Understanding Home Standby Generators
An average home may use more than a hundred electrical appliances and devices to provide convenience, comfort and security. It is, therefore, essential that we install a backup home generator to prepare for a power outage. A residential generator has major advantages over a portable gen set- automatic start, permanent fixture, more power, cleaner fuel (natural gas or propane), low running costs and all-weather operation. Standby power systems start automatically with seconds after a home’s electricity goes out and ensure a continuous electrical supply.
A Transfer Switch immediately senses when power is interrupted and transfers power generation to generator. It also senses when power is restored and transfers the load back to the utility source and signals the generator to shut down. The power generator is installed outdoors and linked directly to home’s permanent fuel supply.
A residential standby generating system typically has three basic elements: a generator, a transfer switch and a service-entrance breaker.
- Generator – Produces electricity for essential or selected systems like cooling, heating, refrigeration, security and lighting. Your backup needs, simple or more extensive, determine the size and output of the unit.
- Transfer Switch – Immediately senses when power is interrupted and transfers power generation responsibility to the generator. Senses when power is restored and transfers the load back to the utility source and signals the generator to cool off and shut down.
- Service Entrance Breaker – Provides protection to your transfer switch, internal breakers and circuits and generator due to electrical strikes and power surges.
Note: You should not attempt to specify and install a power system on your own. Electrical connections must be made and fuel systems installed by qualified and licensed personnel. Improper installations present hazards, which can result in personal injury or property damage. Please contact a licensed residential electrician and your local natural gas or propane supplier for these services. In all cases, you should contract a Cummins Onan Dealer and/or certified technicians. Our Sales and Service Locator will direct you to your nearest qualified Cummins Onan dealer or distributorship.
How the System Works
- 1.Transfer switch monitors voltage coming from utility
- 2.Transfer switch senses when utility power fails or drops below an acceptable level (brown out), and sends a signal to start the generator
- 3.Transfer switch automatically disconnects the utility power from the electrical circuits in your home, and reconnects them to the generator
- 4.Generator continues to supply electrical power to your home until utility power is restored
- 5.Transfer switch senses when the utility power is restored, automatically disconnects the generator from your home circuits, and reconnects the utility power
- 6.The Cummins Onan Generating system automatically re-sets itself for the next power outage
What Happens When
The Power Goes Out
Power Outage Occurs:
When utility power voltage falls to less than 85% of nominal, or fails entirely, the standby power system will automatically go through a start sequence and connect to a home. The transfer panel control constantly monitors the power quality from both the utility source and the generator set. When the transfer panel control senses unacceptable utility power, the control waits for 3 seconds and then sends a signal to start the generator set engine. If the utility power returns before 3 seconds has passed, the generator set engine will not be signaled to start. When the start signal is received, the engine starts and reaches the proper operating speed and AC power is available at the generator set. The transfer panel control senses this, waits for 3 seconds and will then transfer generator set power to the home through the transfer panel contractors. This sequence of operations will usually occur in less than 10 seconds from the time the power outage occurred to the time when generator set power is connected.
Utility Power Returns:
When utility power comes back on and returns to your home, the transfer panel control senses this and will watch for acceptable voltage. After checking for acceptable utility voltage for five minutes, the transfer panel control will signal the transfer panel contractors to re-transfer the load back to the utility source and disconnect the generator set source. At this point, the generator set is "off-line" and will be operated automatically another five minutes to properly cool down. After the cool down cycle, the generator set will be turned automatically off and reset to standby mode
Routine Operation and Maintenance
A common concern for homeowners is how to maintain their Cummins Onan standby generator once it is installed. Not to worry. Maintaining a generator is similar to maintaining an automobile and maintenance is essential for top performance and long life. Just like a car, you will have an owner’s manual for your generator unit with very specific directions and maintenance intervals in grid form. It will tell you how to maintain your generator and allow you to record things like running hours and maintenance performed. You will find that changing the oil, checking the battery/connections, changing an air or oil filter, and visually inspecting your unit’s components are typical maintenance requirements. Warranty work, however, must be performed by an authorized Cummins Onan Dealer or certified technician. For more extensive repairs or peace of mind, feel free to contact your Cummins Onan dealer or distributor for more information.