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Table 2. Input Dry Contact Signals
External Dry Contact Signal
Remote EPO
Remote Select S1
Remote Select S2
Building Alarm 1
Building Alarm 2
Building Alarm 3
Building Alarm 4
Building Alarm 5
Building Alarm 6
Building Alarm 7
Building Alarm 8
6 6 . . 3 3 . . 3 3 R R e e m m o o t t e e S S o o u u r r c c e e S S e e l l e e c c t t O O p p t t i i o o n n
Two external two dry contacts can be used to control the remote selection of the preferred source. Dry contact
closures are generally used when two UPSs supply power to the system. If the preferred UPS goes to bypass
mode, the "good" UPS becomes preferred:
•
Signal 1 (Remote Select S1) dry contact closure will make Source 1 preferred.
•
Signal 2 (Remote Select S2) dry contact closure will make Source 2 preferred.
•
If both dry contacts closures are open, the preferred source control is returned to the system operator
control panel.
Any remote control signal or closure puts the unit into a "Retransfer=Yes" mode to ensure system redundancy.
Normally the closures are controlled by auxiliary contacts in the UPS bypass circuit breakers. If both dry
contacts close, the first input to the STS is recognized.
6 6 . . 3 3 . . 4 4 M M u u l l t t i i - - S S w w i i t t c c h h L L i i n n k k O O p p t t i i o o n n ( ( N N + + 1 1 U U P P S S ) )
In an N+1 UPS Configuration, there are multiple STS units, each with a preferred source fed by a separate UPS.
The alternate source on all STSs is provided by a single backup UPS.
All STS units in an N+1 UPS configuration must have Enhanced Contractor Boards and the Multi-Switch Link
Option installed, providing coordination among the STSs.
Because the backup UPS can only provide power through the STS to a single downstream load, when an STS
transfers its load to the backup UPS, the STS must signal the other STS units that it is using the UPS. The other
STS units are locked out and cannot transfer to the backup source.
An "Inhibit Transfer" alarm is signaled on each STS. The STSs are prevented from transferring until the
Preferred Source on the STS using the backup UPS returns to normal and the STS retransfers the load back to
the Preferred Source.
Eaton Static Transfer Switch 2000A 3-Pole Installation and Operation Manual 164001127—Rev 01
Basic Contractor Board
Available
Not Available
Not Available
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Not Available
Not Available
Not Available
Customer Communications Connections
Enhanced Contractor Board
Available
Switch to Source 1
Switch to Source 2
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