Read the manual thoroughly and understand all of the instructions, cautions, and warnings before using this equipment. If any section of the manual is not understood, contact your nearest authorized dealer, or contact Generac Customer Service at 1-888-436-3722 (1-888-GENERAC), or www.generac.com with any questions or concerns.  

What does "under load" mean? 

This article explains how to determine if your generator is under load and why it matters for safe operation. 

• A generator is "under load" when devices are connected to it and attempting to draw power. Even if the generator is not running or producing power, any connection creates an electrical demand on the generator. 

Environment: 

This article applies to all portable generators and home standby generators. 

Why avoid starting a generator under load?

• Stability: Generators must reach their precise operating speed (RPM) to provide stable electricity. Starting under load can strain the generator and cause it to shut down or fail. 
• Preventing Damage: Sudden power demands from connected devices can damage the generator or appliances. 
• Cold weather consideration: In cold conditions, additional warm-up time is needed for oil circulation to protect the engine; this isn't about electricity production but engine longevity. 
  • For more information on additional warm-up settings, see What is Cold Smart Start?

How do I know if my generator is "under load"?

Portable generators:

For portable generators, "under load" simply means that something is plugged into the generator.

How to check: 

• Ensure that nothing is plugged into the generator before starting it. 
• Confirm all outlets on the generator are empty before you attempt to start. 

Home Standby generators

For stationary generators,  " under load" is determined by whether the transfer switch has shifted to backup power (generator power). 

How to check: 

• Transfer Switch: Check if the transfer switch has transferred power to the generator. If it has, the generator is under load. See this article for more information: How Does an Automatic Transfer Switch Work?
• During an outage event, the generator senses a loss of utility and signals the transfer switch to switch the electrical contacts from utility to backup. This results in the generator being connected to your house's electrical system, and all appliances or devices connected to your home's electrical system will now be drawing power from the generator. 

When is this information relevant for home standby generators?

This guidance is most applicable during an outage when:

• The generator fails to start.
• The generator shuts down unexpectedly during an outage.
• The generator has been shut down for maintenance checks.

In these cases, the transfer switch may already be set to backup power, meaning the generator is "under load." Before attempting to restart the generator, follow these steps:

1. Remove electrical loads:

• Turn off the utility service disconnect.
• Switch off the generator's main line circuit breaker. 
• This prevents any electrical draw or power transfer to the home's electrical system during startup. 

2. Restart the generator: 

• Start the generator and allow it to warm up for 5 minutes.
• In extreme cold weather, allow additional warm-up time for the engine oil to warm and circulate properly. 

3. Reconnect power to the home:

• Once the generator is warmed up, turn on the utility service disconnect. 
• Then, switch on the generator's main line circuit breaker. 
• This will transfer the home's electrical load to the generator, allowing it to supply power.

Where to find your home standby's main line circuit breaker (MLCB) and Utility Service Disconnect

The location of the main line circuit breaker (MLCB) and Utility Service Disconnect can vary depending on the generator model and your home's electrical system. Proper identification and safe handling are critical, so always consult the owner's manual for your generator and transfer switch. 

Main Line Circuit Breaker (MLCB) - Generator: 

• The MLCB is located on the generator itself. However, the exact position depends on the generator model. 
• What to do: Refer to your generator's owner's manual to identify and locate the MLCB safely. 

Utility Service Disconnect: 

• The location of the utility service disconnect depends on your home's electrical design and transfer switch setup. 
• Service Entrance-Rated Transfer Switches: The utility disconnect is integrated into the transfer switch for service entrance-rated switches.
• What to do: Refer to the owner's manual for your transfer switch to locate the utility disconnect and follow all safety instructions. 

Important Notes: 

• Due to the unique configurations of home electrical systems and generator installations, this article cannot definitively outline specific locations and setups. 
• If you are unsure or have difficulty identifying these components, contact Generac Customer Support at 888-436-3722 or your local Generac Independent Authorized Service Dealer (IASD) for assistance.
• Always prioritize safety and never attempt to operate or troubleshoot electrical systems without proper guidance. 

 

Additional Resources 

• How Can I Find a Generac Service Dealer in My Area?