The 4 Main Reasons of Thermal Relay Failure


A motor or thermal relay overheating failure is a common issue. It is more relatable when you manage it poorly or over/under use it. At times, heating is an uncontrollable and unavoidable condition concerning the failure of these relays.

However, you have to find ways to improve the current through the relay. To do so, you should understand the core failure reasons. These top failure reasons for the thermal relay to stop working (not up to the mark) are written below. Refer to them and improve the performance of the motor and relay in the long run.

The Core 4 Reasons For Thermal Relay Failure Are:

Hot Switching

This process often hinders the life of a thermal relay. When the aforesaid relay closes or opens while carrying a signal, it’s often called that. If these signals are not switched properly with the flow, the contacts erode faster in the relay.

Eventually, if this practice continues, thermal relays will fail faster. To avoid this condition, you can ask vendors about the tested life of thermal relays. Check the data available on the condition of the relay.

Further, some issues often compound when mixed with hot switching. Namely, these are:

  • Capacitive loads
  • Hot Switching power supplies
  • Failure mechanisms
  • Arcing failures
  • Hot Switching RF signals
  • Hot Switching with electromagnetic or solid-state relays

Bimetallic thermal overloads

This type of overload happens when the relay contacts shut or open and the metals expand or bend at different rates. This causes the bending of the strip towards the lower side of thermal expansion.

This scenario initiates the opening up of an NC and stops the current flow in the motor. And hence, the current flow is unnatural or abnormal. If continued, it can shorten the life and use of thermal relays.

However, you can improve this situation by trusting CHINT thermal relay. Here, you can have better relays with a higher power to avoid/prevent these overloading issues.

Motor’s operational failure issues

There are problems that the entire motor might be facing regularly. These problems should be treated on time. If not, of course, the thermal relay will fail to perform. These motor issues are:

Motor failure:

The overload breaker can face the trip with excessive current and stop working. This freezes the motor. It burns out eventually. Often, shorts occurring in the armature windings draw excessive current flow.

Besides that, the gearbox failure can lead the motor to stop working. This leads to the overuse of the thermal relay to burn out sooner than expected.

Motor overload:

A certain amount of work should be assigned to the motor per day to function normally. If the workload exceeds the load it’s designed for originally, burns out will be expected more. This eventually leads to the ultimate failure of the thermal relay used.

We know that thermal relays can temporarily take the load. But if this overuse is regular, even thermal relays will fail to work. The current and overload surge can tamper with the entire circuit, basically.

Improper setup of the relay in the motor:

Thermal relays have to be set up properly in the motor to work smoothly against the load and the current. When the measurements are not right, the operations lead to switch or thermal relay overload.

To avoid this situation:

  • Use sensing devices.
  • Check the current and overload flow every second of the operation.
  • Hire professionals or technicians who deal with thermal relay and their pressure daily.

Using damaged relay

One of the core reasons for thermal relay damage is this one. You should check the relay’s health, life, or overall condition beforehand. If you don’t, the entire operation suffers. This can lead to buying more relays later on. Then, it hampers the monthly or daily budget.

If you have no idea, you shouldn’t be the one dealing with thermal relays. For the best supervision, work with electrical and mechanical engineers. They know best how to refine the use of each thermal relay.

They would also explain why there’s been a short-circuit in the previous operation. And if there’s any in the current operations, they are fast to identify the same. So, you can genuinely be done with thermal relay failures when you work with the right equipment, devices, and skilled engineers.


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