Specifications

121
intelligent decision to satisfy the preset temperature and relative humidity levels
in the most effective and energy efficient manner.
The system is intended to either be retrofitted to an existing HVAC system, or to
be installed in a new building but only require essentially the normal wiring that
would be installed for a normal HVAC system. In order to avoid running
additional wire not normally associated with an HVAC system inside either an
existing structure, or a newly constructed building the temperature and relative
humidity measurements taken outside must be transmitted to the Main Control
Unit wirelessly. In order to achieve wireless data transmission, the sensor must
make its readings; pass the data to a microcontroller which, in turn, must pass
the data to a wireless chip that will communicate with another wireless chip on
the Main Control Unit.
The wiring for the air conditioning units to be controlled is already installed in the
building, and therefore controlling the power relays to turn the air conditioning
units on and off can be done via wire. AC units typically run on 240 Volts AC. To
get this voltage to the units, a power relay must be switched to essentially
complete a circuit connecting the units to the main 240V power supply from the
building. Out control system is required to switch appropriate relays to send 24 V
to the 240 V power relays which turn on the AC units. To control each unit, a
signal must be used for each of the following functions of the unit. The HVAC
components of an air conditioning system are, 1
st
Stage Heating, 2
nd
Stage
Heating, Blower / Fan, Compressor, Reversing Valve, and 24V Common. The
American Society of Heating, Refrigerating, and Air-Conditioning Engineers set
standard naming and color coding standards for these functions that we plan to
follow in both our system design and the planned demonstration. Table 36 shows
each HVAC Component along with its ASHRAE (American Society of Heating,
Refrigerating and Air-Conditioning Engineers) Naming and Color Coding
Standard.
Table 36 HVAC Components and the Corresponding ASHRAE Naming and
Color Standards
HVAC Component
ASHRAE Naming & Color
1
st
Stage Heating
W1
2
nd
Stage Heating
W2
Blower / Fan
G
Compressor
Y1
Reversing Valve
O
24V Common
R