PV Disconnect Switch Guide in 2023 - Installation, Safety, Rapid Shutdown

Specifying and installing properly rated PV disconnect switches at strategic array and equipment locations is critical for solar-powered homes and commercial sites. Isolating solar circuits enables vital equipment servicing, maintenance, and upgrades to safely take place after hazardous voltages are removed.

Integrated rapid shutdown capability adds an important layer of protection for first responders when deployed during emergencies. Following NEC guidelines for disconnect placements, signage, andratings ensures code compliance. Regular inspection, testing under load, and maintenance maximize the working lifespan of PV disconnect equipment.

With robust solar disconnect switches guarding solar PV systems, homes and businesses can safely and reliably harness the power of the sun for decades. Contact us for the latest quote.

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Introduction

Photovoltaic (PV) disconnect switches, sometimes referred to as solar disconnects or isolators, are critical components used to manually disconnect solar panels from downstream electrical circuits for maintenance, repairs, or emergencies. Properly installed and utilized PV disconnect switches allow solar arrays to be safely de-energized so workers are protected from dangerous shock hazards when servicing equipment.

This guide provides an overview of common PV disconnect switch applications, installation guidelines according to the National Electrical Code (NEC), locking and tagging procedures, rapid shutdown capabilities, and maintenance best practices. Following proper PV disconnect protocols enhances safety for both homeowners and professionals working with solar power systems.

Installation Guidelines

Correct installation of PV disconnect switches is crucial for performance, electrical safety, and code compliance. Key considerations include:

Location

PV disconnects should be mounted in easily accessible locations so they can quickly isolate solar circuits in an emergency. Typical placement includes:

Near the main service panel for whole home solar disconnecting.
At solar combiner boxes where strings aggregate.
On exteriors of buildings adjacent to rooftop solar arrays.
Near ground mount arrays for nearby isolation.

The NEC dictates that PV disconnects must be installed at a readily accessible location either on the outside of a building or structure or immediately inside nearest the point of entrance of the system conductors.

Section 690.13 specifically applies to the DC PV system conductors, while 690.15 covers AC disconnecting means requirements where inverters are present. Installers must understand both sections to locate PV disconnects properly in each part of a solar system.

Enclosures

PV disconnect enclosures should match the environmental conditions and provide protection against the hazards present:

Use weatherproof NEMA 3R enclosures for outdoor rooftop or ground mount applications exposed to rain, sun and other elements.
Indoor disconnects can use general purpose NEMA 1 enclosures.
NEMA 4X stainless steel enclosures withstand corrosion for seaside installations.
NEMA 12, 3R, and 4 enclosures prevent dust and dirt intrusion in agricultural settings.
NEMA 4X enclosures provide insulation for very cold climates.

Ensure the enclosure size accommodates the number of switches needed along with sufficient wire bending space per NEC guidelines. Larger systems require more switches or larger disconnect enclosures.

Sizing

PV disconnect switches must be rated to safely handle the solar system’s maximum voltage and current:

Use 600 volt switches for common residential systems with voltages up to 600V.
Select switches rated for the maximum input circuit current based on the solar array size. Typically 60A to 100A for homes.
For larger commercial solar installations, high amperage switches like 400A or 600A may be needed.

Oversizing switches slightly allows flexibility for future solar array expansions. Undersized switches present fire and shock hazards and should never be used. Refer to the NEC for proper switch voltage and ampacity sizing.

Wiring Methods

Proper wiring between PV modules, enclosures, switches, and connectors ensures safe, reliable function:

Use only copper wiring rated for wet/sunlight resistant cabling like THWN-2 within conduit runs. Aluminum wiring cannot be used for PV circuits.
Follow NEC conduit fill requirements for the number and size of conductors routed within each conduit segment.
Use wiring lugs and terminals properly sized for the conductors and rated for the system voltage. Avoid combinations not UL listed.
Ensure cables are firmly secured, provide strain relief, and have tight connections with minimal exposed conductor.

Signage

Prominent labels according to NEC 690 requirements alert personnel to the purpose of PV disconnects:

“PV SYSTEM DISCONNECT” labels should identify AC and DC disconnect switches.
Signs indicating “DO NOT DISCONNECT UNDER LOAD” help prevent hazards.
Labels showing maximum voltage like “600 VOLTS MAX” warn of dangerous voltage levels that may be present.
Include any warnings provided by the manufacturer concerning proper operation.

Clear signage reduces confusion and makes solar disconnect switches easy to identify for both homeowners and emergency responders who may be unfamiliar with the system.

Safety Functions

In addition to basic on/off capability, PV disconnect switches provide other vital safety-related functions:

De-Energizing Circuits

The primary purpose of a PV disconnect switch is manually interrupting the flow of electricity from the PV modules to isolate downstream equipment. This allows:

Creating visible air gaps in circuits so they are fully de-energized for maintenance.
Preventing the PV array from producing power to avoid any shock or arc flash hazards.
Allowing qualified personnel to verify de-energization using properly rated voltage testing procedures.
Warning personnel not to re-energize the circuit while servicing is in progress.

