212-M-V2.1
Overview 3
1. OVERVIEW
The Model 212 Heat Calculator is designed to measure the energy consumed
in both heating and cooling (air conditioning) systems. The instrument is
normally supplied complete with temperature probes and power supply, and
will interface to a wide variety of flowmeters, including positive
displacement and inferential water meters, magnetic flowmeters with pulse
outputs, turbine flowmeters & paddlewheel flowmeters.
The Model 212 measures the temperature in the feed and return flow lines and
uses this information to calculate the density and enthalpy of water. By also
measuring the volume of water flowing in the system, the Model 212 will then
determine the energy used. Power is calculated as:
P = V x ᵨ x (h
TV
- h
TR
)
where P = Power (W)
V = Volumetric Flow rate (m
3
/sec)
ᵨ = Density (kg/m
3
)
h
TV
= Specific Enthalpy (J/kg) at Feed Temperature
h
TR
= Specific Enthalpy (J/kg) at Return Temperature
The Model 212 is designed to be used in typical water heating or cooling
systems where pressures do not exceed 16 bars.
The temperature in both the feed and return lines is measured via two
PT100 resistance temperature devices (RTDs). For maximum accuracy, four
wire RTDs should be a matched pair, Class A to IEC 751 standard.
The Model 212 complies with OIML R75 and EN1434 standards and
includes Meter-bus and RS485 (Modbus RTU) communication links.
The Model 212 includes separate peak and off-peak registers as well as the
ability to compute charge and discharge energy in systems where heat may be
stored in underground tanks.
The Model 212 provides pulse output with programmable pulse width from 10
to 500ms.
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