Greito išjungimo laidų schemos: NEC 690.12 atitiktis nuo prijungimo iki etiketės

What Is Rapid Shutdown and Why NEC 690.12 Requires It

Rapid shutdown is a safety function that automatically drops a rooftop solar array’s DC voltage to safe levels the moment AC power is disconnected. The best way to picture it: a gas shutoff valve for your PV system. When firefighters arrive at a burning building, they kill the main electrical service. Rapid shutdown makes sure the panels on the roof stop producing hazardous voltage right then — not minutes later.

The mandate comes from NEC 690.12 straipsnis, which has tightened steadily since 2014. The 2017 edition was the turning point: within 30 seconds of shutdown initiation, DC conductors inside the array boundary must drop to 80 voltų ar mažiau, and conductors outside the boundary to 30 voltų ar mažiau. That effectively made module-level shutdown devices the standard for rooftop installations. The 2020 edition added UL 3741 as an alternative compliance pathway through PV Hazard Control Systems. The 2023 edition kept the core 80V/30-second thresholds while removing the exemption for arrays with no exposed wiring (NFPA, NEC 690.12, 2017–2023).

Why does wiring method matter? Different manufacturers use fundamentally different control mechanisms — power-line communication signals, resistor-based detection, AC control circuits, and dry-contact terminal blocks. Connect them wrong, and the system simply won’t shut down. The sections below walk through each topology with specific diagrams and terminal-level detail.

String-Level vs Module-Level RSD: Key Wiring Differences

Before getting into specific wiring diagrams, understand the two architectural approaches first. The wiring complexity and NEC compliance path depend entirely on this choice.

The practical takeaway: if your AHJ enforces NEC 2017 or newer without the UL 3741 exception, module-level shutdown is the default compliance path. String-level solutions remain viable for ground-mount arrays (where rapid shutdown may not apply) or when paired with a listed PV Hazard Control System.

One more thing to lock down before wiring: all RSD topologies fall into two categories — PLC pagrindu (the control signal rides on the DC power line) and laidinis (a separate physical circuit carries the shutdown signal). The next two sections cover each in detail, starting with the most common.

PLC-Based RSD Wiring Diagrams: Tigo and APsmart

Every PLC-based rapid shutdown system works on the same principle: a transmitter injects a high-frequency keep-alive signal onto the DC bus, and receiver units at each module listen continuously. Cut the transmitter’s AC power (by throwing the building’s main disconnect), the signal stops, and every receiver shuts down its output within 30 seconds. The wiring detail that determines whether it works or doesn’t: how that signal couples to the DC wiring.

Tigo TS4-A-2F Wiring Diagram

The Tigo TS4-A-2F is the most widely deployed module-level PLC rapid shutdown device. Each unit handles two PV modules, cutting connection count by roughly 16% compared to single-channel alternatives on a typical 14-panel string.

Sistemos komponentai:

• Tigo RSS Transmitter (sends the keep-alive signal via PLC)
• One TS4-A-2F per two PV moduliai
• PV inverter (must be compatible with Tigo’s PLC signal)

TS4-A-2F Terminal Layout:
Each unit has two independent input channels and one output. With the label facing you:

• Input 1: Negative (left), Positive (right) — max 80V, 25A, 700W
• Input 2: Negative (left), Positive (right) — max 80V, 25A, 700W
• Output: Negative (left), Positive (right) — feeds into the string home run

Laidų sujungimo žingsniai:

1. prisijungti PV Module 1’s positive and negative leads to TS4-A-2F Input 1 (observe polarity markings on the unit).
2. prisijungti PV Module 2’s positive and negative leads to TS4-A-2F Input 2.
3. Connect the TS4-A-2F output leads to the string — all outputs on the same string are wired in series, terminating at the inverter MPPT input.

RSS Transmitter Wiring (Critical):
The transmitter uses a split-core current transformer (CT). Route all PV+ home-run cables through the CT core in the same direction. This step fails more often than any other: mixing positive and negative conductors through the same CT cancels the PLC signal. Result: zero signal reaches the modules, and the system stays locked in shutdown mode.

