Onicon System-20 BTU Meter

Onicon System-20 BTU Meter

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 Commissioning
  • Multiple Flow Meter Options
  • Multiple Temperature Sensor Option
  • Ideal Submetering Solution
  • Built-In Interval Data Logger
  • User-friendly Interface


Liquid Flow RateSee accuracy statement provided with the flow meter (ordered separately)
Differential TemperatureMeets EN1434/C900.1 accuracy requirement for 3K sensors
Available Options-Precision solid-state current based sensor. Signal (mA) is unaffected 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
CalculatorMeets EN1434 Class 1 requirements with 3K minimum Δt
Computation Error≤0.09% at 30°F Δt
MechanicalDimension5.5" H x 6.5" W x 4.25" D
MaterialEnclosureGlass-filled polycarbonate with a UL-94 flammability rating suitable for use in plenum spaces
EnvironmentalMeet EN1434/C900.1 Class B requirements
Operating Temperature Range-13ºF to 140ºF
Enclosure RatingNEMA 12K
Power Supply Requirements20 - 28 AC/DC, 50/60 Hz
500mA DC or 1A AC maximum input current
Isolated Analog OutputMay be programmed for energy rate, flow rate, supply temperature, return temperature or Δt
Configurable4-20 mA, 0-5V or 0-10V output
Isolated Totalizing Solid State Contact Closure Pulse OutputsMay be programmed for energy, volume, alarm indication, mode indication or MODBUS coil indication
Contact Rating50 mA, 30 V
Contact Pulse Duration50, 100, 500 or 1000 ms
Isolated Totalizing Pulse InputFor use with devices providing sinking open collector or dry contact outputs
Network ConnectionIsolated RS485 serial interface
Communication ProtocolsAvailable Options- BACnet MS/TP per ASHRAE standard 135.1: 2009
Network Configuration & AddressingBaud Rates4800, 9600, 19200, 38400, 76800, or 115200
Device Address Range1 – 127 (1 - 247 MODBUS® RTU)
Device Instance RangeNone, Even, Odd (MODBUS® RTU only)
ParityNone, Even, Odd (MODBUS® RTU only)
ApprovalFCCPart 15, Subpart B
BTLCertified to ASHRAE 135:2009
UL Listed

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