Operation Permission/Prohibition Control; Protective Control Function - Mitsubishi Heavy Industries SRK20ZD-S1 Technical Manual

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(16) Operation permission/prohibition control

The air conditioner operation is controlled by releasing the jumper wire (J3) on the indoor control board and inputting the external signal
into the CnT.
(a) The operation mode is switched over between Permission and Prohibition by releasing the jumper wire (J3)
on the indoor control board.
When the jumper wire (J3) is short circuited
Normal operation is enable (when shipping)
When CnT input is set to ON, the operation starts and
if the input is set to OFF, the operation stops.
For the CnT and remote control inputs, the input which
is activated later has priority and can start and stop the
operation.
(b) When the CnT input is set to ON (Operation permission)
(i)
The air conditioner can be operated or stopped by the signal from the remote control signal line.
(When the "CENTER" mode is set, the operation can be controlled only by the center input.)
(ii) When the CnT input is changed from OFF to ON, the air conditioner operation mode is changed depending on the status of
the jumper wire (J1) on the indoor control board.
When the jumper wire (J1) is short circuited
The signal (i) above starts the air conditioner. (Ship-
ping status)
(c) When the CnT input is set to OFF (Prohibition)
(i)
The air conditioner cannot be operated or stopped by the signal from the remote control signal line.
(ii) The air conditioner operation is stopped when the CnT input is changed from ON to OFF.
(d) When the operation permission / prohibition mode is set to effective by the indoor function setting selected by
the remote control, the operation depends on (a) above.

(17) Protective control function

(a) Frost prevention for indoor heat exchanger (During cooling or dehumidifying)
(i)
Operating conditions
1)
Indoor heat exchanger temperature sensor (detected with Th2) is lower than 2.5ºC.
2)
5 minutes elapsed after the start of operation.
(ii) Detail of frost prevention operation
Compressor
Indoor fan
Outdoor fan
4-way valve
(iii) Reset condition: Indoor heat exchanger temperature sensor (Th2) is higher than 8ºC.
Permission / Prohibition mode
When Cnt input is set to ON, the operation mode is
changed to permission and if input is set to OFF the
operation is prohibited.
When the CnT input is set to ON, the air conditioner
starts operation. After that, the operation of the air
conditioner depends on (i) above. (Local status)
OFF
Protects the fan tap just before frost prevention control.
Depending on the stop mode
Stop mode
When the jumper wire (J3) is released
When the jumper wire (J1) is released
234
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