Defrost Control (Only In Heating Operation) - Toshiba RAS-25E2KVG-ND 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
TE (°C) 0
-0 °C
-3 °C
-7
-25
* The minimum TE value and To value between 10 and 15 minutes after heating operation has
started are stored in memory as TE0 and TO0, respectively.
Table 1
Defrost zone
A zone
B zone
C zone
D zone
Table 2
Heating operation
RAS-25E2AVG-ND RAS-35E2AVG-ND
(time)
a
b
c
d
<Defrost operation>
• Defrost operation in A to C zones
1) Stop operation of the compressor for
20 seconds.
2) Invert (ON) 4-way valve 10 seconds
after stop of the compressor.
3) The outdoor fan stops at the same time
when the compressor stops.
4) When temperature of the indoor heat
exchanger becomes 38°C or lower,
stop the indoor fan.
<Finish of defrost operation>
• Returning conditions from defrost
operation to heating operation
1) Temperature of outdoor heat exchanger
rises to +8°C or higher.
2) Temperature of outdoor heat exchanger is
kept at +5°C or higher for 80 seconds.
3) Defrost operation continues for
15 minutes.
Operation flow and applicable data, etc.
10 15
*
In normal To
TE0-TE≥3°C & SH-SH0≤2
TE0-TE≥2°C & SH-SH0≤2
TE≤ -25°C & SH-SH0≤2
More than 90 minutes accumulate heating operation time condition TE≤ -2°C
Model
43 35
41 33
31 31
70 70
The necessity of defrost operation is
detected by the outdoor heat exchanger
temperature (TE) and outdoor air
temperature (TO). The conditions to
detect the necessity of defrost operation
differ in A, B, C or D zone each. And
starting of defrost operation of each zone
are explain on Table-1.
c b
B zone
C zone
In abnormal To
(TE0-TE)-(TO0-TO)≥3°C & SH-SH0≤2
(TE0-TE)-(TO0-TO)≥2°C & SH-SH0≤2
<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.
- 33 -
Description
a d
A zone
D zone