Limit and Enclosed Switches

Proper Application of Limit Switches

Honeywell Sensing and Control 1-800-537-6945 USA

1-815-235-6847 International 1-800-737-3360 Canada

A27

The following are guidelines for the correct application of Limit

Switches.

Never use the Limit Switch as a physical end stop. Mechanical

damage or incorrect operation may occur if this is done. Always

ensure that the mechanical actuator is protected from excessive

mechanical shock. Never release the actuator suddenly – gradual

actuation and release will ensure that stress on the mechanics of the

switch is kept to a minimum. This has the added benefit that the

switch life will be improved.

The following diagrams illustrate how to actuate your limit switch for

optimum performance.

For limit switches with pushrod actuators, the actuating force should be applied as

nearly as possible in line with the pushrod axis.

Cam or dog arrangements should be such that the actuator is not suddenly

released to snap back freely.

Operating mechanisms for limit switches should be so designed that, under any

operating or emergency conditions, the limit switch is not operated beyond its

overtravel limit position. A limit switch should not be used as a mechanical stop.

For limit switches with lever actuators, the actuating force should be applied as

nearly perpendicular to the lever as practical and perpendicular to the shaft axis

about which the lever rotates.

Tools

The following tools will be needed – depending on the task.

Posidrive screwdriver n° 1& n° 2

Allen key 3 mm

When tightening a screw down the maximum force which should be

applied should not exceed 80N.cm (7in.LB) on any screw on the

complete assembly or basic switch terminal.

Mounting Instructions

Mounting, Installation and Wiring of the Limit Switch plays a critical

role in the performance of the switch in service. Care should be

taken in the position and orientation of the switch for optimum

performance. All of the guidelines given below apply equally when

replacing parts on the switch.

Wiring

The GLS series has been designed to accept 14AWG wire maxi-

mum. Care should be taken to ensure that the wires are carefully

arranged in the switch so that they do not overlap or otherwise

interfere with the operation of the switch when the switch cover is

replaced. If the wires are trapped between the basic and the cover

then the switch may fail to operate correctly – ensure that an

adequate gap exists between the fitted wires and the cover when

fitted. It is not good practice to have very different diameter wires

share the same terminal in the switch – uneven pressure on the wires

will result.

Mounting

The GLS series has been designed to be extremely flexible in

mounting. Elongated mounting holes mean that the switch can be

adjusted substantially prior to fixing in position. We recommend M4

maximum screws be used for mounting the switch in its application.

Fix and test the switch for intended switch point in the application.

When mounting the switch ensure that it is positioned to allow

natural drainage of any moisture which may enter the enclosure

during service. Natural drainage can be achieved by mounting the

switch upright with the conduit entry at the bottom of the switch.

Mounting the switch in the upright position will enable maintenance

and replacement procedures to be carried out easily.

Adjustment and Set-up

In general no adjustment of the GLS should be necessary beyond

correct mounting of the switch body as required. It is possible to

change the switch actuator orientation. The example below shows a

top roller plunger head rotated through 90°. The other head styles

can also be rotated.

The head can be rotated by carefully removing the four combination

head screws holding the head in position. Carefully remove the

head assembly and rotate to the desired position. Replace the head

assembly and tighten the mounting screws. Ensure that the head is

properly located. Hand test the actuator to ensure that the switch

functions and the actuator moves freely (sticking can occur if materi-

al has been deposited inside the drive train whilst the head assem-

bly was removed).