Hitachi RAD-18NH7A

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– 58 –

7. Drain pump drive circuit

When cool or dehumidifying operation, pin 58 of the micro computer goes “Hi”, Q333 and Q932 turn on

and the drain pump drive.

L933 R931

R932 C932

Q933

Q932

L932

D932

21V

RED

Drain pump motor

BLK

CN3

Micro computer

Drain pump

8. Drain pump trial run switch

● This switch forcibly turns the drain pump on. When the drain pump trial run switch is turned on, the

timer indicator will blink seven times, and no remote signal will be accepted.

R533

Drain pump

trial run SW

(normally, Hi)

R534

Microcomputer

9. Float switch

● This is a float type switch that monitors the drain level of drain pan. The switch will be activated and

will stop operation if the drain pump is faulty or drain hose is stopped up, disabling drainage, causing the

drain level to rise abnormally.

● When the float switch is activated, the timer indicator will flash six times. Note that the float switch will

also be activated, disabling operation if the connector of float switch has defective contact or is

connected incompletely.

R621C620R539Microcomputer

R620

CN16

FLOAT SW

Normally Hi (4.5V)

—

Fig. 7-1

Hitachi RAD-18NH7A - Page 48