conditions
  • Code compliance support
  • Faster iteration compared to large OEMs

Q: What outcomes does ESL help engineers achieve?

A:

  • Reduced design risk
  • Smoother approvals
  • Safer installations
  • More reliable long-term performance

Quick Answers for Specifying Engineers

Q: What is the most important factor when specifying hospital emergency power systems?

A: Ensuring safety and reliability in real-world operation; not just code compliance.

Q: What reduces risk in emergency power specifications?

A: Safety-interlocked systems and custom engineering aligned to the facility.

Q: What codes must be referenced?

A: NEC Article 517, NFPA 110, NFPA 99, and NFPA 101.

Q: Why are custom-engineered solutions important?

A: Because hospitals have unique layouts, loads, and operational risks that standard equipment cannot fully address.

Key Takeaways for Engineers

  • Emergency power systems must be treated as life safety systems
  • Code compliance is essential but not sufficient
  • The highest risks occur at human interaction points
  • Safety-interlocked systems reduce operational risk
  • Custom engineering ensures alignment with real-world conditions

Understanding the Electrical Differences Between Reefer Containers and eTRUs: Why Precise Identification Matters

Erika Thorson

Generic terms like reefer, van, or freezer are often used to describe a variety of refrigerated equipment, but each type can have different electrical requirements. To ensure we quote the correct product, it’s important to understand exactly what kind of equipment will be plugged in.

Reefer Containers: The Ocean and Intermodal Workhorses

Reefer containers are typically used for ocean or intermodal shipping and come with a built-in cord and a male pin-and-sleeve plug, usually 440/480V 3-phase, 32A (IEC 60309). These cords are often visible coiled in a tray or hook on the container’s side. The container itself is a self-contained metal unit, similar in appearance to a standard shipping container, often 20 or 40 feet long.

Electric Transport Refrigeration Units (eTRUs): The Overland Option

Electric Transport Refrigeration Units (eTRUs), on the other hand, are usually mounted on trailers or trucks. Instead of a cord, they are equipped with a male inlet mounted on the unit’s exterior. The cord with the female connector is provided at the power source (dock, pedestal, or building).

Visually, eTRUs blend into the body of the trailer or appear as nose-mounted units on the front wall. At first glance, they may look like conventional diesel-powered TRUs, but the giveaway is the small inlet plate or recessed power port replacing the familiar fuel tank.

Quick visual differences:

  • Reefer Containers: Large, box-like units with a coiled power cord and male plug. Often have corner castings for stacking/shipping.
  • eTRUs: Mounted on trailers, often with no external cord. Look for an inlet plate or recessed power port on the side or front of the unit.

Why This Matters for Electrical Quotes

It’s important to note that not all containers or eTRUs use the same standard configuration. Some may have non-standard connectors or voltages depending on origin, manufacturer, or retrofit. Since pricing and product selection can vary significantly depending on the required connector or receptacle, confirming the exact electrical configuration — including voltage, phase, amperage, and plug type — helps avoid misunderstandings and ensures a safe, cost-effective solution.

Photos of the connection point, nameplate data, or equipment specifications are very helpful in making the correct selection.

If you’re looking for further assistance or ready for a project quote, Contact our team now!

Contact ESL!

RAMTEK Joins ESL as the Newest Manufacturer’s Representative Group for Southern California

Erika Thorson

CORONA, CA – April 10, 2025 – ESL Power Systems, Inc. is excited to announce that RAMTEK has joined our growing network of Manufacturer’s Representative Groups (MRGs). As our newest MRG, RAMTEK will represent ESL’s Emergency Power Product line throughout Southern California.

About RAMTEK

Founded in 1999, RAMTEK has built a strong reputation as a premier manufacturer’s representative firm specializing in electrical, energy, industrial, mechanical, and OEM markets. With over 25 years of power industry experience, RAMTEK provides exceptional customer service, technical expertise, and tailored solutions in vertical markets such as emergency power & energy, data center, healthcare, entertainment, biotech and higher education. RAMTEK is positioned to meet the needs of contractors, distributors, and end users. Their dedication to innovative and reliable power solutions aligns seamlessly with ESL’s mission to deliver high-quality products for critical power applications.

A Strong Partnership for Emergency

ESL’s partnership with RAMTEK strengthens our ability to serve customers in Southern California by providing localized support and expertise in Emergency Power Connection Solutions. RAMTEK’s established industry relationships and deep market knowledge will enhance ESL’s reach and ensure customers receive best-in-class service and solutions for their power connectivity needs.

Looking Ahead

We are confident that this collaboration will provide greater accessibility, technical support, and tailored solutions to our valued customers in the region. ESL is thrilled to welcome RAMTEK to our expanding network of trusted partners.

For more information about RAMTEK, visit their website at ram-tek.com.

For inquiries or project quotes on ESL’s Emergency Power product line, visit our representative map to locate the suitable representative for your project.

Media Contact:
Erika Thorson, Marketing Manager
ethorson@eslpwr.com