ATS models may include the following internal protections:
• Input relays in every model open
when their source is disconnected to
prevent electric backfeed from one
input cord into another (ATS 1).
• Two or four non-replaceable fuses
(depending on the model) protect the
ATS from short circuits (ATS 2).
• Some 2U models have circuit
breakers for bank overload
protection (ATS 3).
The rack ATS does not include power surge protection. To protect your ATS from external power surges, it is
always recommended that you connect each ATS source to a Double Conversion On-Line Uninterruptible
Power Supply (UPS).
How Switching Works
1. You configure the ATS to accept power that meets the needs of your equipment by adjusting the
following settings (see “Configuration Tab” on page 70 for more details).
– Line VRMS: the ideal voltage for your equipment. Acceptable line voltages vary per ATS
model and can be found on your ATS specification sheet (visit www.apc.com).
– Transfer limits: The maximum and minimum voltages the ATS will accept before switching to
the other source. These are meant to allow for small, acceptable surges and drops in power.
The ATS should not run near the upper transfer limit for long periods of time.
– Transfer ranges: Pre-defined sets of transfer limits. You can configure up to three transfer
ranges.
– Sensitivity: How long the ATS waits to determine whether or not it will switch sources.
High sensitivity provides extra responsiveness for delicate equipment. Low sensitivity prevents
excessive switching in cases of fluctuating power inputs.
2. The ATS constantly monitors the quality and amount of power coming from sources A and B. If
one source begins to supply power that does not meet your settings, the ATS will disqualify that
source.
a. If the disqualified source is not in use, the ATS will generate an alarm indicating
redundancy has been lost.
