Space Heater For Motor and Panels

Motor space heaters operate by using resistive heating elements to generate heat when the temperature inside the motor drops below a specified setpoint.

A thermostat or temperature controller ensures that the heater is activated as needed to prevent condensation and maintain the motor’s temperature within the desired range, thus ensuring the safe and reliable operation of the motor.

What is a Space Heater in a Motor And Electric Panels?

A space heater in the context of motors and electric panels is a device designed to provide controlled heating within an enclosed space, such as an electrical motor or a panel enclosure.

These heaters are used to maintain the temperature inside the equipment or enclosure within a specified range, ensuring that it operates safely and reliably, especially in colder environments. Here’s how space heaters are used in motors and electric panels:

  1. Motor Heaters: Electric motors, particularly large ones, can be subjected to temperature extremes that can affect their performance and longevity. In cold environments, motors may not operate efficiently or could suffer damage due to condensation and the effects of low temperatures. To address this, space heaters are installed within or near the motor housing. These heaters are typically low-wattage resistive heaters that generate enough heat to prevent condensation and maintain the motor’s temperature within an acceptable range when it’s not running. The heaters are controlled by a thermostat that activates them when needed.

  2. Electric Panel Heaters: Electric panels, such as distribution panels, switchgear, or control panels, contain various electrical components. These components can be sensitive to temperature variations. In some situations, especially in outdoor or unheated indoor locations, panels can be exposed to cold temperatures that could cause problems like condensation, icing, or the failure of certain components. Space heaters are used within these panels to prevent these issues. They are typically small, low-wattage heaters controlled by thermostats or temperature controllers. The heaters maintain the panel’s internal temperature above the dew point, preventing moisture-related problems.

Space heaters in motors and electric panels are a proactive measure to ensure the reliability and safety of electrical equipment, especially in environments where temperature fluctuations can be a concern.

They help maintain the equipment within its specified temperature range, which is essential for the proper functioning and longevity of electrical components.

Why space heaters Are being used in electrical motors?

electrical short circuit damaged an electrical generator
The electric generator burnt out due to moisture

The space heater for the motor keeps the temperature above the ambient dew point at a motor-off time.

The heater works to prevent condensation from forming in the motor which can cause motor winding damage.

In my work site, humidity and moisture are very high, In many cases, we face electric motors and generators winding burn out. Of course, these motors and generators have no space heater.

Humidity decreases the winding resistance causing it to break down. The result is, as you know, an internal short circuit between windings.

Motor insulation and electrical components of electrical panels and switch gears could get damaged and short-circuited because of high humidity and water condensation.

In the case of generators in my workplace, the windings are totally burned and the fire catches all other generator’s parts.

Unfortunately, some generators continue running while the fire continues catching everything it can. The result is obvious, a totally destroyed electrical generator.

Working principle of motor space heater

A space heater is a simple heater, that usually works on a single-phase AC power source. It consists of a resistive coil that produces heat when an electric current passes through it.

It’s simply just like the electrical water heater in our houses. It’s connected to a simple control circuit to work in times the panel or the motor is stopped for any reason.

Usually, space heaters are connected to the motor starter. But keep in mind that space heaters need power while the motor is out of service.

So, its power supply is not the same as the motor. This is clear, in case the motor main power source is disconnected, the space heater power should not be disconnected too.

Here’s how the working principle of a motor space heater typically operates:

  1. Electrical Resistance: Motor space heaters are essentially resistive heating elements made of materials with a high resistance to electrical current flow. When an electric current passes through a resistive heating element, it encounters resistance to its flow. This resistance causes the electrical energy to be converted into heat energy.

  2. Energy Conversion: As the current flows through the heating element, it releases energy in the form of heat. The heating element is designed to generate sufficient heat to maintain the motor’s temperature above the dew point, which prevents condensation and moisture-related issues within the motor.

  3. Temperature Control: To ensure that the motor space heater operates within a desired temperature range, a thermostat or temperature controller is typically integrated into the system. The thermostat monitors the temperature inside the motor housing.

  4. Activation and Deactivation: When the temperature inside the motor drops below a certain setpoint (often slightly above the dew point), the thermostat activates the space heater. This action allows electric current to flow through the heating element, generating heat.