Lockout/Tagout Capability

Photovoltaic disconnects allow workers to secure switches in an isolated OFF position using lockout devices and tags according to formal lockout/tagout safety procedures. Lock mechanisms prevent reactivation while tags provide warning.

Locking out solar production at the source is essential during:

Rooftop equipment and array servicing
Inverter, combiner box, and junction box maintenance
Battery bank repairs
Electrical upgrades

Lockout/tagout ability allows solar circuits to remain safely de-energized for the duration of any hazardous work.

Rapid Shutdown

PV disconnects installed in arrays may contain integrated rapid shutdown capability, either as a built-in or add-on component. Rapid shutdown immediately removes voltage from array conductors when activated, reducing arc flash dangers for emergency response personnel.

When enabled by first responders, integrated rapid shutdown PV disconnects:

Cut off power from modules to isolate equipment.
Discharge any stored energy in arrays and conductors within 10 seconds.
Limit voltage to 30V or less when switched off.

Increasing Responder Safety

The ability to quickly isolate solar systems with visible disconnect switches and rapid shutdown improves responder safety. PV disconnects allow firefighters to safely:

Access rooftops with active solar arrays to ventilate smoke and perform suppression.
Create safe rescue pathways on buildings involved in a fire.
Prevent additional risks from live electrical equipment if solar systems cannot be de-energized remotely.

Clearly labeled, prominent disconnects warn personnel of solar hazards and enable emergency isolation of systems if needed. This empowers responders to act swiftly to save lives in fire or medical crisis events.

Codes and Standards

PV disconnect switches must adhere to all relevant local, state, and national codes and standards concerning installation and capabilities:

NEC Requirements

Key sections of the National Electrical Code apply to properly installing PV disconnecting means:

690.13 – Covers DC PV source circuits. Requires readily accessible disconnecting means for all current-carrying conductors.
690.15 – Applies to PV AC output circuits. Requires disconnects for ungrounded conductors if utility interactive.
690.56(C) – Disconnects used as rapid shutdown switches must be listed, identifiable, and accessible.
690.17 – Addresses disconnecting means rating requirements for voltage and ampacity.

Adhering to the latest published NEC ensures PV disconnects are sized, located, and installed according to code for safety.

Rapid Shutdown Mandates

Recent NEC editions have strengthened rapid shutdown provisions for PV systems on buildings. Key requirements include:

All solar arrays must integrate listed rapid shutdown equipment able to discharge conductors within 10 seconds of initiation.
Control mechanisms must be clearly labeled as initiating rapid shutdown.
Equipment that performs rapid shutdown must be listed as required under UL Standard 1741.

Refer to sections 690.12, 705.12, 706.15 of the updated NEC for the latest mandates concerning rapid shutdown capabilities.

AHJ Approval

The local Authority Having Jurisdiction (AHJ) – typically the city building department – must approve solar and PV disconnect installations. The AHJ inspects for code compliance and issues permits.

A licensed electrical contractor familiar with local requirements can ensure PV disconnects and associated equipment meet existing codes and pass inspections by the AHJ.

Maintenance

While PV disconnect switches generally require very little maintenance, periodic inspections and testing will maximize safety and longevity:

Inspections

Visually inspect switches, enclosures and connections for damage, corrosion, dirt/debris buildup, etc.
Ensure switches exhibit no binding, the operating handle moves smoothly, and contacts close fully.
Check for overheated terminals, conductors, or discolored components.
Verify enclosures remain tightly sealed to protect internal components.
Inspect signage and labels to make sure all remain clean, legible, and attached.

Testing

Test operation of PV disconnect switches under load at least annually.
Use infrared scanning to check for hot spots on terminals and bus bars indicating loose connections.
Test grounding integrity according to manufacturer recommendations and electrical code.

Issues to Watch For

Overheating, arcing or excess voltage drop point to loose connections.
Corroded or oxidized terminals and bus bars.
Cracked insulation, damaged conductor jacketing, moisture in enclosures.
Switches failing to open/close fully or blades not making solid contact.
Stiff operating handles that have become hard to switch on/off.

Monitoring PV disconnects through periodic inspection, testing under load, and thermal scanning helps maximize system uptime and catch any deficiencies before they become hazards.

Costs

PV disconnect switch costs vary based on amperage, voltage rating, and enclosure size. Typical price ranges include:

60A Non-Fused Disconnect

600V 31⁄2 x 31⁄2 x 6 NEMA 3R disconnect: $75 – $150

100A Non-Fused Disconnect

600V 31⁄2 x 31⁄2 x 6 NEMA 3R disconnect: $100 – $175

30A Fused Disconnect

600V 4x4x6 NEMA 3R fused pullout switch: $200 – $325

200A Non-Fused Disconnect

600V 8x8x4 NEMA 3R heavy duty safety switch: $550 – $700

100A Disconnect with Rapid Shutdown

600V 4x4x6 NEMA 3R fused switch with PV rapid shutdown: $650 – $900

400A Non-Fused Disconnect

600V 16x12x6 NEMA 3R high capacity switch: $900 – $1200

600A Fused Disconnect

600V 24x16x8 NEMA 3R switch with 400A fuses: $2500 – $4000

Prices rise for higher voltages like 1000V DC systems. Using qualified electricians for installation is recommended to reduce labor costs if constructing DIY off-grid solar.

