Four-stage board
Figure 73: Four-stage board
The following tables describe the details of the four-stage board, see the previous figure for the connection
locations.
Table 94: Four-stage board - power and communication terminals
Location Label Description Function and comments
C 24 VAC common for 4-stage board power
A
R 24 VAC hot for 4-stage board power
PWR Sensor Actuator (SA) Bus Power for SA bus devices Not used on 4-stage board
COM Common for SA BUS power and communication circuits Negative of the SA BUS circuits
SA- Communication for SA BUS devices
Negative of the VDC (typically, a fluctuating 1.5 to 3.5 V reading to C; at least
0.25 V lower than +) SA BUS communication circuit to optional economizer
board, 4-stage board, fault detection and diagnostics board, netstat and/or MAP
Gateway
B
SA+ Communication for SA BUS devices
Positive of the VDC (typically, a fluctuating 1.5 to 3.5 V reading to C; at least 0.25
V higher than –) SA BUS communication circuit to optional economizer board, 4-
stage board, fault detection and diagnostics board, netstat and/or MAP Gateway
Table 95: Four-stage board - temperature sensor connections
Location Label Description Function and comments
CC3+
#3 refrigerant circuit Condenser Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for heat pump units, not required for A/C units; 3.625 VDC reading CC3+ to CC3–
with open circuit. Used in heat pump demand defrost calculation.
EC3+
#3 refrigerant circuit Evaporator Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for operation; 3.625 VDC reading EC3+ to EC3– with open circuit. Used in suction
line temperature safety.
C
CC4+
#4 refrigerant circuit Condenser Coil temperature
sensor input from 10KΩ @ 77°F, Type III negative
temperature coefficient thermistor
Input required for heat pump units, not required for A/C units; 3.625 VDC reading CC4+ to CC4–
with open circuit. Used in heat pump demand defrost calculation.
Installation Manual: YORK
®
Sun
™
Select YV28 to YV50
101
Johnson Controls Ducted Systems
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