• CT must enclose all positive conductors from all strings, or all negative conductors — never both
• For long home runs (200+ feet), loop the wire through the CT twice to boost signal amplitude
• Signal verification needs an oscilloscope (a standard multimeter can’t detect the carrier waveform)

Pagrindiniai parametrai:

• TS4-A-2F per-channel limit: 80V / 25A / 700W (1,400W total per unit)
• Max string voltage: 1,000V or 1,500V DC (connector-dependent)
• Darbinė temperatūra: nuo −40 °C iki +80 °C
• Enclosure: IP68 / NEMA 3R
• Wait 30 seconds after rapid shutdown activation before disconnecting DC connectors — residual voltage risk

APsmart RSD-S-PLC Wiring Diagram

APsmart’s PLC-based system follows the same signal-on-DC-bus principle as Tigo but adds SunSpec Alliance interoperability. A SunSpec-certified transmitter built into a compatible inverter eliminates the external Transmitter-PLC — one less wiring step and one less failure point.

Sistemos komponentai:

• Transmitter-PLC (external) or inverter-integrated SunSpec transmitter
• RSD-S-PLC units (one per PV module, single-channel)
• Inverter with MPPT inputs

Wiring Differences vs Tigo:

• The external Transmitter-PLC routes only the PV+ home-run cable through its CT core — same single-polarity rule as Tigo
• If the inverter has a built-in SunSpec-certified rapid shutdown transmitter, drop the external Transmitter-PLC from the diagram entirely — the inverter handles signal generation
• Transmitter power supply: 85–264V AC for residential installations, 180–550V AC for commercial/three-phase sites

NEC atitiktis:
APsmart RSD-S-PLC is listed for NEC 2017, 2020, and 2023 compliance. The SunSpec compatibility also future-proofs the installation — upgrade the inverter later, and the RSD units work with the new inverter’s integrated transmitter without touching the roof wiring.

Hardwired and AC-Controlled RSD Wiring: SolarEdge, Solis, and SMA

PLC systems superimpose a signal onto the DC bus. Hardwired RSD solutions take a different path — a resistor loop, an AC control circuit, or a dry-contact signal terminal block. Three design philosophies, three sets of wiring rules.

SolarEdge Rapid Shutdown Kit Wiring (Resistor Cable Method)

SolarEdge uses a resistor-equipped cable pair inside the inverter’s DC Safety Switch enclosure. The inverter monitors resistance across a dedicated detection circuit continuously. Open the safety switch, the resistor loop breaks, and the inverter triggers rapid shutdown.

Komponento identifikavimas:

• Red cable: integrated resistor at one end (do NOT remove or bypass)
• Black cable: standard, no resistor

Wiring Rules (Two Options, Depends on Existing Line Order):

First, look at the top cables entering the DC Safety Switch from the conduit side:

• Option 1 — Red (+), Black (−) from left to right on top: Connect the rapid shutdown cables in reverse — black on the right (DC+), red (with resistor) on the left (DC−) at the bottom terminals.
• Option 2 — Black (−), Red (+) from left to right on top: Connect black on the left (DC−), red (with resistor) on the right (DC+) at the bottom terminals.

The golden rule: the resistor must be on the switch side, not the DC terminal block side. Install the resistor cable backwards (resistor at the DC spring-clamp terminals instead of at the switch) and the inverter can’t detect the resistor break when the switch opens.

Žingsnis po žingsnio:

1. Turn off inverter and Safety Switch. Wait for DC voltage to drop below 50V.
2. Disconnect existing DC cables from the switch terminals.
3. Connect the resistor-equipped red cable and black cable to the switch terminals per the line-order rule above. Torque: 2 N·m (18 lb·in).
4. Connect the other ends to the DC spring-clamp terminals: black → DC−, red → DC+.
5. Close switch cover and tighten four screws to 1.2 N·m (0.9 ft·lb).