Frequently Asked Questions

What is a PV disconnect switch?

A PV disconnect switch, also called a solar disconnect or solar safety switch, is a manually operated electrical switch used for disconnecting solar photovoltaic (PV) systems from circuits or connected equipment. PV disconnect switches:

Create a physical break in solar PV circuits to isolate equipment for service
Allow solar arrays and electronics to be completely de-energized for maintenance or emergency response
Enable lockout/tagout for improved worker safety during repairs
Provide a termination point for grounding conductors to eliminate voltage
Are required by electrical code for all interactive PV systems

Common types are fused, non-fused, and circuit breaker PV disconnects. When opened, a PV disconnect switch cuts off electricity flowing from solar panels to inverters, batteries, electrical panels, and other system components.

Where is a PV disconnect required?

The National Electrical Code (NEC, NFPA 70) mandates PV disconnects must be installed in the following locations:

For residential systems, a rooftop DC PV disconnect switch must be installed for each solar array grouping. It must be mounted on the exterior of the building or structure at a readily accessible location near the point where the array conductors enter the building. This allows emergency isolation of DC current from modules.
For residential systems, an AC disconnect is required adjacent to the inverter where it converts DC to AC. This disconnects inverter output to the premises wiring and AC equipment.
For commercial systems, both DC and AC disconnects must effectively isolate all current carrying conductors derived from the PV system while remaining readily accessible.
Additional NEC requirements depend on the design, power sources, and type of interconnection. Consult sections 690.13-690.15.

Following NEC guidelines ensures properly placed PV disconnect switches allow isolation of solar systems for maintenance, repairs or electrical emergencies.

What are the different types of PV disconnects?

Major PV disconnect and isolator switch types include:

Fused Disconnects – Enclosed safety switch with fuses that provides both overcurrent protection and disconnect capabilities for a PV circuit. Fuses are replaceable.

Non-Fused Disconnects – Disconnect switch without fuses. Used for isolation only. Has visible blade disconnect mechanism. Requires separate external overcurrent devices. Lower cost.

Circuit Breaker Disconnects – Combines circuit breaker overcurrent protection with switch in one unit. Breaker internally trips open automatically on overloads versus needing to replace fuses. More expensive.

Rapid Shutdown Disconnects – Special PV disconnect switches with integrated rapid shutdown control functionality. Can be fused, non-fused or circuit breaker types. Discharge stored PV voltage to safe <30V level when activated. Required by recent NEC editions for certain systems.

Double Throw Safety Switches – Allows dual-direction disconnect of both PV source and loads for maximum isolation during maintenance.

How do you choose the right PV disconnect?

Choosing the optimal PV disconnect switch involves verifying:

Voltage Rating

Use 600V switches for common residential solar arrays under 600V.
For larger commercial > 600V systems, choose 1000V+ rated disconnect.

Current Rating

Current must meet or exceed maximum short circuit current rating of PV array.
Typically sized 125% – 150% greater than max PV circuit current.

Number of Poles

2-pole for residential 120/240V single phase systems.
3-pole for 208V or 480V three phase systems.
4-pole for combining dual AC/DC disconnect functions.

Enclosure Type

NEMA 3R rainproof enclosures for outdoor rooftop or pole mount installations.
NEMA 1 general purpose enclosures for indoor installation.
NEMA 4X for corrosive environments.

Standards

UL 1741, CAN/CSA C22.2 No.107.1 and other standards for safety.

Carefully matching PV disconnect specifications to the system’s design and code requirements ensures safe, compliant operation and functionality.

Can you put multiple PV disconnects in series?

It is permissible to connect multiple PV disconnect switches or isolators in series on the same circuit if they are required by design and properly rated. For example:

A facility may utilize a main PV disconnect for the entire array, and additional disconnects at each inverter or equipment section.
Combiner boxes with multiple string inputs can use a disconnect on each string, all feeding a larger shared disconnect.

Key considerations when using multiple PV disconnects in series:

All switches in series must have the same or higher voltage and current ratings as the system.
Additional series disconnects increase total voltage drop along the circuit. Keep conduit/wire runs as short as possible.
Label each disconnect clearly to identify which circuits or equipment it isolates.
Locate in accessible areas so individual disconnects can be accessed quickly.

While allowed, limit the number of disconnects in series to the essentials required by code and system functionality. Follow NEC guidelines.

What size PV disconnect is needed for a solar system?

Properly sizing PV disconnect switches involves:

Voltage

Use 600VDC rated switches for arrays up to 600 volts.
For large commercial > 600V systems, choose 1000V+ rated disconnect.