Limit Switch And Its Applications

Limit Switch

In this post I will discus  about Limit Switch, High Limit Switch, Fan Limit Switch and Its Applications.  A  Limit Switch is electromechanical device it having mechanical actuator which is connected with electrical contacts. The actuator is physically forced by any object then the Switch operate either circuit On or Off which is depend on what is requirement  of system. Limit Switch is use for the control the machine movement. Production unit used for detection of  product absence or presence. Also used in the control system for machine status.

Types Of Limit Switch

There are five basic types of Limit Switches listed below

1. Roller Limit Switch
2. Lever Limit Switch
3. Plunger Limit Switch
4. Whisker Limit Switch
5. Roller-lever Limit Switch

Parts Of Limit Switch

There are three main parts of Limit Switch

• Actuator
• Case/Switch Body
• Terminals

Actuator 

It is essential parts of limit switch that is Physically contact with an object. It is also called operating head of Limit Switch. Actuators are different style like roller, lever, roller-lever, Plunger and flexible rod.

Case/Switch Body

A Limit Switch all parts are assembled on it and the switch body protect from external force.

Terminals

It is the point of connection for termination.

Application Of Limit Switch

Limit switches are used in a various  applications  like Manufacturing sector, Automobile sector and process industries etc.

High Limit Switch

 A high-limit switch is also known as furnace limit switch, this small switch helps keep your place safe by automatically turn off the system when your furnace gets too hot. A high-limit has two functions in the operation of furnace. One is blower fan ON-OFF during the normal cycle.2nd is when the furnace getting too high temperature then shutdown the furnace.

Fan Limit Switch

A Fan Limit Switch control the blower fan means turns ON or OF accordioning to the furnace requirement. It having main parts are On-Off Switch, High temperature setting ,sensor, and manual ON switch.

ON-OFF Switch

It is for the blower fan operation.

High Limit Setting

It is allows to turn off  heat source when exceed the limit.

Sensor

A temperature sensor turn ON or OFF of blower fan according to the furnace temperature.

Manual ON Switch

Manual On Switch allows the blower fan set to be run continuously.

FAQ

How does a limit switch work HVAC?

A limit switch is a device that's located under your furnace supply plenum. It reads the temperature of the plenum and waits until it gets appropriately warm. Once the plenum reaches a specific temperature, the limit switch sends a signal to blower fan to begin running and delivering warm air to your home.

Is a limit switch an input or output?

Yes, it is Input device.

What is the function of a fan limit switch?

The fan limit switch controls when the furnace blower fan turns on and off. This control also provides a safety limit that turns off the burner or furnace if temperatures at the furnace get too high.

What causes limit switch failure?

Improper airflow can cause the furnace to overheat repeatedly, causing your limit switch to undergo excessive damage, that the reason it malfunctioning.

Is a limit switch analog or digital? 

It  is digital device because it contains two possible positions, ON-OFF.