Fujitsu ASUH18LMAS Service Manual page 211

 Auxiliary heat pump control by outdoor temperature 2
• External heater output
Operation
Heater on
Heater off
– Temperature of heater on (Thon): Set temperature (Ts) - 0.9 °F (- 0.5 °C)
– Temperature of heater off: Set temperature (Ts) + 0.9 °F (+ 0.5 °C)
Tr-Ts ≥ 0.9°F
(0.5°C)
• Auxiliary heat pump On/Off
– Temperature of heater on (Thon): Adjustable by function number 62 (Operating temperature
switching of heat pump).
– All control temperatures will shift by adjusting "Thon".
Tr-Ts ≥ -1.8°F
(-1°C)
• Outdoor temperature zone
B + 3.6°F (2°C): 46.4°F (8°C)
*: Adjustable by function setting 67
2-4. Details of function
Heater is on as shown in following diagram of heating temperature.
• Heater is off as shown in following diagram of heating temperature.
• Other than heating mode
• Error occurred
• Forced thermostat off
Tr-Ts
Off
Tr-Ts (=Thon) ≤ -0.9°F (-0.5°C)
On
Tr-Ts
Off
Tr-Ts (=Thon) < -5.4°F (-3°C)
On
Outdoor temp.
Heater only zone
*B: 42.8°F (6°C)
Combination zone
(Heat pump + Heater)
Condition
Tr: Room temperature
Ts: Set temperature
Thon: Heater on temperature
Tr: Room temperature
Ts: Set temperature
Thon: Heater on temperature
- (05-37) -
2. External input and output