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APPENDIX B:
REAR PANEL RELAY CONTACT FUNCTIONAL OPERATION
The UPS has status relay contacts accessible from the rear of the unit. The status of these contacts
(open or closed) is controlled by the internal microcontroller to reflect operational conditions of the UPS.
Section 2.2 of this manual defines the electrical operation of these relay contacts. This Appendix
defines the functional operation of these relays. Presently, these relay contacts can be set up to
function in one of three different modes of operation. The mode used by a particular UPS can be
determined by connecting a computer or terminal to the serial communications port (see section 2.2)
and typing
OPT
followed by the
<enter>
key. Following is a description of the modes presently in
existence. Note that if the UPS’ controls are receiving no power because either the Transfer Switch is
in the OFF position, the DC breaker is in the off position, or an internal UPS failure exists that prevents
the controls from receiving power, all contacts will be open.
MODE 0:
Relay Normally Open Contacts Closed if These Conditions Exist
1
Battery is being discharged (UPS may or may not be producing output power).
2
UPS is producing output power BUT needs attention. UPS needs attention if one or more of the
following is true: an overload exists, an over-temperature condition exists, a diagnostic condition
exists, or a warning condition exists.
3
Transfer Switch is in the ON BYPASS position.
4
UPS is producing output power AND Transfer Switch is in the ON UPS position.
MODE 1:
Relay Normally Open Contacts Closed if These Conditions Exist
1
UPS is producing output power AND either battery has been discharging for at least 10 seconds OR a
new alarm condition exists. A new alarm (overload, over-temperature, diagnostic, or warning) is an
alarm that has occurred since the last time this status has been acknowledged. (Can be connected to
control an audible alarm. Alarm may be acknowledged, and thus silenced, by shorting pins 3 & 4 of
the “Custom I/O” connector on the UPS after the alarm has occurred.)
2
UPS is producing output AND battery is charging AND Transfer Switch is in the ON UPS position
(UPS is operating normally).
3
UPS is producing output BUT battery is discharging AND Transfer Switch is in the ON UPS position
(UPS is operating normally except battery is discharging).
4
UPS has either shut down due to an abnormal condition, is in an overload or over-temperature
condition, or has detected a diagnostic or warning condition (UPS needs attention).
MODE 2:
Relay
Normally Open Contacts Closed if These Conditions Exist
1
UPS is producing output power AND battery has been discharging for at least 10 seconds.
2
UPS has either shut down due to an abnormal condition, is in overload or over-temperature condition,
or has detected a diagnostic or warning condition (UPS needs attention).
3
Same as Relay 1
4
Same as Relay 2
