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 The Sentinel is a 24/7 cooling tower maintenance monitor that will display and record system critical values and levels that are vital to cooling tower performance and reliability. When values or levels exceed the user adjustable alarm points, the Sentinel will instantaneously provide notification to maintenance personnel.
The standard Sentinel is user configurable and available with any or all of the following sensor inputs: Water Temperature, Water Pressure, Water Conductivity, Water pH, Water Level, Vibration and Fan Motor Current. Custom configurations and control options are available on request.
A series of operator interfaces have been provided, local display, keypad, and series of light Emitting Diodes (LEDs), for use in day-to-day operation. The LEDs are bright enough to allow a quick at-a-glance view of present and past system performance. The local display and keypad are useful for determining more detailed information such as the current status of all sensors or the time and date of past alarm events.
A PC, laptop or other hand-held device may be permanently or temporarily connected to up to 16 Sentinels through an RS-422 communications network for access to system configuration, historical log viewing, graphing, and report printing. Remote, off-site, access to a local PC is available through a phone line or IP address. If an open protocol is required, the Modbus RTU protocol and BACnet protocol are supported on an RS-422/RS-485 interface. All real-time analog, discrete, and state data are available; as well as access to a limited number of control and monitoring setpoints.
Custom configurations and control options are available to end-users, service centers and private label (OEM) opportunities for manufacturers.
The Sentinel is a UL and cUL listed industrial control panel built to UL508A specifications and is housed in a NEMA 4X housing.
For more information on this product or OEM applications, Contact Us or submit a on-line Information Request.
The Sentinel Cooling Tower Control System consists of the following standard components and sub-systems:
Controller
Private Label Opportunity
The Cooling Tower System is available for OEM applications. The flexibility of platform allows control features to be incorporated make this system customizable to meet any manufactures requirements. For additional information this or any other private label needs Contact Us or submit a on-line Information Request.
Operator Interface
The Operator Interface consists of 15 Light Emitting Diode (LED) indicators on the front panel, a 2-Line Liquid Crystal Display, and keypad on the front of the enclosure.
- Local Two-line Display with Control Keys
- Front-Panel LED Indicators
- Remote Access via PC
- Remote Access via Modbus RTU Protocol (RS-422) or BACnet Protocol
- Optional TCP/IP (Ethernet)
- Optional Remote Access via Modem and Telephone Lines
The front panel LED indicators are red and arranged in two columns.
The ACTIVE ALARM column indicates the current value of any alarm or failure associated with each parameter. LEDs in this column will illuminate when the associated alarm or failure condition is active.
The PAST ALARM column is the latched value of the alarm or failure. LEDs in this column will illuminate upon the first occurrence of any alarm or failure condition. Latched alarms need to be manually reset by the operator.
Control Software
The control software runs out of non-volatile memory which requires no operator intervention in the event of a power failure. The software is designed to provide a means to monitor the cooling tower for the primary purpose of notifying plant personnel that there is a problem with the system before a failure occurs. Also included are various optional safety controls and monitoring points to improve system performance.
Analog inputs and front panel LED indicators:
The control system monitors up to eight analog sensors. The hardware signal conditioning for each sensor is fixed for each particular sensor type. All sensors are optional and can be selected at start-up.
- Water Temperature
The water temprature sensor intended to monitor the temperature of the water. High or low temperatures indicate problems with the water heater. Water Temperature High and Low Alarm Setpoints will be provided. The Heater can be optionally controlled by the Water Temperature sensor.
- Water Pressure
The water pressure transducer monitors the condition of the spray nozzles, water pump, and suction strainer. A high pressure reading indicates that the spray nozzles have become blocked by debris or corrosion and maintenance on the spray nozzles is required. A low pressure reading indicates a problem with the water pump or blockage at the suction strainer and indicates that there is a problem with the water pump or suction strainer.
- Water Conductivity
The water conductivity sensor is intended to monitor the condition of the water. Excessive conductivity indicates the presence of impurities in the water which will cause damage to many system components. A Bleed Solenoid can be optionally controlled based on high Conductivity conditions.
- Water pH
The water pH sensor is intended to monitor the condition of the water. Excessive acidity or alkalinity of the water will cause damage to many system components.
- Water Level
Two methods of sensing water level in the sump have been provided, a water level sensor and two water level switches. High or low level conditions indicate problems with the water level control or water circulation system. The Water Makeup Solenoid can be optionally controlled by the Water Level sensor.
- Vibration
The vibration sensor is intended to monitor the condition of the fan blades, shaft, and bearings. Damage to the fan blades or excessive bearing wear will cause an increase in vibration. The Vibration High failure will be used to de-energize the Fan Motor Lockout relay discrete output.
- Fan Motor Current
The fan motor curent sensor will be mounted on one of the three AC power leads to the fan motor. Excessive motor current indicates damage to the motor, starter circuit, or fan assembly. The tower will be considered in the running state if the Fan Motor Current exceeds 5% of the sensor range. Run-time hours are accumulated only when the tower is in the Running state.
- Fan Run-Time (active condition only)
Run-time hours are only accumulated when the tower is in the Running state. The overall run-time is accumulated as well as the total run-time each day. In addition, the number of starts today and the overall number of starts is accumulated whenever the tower transitions from the Stopped state to the Running state.
