Design Alert 11 - Device Cables in Telecom Spaces.pdf

HEFP SEP/14APR2023

Some Stations are acquiring incompatible power cordsets for IT devices in Telecommunication Rooms (TRs). Certain networking equipment requires a specific configuration. This Design Alert clarifies selection criteria for power cordsets which connect Rack Power Distribution Units (PDUs) to IT to access-layer network devices resident in TRs.

Additionally, sites shall verify IT equipment Power Supply Unit (PSU) compatibility with 208VAC input voltage before connecting power to prevent possible damage to equipment.

VA OIT power distribution topology leverages vertical Rack PDUs for modularity. The topology also increases the expected circuit voltage delivered to IT devices from 120VAC to 208VAC. The Infrastructure Standard for Telecommunications Spaces (ISTS) v3.1 lists the most common device power cordsets within data centers (Section 4.2.7, Implementation Guidance and Figure 11), although device-specific scenarios are not described. Cordsets consist of two couplers and a cable manufactured as single unit. A specific cordset configuration is necessary to support access-layer networking equipment in TRs.

Enterprise-grade IT devices use paired couplers for power delivery, allowing the use of detachable country-specific power cordsets. These coupler variations are defined by the International Electrotechnical Commission (IEC) in their IEC 60320 standard. Typically, even-numbered couplers hold exposed blades within a recess, and the blades point towards the power source; and odd-numbered couplers fit in the recess and receive the blades. According to IEC 60320, plugs on cordsets are paired with and provide power downstream to devices through recessed blades in Inlet housings; interconnection Outlets provide power from one device to another device through cordsets with bladed Plug Connectors. This Design Alert will use those terms; however, vendor descriptions of the necessary couplers may not adhere to exact terminology used in IEC 60320. Ambiguous descriptions should be visually confirmed through pictures or drawings. Stations may submit an HEFP-SEP EHRM Station Inquiry for assistance with situations not addressed in this Design Alert.

Rack PDUs are considered intermediate devices in IEC 60320 coupler architecture, because they both receive and provide power. Thus, Rack PDU outlet banks are populated with IEC 60320 C13 Outlets. Devices supported from C13 Outlets require cordsets with matching C14 Plug Connectors (Figure 1).

Access-layer networking equipment PSUs use C16 Inlet couplers rated for elevated temperature environments up to 120°C (248°F). Similarly rated C15 Plugs are required at the device end of the cordset (Figure 2). By design, C16 Inlets are specifically keyed to prevent insertion of lower temperature rated C13 Plugs, although C14 Inlets will accept both C13 and C15 Plugs (Figure 3).

Background

HEFP SEP (SOCAMES 6) Design Alert 11

Problem

Figure 1: IEC 60320 C14 Plug Connector.

Source: Cisco Systems Inc. Illustration #113165

Figure 2: IEC 60320 C15 Plug.

Source: Cisco Systems Inc. Illustration #113165

Figure 3: Keying difference between IEC 60320 C13-C14 Couplers and IEC 60320 C15-C16 Couplers.

Additional care must be taken when converting from 120VAC power distribution to 208VAC power distribution within a space. Installers must confirm that every cordset and every device is compatible with the source power voltage before connecting them, otherwise equipment damage may result.

Although IEC 60320 requires cable voltage ratings up to 250VAC, localized cordsets which may only be rated for 125VAC have been manufactured to support consumer devices. Voltage ratings for cordsets should be imprinted along the cable jacket or on the coupler ends. Even if a cordset’s couplers are compatible with the Rack PDU Outlets and the device Inlet, cordsets rated for only 120VAC should not be used with 208VAC distribution.

Installers must confirm that every cordset, and device is compatible with the source power voltage before connecting them, otherwise equipment damage may result.

Most enterprise-grade IT devices are manufactured with auto-ranging PSUs, which can detect and adjust to local power circuit characteristics. PSU Inlets should be clearly marked with the ranges they can accept. Usual power input ranges cover combinations of 100-125VAC and 200-250VAC as well as 50Hz and 60Hz frequencies. However, other devices with consumer-grade PSUs which accepts only 120VAC and cannot accept 208VAC power may be encountered in Telecommunications Rooms. These device PSUs will generally have C14 Inlets, so there may be no physical barrier to prevent inadvertent connection of 208VAC cordset couplers to 120VAC rated Inlets.

Installers must confirm that every cordset, and every device is compatible with the source power voltage before connecting them, otherwise equipment damage may result.

In TRs where power distribution has been updated to use 208VAC, specify and use IEC 60320 C14-C15 device power cordsets to connect access-layer networking equipment in TR racks with 208V Rack PDU Outlets.

IEC 60320 C14-C15 device power cordsets should be functionally equivalent to Cisco Systems Cable Part CAB-C15-CBN for commonality and compatibility (Figure 4).

Rated for at least 250 Volts AC, 13 Amps, 60 Hz, 120°C (248°F) at coupler pins Underwriters Laboratories (UL) listed 4 ft (1.22m) maximum overall length; shorter lengths may be used to reduce excessive slack Coupler terminations on cordset:

o IEC 60320 C14 Plug Connector (Rack PDU End) o IEC 60320 C15 Plug (Device End)

Selection of contrasting cordset colors indicating diverse (A/B) power distribution sources is recommended.

Figure 4: Cisco IEC C14-C15 Cabinet Jumper Power Cord, Power Cable Part Number CAB-C15-CBN.

Source: Cisco Systems Inc. Illustration #307652

Verify cordset compatibility with 208VAC source power before connecting.

Verify device compatibility with 208VAC input power before connecting.

Solution