Toshiba RAS-13UAV-E Service Manual Download

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Fig. 8-2-8

(4) Defrost control

1) Detection of frost

In heating operation, time duration while the
compressor operates is counted, and defrost
operation starts by any condition described
below.

a. The counted time is 28 minutes or more,

and status that temperature of the outdoor
heat exchanger detected by the outdoor
heat exchanger is –20°C or lower contin-
ued for 2 minutes or more.

The outdoor unit controls the outdoor fan based
upon the operation signal sent from the indoor unit,
and also controls revolution speed of the compres-
sor motor.

The power coupler (IC20) for four-way valve is
turned on, and turned off in defrost operation.

(1) Heating capacity control

Calculate the difference between temperature
detected by room temp. sensor every minute and
the set temp. set on “Temp. indicator” and
variation amount of room temp.

Then, obtain the correction amount of the
command signal, and correct the current fre-
quency command signal.

(2) High-temp. release control

If temperature of the indoor heat exchanger
detected by the indoor heat exchanger sensor is
55°C or higher, compressor motor speed is
gradually lowered to prevent over-temp. rising of
compressed pressure.

If temperature becomes below 48°C, return to
above item (1).

(3) Current release control

The input current of compressor and outdoor fan
motor (Precisely inverter main circuit control
section) which occupy most of air conditioner
input is detected by the outdoor current sensor.
The compressor motor speed is lowered gradu-
ally according to the range of TO (outside air
temp.) if the input current exceeds the current
value determined in each zone as shown in Fig.
8-2-8 so that the input current does not exceed
the set value.

In case that the current lowered by approx. 0.5A
than each set value, return to above item (1).

b. The counted time is 28 minutes or more,

and status that temperature of the outdoor
heat exchanger detected by the outdoor
heat exchanger is –7°C or lower and
temperature lowered by 2.5 °C than the
minimum value of the outdoor heat ex-
changer during 10 to 15 minutes count
time continued for 2 minutes or more.

c. The counted time is 34 minutes or more,

and status that temperature of the outdoor
heat exchanger detected by the outdoor
heat exchanger is –5°C or lower and
temperature lowered by 3.0 °C than the
minimum value of the outdoor heat ex-
changer during 10 to 15 minutes count
time continued for 2 minutes or more.

d. If the following three conditions are satis-

fied, defrost operation (Timer defrost)
starts after heating operation for 37
minutes.

1) Setting on remote controller, HEAT

(mode), HIGH

(Fan), 30°C (temp.).

2) Room temp. is 19°C to 24°C, and

outside air temp. is 5°C or lower.

3) Defrost operation has been already

performed once.

2) Defrost operation

Operation of the compressor is stopped
once, turn off power coupler for four-way
valve after 10 seconds, and then exchange
the four-way valve.

After 20 seconds, restart operation of the
compressor. Turn off the outdoor fan just
when the compressor stopped.

If temperature of the indoor heat exchanger
lowered than 38°C, stop the indoor fan.

3) Defrost reset

Resetting operation from defrost to heating is
performed when any one of the following
conditions is satisfied.

a. Temperature of the outdoor heat ex-

changer rose to +8°C or higher.

b. A status that temperature of the outdoor

heat exchanger is +5°C or higher contin-
ued for 80 seconds.

c. Defrost operation continued for 15 min-

utes.

In resetting defrost operation, the compressor
stops for 50 seconds if defrost has started
under condition a. to c. in item 1), but the
compressor is reset to heating operation
keeping operated if defrost has started under
condition d. in item 1).

(5) Louver control

When the compressor is turned off by high-temp.
release control, the vertical air flow louvers close
once and then return to the position of previous
time.

Outside air temp

. (

˚C)

16.0

10.3A

10.8A

9.8A

15.5

11.0

10.5