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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.
All 240 & 480V heaters are provided with man-
NOTE:
ual reset backup protection limits. These will
de-energize the heaters should the primary
limit fail to open or the contactors fail to open in
a failure mode.
HEATING 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 sta-
tus, 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 35).
SAFETY CONTROLS
The unit control board monitors the temperature limit
switch of electric heat units.
The control circuit includes the following safety con-
trols:
1. Temperature Limit Switch (TLS 1, 2).
This control is located inside the heater compart-
ment and is set to open at the temperature indi-
cated in the Limit Control Setting Table 30. 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.
2. Temperature Limit Switch (TLS 3, 4, 5 and 6).
This control is located inside the heater compart-
ment and is set to open at the temperature indi-
cated in the Limit Control Setting Table 30. It is a
50
manual reset limit. These limit switches will de-
energize the heaters should the primary limit fail to
open or the contactors fail to open in a failure
mode.
TABLE 30: LIMIT CONTROL SETTING
UNIT
HEATER
VOLTAGE
(Tons)
kW
18
36
15
240
54
72
18
36
20, 25
240
54
72
18
36
15, 20,
460
25
54
72
18
36
15, 20,
600
25
54
72
FLASH CODES
The UCB will initiate a flash code associated with
errors within the system. Refer to UNIT CONTROL
BOARD FLASH CODES Table 35.
RESET
Remove the call for heating by lowering the thermostat
setting lower than the conditioned space temperature.
This resets any flash codes.
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 low-
ering of the temperature within the conditioned space.
Refer to Table 31 for the required heat anticipator set-
ting.
175244-BIM-A-0706
TEMPERATURE
TEMPERATURE
LIMIT SWITCH
LIMIT SWITCH
3, 4, 5, 6
1, 2 OPENS, °F
OPENS, °F
120
170
120
170
120
170
120
170
140
200
140
200
140
200
140
200
120
170
120
170
120
170
120
170
120
~
120
~
120
~
120
~
Unitary Products Group
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Troubleshooting
