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

Features :

  • 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

Specification :

Liquid Flow Rate

See the Accuracy statement provided with the flow meter (ordered separately)

Differential Temperature

Meets EN1434/C900.1 accuracy requirement for 3K sensors


-Precision solid-state current-based sensor. The 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


Meets EN1434 Class 1 requirement with 3K minimum Δt

Computation Error

≤0.09% at 30°F Δt



5.5" H x 6.5" W x 4.25" D



Glass-filled polycarbonate with a UL-94
flammability rating suitable for use in plenum spaces


Meet EN1434/C900.1 Class B requirements

Operating Temperature Range

-13ºF to 140ºF

Enclosure Rating


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


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 a sinking
open collectors or dry contact outputs

Network Connection

Isolated RS485 serial interface

Communication Protocols

Available Options

- BACnet MS/TP per ASHRAE standard 135.1: 2009

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)


None, Even, Odd (MODBUS® RTU only)



Part 15, Subpart B


Certified to ASHRAE 135:2009

UL Listed


Baca juga: Onicon Flow Energy and Measurement

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