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BTU Meters
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System 10

The System-10 BTU Meter is a highly accurate microprocessor-based instrument designed to provide full energy, flow and temperature data both at the front panel LCD and over an optional serial network interface. The System-10 is also available with optional analog output signals for energy, flow and temperature. The System-10 is the ideal choice for networking to control systems with the availability of BACnet®, MODBUS®, LonWorks®, Johnson Controls-N2®, Siemens-P1® interface cards.

Chilled water, hot water and condenser water systems for:

  • Commercial office tenant billing

  • Central plant monitoring

  • University campus monitoring

  • Institutional energy cost allocation

  • Performance / efficiency evaluations

  • Performance contracting energy monitoring

  • Cogeneration heat recovery monitoring

Single Source Responsibility

One manufacturer responsible for the manufacture, compatibility of components, and calibration of the entire BTU measurement system. ONICON is committed to providing highly accurate and reliable systems which guarantee successful installations.

NIST Traceable Calibration with Certification

Complete system-wide calibration for the entire BTU measurement system for each specific application with certification of calibration.

Precision Solid State Temperature Sensors

Custom calibrated and matched to an accuracy better than ±0.15° F from 32-200° F.

Simple Installation and Commissioning

Factory programmed and ready to use upon delivery, all process data and programming functions are accessible via front panel display and keypad.

Easy-to-Operate User Interface

Menu driven display and membrane keypad make viewing data easy and simplifies field re-programming when necessary.

Network Compatible Serial Communications

Optional communications card provides complete energy, flow and temperature data through a single network connection. Available with BACnet®, MODBUS®, LonWorks®, Johnson Controls-N2® and Siemens-P1® interface cards.

Highly Accurate Flow Meters

Each System-10 BTU Meter works with ONICON's insertion, inline, electromagnetic, clamp-on ultrasonic and vortex flow meters.

Installation Hardware Package

Thermowells and the associated installation hardware are provided along with installation instructions to ensure error-free installation and accurate system performance.

System 20

The System-20 BTU Measurement System provides highly accurate and reliable thermal energy measurement in heating and cooling systems. Designed for maximum versatility, the System-20 provides energy, flow and temperature data on the local display, and communicates via RS485 BACnet® MS/TP or MODBUS® RTU directly with your BMS/BAS. In addition, the System-20 provides an analog output signal, pulse outputs, and auxiliary pulse inputs, all of which are configurable via an intuitive user interface.

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

  • Residential apartment and condominium tenant billing

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Multiple Outputs

Each meter is provided standard with three programmable pulse outputs and one analog output. An RS485 output is also provided for BACnet® MS/TP or MODBUS® RTU.

Multiple Flow Meter Options

The System-20 may be ordered with any of ONICON’s inline, insertion, or clamp-on style flow meters. This allows you to match specific flow meter features and benefits to your application.

Multiple Temperature Sensor Options

The System-20 may be ordered with ONICON’s precision current based sensors or a pair of matched Platinum RTDs. Each option offers exceptional accuracy and reliability.

Auxiliary Pulse Inputs

Three user defined pulse inputs are provided standard. Pulses from water, gas or electric meters may be totalized in the System-20 to simplify network connectivity at the metering location.

Built-In Interval Data Logger

Energy and volume totals are date/time stamped and logged within the meter along with operating status and other analytical data. Data is available via BACnet® or MODBUS®.

Suitable for Water and Water/Glycol Solutions

System-20s are field programmable for water or water/glycol solutions to ensure accurate flow and energy measurement.

User Friendly Interface Display

The bright, easy-to-read, back-lit display uses “smart button technology” to simplify programming and commissioning, eliminating the need for special configuration tools.

System 40

The System-40 provides highly accurate thermal energy measurement in chilled water, hot water or condenser water systems. It is provided as a complete meter and includes a matched pair of platinum RTD temperature sensors and an integral inline ultrasonic flow sensor. It is available for use in ½” through 2½” piping systems with flow rates ranging from 0.03 to 250 GPM.


The native BACnet® MS/TP and MODBUS® RTU versions of the meter communicate energy, flow and temperature data directly to the network. Three auxiliary terminals can be configured at the factory to provide pulse outputs, inputs, a combination of the two, or even a single analog output.

Pulse outputs provide volume or energy totalization to the BMS.


Pulse inputs can bring in totalization pulses from local meters such as water, natural gas, or electric meters. Pulse input totals are accumulated in the internal registers and then transmitted to the RS-485 network. These totals are also available on the built-in display.


Analog output can be programmed to provide energy rate, volume rate, or temperature data to the BMS via a 4-20 mA / 0-10V / 0-5V signal.

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Reliable No-Moving-Parts Design

The System-40 utilizes direct path wetted ultrasonic transducers to measure flow. This no-moving-parts design optimizes signal strength and ensures long-term reliability.

Operates Over a Very Wide Flow Range

The built-in ultrasonic flow meter has a 500:1 turndown

Precision Matched Platinum RTD Temperature Sensors

1000 ohm sensors are matched to a differential uncertainty of better than ±0.18° F.

Auxiliary Pulse Inputs

The System-40 with BACnet® MS/TP or MODBUS® RTU can be ordered with three auxiliary pulse inputs for totalizing pulses from water, gas or electric meters. This simplifies network connectivity in the tenant space.

Simple Installation and Commissioning

Each meter is delivered fully programmed and ready for use upon delivery. Commissioning is done through the user interface/display without the need for special tools.

Detachable Calculator

The System-40 electronics enclosure is easily detached from the flow body to allow for remote wall mount installations using the 5’ cable provided with the meter.

C900.1 / EN1434 Compliant

The System-40 is designed to meet the requirements of C900.1 and EN1434

System 1000

ONICON's System-1000 Flow and Energy Measurement System is the advanced multi-channel interface for accurately measuring and reporting thermal energy usage, flow, temperatures, efficiency, and other engineering parameters required by today's High-Performance Buildings.



The System-1000 provides highly accurate thermal energy measurement in chilled water, heating hot water, condenser water, and domestic water systems. Energy measurement is based on signal inputs from matched precision temperature sensors and any of ONICON’s inline, insertion, or clamp-on style flow meters. Additionally, the System-1000 can accept input from non-ONICON flow meters (4-20mA & pulse).

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Total System Integration

The System-1000 works simultaneously with any of ONICON's inline, insertion, or clamp-on style flow meters ensuring the best metering technology can be chosen for all applications and installation.

Multiple Flow Meter Options

The System-1000 may be ordered with up to eight flow meters. Two reserved for energy calculation, two auxiliary inputs for electric, steam, gas or water flow rates, and 4 auxiliary inputs for totalization or alarm contact such as leak detectors.

Multiple Temperature Sensor Options

System-1000 may be ordered with a pair of ONICON's matched precision current based sensors or a pair of platinum RTDs.

Output and Network Communications

Eight pulse outputs are provided for totalization, alarm, and system status and Eight analog outputs are provided for energy, flow, temperature, efficiency, or other calculated variables. Data is reported via BACnet/IP or MS/TP directly to the BAS/BMS through a single network connection.

Wall Space Reduction

The multiple inputs of the System-1000 reduce the number of local displays needed in the room.

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