How does a compressor overload relay work?

Asked By: Virgelina Pernas | Last Updated: 23rd March, 2020
Category: home and garden indoor environmental quality
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The overload relay is a protection device used in the compressor circuit on your refrigerator. Power is applied to the compressor motor windings through the overload device, and the relay is used to add the start winding in the circuit until the compressor is at running speed.

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Keeping this in consideration, how does an overload protector work?

The overload protector sits near the condenser by the current start relay and ensures the condenser does not overheat while working. If the overload protector senses that the compressor is approaching failure from overheating, it will temporarily shut the compressor down to allow it to cool.

Beside above, how do I reset my compressor? How to Restart an AC Compressor

  1. Turn the control on the thermostat to "Off."
  2. Locate the breakers for the air conditioning and heating circuits in the main circuit breaker box.
  3. Pull the heating and air conditioning circuit breakers to the "Off" position.

Herein, what causes compressor overload?

The following are just some of the most common causes for compressor overheating.

  • Dirty Air Filters Can Be Problematic.
  • Refrigerant Leaks Can Lead to Overheating Compressors.
  • Problems With the Outdoor Portion of the Unit.
  • Insufficient Electrical Power.

How do you check a relay?

Listen for a click when the relay is energized. Check the energized condition of the relay contacts. Use a digital multimeter (DMM) to test the resistance between each pole of the relay and the corresponding NC and NO contacts for that pole. All NC contacts should read infinite resistance to the corresponding pole.

39 Related Question Answers Found

How does a PTC relay work?

A PTC relay uses a positive temperature coefficient thermistor to remove the start winding and/or start capacitor from the circuit. A PTC thermistor is basically a resistor whose resistance increases on an increase in temperature. Another use for a PTC relay is with a permanent split capacitor (PSC)-style compressor.

How do you test an overloaded switch?

How to Test a Thermal Overload Switch
  1. Unplug your appliance from its power supply before attempting to test its thermal overload switch.
  2. Remove the appropriate appliance panel to access the thermal overload switch in your appliance.
  3. Locate a thin strip of white plastic with two wires connected to it.

What is an overload relay?

An overload relay is an electrical device used to protect an electric motor from overheating. So it is essential to have sufficient motor protection. For instance, an overload relay can explore without the tripping of a CB (circuit breaker).

How do you check an overload relay with a multimeter?

To run the test perform the following steps:
  1. Turn the FLA dial back to its proper setting and let the motor run for at least 5 minutes.
  2. Open the contact(or) while the motor is running and start a timer.
  3. The overload should trip in around 3 seconds, or within 10 seconds maximum.

How do you bypass the overload relay on a refrigerator?


How to Bypass a Refrigerator Relay
  1. Unplug the refrigerator power cord and move the appliance away from the wall so you can get to the back of the cabinet.
  2. Remove any cover plate from the bottom of the refrigerator using a screwdriver to take out the screws.

What causes an overload relay to trip?

Short in the Wiring
Short circuits can be caused by wires overheating and the insulation melting, or by accidents where the insulation is stripped away or the wire is cut by a metal object and shorted to ground. A short circuit will draw current above the overload and surge ratings and cause the relay to trip.

What is an overload protector?

The overload protector is designed to protect the compressor motor from damage. The location of the overload protector is with the start relay on or near the compressor. Also, if the compressor uses a capacitor, it may contain a lethal electrical charge.

How do you set a motor overload relay?

3. Thermal Overload Relay
  1. Min. Thermal Overload Relay setting = 70%x Full Load Current(Phase)
  2. Min. Thermal Overload Relay setting = 70%x4 = 3 Amp.
  3. Max. Thermal Overload Relay setting = 120%x Full Load Current(Phase)
  4. Max. Thermal Overload Relay setting = 120%x4 = 4 Amp.

What are the two basic types of overload relays?

There are two major types of overload relays: thermal and magnetic. Thermal overloads operate by connecting a heater in series with the motor. The amount of heat produced is dependent on motor current. Thermal overloads can be divided into two types: solder melting type, or solder pot, and bimetal strip type.

How do you size a motor overload?


Divide by the rated full load current from the motor nameplate. This will be the load factor for the motor. If the motor current is 22A and the rated full load current is 20A, then the load factor is 22/20 = 1.1. This means the motor is overloaded by 10%.

What causes an overload current?

An overcurrent occurs when the current exceeds the rated amperage capacity of that circuit or of the connected equipment (such as an appliance) on that circuit. An overcurrent can be caused by overloading the circuit or by a short circuit, a ground fault, or an arc fault.

What is overload protection on a motor?

1). Motor overload protection devices like heaters protect the motor, the motor control equipment, and the branch-circuit conductors from motor overload and the resultant excessive heating (430.31). They don't provide protection against short-circuits or ground-fault currents.

What is the function of a motor overload device?

Circuit breakers operate by stopping power in very high overcurrent situations such as those that would occur from a short circuit or a ground fault. An overload protection device is meant to protect a motor from operating for prolonged periods of time at a current that is moderately above full load amperage.

How do you test a freezer relay?

Turn the dial on a multimeter to "Ohms X1." Insert both the probes from the multimeter into the two female terminals on the relay. The display on a digital multimeter should read zero, or the needle should sweep across the face of the display to zero on the far right on an analog multimeter.

How do you test a refrigerator overload relay?


Put the probes of a multimeter on the left and right prongs of the compressor. Locate the 3 prongs that the PTC relay plugs into on the side of your compressor. Put one probe on the prong that's furthest to the left and the other probe on the prong on the right to take a resistance reading.

How do you test a compressor?

Here is how to check the compressor motor if you suspect it has failed;
  1. Disconnect power.
  2. Remove the top of the outdoor condensing unit.
  3. Unplug the 3-prong plug on the compressor.
  4. Set your multimeter to ohms.
  5. Measure and record the resistance (ohms) measurement of each winding.

What are the signs of a bad refrigerator compressor?

The Telltale Compressor Noise
Your compressor kicking on and off is what you hear (or don't hear) at various points during the day – you hear a faint humming noise coming from the fridge, and you know that it's running. That's the compressor you hear.