Discrete Inputs and Outputs:
All discrete outputs are connected to Form-C mechanical relays rated for up to 5 Amps at 240 VAC. The normal condition of the relay coil will be de-energized.The status inputs monitor the presence or absence of control voltages from mechanical dry contacts or other voltage sources. The inputs are rated for 120 VAC or 240 VAC, depending on the requirements of each particular installation.
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Active Alarm Output
The Active Alarm Output is used to report current active alarm and failure information to remote monitoring systems. The relay coil is normally energized when there are no active alarms or failures and will be de-energized whenever any alarm or failure condition is in the active state.
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Latched Alarm Output
The Latched Alarm Output is used to report any past alarm or failure condition to remote monitoring systems. The relay coil is normally energized when there have been no alarm or failure conditions and will be de-energized whenever any alarm or failure condition has occurred.
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Fan Motor Lockout Output
The Fan Motor Lockout Output relay coil is energized whenever the Vibration High Failure occurs. The Fan Motor Lockout relay coil is de-energized when the failure has been cleared and the operator selects the Clear Fan Lockout function.
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Condenser Pump Lockout Output
The Condenser Pump Lockout output relay coil is energized whenever the Water Level Low failure occurs. The Condenser Pump Lockout relay coil is de-energized once the failure has been cleared and the operator selects the Clear Pump Lockout function.
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Bleed Solenoid Output
The Bleed Solenoid Outputs controlled by the Water Conductivity Sensor. The Bleed Solenoid opens when the Conductivity rises above the Conductivity High Bleed Open setpoint and closes when the Conductivity falls below the Conductivity Low Bleed Close setpoint.
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Fan Bearing Lubrication Output
The Fan Bearing Lubricator is used to automatically supply grease to the fan bearings on a periodic basis. The lubrication cycle time is currently fixed at 240 hours of fan run-time but may be changed by qualified maintenance personnel.
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Water Makeup Solenoid Output
The Water Makeup Solenoid Output is available for use only when the Water Level sensor is enabled. User-programmable makeup valve open and close setpoints are provided which are used to control the Water Makeup Solenoid. When the water level falls below the makeup valve open setpoint, the Water Makeup Solenoid relay coil is energized to open the Water Makeup Valve. When the water level rises above the makeup valve close setpoint, the Water Makeup Solenoid relay coil is de-energized to close the Water Makeup Valve.
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Heater Control Output
The Heater Control Output is available for use to regulate the sump water temperature, but only when the Water Temperature sensor is enabled. User-programmable heater on and off setpoints are provided. If the water temperature falls below the heater on setpoint, the Heater Control output is energized to turn on the Sump Heater. When the water temperature rises above the heater off setpoint, the Heater Control output is de-energized to turn off the Sump Heater. As an additional safety, the Heater Control output is de-energized when the Water Level Heater Lockout occurs. Normal operation of the Heater Control output resumes when the water level returns to normal.
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Fan Motor Auxiliary Status Input
The Fan Motor Aux. Status discrete input indicates that the fan motor is running. The tower will be considered in the Running state if the Fan Motor Aux. contact is closed. Run-time hours are accumulated only when the tower is in the Running state.
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Pump Motor Axillary Status
The Pump Motor Aux. status discrete input indicates that the pump is running. This signal is used as an alarm inhibit for the Water Pressure Low alarm. If the Pump Motor Aux. is enabled, then Water Pressure Low alarms will not be reported when the Pump Motor Aux. contact is open.
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Water Level High Alarm Input
The Water Level High Alarm indicates excessive water in the sump. The alarm will be generated if the Water Level High Alarm contact is closed (energized) for the duration of the Water Level High alarm delay time on the Water Level setpoints screen. In addition, if Water Level control is being performed using a Makeup Valve, the valve will be closed.
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Water Level Low Failure Input
The Walter Level Low failure indicates insufficient water in the sump. The alarm will be generated if he Water Level Low Alarm contact is closed (energized) for the duration of the Water level Low alarm delay time on the Water level setpoints screen. In addition to generating an alarm, the Condenser Pump Lockout discrete output will be energized.
Communication and Remote Monitoring
There are multiple communications options available in the Sentinel.
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Comm0
Comm0 is used to interconnect multiple Sentinel units within the same facility. Interconnection of multiple units is primarily used to consolidate data from each unit for use by the PC or other device on Comm1 or the Modem on Comm2.
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Comm1
Comm1 is the primary connection point for other data monitoring equipment including a PC running the PC Monitor software, a PLC running Modbus RTU protocol, or a BACnet MS/TP connection. When used with PC Monitor, Comm1 can be used for all setpoint programming, baseline recording, and real-time data monitoring. Once con-figured, the Sentinel does not require a PC to be connected. The software protocol is Modbus RTU, BACnet MS\TP, or M&M standard. When COMM1 is setup for Modbus RTU or BACnet MS\TP, COMM2 may be used for the PC Monitor connection.
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Comm2
Comm2 is the primary connection point for a remote PC, laptop, or other hand-held device. When used with PC Monitor, COMM2 can be used for all setpoint programming, baseline recording, and real-time data monitoring. In addition, if a modem or Ethernet adapter are connected, remote PCs using PC Monitor can access all data as if the PC was connected locally. The PC Monitor software protocol is M&M standard.
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