Contact Closures

Most leading generator manufacturers support contact closures as a method for alarming. The type of alarms will vary by generator manufacturer.    Contact closures will display similar to the “check engine” light in your car.   The information will be basic letting you know the generator is running or in alarm.   Critical Labs will display contact these alarms in a green, yellow, red format.  For example, if the generator is idle and the generator contact closure is open, Critical Labs will display Generator idle (green), red (running).  In the event you are looking for information such as volts, amps, and actual coolant temperature, Modbus TCP or Modbus RTU will be better options. 

Hardware Requirements

  • Verify the generator controller supports contact closures 
  • The contact closure to TCP/IP converter is also referred to as an I/O controller in the industry.  Any I/O controller that supports contact closures to SNMP conversion will work with Critical Labs.  Since generators vary in the number of contact closures, and available power, one sizes dos not fill all.  Reference the Generator Contact Closure Comparison Chart below to select the best controller based upon the number of contacts you need and the best power option.  
  • Typically the I/O controller is installed in the generator control panel or the Automatic Transfer Switch (ATS).

Cable Requirements

  • Cat 5/6 cable from the IT network to the I/O Controller 
  • A twisted pair cable is to be installed between each contact and the I/O controller, If the generator supports 8 contact closures, an 8 pair cable is needed between the generator controller and the I/O controller.  

Power Requirements

  • External power is needed to power the I/O controller.
    • Option 1 (Preferred) – Select an I/O controller that supports Power from the generator battery circuit.  
    • Option 2 (Very good) – Select an I/O controller that is power from the IT network switch using PoE+.
    • Option 3 (Acceptable) Install a PoE to DC power splitter near the I/O controller.   The output of the splitter will need to supply voltage
  • The IT network switch is to be backed up by a battery back up system.   

Generator Programming

In many cases, the generator will not require programming.  The contact closures will simply work.  Sometimes generators support flexible contacts that can be programmed.  Reach out to your generator support vendor to determine if programming is necessary.

Adding to Critical Labs

See our list of articles under Adding a Device to learn how to connect your fully wired and network-connected generator to Critical Labs.

Configuration Checklist

  • Verify generator is capable of contact closures
    • Determine the number of contact closures to be monitored, 
  • Verify Critical Labs gateway is on the customer network
    • if yes, no additional gateway is needed
    • if no, add a Critical Labs gateway and Critical Labs gateway onboarding
  • Choose the best I/O controller from the chart below that best matches the number of contact closures being monitored, power option, and price range. 
  • Verify a Cat 5/6 cable is run between the IT network and the I/O controller
    • If no, add a Cat 5/6 cable from the IT network to the I/O controller
  • Verify a twisted pair cable is run between the I/O controller and each contact closure to be monitored on the generator.  Up to 24 pairs of wires can be bundled into one shielded cable.
    • If no, add a cable
  • Add professional services as needed to configure the generator controller and setup Critical Labs software

Quick Scope of Work

  • Critical Labs gateway is a prerequisite and is to be installed on the same network as the generator
  • Generator controller is to support contact closure as a prerequisite, field verify by others
  • Cat 5/6 cable is to be installed from IT network to I/O controller by others
  • Twisted pair shielded cable is to be installed from the generator to the I/O controller by others
  • External Power from the generator battery is to power the Critical Labs Modbus converter.
  • The generator controller is to be configured by the generator support vendor to support contact closures
  • If Generator requires additional relays to support contact closures, to be provided by the generator vendor
  • Program and configure Critical Labs to support generator over Modbus TCP

List of Available Contact Closures

Manufacturer Contact Count Power Options Other Capabilities When to use Protocols Cost
Vertiv Watchdog 100
PoE, 120VAC, 6VDC
Temp Sensors
Less than 4 contact closures + PoE power
RLE F200
4 Sensor inputs, 1 relay, 1 leak detect
When 8 contract closures are needed and 120VAC power acceptable
PoE, USB, 10-32VDC Screw Term
Industrial I/O controller with 4-20ma sensor support
battery voltage is available from the generator to power the I/O controller. Hardwire Opto22 from the battery circuit via skrew down terminals.
Modbus TCP
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