What causes a pitted contactor?

Pitting occurs when the contactor has encountered extreme voltage and heat. A pitted contactor tends to stick, causing a continuous flow of electricity to the unit.

What causes pitting on electrical contacts?

Pitting is a deterioration process that happens to metals and in this case, contactors when they have been exposed over a period of time to excessive voltage and heat.

Why contactor is used in motor?

Why are Contactors Used? Contactors are used for high power applications. They allow a lower voltage and current to switch a much higher power circuit, so they are generally larger and more heavy-duty than control relays, enabling them to switch higher power loads on and off for many thousands of cycles (Figure 1).

What is the function of contactor?

A contactor is a special type of relay used for switching an electrical circuit on or off. They are most commonly used with electric motors and lighting applications.

What are the symptoms of a bad contactor?

How Can You Tell If Your Contactor Is Failing?

  • Charred or Melted Casing – Arcs can melt the contactor’s plastic box.
  • Chattering and Humming Noises – When the metal coils, plunger, and contacts erode, they gradually become loose.
  • AC Not Turning On or Off – The contacts need to be separated to turn an appliance off.

How do you know if your contactor is bad?

These bad AC contactor signs may include:

  1. Humming. When your AC is on, it may produce a humming sound – but, it won’t power on.
  2. Chattering. When the contacts are dirty, or the coil has become weak, you may hear the plunger make a chattering sound.
  3. Melting.

What happens when a contactor goes bad?

When a contactor begins to fail or break, it won’t pull close. This forfeits the connection between the two sides. In some cases, your thermostat will click on, but your AC unit won’t operate. This means that the contactor is completely broken and isn’t providing the electrical current needed to run your system.

What are some common causes of contactor failures?

The most common situation in contactor failures is contact sticking and coil burning. The reason for contact sticking; If more current is passed through the main power contacts than it can carry, the contacts will overheat after a while and the contacts may stick as a result of this warming.

What are starter contacts made of?

The material of choice, however, is most often silver-cadmium oxide. The mix is usually 85/15 or 90/10. These contacts are found in most AC contactors for NEMA size 00-6. A 50/50 silver tungsten mix is used for high-amp applications.

What is the difference between a contactor and a motor starter?

The contactor applies voltage to a contactor coil to close the contacts and to supply and interrupt power to the circuit. A motor starter is simply a contactor PLUS an overload relay and is rated by motor HP or amperage. If there is no overload relay it is not a starter any longer. It’s back to being just a contactor.