Appendix: External Bypass Switches. Best Power Unity/I UT3K

Appendix: External Bypass Switches

If your UPS does not have output receptacles, you may have an external UPS Bypass Switch with an

AC Line Disconnect Switch. Figure 3 on page 5 shows a Best Power bypass switch.

The UPS Bypass Switch has three positions: Line, Off, and UPS (see Table 13).

Table 13: External Bypass Switch Positions

UPS Bypass Switch Position

LINE

OFF

UPS

Explanation

Connects AC input power (line) directly to the load equipment.

Disconnects the load equipment from both UPS output power and AC input power (line).

Connects the UPS output to the load equipment.

NOTE: In all three UPS Bypass Switch positions, AC input power may still be connected to the input terminals inside the UPS. To disconnect AC input power to the UPS, you must use the AC

Line Disconnect Switch.

An external bypass switch may be “Make-Before-Break” (MBB) or “Break-Before-Make” (BBM).

• A Make-Before-Break (MBB) switch makes a new connection before it breaks the present connection. If you turn the switch from “UPS” to “Line,” the bypass switch connects the load equipment to AC input power before disconnecting the equipment from UPS output power. In other words, there is no break in power to the load equipment during the switch from UPS output power to AC input power.

• A Break-Before-Make (BBM) switch breaks the present connection before it makes the new one. When you turn the switch from “UPS” to “Line,” the switch moves through the “Off” position. The bypass switch disconnects the load equipment from UPS output power before connecting it to AC input power.

CAUTION!

Before switching an external make-before-break (MBB) bypass switch, the BYPASS light on the

UPS front panel must be lit. If you operate an external MBB bypass switch while the UPS is operating on line power or on battery power, equipment damage may result. Refer to Best Power publication TIP 410 for proper bypass switch operating instructions.

For external bypass switch models and ratings, see Section 101 .

For external bypass switch dimensions, see Section 102 .

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