Specifications

567040-YIM-B-1210
Johnson Controls Unitary Products 49
Figure 32: System Piping Schematic
Electric Heating Sequence Of Operations
The following sequence describes the operation of the electric
heat section.
Two-stage heating:
a. Upon a call for first stage heat by the thermostat, the
heater relay (RA) will be energized. After completing the
specified fan on delay for heating, the UCB will energize
the blower motor. If the second stage of heat is required,
heater relay (RB) will be energized. After completing the
specified fan on delay for heating, the UCB will energize
the blower motor.
b The thermostat will cycle the electric heat to satisfy the
heating requirements of the conditioned space.
Electric Heat Operation Errors
Temperature Limit
If the UCB senses zero volts from the high temperature limit,
the indoor blower motor is immediately energized.
This limit is monitored regardless of unit operation status, i.e.
the limit is monitored at all times.
If the temperature limit opens three times within one hour, it will
lock-on the indoor blower motor and a flash code is initiated
(See Table 30).
C1
TXV
FS
LPS
HPS
Condenser
Fan
Air Flow
Air Flow
Indoor Blower
Hot Gas
Coil
Compressor
Piping T
Piping T
Check
Valve
Check
Valve
Sol 2
Suction line
bleed
Open in
Reheat
Open in
Cooling
HPS
Sol 1
Refrigerant flow in reheat mode
Refrigerant flow in cooling mode
PS4
Air Flow
Sol 3
Hot Gas Re-Heat
Solenoid Valve
Condenser
Coil
Evaporator
Coil
Sol 4
(12.5 Ton Only)
Opens when PS4 pressure rises
above 400 psig and Closes when
PS4 pressure falls below 320 pisg
(12.5 Ton Only)