66369-YIM-D-1004
Unitary Products Group
45
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 con-
tactor (7M) will be energized. Note that on the 54
KW, 240V heater, heater contactors (7M & 8M) will
be energized and on the 72 KW, 240V heater,
heater contactors (8M & 9M) 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.
NOTE:
All 240 & 480V heaters are provided with man-
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 26).
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 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.
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 21. It is a
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.
FLASH CODES
The UCB will initiate a flash code associated with
errors within the system. Refer to UNIT CONTROL
BOARD FLASH CODES Table 26.
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 22 for the required heat anticipator set-
ting.
TABLE 21: LIMIT CONTROL SETTING
UNIT
(Tons)
VOLTAGE
HEATER
kW
TEMPERATURE LIMIT
SWITCH 1, 2
OPENS, ºF
TEMPERATURE LIMIT
SWITCH 3, 4, 5, 6
OPENS, ºF
15
240
18
120
170
36
120
170
54
120
170
72
120
170
20
240
18
140
200
36
140
200
54
140
200
72
140
200
15, 20
460
18
120
170
36
120
170
54
120
170
72
120
170
15, 20
600
18
120
-
36
120
-
54
120
-
72
120
-
