UPS with Bypass Electrical Installation
22
Powerware
®
9170
+
UPS User’s Guide S Rev B www.powerware.com
See Table 2 f or recommended conductor sizes to wire the input circuit
breakers.
Table 2. Recommended Wire Sizes
Input Circuit Breaker Size 75°C Copper Wire Size Conductor Screw Torque
25A 10 AWG (5.3 mm
2
) 35 in lb (4.0 Nm)
40A 8AWG(8.4mm
2
) 40 in lb (4.5 Nm)
60A 4AWG(21.2mm
2
) 45 in lb (5.1 Nm)
80A 3AWG(26.7mm
2
) 50 in lb (6.6 Nm)
100A 2AWG(33.6mm
2
) 50 in lb (6.6 Nm)
125A 1AWG(42.1mm
2
) 50 in lb (6.6 Nm)
FOR U.S. INSTALLATIONS, READ THIS IMPORTANT NOTE!
This table lists the AWG and mm
2
wire size for each circuit breaker size shown on the wiring diagrams. The
minimum recommended circuit breaker sizes for each model and voltage application are listed on the wiring
diagrams.
Conductor sizes shall be no smaller than the 75°C wire size based on the ampacities given in Table 310–16 of
the National Electrical Code, ANSI/NFPA 70-1999, and article 220. All circuit conductors, including the neutral
conductor, must be the same size (ampacity) wire. Code may require a larger AWG size than shown in this
table because of temperature, number of conductors in the conduit, or long service runs.
Follow local
code requirements.
Bypass Switches
Bypass switches are available in two types: Make-Before-Break (MBB)
and Break-Before-Make (BBM).
An MBB switch makes a new connection before it breaks the original
connection. For example, if you turn an MBB switch from UPS to LINE,
the bypass switch connects the load to AC input power before
disconnecting the load from UPS output power. (As noted in Figure 38
on page 55, MBB switches may not be used in certain system
configurations.)
A BBM switch breaks the original connection before it makes a new one.
IfyouturnaBBMswitchfromUPStoLINE, the switch disconnects the
load from UPS output power before connecting the load to AC input
power.
ThebypassswitchhasfourpositionsasdescribedinTable3.
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