Defrost Control (Only In Heating Operation) - Toshiba RAS-18, 22SKV-E Service Manual

Item
7. Defrost control (This function removes frost adhered to the outdoor
(Only in heating heat exchanger.)
operation)
The temperature sensor of the outdoor heat ex-
changer (Te sensor) judges the frosting status of the
outdoor heat exchanger and the defrost operation is
performed with 4-way valve reverse defrost system.
Start of heating operation
0' 10' 15'
–3˚C
–7˚C
–26˚C
*
Te0 detection time
* The minimum value of Te sensor 10 to 15 minutes after start of
operation is stored in memory as Te0.
When Te0 - TE ≥ 2.5 continued for 2 minutes in A zone,
A zone
defrost operation starts.
When the operation continued for 2 minutes in B zone,
B zone
defrost operation starts.
When Te0 - TE ≥ 3 continued for 2 minutes in C zone,
C zone
defrost operation starts.
Operation flow and applicable data, etc.
Operation time
29' 35'
(Minute)
C zone
A zone
B zone
Table 1
The necessity of defrost operation is
detected by the outdoor heat exchanger
temperature. The conditions to detect the
necessity of defrost operation differ in A,
B, or C zone each. (Table 1)
<Defrost operation>
• Defrost operation in A to C zones
1) Stop operation of the compressor for
2) Invert (ON) 4-way valve 10 seconds
3) The outdoor fan stops at the same
4) When temperature of the indoor heat
<Finish of defrost operation>
• Returning conditions from defrost
operation to heating operation
1) Temperature of outdoor heat ex-
2) Temperature of outdoor heat ex-
3) Defrost operation continues for
<Returning from defrost operation>
1) Stop operation of the compressor for
approx. 50 seconds.
2) Invert (OFF) 4-way valve approx. 40
seconds after stop of the compressor.
3) The outdoor fan starts rotating at the
same time when the compressor starts.
– 40 –
FILE NO. SVM-10050
Description
20 seconds.
after stop of the compressor.
time when the compressor stops.
exchanger becomes 38°C or lower,
stop the indoor fan.
changer rises to +8°C or higher.
changer is kept at +5°C or higher for
80 seconds.
15 minutes.