  5. Maintaining Temperature: As the space heater generates heat, it warms the air inside the motor housing, preventing condensation. Once the temperature reaches the desired level, the thermostat deactivates the heater to avoid overheating. This cycle repeats as needed to maintain the motor’s temperature within the specified range.

  6. Energy Efficiency: Motor space heaters are designed to be energy-efficient and are sized appropriately for the motor’s requirements. They are not intended to provide continuous heating but rather to activate only when necessary to maintain the desired temperature.

Safety tip for working with anti-condensation heater

As mentioned above the heater has its own power source. i.e. its power is not the same source as the panel or the motor.

This makes it tricky when you need to electrically isolate the panel for maintenance or inspection. You should pay attention to the right isolation of the heater.

Don’t just isolate the panel power source main circuit breaker.

Once, I was working on a medium-voltage panel, and it had a space heater. I didn’t realize that the space heater had its own power source.

This situation was very risky for the people working on the panel. Surprisingly, my boss was among them, and he got an electric shock. Thankfully, he let go of the wire quickly.

Don’t worry, my boss was understanding and didn’t punish me. But the most important thing is the lesson I learned, and I want to share it with you now: always be careful because your boss might not be as forgiving. Stay safe!

Motor Space Heater Voltage Drop

In many cases, the motor power source and starter are located away from the motor itself. As the space heater voltage is usually 220V or 110V, this distance may cause some voltage drop in the space heater.

The question is what will happen? Will the space heater voltage drop affect its efficiency?

The answer is, that the space heater voltage drop will of course affect its heating ability. But it still working. It will need a longer time to heat the space of the motor or the panel.

It’s a heater, not a motor. I mean it has no starting current. It will work on any voltage. But you should check its user guide data and make sure to keep this voltage within allowable limits.

Motor anti-condensation heater resistance calculation

Motor anti-condensation heater resistance is just like any other resistive load. You can measure it with a multimeter. The value varies from one to one.

The motor or the panel nameplate should tell you the motor’s anti-condensation heater resistance. If the value is not on the nameplate, then you will find the voltage and the power of the heater.

As the heater has no power factor, then you can calculate its resistance by applying the formula

R = V2 / P


  • R is the space heater resistance.
  • V is the space heater operating voltage.
  • P is the power in watts.


If the motor space heater is 500 watts and its voltage is 110 V then its resistance is 1102/500 = 24.2 Ohm

Do all Motors and Panels Have a Space Heater?

No, not all motors and electrical panels have space heaters. The use of space heaters in motors and panels depends on various factors, including the specific application, environmental conditions, and the need for temperature control. Here are some considerations:

  1. Environmental Conditions: Space heaters are more commonly used in motors and panels that are exposed to harsh environmental conditions, such as outdoor installations, cold climates, or areas with high humidity. In such conditions, there is a higher risk of temperature-related issues like condensation, which space heaters can help prevent.

  2. Motor Size: The use of space heaters in motors often depends on their size and design. Large motors, especially those used in industrial settings, are more likely to have space heaters to maintain proper operating temperatures during idle periods.

  3. Panel Size and Contents: In electrical panels, the decision to use space heaters depends on the size of the panel and the types of components inside. Large electrical panels with sensitive equipment may have space heaters to prevent temperature-related problems.

  4. Application Criticality: In critical applications where equipment uptime is essential, space heaters may be employed to ensure that components remain within their specified temperature ranges, preventing malfunctions and downtime.

  5. Local Environmental Factors: Local climate conditions and temperature variations play a role in determining whether space heaters are necessary. In regions with extreme temperatures, space heaters may be more common.

  6. Design Specifications: Electrical systems and equipment are designed based on specific requirements and standards. Engineers and designers consider environmental factors and criticality when deciding whether to include space heaters in the design.

In summary, the use of space heaters in motors and electrical panels is not universal. It varies based on the specific needs of the application, environmental conditions, and the design of the equipment.

Space heaters are primarily used to prevent issues related to temperature variations, condensation, and moisture, and their inclusion is determined by the designers and engineers responsible for the equipment.