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Identifying Potential Motor Stalls in Home Appliances

Sense Team
May 28, 2020

A modern home is filled with many different appliances and electronic devices. Many larger household appliances are made up of separate components like motors, fans, and pumps. One of the most common components found in an appliance is a motor, which can be found in everything from your blender to your clothes dryer.

In this article, we’ll explore what a stalled motor is, the different devices that may experience motor stalls in a home and some telltale signs that an appliance is experiencing motor stalls

What is a motor stall?

When a motor stall occurs, a motor has stopped rotating even when there is enough voltage at its terminals. This happens when the torque required by the load is more than the maximum torque that can be generated by the motor. Motor stalls can occur for electrical (missing a phase of input supply) or mechanical reasons (rotor jam, overloaded or unable to move)

What does a stalled motor energy signature look like in the Sense App?

When the internal motor breaks down, the appliance will start to malfunction. Sense users may be able to observe motor stalls in the Power Meter by looking for abnormal spikes in the energy signature as a motor starts up.

Above: Left is a functioning motor, right is a motor stalling

Above: Visual of an AC Compressor motor stall during the weeks before failure

What are some signs that my appliance is experiencing a motor stall?

If you suspect that your appliance is behaving abnormally, you may be able to observe or hear some telltale signs that something is malfunctioning so you can proactively schedule a maintenance check-in before a potential failure. Below are some early warning signs that your appliance might be experiencing a motor stall.

If you notice one or more of the below issues, it’s worth having a professional technician perform a routine maintenance check-in.

1. Is your appliance operating abnormally?

When an appliance struggles to start or stops working periodically, it may be because the motor is overheating. Is your appliance unusually hot? If yes, turn off your appliance immediately to avoid critical failure and call a technician for an inspection.

Does your appliance start?

A. If not, the most common issue is a start capacitor but could also be caused by the run capacitor, the control board, or the contactor. In an HVAC, this is primarily an issue with the start capacitor in the outside compressor/condenser unit.

B. If your appliance takes a few moments to start-up and is making an atypical noise, this is typically an early warning sign that your appliance requires an inspection.

C. If your appliance starts instantly but is still making an atypical noise or is overheating, this could be an early indication of a potential upcoming appliance failure.

Above: A faulty start capacitor in a Heat Pump.

Tip: For experienced technicians, the most common cause of a motor stall is a faulty start capacitor, which can typically be replaced for under $20.

• Replacing a start capacitor in a heat pump.
• Replacing a start capacitor in a pool pump motor.
• Replacing a start capacitor in a HVAC blower motor.
• Replacing a start capacitor in a A/C compressor.

2. Is your appliance operating abnormally?

An abnormal humming or buzzing sound from your appliance might be an early sign of a motor stall.

Can you identify what part of your appliance is making a noise?

Based on the appliance and the location of the noise, there could be different faulty components.

Example: The outside condenser of an HVAC unit houses the compressor and tends to be caused by the capacitor, relay, bad fan motors or bearings. The part of your HVAC that is located indoors (e.g. in the attic or basement) is where the evaporator, fan, and filter are located. If you notice your appliance is making an abnormal noise, call a technician as soon as possible and share your observations with them.

3. Have you noticed an increase in your utility bills or electricity usage?

Increases in your home utility bill can be an early indication that a large home appliance is not performing as intended. If you’re noticing irregularities in your energy bill, it’s worth taking a deeper look at some of your larger appliances.

Example: If you own an HVAC system, an increase in your traditional heating bill can be an early warning sign that something is wrong. This could potentially be caused by a heat pump that is unable to start and triggering an auxiliary heat to turn on.

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