Electric Motor Overheating: Why Summer Heat Can Expose Problems

An electric motor naturally produces heat while it operates.

The problem is when it can no longer get rid of that heat effectively.

Electric motor overheating often becomes more noticeable during summer because the air surrounding the motor is already warmer.

Standard industrial motors are commonly designed around specific ambient-temperature conditions. ABB, for example, identifies 40°C as the typical maximum ambient temperature for normal motor ratings unless otherwise specified.

That does not mean every motor operating in warm weather will overheat.

It means cooling conditions matter.

What Causes Electric Motor Overheating?

Heat problems usually deserve investigation rather than simply more airflow pointed toward the equipment.

Common contributors can include:

• Restricted ventilation

• Dirty cooling surfaces

• Excessive mechanical load

• Electrical problems

• Frequent starting

• High ambient temperature

• Incorrect motor selection

• Problems with the driven equipment

The motor may be responding to a problem somewhere else.

Start With Airflow

Many motors rely on surrounding air to remove heat.

If ventilation openings are blocked or cooling surfaces become covered with dirt and debris, heat transfer can be reduced.

Inspect the motor exterior.

Look for dust, grease, debris or other material accumulating around cooling fins, fan covers and ventilation openings.

Also look at the room.

Has equipment been installed close to the motor?

Has airflow through the mechanical room changed?

Is hot air from other equipment being discharged toward it?

ABB motor guidance emphasizes maintaining adequate ventilation and keeping cooling arrangements functioning as intended.

Check the Load

The motor may be running hot because it is working harder.

For a pump motor, that means investigating the pump and hydraulic system too.

Changes in system flow, pump operation or mechanical condition can change motor load.

Do not treat electric motor overheating as an isolated motor problem until you know what the motor is driving.

Look at Starts and Stops

Starting creates additional electrical and thermal stress.

If a motor that was designed to run for longer periods begins starting repeatedly, temperature can increase.

Ask whether anything changed in:

• Pressure settings

• Float operation

• Level controls

• Tank conditions

• Building demand

• Control programming

A control issue can become a motor-temperature issue.

Compare Temperatures Over Time

One temperature reading gives you a snapshot.

A trend is more useful.

If the same motor historically operated at a relatively stable temperature and is now consistently hotter under similar loading, investigate why.

Document:

• Ambient temperature

• Motor surface or winding temperature where monitored

• Current

• Load

• Pump operating conditions

• Runtime

• Number of starts

That context helps separate normal seasonal temperature changes from a developing equipment problem.

Don't Ignore a Motor That Keeps Getting Hotter

Heat can shorten insulation and bearing life.

If a motor repeatedly trips on temperature or is noticeably hotter than similar equipment operating under comparable conditions, find the cause.

Simply resetting thermal protection does not improve ventilation, reduce mechanical load or correct an electrical problem.

Summer Heat Can Reveal a Problem That Was Already There

The weather may not be the root cause.

It may simply reduce the margin the equipment had available.

A marginal ventilation issue in April can become an obvious electric motor overheating problem in July.

Academy Pump & Motor provides electric motor sales, service, troubleshooting and repair throughout Calgary and surrounding areas.

If a motor is running hotter than normal, call Academy Pump & Motor at 403-437-7888 or visit academypump.ca.