Table 95: Four-stage board - temperature sensor connections
Location Label Description Function and comments
EC4+
#4 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 EC4+ to EC4– with open circuit. Used in suction
line temperature safety.
AUX-2+ Not used Not used
C
AUX-1+ Not used Not used
Table 96: Four-stage board - quick connect
Location Label Description Function and comments
COM Common for Modbus connection to staged heat board Future
MB_B Terminal B for Modbus connection to staged heat board Future
MB_A Terminal A for Modbus connection to staged heat board Future
C Common for HW Valve connection 0-10 VDC
D
HWV Analog out for HW Valve 0-10 VDC
VAV VAV box Common relay contact Used to interlock the VAV boxes with RTU morning warm-up
F
BOX VAV box normally open relay contact Used to interlock the VAV boxes with RTU morning warm-up
Table 97: Four-stage board - harness connectors
Location Label Description Function and comments
C Common for analog outputs Future
HGR MOD 0-10 VDC analog output for hot gas reheat Future
C1 MOD 0-10 VDC analog output for C1 modulation Future
CF1 MOD 0-10 VDC analog output for Condenser Fan 1 modulation Future
E
CF2 MOD 0-10 VDC analog output for Condenser Fan 2 modulation Future
Table 98: Four-stage board - outputs and cool and heat section connections
Location Label Description Function and comments
G
24V FOR
OUTPUTS
24 VAC hot for C3, C4, CF2, H3, and HGR
Output relay circuitry is isolated from other 4-stage components and the 24 VAC hot source may
be from a second transformer in the unit
C3 24 VAC hot output for compressor 3 If demand is present and permissions allow compressor 3 operation
C4 24 VAC hot output for compressor 4 If demand is present and permissions allow compressor 4 operation
CF2 24 VAC hot output for the condenser fan contactor coil Output with either C3 or C4 output.
H3 24 VAC hot output for heat section stage 3
Not effective for cooling-only units. Output if demand is present and permissions allow heat
section operation
H
HGR 24 VAC hot output for hot gas reheat Future
Table 99: Four-stage board - refrigerant circuit safety switches
Location Label Description Function and comments
LPS3
(right pin)
24 VAC hot out for refrigerant circuit 3 Low Pressure
Switch
Connects through circuit trace to the left HSP3 pin
LPS3
(left pin)
24 VAC hot return from refrigerant circuit 3 Low
Pressure Switch
Input is only considered after 30 seconds of C3 output; afterwards, input must be present to allow
C3 output. Three LPS3 trips in a one hour period cause a “Low Pressure Switch 3 Lockout” and C3
output is then prevented until alarm reset.
HPS3
(right pin)
24 VAC hot out for refrigerant circuit 3 High Pressure
Switch
Connects through circuit trace to the R terminal
HPS3
(left pin)
24 VAC hot return from refrigerant circuit 3 High
Pressure Switch
Input is only considered if C3 output is needed; input must be present to allow C3 output. Three
HPS3 trips in a two hour period cause a “High Pressure Switch 3 Lockout” and C3 output is then
prevented until alarm reset. Connects through circuit trace to the right LPS3 pin.
LPS4
(right pin)
24 VAC hot out for refrigerant circuit 4 Low Pressure
Switch
Connects through circuit trace to the left HSP4 pin
LPS4
(left pin)
24 VAC hot return from refrigerant circuit 4 Low
Pressure Switch
Input is only considered after 30 seconds of C4 output; afterwards, input must be present to allow
C4 output. Three LPS4 trips in a one hour period cause a “Low Pressure Switch 4 Lockout” and C4
output is then prevented until alarm reset.
HPS4
(right pin)
24 VAC hot out for refrigerant circuit 4 High Pressure
Switch
Connects through circuit trace to the R terminal
I
HPS4
(left pin)
24 VAC hot return from refrigerant circuit 4 High
Pressure Switch
Input is only considered if C4 output is needed; input must be present to allow C4 output. Three
HPS4 trips in a two hour period cause a “High Pressure Switch 4 Lockout” and C4 output is then
prevented until alarm reset. Connects through circuit trace to the right LPS4 pin.
Installation Manual: YORK
®
Sun
™
Select YV28 to YV50
102
Johnson Controls Ducted Systems
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