5742640-TIM-A-0419
Johnson Controls Ducted Systems
51
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 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 send an error message to
the LCD Smart Equipment™ Control.
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.
Error Messages
The UCB will initiate an error message to the LCD Smart
Equipment™ Control.
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. Refer to Table 22 for the required electric
heat anticipator setting.
Table 21: Electric Heat Limit Setting
Voltage
kW
Temperature Limit
Switch
Open Temperature
°F
208-1-60
5
1
140
7
1,3
140
10
1,2,3
140
15
2,4,6
140
20
1,2,3,4,5
140
6
150
30
1,2,3,4,5,6
150
230-3-60
5
1,2,3
140
7
1,2,3
140
10
1,2,3
150
15
2,4,6
140
20
1,2,3,4,5,6
150
30
1,3,5
160
2,4,6
150
460-3-60
7
2,4,6
140
10
2,4,6
140
15
2,4,6
140
20
3
160
30
3
150
575-3-60
10
2,4,6
140
15
2,4,6
140
20
5
160
30
5
150
Table 22: Electric Heat Anticipator Setpoints
Heater
Kw
Voltage
Setting, Amps
TH1
TH2
5
230-3-60
0.35
-
7
0.35
-
10
0.35
-
15
0.35
0.19
20
0.35
0.38
30
0.35
0.38
7
460-3-60
0.35
-
10
0.35
-
15
0.35
-
20
0.37
0.29
30
0.37
0.29
