How Does a House Generator Transfer Switch Work?

The transfer switch is an integral part of a whole house standby generator system. The transfer switch performs these essential functions:

  • Monitors utility company power that normally powers the home.
  • Detects an interruption in utility company power and sends the “utility power unavailable” signal to the backup house generator control.
  • Receives the transfer command from the house generator control and switches the home’s power source to the house generator.
  • Senses the restoration of utility company power and sends the “utility power available” signal to the house generator control.
  • Receives the transfer command from the house generator control and switches the home’s power source to utility company power.

Automatically switching the source of your home’s power from the normal utility power to backup home generator power when an outage occurs helps keep your home constantly supplied with power.

Frequently asked questions about backup home generator transfer switches

Will a transfer switch prevent brownouts or power surges?

A simple transfer switch used for a standby whole home generator typically only transfers the source of power to the generator when a complete power outage occurs. The transfer switch won’t protect your home from power surges or brownouts. Consider installing a whole house surge protector to help prevent damage that can be caused by power surges and brownouts.

How long will my automatic transfer switch last?

An automatic transfer switch typically lasts at least 20 to 25 years. Relays and contacts in the transfer switch can fail sooner in some situations. Cleaning and maintaining the automatic transfer switch regularly will help it last longer.

Why won’t my automatic transfer switch transfer to the backup house generator power source?

If your whole house backup generator is running but your home has no power, check the circuit breaker on the generator. If that breaker is shut off, no current will flow through the transfer switch to your house electrical system.

Several failures inside the transfer switch cabinet can prevent the transfer switch from connecting to a running standby whole house generator to provide your home with power. Failed wiring, relays, solenoid coils or electrical contacts in the transfer switch can prevent transfer of the power source.

Try transferring the power source using the manual transfer switch. If your home gets power through from the backup generator using the manual transfer switch, then you’ll likely need to have the transfer switch repaired or replaced by a professional service provider.

Why won’t my transfer switch restore utility power when a power outage ends?

The transfer switch won’t restore utility power if the manual switch is in connected to the backup house generator. Check the position of the manual switch and position it to provide utility power if necessary. A tripped utility power feeder breaker will prevent the transfer switch from getting utility power. The transfer switch also won’t get utility power if the utility service disconnect switch if in the OFF position. Check the feeder breaker and disconnect switch. Reset the feeder breaker and turn on the utility service disconnect switch if necessary to restore utility power to the transfer switch and your home.

Failures inside the transfer switch cabinet such as bad wiring, defective relays, dead solenoid coils or burnt electrical contacts can prevent the transfer switch from restoring utility power when a power outage ends. Have a service professional repair or replace the transfer switch when basic troubleshooting doesn’t fix the problem.

When your whole house backup generator and transfer switch reach the end of their useful lives and it’s time to replace them, schedule an appointment with a home generator expert to install a new backup power system for your home.

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