System-20 BTU Meter ONICON

The System-20 BTU Meter provides highly accurate thermal energy measurement in water and water/glycol cooling, heating and condenser water systems. Energy measurements are based on signal inputs from a matched pair of temperature sensors and any of ONICON’s flow meters that are ordered separately. The flexible design provides energy, flow and temperature data on the local display via analog and pulse outputs, and over BACnet® MS/TP or MODBUS® RTU networks. Three auxiliary inputs are also provided to totalize pulses from other devices and communicate these totals directly to the network. Chilled water, hot water and condenser water systems for:
  • Central plant monitoring
  • Campus energy monitoring and cost allocation
  • Performance/efficiency evaluations
  • Energy monitoring for performance contracts
  • AHU and CRAC units for commercial office tenant billing
  • Solar, geothermal and ground-source energy monitoring


  • Multiple Output
  • Simple Installation and Commisioning
  • Multiple Flow Meter Options
  • Multiple Temperature Sensor Option
  • Ideal Submetering Solution
  • Built-In Interval Data Logger
  • User-friendly Interface


Liquid Flow Rate See accuracy statement provided with the flow meter (ordered separetly)
Differential Temperature Meets EN1434/C900.1 accuracy requirement for 3K sensors
Available Options -Precision solid state current based sensor. Signal (mA) is unafected by wire length. Overall differential temperature measurement uncertainty of ±0.15ºF over the application range. - 1000Ω platinum RTDs calibrated to a differential measurement uncertainty of ±0.18ºF over the stated range
Calculator Meets EN1434 Class 1 requirements with 3K minimum Δt
Computation Error ≤0.09% at 30°F Δt
Mechanical Dimension 5.5" H x 6.5" W x 4.25" D
Material Enclosure Glass filled polycarbonate with a UL-94 flammability rating suitable for use in pleum spaces
Enviromental Meet EN1434/C900.1 Class B requirements
Operating Temperature Range -13ºF to 140ºF
Enclosure Rating NEMA 12K
Power Supply Requirements 20 - 28 AC/DC, 50/60 Hz 500mA DC or 1A AC maximum input current
Isolated Analog Output May be programmed for energy rate, flow rate, supply temperature, return temperature or Δt
Configurable 4-20 mA, 0-5V or 0-10V output
Isolated Totalizing Solid State Contact Closure Pulse Outputs May be programmed for energy, volume, alarm indication, mode indication or MODBUS coil indication
Contact Rating 50 mA, 30 V
Contact Pulse Duration 50, 100, 500 or 1000 ms
Isolated Totalizing Pulse Input For use with devices providing sinking open collector or dry contact ouputs
Network Connection Isolated RS485 serial interface
Communication Protocols Available Options - BACnet MS/TP per ASHRAE standard 135.1: 2009 - MODBUS RTU
Network Configuration & Addressing Baud Rates 4800, 9600, 19200, 38400, 76800, or 115200
Device Address Range 1 – 127 (1 - 247 MODBUS® RTU)
Device Instance Range None, Even, Odd (MODBUS® RTU only)
Parity None, Even, Odd (MODBUS® RTU only)
Approval FCC Part 15, Subpart B
BTL Certified to ASHRAE 135:2009
UL Listed