430648-JIM-D-1010
Johnson Controls Unitary Products
23
• Relay BR1 sends a 24V signal to G1 of terminal block
TB2. It may be used to control operation of an indoor
blower.
When the call for cooling (Y1) is satisfied, the UCB disables the
signal to RY1, M1 and M3 as long as the specified minimum run
time (ASCD) has elapsed.
The UCB disables the signal to BR1 after completing the fan
off-delay period.
Dual Stage Condenser Unit (J10 thru J25YC or J10 thru
J12YD)
A two stage cooling thermostat is required to operate the
condenser unit.
• When the thermostat calls for first-stage cooling (Y1), the
Simplicity control board (UCB) closes the coils of relays
RY1 and BR1 and contactor M1.
• Relay RY1 has three functions. 1) control the crankcase
heater CCH1, 2) control the coil of contactor M3 and 3)
control the 24V output signal to S1 on terminal block TB2.
• Relay BR1 sends a 24V signal to G1 of terminal block
TB2. It may be used to control operation of an indoor
blower.
• Contactor M1 controls compressor COMPR1.
• Contactor M3 controls all outdoor fans.
When the thermostat calls for second-stage cooling (Y2), the
Simplicity control board (UCB) closes the coils of relays RY2
and BR2 and contactor M2.
• Relay RY2 has three functions. 1) control the crankcase
heater CCH2, 2) control the coil of contactor M3 and 3)
control the 24V output signal to S2 on terminal block TB2.
• Relay BR2 sends a 24V signal to G2 of terminal block
TB2. It may be used to control operation of an indoor
blower.
• Contactor M2 controls compressor COMPR2.
If the initial call for cooling requires both stages (Y1 and Y2), the
UCB will delay the second stage by 30 seconds to avoid an
excessive power inrush.
NOTE:
For lead-lag compressor operation, the jumper between
terminals G1 and G2 on terminal block TB2 must
remain in place to assure proper blower operation.
When the call for cooling (Y2) is satisfied, the UCB disables the
signal to RY2, BR2, and M2 as long as the specified minimum
run time (ASCD) has elapsed.
When the call for cooling (Y1) is satisfied, the UCB disables the
signal to RY1, BR1 and M1 as long as the specified minimum
run time (ASCD) has elapsed.
Dual Stage Condenser Unit (J15 thru J20YD)
A two stage cooling thermostat is required to operate the
condenser unit.
When the thermostat calls for first-stage cooling (Y1), the
Simplicity control board (UCB) closes the coils of relays RY1
and BR1 and contactor M1.
• Relay RY1 has three functions. 1) control the crankcase
heater CCH1, 2) control the coil of contactor M3 and 3)
control the 24V output signal to S1 on terminal block TB2.
• Relay BR1 sends a 24V signal to G1 of terminal block
TB2. It may be used to control operation of an indoor
blower.
• Contactor M1 controls compressor COMPR1.
• Contactor M3 controls outdoor fans ODFAN1 & 2.
When the thermostat calls for second-stage cooling (Y2), the
Simplicity control board (UCB) closes the coils of relays RY2
and BR2 and contactor M2.
• Relay RY2 has three functions. 1) control the crankcase
heater CCH2, 2) control the coil of contactor M4 and 3)
control the 24V output signal to S2 on terminal block TB2.
• Relay BR2 sends a 24V signal to G2 of terminal block
TB2. It may be used to control operation of an indoor
blower.
• Contactor M2 controls compressor COMPR2.
• Contactor M4 controls outdoor fans ODFAN3 & 4.
If the initial call for cooling requires both stages (Y1 and Y2), the
UCB will delay the second stage by 30 seconds to avoid an
excessive power inrush.
NOTE:
For lead-lag compressor operation, the jumper between
terminals G1 and G2 on terminal block TB2 must
remain in place to assure proper blower operation.
When the call for cooling (Y2) is satisfied, the UCB disables the
signal to RY2, BR2, and M2 as long as the specified minimum
run time (ASCD) has elapsed.
When the call for cooling (Y1) is satisfied, the UCB disables the
signal to RY1, BR1 and M1 as long as the specified minimum
run time (ASCD) has elapsed.
Low Ambient Cooling
These units are factory equipped with low ambient switches
that work through the Simplicity control board to operate the
compressors and condenser fans normally to 40ºF ambient
temperature. The Electronic Low Ambient Controller
2LA04703000 Accessory is designed to assure safe operation
through condenser head pressure regulation down to 0ºF
ambient temperature.
Low Ambient Control Operation
• A call for cooling closes contactor M3 which energizes all
condenser fans. The Low Ambient Control starts all fans
at full speed then adjusts according to the liquid line
temperature.
Refer to the appropriate 2LA low ambient kit instructions for
additional detail on the factory or field installed low ambient kit
and its operation.
