Operator Preparation - Chamberlain LiftMaster Professional SW420 Installation And Maintenance Instructions Manual

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Preparing the Installation

Operator Preparation

Open the service cover on the operator by removing 6 screws and pulling down and out.

Inside you will find the electrical enclosure stored vertically. All the electrical connections for

controls that the installer needs are provided here on the electrical box.

To service the solid state controller or other components of the electrical box, slide the

electrical box out, then pivot down.

Remove 1 screw securing the electrical box cover.

The S3 PCB is the major component of the electrical box and settings can be made by

changing the two dip switches. There is mixed voltage in this box, both line voltage, and

control voltage 24 VAC.

Select the preferred method of electrical wire entry. The SW420 is provided with (6) holes in

the bottom of the chassis for electrical entry. Power supply wiring will be routed to the large

double gang electrical box on the left side of the operator.

Doc 01-G0610

Rev A

CAUTION

Never remove cover of high voltage compartment unless power is off. Electric shock

and serious injury could result.

Controls and

Accessories

Line Connector

Cover

01-G0610F5

Wire Nut

Connections

Figure 4

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