Control; Optional Low Temperature Control Board "Ltc" - 208-230/60/3, Unit Sizes 036, 048, 060 And 072 - Daikin WRA Installation And Maintenance Data

Control

Optional Low Temperature Control Board
"LTC" – 208-230/60/3, Unit Sizes 036, 048,
060 and 072
The control board is powered by 24 volts AC, 50/60 hertz
which is applied to the 24 VAC terminals. The control will
energize the output relays (COM 1 makes connection with NO
1 and COM 2 makes connection with NO 2), only if the tem-
peratures of both Sensor 1 and Sensor 2 are above the selected
temperature which is 20°F or 35°F.
Note: Always disconnect power to WW* unit before moving
jumpers.
While the output relays are energized, the control keeps
monitoring Sensor 1 and Sensor 2 to make sure that the tempera-
ture of the sensors is always above the selected temperture, the
control will de-energize both ouput relays until the temperature
of the sensor is 2.5 degrees above the selected temperature. For
Figure 4: "LTC" board jumper settings
NO 2
DISCONNECT POWER TO
COM 2
WW* UNIT BEFORE MOVING
NO 1
JUMPERS
COM 1
24 VAC
SEN 1
Figure 5: Thermistor temperature vs. resistance graph
70000
60000
50000
40000
30000
20000
10000
0
10 20
Page 20 of 44
AL7815 The 20˚F settings are used only on
closed loop systems with antifreeze
solution.
35F 35F
20F 20F
S2 S1
Jumper "S1" selects cutout temperature
setpoint for Sensor "SEN 1".
SEN 2
Jumper "S2" selects cutout temperature
setpoint for Sensor "SEN 2".
Thermistor Temperature Vs. Resistance
30 40 50
Temperature (ºF)
Water to Water Source Heat Pumps
example, you set the temperature to 20°F. The output relays will
de-energize when the sensor temperature drops below 20°F.
The control will re-energize the output relays when the sensor
temperature rises above 22.5°F. Additionally, the control will
monitor each individual sensor to make sure it isn't broken or
shorted. If either Sensor 1 or Sensor 2 fails short or open before
or during operation, the control will de-energize both output
relays until the sensor is repaired or replaced.
Table 7: LTC board sensor locations
Model
WCA
WHA
WRA
60 70 80
Sensor 1
Liquid Out - Load Coil Liquid Out - Source Coil
Liquid Out - Load Coil Liquid Out - Source Coil
Liquid Out - Load Coil Liquid Out - Source Coil
90 100 110
Sensor 2
IM 1072-1