Input Devices and Sensors
The measurement of energy is a very important aspect of the DDC
system. Savings due to operational procedures and equipment performance can be
directly determined through this measurement. A variety of devices and methods
are currently available.
Types of Energy Measurement Devices
The three most common energy measurements used for DDC systems are
airside, waterside and electrical energy measurements. Airside energy
measurements are typically calculated in the DDC system using air temperature
and flow rate measurements. Waterside energy can be calculated in the DDC
system or with energy measuring devices called BTU meters. Electrical energy
measurements can be calculated in the DDC system or with Power Monitoring
BTU Metering Devices
BTU meters are used to determine energy flows in hydronic systems within a
facility for accounting or control purposes. Determination of heat flow
requires measuring the heat transfer medium flow and the difference in
temperature between the supply and return to the metered load or producer.
With suitable software, this can be accomplished using the DDC
system. This may also be accomplished external to the DDC system using a
microprocessor-based computer with flow and temperature inputs, and analog
output to the DDC system representing totalized energy consumption in BTU or
ton-hours, or energy flow in BTU per hour, tons, or similar units. Many
manufacturers of flow measurement devices offer this type of system.
Power Monitoring Devices
Power monitoring devices can be used to monitor electrical energy usage. They
can either directly measure the energy usage by providing pulses that represent
kW per hour, or can provide an analog signal that measures power which can be
used in an energy calculation (over time) in the DDC system. For more details
please refer to the previous section on Power Monitoring Devices.
Getting Started | Chapter 2: Electrical | Top | Chapter 2: Occupancy