Defrost Operation Control; Defrosting Start Condition; Defrosting End Condition - Fujitsu Airstage VR-II Series Service Manual

2-8-3 Defrost Operation Control

< Defrosting start condition >
Accumulated heating operation time is 40 minutes or longer
(Accumulated heating operation time is reset at the end of cooling operation or defrosting operation.)
And
One of Heat-Ex satisfies condition
Condition : Accumulated operating time is 150 minutes* or longer:
"Heat exchange liquid temperature (TH9 and TH10)
*75 minutes: when indoor unit connection capacity
Condition : Accumulated time 10 minutes:
"Heat exchange liquid temperature (TH9 and TH10)
And
"During heat exchange liquid temperature keeps droping "
*Defrosting Start Judgment Temperature(°F) = 0.8 x Outdoor temperature (°F) - 52.9
However, -17.7°F to 21.2°F
If the calculated result is lower than -17.7°F, the judgment temperature is defined as -17.7°F
If the calculated result is higher than 21.2°F, the judgment temperature is defined as 21.2°F
(Defrosting start judgment temperature are determined by the outdoor temperature.)
*Defrosting Start Judgment Temperature(°C) = 0.8 x Outdoor temperature (°C) - 11.6
However, -27.6°C to - 6°C
If the calculated result is lower than -27.6°C, the judgment temperature is defined as -27.6°C
If the calculated result is higher than -6°C, the judgment temperature is defined as -6°C
(Defrosting start judgment temperature are determined by the outdoor temperature.)
: Less than 10 minutes operation at outdoor temperature below 35.6
Condition
< Defrosting end condition >
At all outdoor units, heat exchange liquid temperature
and all of outdoor unit's Suction temperature - Low pressure saturation temperature
or
When 15 minutes have elapsed from the start
*Defrosting End Judgment Temperature(°F)= 0.39 x outdoor temperature(°F) + 54.8
-However, 41.0°F to 53.6°F range
If the calculated result is lower than 41.0°F, the judgment temperature is defined as 41.0°F.
If the calculated result is higher than 53.6°F, the judgment temperature is defined as 53.6°F.
*Defrosting End Judgment Temperature(°C)= 0.39 x outdoor temperature(°C) + 12.7
-However, 5°C to 12°C range
If the calculated result is lower than 5°C, the judgment temperature is defined as 5°C.
If the calculated result is higher than 12°C, the judgment temperature is defined as 12°C
or or below
Defrosting End Judgment Temp.* and 180sec elapsed,
02-12
28.4°F ( -2°C)"
90% at 1 outdoor unit connection.
Defrosting Start Judgment Temperature*
2
°F ( °C)
10
occured 20 times
5°C)
°F (