14
NG-IOM-ATT Release 1.2
July 12, 2019
4.5 HVAC Unit
4.5.1 Hardwired Interface (Default)
The hardwired interface provides control for the mechanical cooling and heating functions of the HVAC unit. At a
minimum, a five-wire thermostat cable (not supplied) is required for control of the compressor, evaporator blower, and
heating element. If required, an additional two-wire input for monitoring the HVAC pressure lockout relay can be
connected. Note that the controller requires a normally closed lockout contact from the HVAC unit. The wire connections
for the terminal blocks labeled HVAC #1 and HVAC #2 are as follows:
Terminal Block
Wire Color
HVAC Unit
R
Red
24VAC Power
C
Black or Blue
24VAC Neutral
Y1
Yellow
Call for Cooling
G
Green
Call for Blower
W
White
Call for Heating
COM
Lockout Relay Common
NC
Lockout Relay NC Contact
Table 7: DX Unit Wiring Connections
Figure 9: HVAC Unit Wiring Connections (HVAC #1 Shown)
Hardwired Unit 2 DX HVAC (see figure 1) must ALWAYS be connected to terminal blocks labeled for HVAC #1. Hardwired
Unit 3 DX HVAC (see figure 1) must ALWAYS be connected to terminal blocks labeled for HVAC #2. The HVAC unit must
only be connected to those terminals identified in the wiring connections table. The unused terminals for HVAC #1 and
HVAC #2 are reserved for future use.
