11.120.350 Alarms and indications.
The following local and remote alarms and indications shall be provided:
|
Alarm/Status Point |
Local Indication |
Remote (via SCADA) |
|---|---|---|
|
Generator Running or Feeder No. 1 Available (as applicable) |
Yes (at the auto-transfer switch) |
Yes |
|
Generator Running or Feeder No. 2 Available (as applicable) |
Yes (at Generator Control Panel – by manufacturer) or at the auto-transfer switch (as applicable) |
Yes |
|
Power Failure |
None |
Yes |
|
Low Wetwell Level |
Yes (white light at Instrumentation Cabinet) |
No |
|
Battery Charger Failure (as applicable) |
Yes |
Yes |
|
High Wetwell Level |
Yes (white light at Instrumentation Cabinet) |
Yes |
|
Low Oxygen in Wetwell |
Yes (on air analyzer by manufacturer) |
Yes |
|
High Combustibles in Wetwell |
Yes (on air analyzer by manufacturer) |
Yes |
|
High Hydrogen Sulfide in Wetwell |
Yes (on air analyzer by manufacturer) |
Yes |
|
Pump No. 1 Running |
Yes (on motor starter) |
Yes |
|
Pump No. 1 Malfunction |
Yes (on motor starter) |
Yes |
|
Pump No. 2 Running |
Yes (on motor starter) |
Yes |
|
Pump No. 2 Malfunction |
Yes (on motor starter) |
Yes |
|
Wetwell Ventilation Failure |
Yes (on panel near air analyzer) |
Yes |
|
Wetwell Level |
Yes (digital LED indicator at Instrumentation Cabinet) |
Yes |
|
Station Flow |
Yes (digital LED indicator at Instrumentation Cabinet) |
Yes |
|
Sanitary Sewage Overflow (SSO) |
Yes (white light at Instrumentation Cabinet) |
Yes |
Interface relays shall be provided to isolate the inputs to the remote terminal unit (RTU) from the field contacts for status, alarms and controls. A 120V AC relay to switch the 24V DC in the RTU shall be provided for each point. Relays shall be Potter and Brumfield type R10-El-Y2-115V AC mounted in an Iniven (Conolog Corp.) relay rack type ISK-12-120V AC. Each rack holds 12 relays and takes up approximately an eight-inch-high-by-24-inch-wide space. Provide a total of 24 relays in two racks in a 24-inch-wide-by-30-inch-high-by-12-inch-deep NEMA 4X cabinet enclosure.
A mercury-type float switch shall be provided in an appropriate and accessible part of the station wetwell to provide a prompt indication of a sanitary sewage overflow (SSO). The SSO alarm setpoint shall be coincident with the lowest manway cover elevation of any mainline gravity sewer manway that will be located on the upstream side of the WWPS. The SSO alarm setpoint shall instead be coincident with the top elevation of the WWPS wetwell if the wetwell top elevation is lower than the elevations of any manway cover connected to the mainline gravity sewer feeding the WWPS.
Field wiring to the relays and wiring to the RTU shall be color coded as follows:
|
Control Wiring |
RED, for ungrounded conductors |
|
WHITE, for neutral conductors |
|
|
GREEN, for grounded conductors |
(Note: All field wiring (including Status and Alarm) for Process Control I/O shall be 120V AC rated and shall be No. 14 AWG copper stranded THHN.)
|
Analog Wiring |
RED, for ungrounded conductors |
|
BLACK, for ungrounded conductors |
(Note: These two conductors for the analog wiring shall be No. 18 AWG, twisted and shielded as a single pair instrumentation cable.)
The WSSC will terminate all the wiring in the RTU and at the low voltage side of the interface relay panel. The contractor is to leave a sufficient amount of slack at the RTU and at the interface relay panel, a minimum of four feet at each end to allow terminating any wire on any terminal in the cabinets.
A separate 120V AC branch circuit shall be run from the lighting and control panel to the interface relay panel. Each relay rack shall be fed through a local five-amp circuit breaker. (Design Guideline DG-08 § 16.7, dated August 2006)