Remote Emergency Power Off Switch

Chapter 4 - Electrical Requirements and Procedures

The Power Array can be de-energized with a remote emer- gency power off (REPO) switch. REPO switches are com- mon in computer rooms where, for safety reasons, power to the loads must be quickly disconnected. The REPO switch physically flips the system enable switch to “stand by” mode. This cuts power to the main intelligence module, which in turn cuts power to the Power Array and to the load equip- ment. The system enable switch must be physically reset.

IMPORTANT: The system enable switch cuts power to the in- telligence module only. All internal circuitry that is connected to incoming utility (mains) voltage is still powered if incoming utility power is still present.

The REPO can be connected to either a switched, 24Vdc cir- cuit, or a simple contact closure.

REPO Specifications

The REPO circuit is considered a Class 2 and SELV circuit. SELV is an acronym for “Safety Extra Low Voltage.” SELV is a common term in Europe and IEC standards. A SELV circuit is isolated from primary circuitry through an isolating trans- former and designed so that under normal conditions, the voltage is limited to 42.4 Vpeak or 60 Vdc.

A Class 2 Circuit is a common term in North America and in UL and CSA standards. It is defined in the Canadian Electri- cal Code (C22.1, Section 16) and in the National Electrical Code (NFPA 70, Article 725).

SELV and Class 2 circuits must be isolated from all primary circuitry. Do not connect any circuit to the EPO terminal block unless it can be confirmed that the circuit is SELV or Class 2. If there is a question, use a contact closure switch.

Cable Specifications

The cable that connects SymmetraTM to the Emergency Power Off switch should be one of the following UL Listed types: CL2 - Class 2 cable for general purpose use; or

CL2P - Plenum cable for use in ducts, plenums, and other space used for environmental air; or

CL2R - Riser cable for use in a vertical run in a shaft or from floor to floor; or

CL2X - Limited Use cable for use in dwellings and for use in raceway.

For installation in Canada, the cable should be CSA Certi- fied, type ELC (Extra-Low-Voltage Control Cable).

REPO Switch Installation

nVerify that all incoming line voltage (mains power) and low voltage (control) circuits are de-energized and locked out before installing cables or making connec- tions, whether in the junction box or to the SymmetraTM Power Array.

nAlways verify that all battery modules are removed and all battery extension frames are disconnected from the Power Array before installing any wiring to the Power Array.

REPO Wiring Procedures

1.Refer to figure 4-8. Remove the screw holding the two- piece access panel at the rear of the Power Array. Remove the panel. Set the screw and the panel pieces aside.

Fig 4-8 Removal of REPO Wiring Panels

2.Refer to figures 4-9 and 4-10. Select the configuration that matches the type of REPO switch that is to be installed. Note: An existing jumper must be removed from the terminal block if a 24Vdc REPO switch (figure 4-10) is to be installed.

3.Extend the wiring from the switch to the Power Array. Strip

13mm (1/2") of insulation from the end of each of the in- coming wires.

4.Feed the wires through the knockout in the access panel, and install a strain relief (Romex) connector.

5.Make sure there are no loose strands and that the terminal connection screws are sufficiently tightened.

6.After the electrical wiring test/checklist at the end of this chapter is completed, replace the REPO access panel.

4-5