After installing the PDU and connecting
equipment, you may test the Automatic Transfer
Switch function by temporarily shutting down the
UPS system connected to the Primary AC input. When
the Primary input UPS is no longer supplying AC
power, the PDU will switch from the Primary input to
the Secondary input, and the Secondary input LED
will illuminate. When the Primary input UPS has been
restarted and resumes supplying AC power, the PDU
will switch back to the Primary input.
Note: The primary and secondary inputs must be connected to separate
sources of utility power. The automatic transfer switch function will be
compromised if the primary and secondary inputs are connected to the
same utility power source. Do not perform a test with equipment that
must remain in productive operation. Any test procedure must prepare
for the contingency that the equipment may lose power. Do not test the
PDU by detaching power cords which are connected to live power
sources, as this eliminates the connection to ground and places your
equipment at risk.
Primary Input Active Secondary Input Active
The PDU provides remote monitoring, outlet control and more via Web browser, telnet and SNMP-based
Network Management Systems. For more information about configuration and operation of the PDU via
the PowerAlert Web browser interface, refer to the SNMPWEBCARD User's Guide, included on the
CD-ROM bundled with the PDU.
Load "Ramping" on Startup: All models arrive from the factory programmed so that, when first
powered up, their outlets turn on in sequential order at intervals of approximately 250 ms. This prevents
circuit overloads by staggering the startup of multiple devices. Models PDUMH15ATNET,
PDUMH20ATNET and PDUMH20HVATNET support user-programmable startup of outlets, in any
order or time interval. This ensures that network items are turned on in the proper sequence, with the
appropriate delay, so that network items are reliably discovered on startup.
Programmable Load "Shedding" During a Power Failure: In the event that the primary power source
fails and the PDU is relying on the secondary power source, load shedding allows you to program the
shutoff of specific outlets at timed intervals. This enables you to turn off less critical loads (monitors, for
example) to maximize the UPS runtime for the most critical items.
4.2 Remote Monitoring and Control
4. Configuration and Operation (continued)
4.1.3 Quick Test
The PDU will power up if one of the input sources is greater than the minimum startup voltage. In normal
operation (after power-up), if the presently selected source (primary or secondary) degrades to a lesser
condition, the unit should switch to the alternate source, if that source is of better quality. The unit
prefers the primary source, and will always switch to it in the event that both sources are of the same
(fair or good) quality. If the present source is becoming bad and the alternate source is at least fair, the
unit will switch to the alternate source.
Nominal Voltage of PDU
Low-Voltage Models High-Voltage Models
120V 200-208V 220-240V
Minimum Startup Voltage 85V 163V 163V
Good Voltage Range 99-139V 172-241V 190-266V
Fair Voltage Range 75-98V 144-171V 144-189V
Bad Voltage Range 0-74V 0-143V 0-143V
4.1.2 Automatic Transfer Switch Source Selection