18 August 1998
a. Existing equipment being connected to the UMCS will require the installation of disconnect
switches or locking starters within sight of the controlled equipment as required by NFPA 70.
b. Spare electrical circuits may be locally available to supply power to UMCS equipment. If these
circuits do not exist, or are inadequate for the intended service, new panels or circuit breakers will be
9. SUBSTATIONS. Selection and installation of current and voltage transducers for UMCS must be
coordinated with the facility and with the equipment manufacturer. Placement of transformer winding
temperature sensors must also be coordinated with the manufacturer.
10. SWITCHGEAR. UMCS can monitor the status of electrical distribution switchgear equipment such
a. Circuit breakers.
b. Breaker over current trip relays.
If there are no spare contacts in the switchgear monitoring relays, interposing relays must be provided.
Interposing relay kits must be obtained from the original breaker manufacturer. The UMCS will not
perform switchgear control functions. These functions may be provided by a Supervisory Control and
Data Acquisition (SCADA) system.
11. EMERGENCY GENERATOR. The remote start/stop of emergency generators must be coordinated
and reviewed with the installation electrical engineer and with the generator manufacturer. The UMCS
will monitor generator status and common alarms either from available contacts at the generator control
panel or by means of interposing relays in series with existing control panel status and alarm indicating
lights. Generator main fuel storage and day tank level sensors may have to be replaced for the
measurements to be monitored by UMCS.
12. MOTOR STARTERS. Starter control circuits must be modified for UMCS interfacing. Typically,
existing momentary type starters require parallel starting contacts and series stop contacts, while starters
with on/off and hand-off-auto (HOA) switches will require maintained contacts in series with the local
automatic control device. Start/stop switches will be replaced with HOA switches. New starter control
circuits interfaced with a UMCS for controlling equipment from the UMCS are shown in Appendix B.
Since a push-button control circuit requires magnetically operated contacts for momentary operation,
latching relays cannot be used. During field equipment panel failure, the controlled equipment remains in
the last commanded state. No definitive failure mode can be designed with push-button control circuits.
The HOA and start-stop selector control circuits allow magnetically held relays or latching relays to be
used for contact operation, depending on the required failure mode. Latching relays will be used when
the design requires equipment to remain in the last commanded state during a field equipment panel
failure. Magnetically held, normally open relays will be used when the required failure mode is off (or an
open circuit), and magnetically held, normally closed relays will be used when the required failure mode is
on (or a closed circuit). The design requires definition of the failure mode during a field equipment panel
failure for all types of starter circuits. Magnetically held or latching relays will be selected to provide the
required failure mode operation. A magnetically held relay requires one DO to control it, while a latching
relay requires two DOs to control it.
13. MECHANICAL EQUIPMENT.