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3.2.10 Maintenance Bypass
Maintenance Bypass switchgear (cabinet, panelboard, switchboard or custom switchgear) allows you to totally
isolate the UPS system fr om all power sources, while you maintain power to the critic al load.
Your installation may have a two-breaker, three-breaker, or four-breaker Maintenance Bypass, or none at all.
The main differences are the locations of the Rectifier Input Breaker and the Bypass Input Breaker (BIB).
Another option that may be present at your site is an alternate power source (generator) and an automatic transfer
switch (ATS).
Note that to totally isolate the UPS system from all power sources, the Main Input switchgear and battery circuit
breakers must also be opened.
Figure 57 Load on Mainten ance Bypass (Two Breakers)
CAUTION
Instructions for operating the Maintenance Bypass circuit breakers are on the
Maintenance Bypass cabi net. Make sure you understand the proper sequence
before operating any circuit breaker. Operating a Maintenance Bypass circuit
breake r out of sequence could cut o ff powe r to the critical load.
I
R
CB2
System
Controls
BFB
Output
SBB
SBS
BFB
I
R
I
R
CB2 CB2
#2UPS
CB1
#1UPS
CB1
#3UPS
CB1
RIB RIB
BIB
RIB
SCCT
SCCT
(can accommodate up to 6UPS modules)
ToCriticalLoad
Battery
MBD
Battery
MBD
Battery
MBD
SKRU
MIB
MBB
DISCONTINUED
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