Solis AC-Controlled RSD Wiring

Solis takes a fundamentally different approach: instead of manipulating the DC side, rapid shutdown triggers through a 240V AC control circuit running from the inverter to the roof-mounted RSD units. Building loses AC power (main breaker thrown), the control circuit de-energizes, and all RSD units shut down. This was deliberate — firefighters don’t need to locate a special PV shutdown switch. Cutting the main breaker covers it.

Control Circuit Wiring:

• L1 and L2: 240V AC, draws only 0.1A
• Wire specification: THHN/THWN-2, #14 or #16 AWG
• Run the control cable from the inverter (or point-of-connection breaker) to each RSD unit on the roof

Conduit Sharing Rule (Critical Compliance Point):
už NEC 300.3(C)(1), AC control conductors may share the same conduit as PV DC source circuits. This is a specific allowance. Inverter output circuits, however, are Draudžiama from sharing a raceway with PV DC circuits per NEC 690.31(B). Getting this distinction right saves conduit runs and labor.

Įžeminimas:
Bond the RSD enclosure to the rooftop grounding system (rails, WEEB washers, MLPE grounding kit). Do not use the ground conductor in the AC control cable — the AC ground serves a different function.

Diagnostinis patarimas:
After shutdown, each receiver module outputs approximately 0.67V. Divide total string voltage by 0.67 to count how many modules are connected — a useful field check.

Backup Mode Note:
If the inverter is in backup/off-grid mode, the DC switch on the inverter must also be turned off for RSD to engage. AC loss alone may not trigger shutdown when the inverter is islanding.

SMA Rapid Shutdown Box Wiring (Signal Terminal Method)

SMA’s RSD system uses a dedicated Rapid Shutdown Controller connected to one or more Rapid Shutdown Boxes via a multi-conductor signal cable. The wiring follows industrial control panel conventions — each pin has a specific function, and getting the mapping wrong means the controller can’t arm the system.

RSD Box Terminal Block (Lower Pin Row):

Controller-to-Box Mapping:

• RSD Box Pin 1 → Controller terminal X2 (+12V supply)
• RSD Box Pin 2 → Controller terminal 2 (switch)
• RSD Box Pin 3 → Controller terminal NC 1 (ground)
• RSD Box Pin 4 → Controller terminal X1 (green LED)
• RSD Box Pin 5 → Controller terminal X1 (red LED)

Multi-Box Daisy Chaining:
Connect the first RSD Box to the Controller per the mapping above. For each additional RSD Box, wire in parallel from the previous box — all boxes must be linked before the system can arm.

Kabelio lankstumas:
SMA permits TC-ER (Tray Cable — Exposed Run) rated cable as an alternative to conduit, with appropriate cable glands at enclosure entry points to maintain the weather seal.

Rapid Shutdown Labels and Placards: NEC 690.12 Compliance Guide

A perfectly wired rapid shutdown system fails inspection every time if the labels are missing, wrong, or illegible. NEC 690.12 requires two specific markings — they serve different audiences at different locations. Missing labels remain one of the most common causes of failed solar PV patikrinimai.

Here’s the framework: “A placard at the meter, a label at the switch.” A first responder needs to identify within seconds that (1) a rapid shutdown system exists and (2) where to activate it. If either piece is missing, the labeling is non-compliant.

Building Rapid Shutdown Placard: Requirements and Placement

This is the larger, more detailed marking — installed at the service equipment location where firefighters arrive first.

