What is Overload Protector and What is role of Overload Protector in Refrigeration

Welcome back to the refrigerator topic and in this post, we discuss the overload protector which we use to protect the refrigeration compressor. In this post, you will learn the function of an overload protector and its working principles.

What are the overload protectors and their function in the refrigerator and air conditioners?

An overload protector is an electrical device that we use for compressor protection, whenever the compressor temperature high from his range the compressor overload cuts off the electric supply from the compressor motor that's why we called him thermal overload.
The connection of overload with the compressor in series and inside the overload we connect a heating resistance and with heating resistance we connect a bimetallic strip metal. The heating resistance and bimetallic strip metals both make an overload relay.
The working of overload relay is simple whenever the compressor motor getting heat up, due to the overload connected with the compressor body, the internal overload heating resistance heat up and due to heat up the bimetallic strip metals cut up the connection between one another and its make compressor circuit to an open electric circuit. When the compressor comes back to his normal state/temperature, the thermal overload protector makes a close electric circuit inside and connect the electric supply to the motor.

Note that the compressor is getting heat by flowing a high amount of current, however, if the compressor getting normal current (Ampere) and it is heating, then also Overload protector will be trip or make an open circuit if it's connected with the compressor body.

The cut off the supply overload makes safe compressor motor from internal winding damages/ burned. However, you will not understand the working principles of overload without a diagram. That's why I designed a diagram about the internal structure of a thermal overload protector.

overload protector diagram

In the above figure, I have shown overloads 2 types and I light its terminals with the name of IN and Out. The (IN) means that we gave electric supply to this terminal and (Out) means that we get electric supply for compressor or we can say that this point is going to connect the compressor common terminal.

Also, read
How to find out Start, Run, Common terminals in a Compressor

I also have shown an internal structure of overload in the above example diagram. In the diagram, I have shown the bimetallic strip metals with heating resistance with incoming and outgoing supply. Whenever the compressor starts getting high current the heating resistance heat up and creates an open electric circuit.
This one of the main reasons that we use a thermal overload protector in refrigerator compressor, I hope you will get a piece of good information from this post, however, we will soon discuss the main reason for the compressor getting high current or heat up.

Sikandar Haidar

Electricalonline4u.com is a hub of electrical and electronics tutorials and easy diagrams.


  1. hi
    my friend
    i am Kurosh from Iran
    i have one question about overload relay in refrigerator 's hermetic compressor
    where is this equip location in circuit
    and whether both overload relay and current relay have been ever combined together?

    1. This comment has been removed by the author.

  2. You really need to learn much, much better English if you are going to write for other's to read. I would have fully understood your article.

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  4. perfectly and beautifully explained.

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