PV-Off - Installing a Manual Latching Push Button Safety Switch

This article discusses the installation of a PV-Off command switch, button or relay.

Contents: 

• Switch/Button Overview
• Types of Systems
• Connecting the PV-Off Switch
• How to Wire Multiple Data Loggers to a single Shut-off Button

Switch/Button Overview

All models of Tigo Management Devices (i.e., Data Loggers) offer a PV-Off solution for manual DC-Disconnect at the PV Module level. On some models of management devices, this function requires the installation of a relay or a switch. The most common is a manual push button latching switch (not included with Tigo purchase).

A switch allows the installer or system owner to manually de-energize all Tigo MLPEs (that offer the PV-Safe or Rapid Shut Down (RSD) solutions), while also allowing the management device to remain connected to the AC Grid. The effect is similar to RSD, but does not require the Management Device to re-start. 

When the button is pressed, the latching mechanism will lock the button which closes the AUX circuit. The management device then issues a command all MLPEs to disconnect themselves from the DC Circuit, which will de-energize the string within 30 seconds. Power production will only resume upon releasing, unlatching, or returning the switch to its Open position (AUX terminals no longer connected).

Disclaimer: The button shown above is a standard off-the-shelf item (not included with Tigo purchase). Your choice of buttons should have these features:

• Operation mode: Normally Open (NO) button
  In most cases, NO or NC operation can be configured within the switch housing.
• Latching mechanism: Button must have latching mechanism (twist to release, key lock, etc.)

Types of Systems

Any TS4 model that is capable of PV Module (solar panel) disconnect, offers an automatic Rapid Shut Down (RSD) response as well as a manual PV-Off option. Each function will disconnect the panel from the string wiring (resulting in a total DC-Loss (0 Volts DC) to the Inverter), but the PV-Off is sometimes easier to manage. Without a PV-Off enabled switch/button, the data logger requires an autonomous RSD response to shut down. This means that the Tigo System must experience a full AC-Loss, in order to be effectively powered off.

TS4 models capable of module-level disconnect are:

• Safety - TS4-S, TS4-R-S, TS4-A-S
• Optimizer - TS4-O, TS4-R-O,  TS4-A-O
• Long String - TS4-L

TS4 models that are not capable of module-level disconnect are: 

• Diode Only - TS4-D
• Monitoring Only - TS4-M, TS4-R-M

A PV-Safe Switch can also be installed on the Tigo Fire Safety model systems (which use PLC signaling over the string wiring). In these cases, you would attach the switch/button the 3rd Terminal (ground terminal), and the other end to a true ground. 

For activating a manual PV-Off style reaction from older Legacy systems, see our article on PV-Safe

Connecting the PV-OFF Switch

When viewing the wiring ports on the CCA, the AUX terminals are located on the left side. This port is normally in the Open position, until a latched switch has been connected and the button has been pressed.

A latching button is very simple to install. There should only be 2 wires (positive and ground).

Note: Cloud Connect / CCA may require a software update to support this feature. If the button does not function as expected (PV modules are not disconnecting from strings), please contact the Tigo Support Team and request the necessary software update.

How to Wire Multiple Data Loggers to a single Shut-off Button

• Up to 5 data loggers can be connected to a single switch.
• Be sure to wire the grounds together, and the signal switch wires together, as shown in the diagram below.
• No outside-source voltage MAY EVER be placed on the AUX port (voids Warranty)
• The ground of the system should be connected to the 24 VDC "-" Negative terminal
• The left-hand pin should read close to 3.3 VDC when the switch is OPEN. 0 VDC when the switch is CLOSED (activated)
• When connecting multiple CCAs to the same switch be sure that the maximum distance between the shut-off button and the first CCA is under 100 meters.
• Additional CCA's also must be less than 100 meters apart from each other

For a shutoff button to work on a system with multiple MMU type data loggers, each logger must be connected to the shutoff button on its own individual wires that run directly from the switch and are not daisy-chained in parallel.

Tigo Legacy products (MMU and Cloud Connect) offer the same terminal interface and must be wired in the same fashion. 

Cautions and Disclaimers:

1. During installation of any switch, relay or button, please follow all safety precautions 

2. DANGER: Prior to servicing a system, please use a voltmeter to confirm that neither voltage nor current are present and flowing through the PV array after having pushed the external shutdown button.

3. External mushroom buttons are a convenient way to disconnect a system, but are not NEC 690.12 2014 or 2017 compliant; please always follow NEC required procedures to provide the appropriate means of disconnection and signage to emergency personnel.