Required Content (NEC 2023, 690.12(D)):

• Standard wording: “SOLAR PV SYSTEM IS EQUIPPED WITH RAPID SHUTDOWN. TURN RAPID SHUTDOWN SWITCH TO THE ‘OFF’ POSITION TO SHUT DOWN PV SYSTEM AND REDUCE SHOCK HAZARD IN ARRAY.”
• A simple diagram of a building with a roof, showing the PV array boundary
• Indication of which conductors are controlled (inside boundary only, or both inside and outside)
• Geriausios fizinė vieta of the rapid shutdown initiation switch stated on the placard

Placement Rules:

• At each service equipment location (main panel, meter, or grouped metering area)
• Plainly visible to first responders approaching the service entrance
• If the RSD initiation switch is not at the meter, the placard must describe where it is

Wording Variants by System Type:

• String-level (outside-only control): “…CONDUCTORS OUTSIDE THE ARRAY BOUNDARY REDUCE TO A SAFE LEVEL…”
• Module-level (inside + outside control): “…CONDUCTORS INSIDE AND OUTSIDE THE ARRAY BOUNDARY REDUCE TO A SAFE LEVEL…”

NEC Version Differences:

• NEC 2017/2020 (690.56(C)): Required yellow background with black lettering (or red with white lettering), reflective, 3/8-inch minimum letter height
• NEC 2023 (690.12(D)): Color requirement removed — only requires text contrast. Red/white remains the industry convention accepted by most AHJs

Patvarumo standartas:

• Must comply with NEC 110.21(B) for field-applied hazard markings: weather-resistant, UV-stable, permanently affixed
• Recommended material: UL 969-rated polyester or polycarbonate with UV overlaminate

Rapid Shutdown Initiation Device Label: Specifications

This is the simpler but equally mandatory label — it confirms for the first responder “this is the switch.”

RAPID SHUTDOWN SWITCH FOR SOLAR PV SISTEMA

This exact wording is not negotiable — don’t abbreviate, don’t substitute. It has remained unchanged across all recent NEC editions.

Specifications (Unchanged Across All NEC Versions):

• Red background, white lettering
• All capital letters, minimum 3/8 inch (9.5 mm) character height
• Must be reflective
• Place on or within 3 feet (1 meter) of the rapid shutdown initiation switch

The two labels work together: the building placard tells responders what exists and where the switch is; the switch label confirms they found it.

RSD Wiring Troubleshooting: Common Mistakes and How to Avoid Them

Even experienced installers hit the same rapid shutdown wiring pitfalls. Here are the four most frequent errors, with symptoms and fixes.

Beyond wiring, device quality matters for long-term reliability. Rapid shutdown devices carrying multi-jurisdiction certifications — UL 508i, UL 2202, CE, TUV, UKCA, and CB — have passed far more rigorous testing cycles than single-certificate alternatives. Beny, the first Chinese manufacturer to earn UL 508i listing for DC isolator products, offers rapid shutdown devices spanning both module-level and string-level configurations with a 25-year warranty (Beny’s rapid shutdown device catalog) — matching the expected service life of the PV modules they protect.

Nuorodos

1. NFPA. “NEC Article 690.12 — Rapid Shutdown of PV Systems on Buildings.” National Electrical Code, 2017/2020/2023 Editions. https://www.nfpa.org/
2. Electrical License Renewal. “690.12(B)(2) Rapid Shutdown — Inside the Array Boundary.” https://www.electricallicenserenewal.com/…/NEC-Content.php?sectionID=963
3. Solar Power World. “Tigo Energy releases rapid shutdown devices for up to 700-W panels.” 2022. https://www.solarpowerworldonline.com/2022/08/tigo-energy-releases-rapid-shutdown-devices-up-to-700-w/
4. Solar Builder Magazine. “PV Hazard Control: Understand UL 3741 and new rapid shutdown solutions.” https://solarbuildermag.com/featured/pv-hazard-control-understand-ul-3741-and-new-rapid-shutdown-solutions/
5. Solar Permit Solutions. “NEC 690.56(C) Labels For PV Rapid Shutdown Systems.” https://www.solarpermitsolutions.com/blog/nec-690-56c-labels-pv-rapid-shutdown
6. Beny New Energy. “Rapid Shutdown Product Catalog.” https://www.beny.com/products/
7. Beny Nauja energija. „Susisiekite su mumis“. https://www.beny.com/contact-us/