Johnson Controls ZY Series, Installation Manual

Page: 112 / 144

Reset
Remove the call for cooling, by raising thermostat
setting higher than the conditioned space
temperature. This resets any pressure or freezestat
lockouts.
Electric Heating Sequence of
Operations
The following sequence describes the operation of
the electric heat section.
Single-stage heating (applies only to 5, 7 & 10 kW
230V heaters and to 7, 10, & 15 kW 460V and 575V
heaters. All other heaters MUST use a two-stage
thermostat):
a. Upon a call for heat by the thermostat, the heater
sequencer (1S) 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.
Two-stage heating (applies only to 15, 20 and 30
kW 230V heaters and 20 and 30 kW heater 460V and
575V heaters.):
a. Upon a call for first-stage heat by the thermostat,
the heater sequencer (1S) (15, 20, 30 kW 230 volt)
and contactor (2M) (20, 30 kW 460 and 575 volt) 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
sequencer (2S) (12, 20, 30 kW 230 volt) or contactor
(3M) (20, 30 kW 460 and 575 volt) 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 Operating 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, the UCB will lock-on the indoor blower
motor and will initiate a flash code on the ETC, or
send an error message to the LCD Display on Smart
Equipment™.
Safety Controls
The UCB monitors the temperature limit switch of
electric heat units.
The control circuit includes the following safety
controls:
Temperature Limit Switch (TLS)
This control is located inside the heater
compartment and is set to open at the temperature
indicated in the Electric Heat Limit Setting Table 21.
It resets automatically. The limit switch operates
when a high temperature condition, caused by
inadequate supply air flow occurs, thus shutting
down the heater and energizing the blower.
Flash Codes or Error Messages
The UCB will initiate a flash code on the ETC, or
send an error message to the LCD Display on Smart
Equipment™ associated with errors within the
system.
Reset
Remove the call for heating by lowering the
thermostat setting lower than the conditioned space
temperature. This resets any flash codes.
Electric Heat Anticipator Setpoints
It is important that the anticipator setpoint be
correct. Too high of a setting will result in longer
heat cycles and a greater temperature swing in the
conditioned space. Reducing the value below the
correct setpoint will give shorter “ON” cycles and
may result in the lowering of the temperature within
the conditioned space.
Gas Heating Sequence of
Operations
When there is a W1 call for heat, the heat relay
(RW1) is energized by the unit control board (UCB).
The RW1-1 contacts immediately close energizing
the ignition control board (ICB). The ICB checks
the state of the flame sense circuit, the roll out
switch, the centrifugal switch and the primary /
auxiliary temperature limit switch circuit. If they
are in the expected state, then the ICB energizes
the draft motor and verifies that the centrifugal
INSTALLATION MANUAL ZY SERIES 3 - 10 ton 60 Hertz R-410A 112
Johnson Controls Ducted Systems