When a power outage occurs, there is no doubt that the best way to provide backup emergency power to a home is with standby generator system. An automatic transfer switch controls the home’s source of power and switches it between the utility supply and the standby generator supply as required. It happens automatically and the generator runs on municipal natural gas or LP gas from a residential storage tank.
In cases where a standby generator is not practical or can’t be installed for some reason, a portable generator can supply power during an outage.
Portable Connection Options
Connecting appliances to a portable generator with extension cords is the most basic option. The cords plug into the generator’s receptacle panel and then connect inside the house to the required appliances. This works fine for appliances such as refrigerators and freezers, or a sump pump that is keeping the basement dry during a storm. However, permanently wired appliances won’t receive power this way, and that includes furnaces, central air conditioners, electric ranges, and well pumps.
A manual transfer switch can supply essential circuits with electricity. Electricity is distributed through circuit breakers in a dedicated panel that is controlled by the switch. During an outage, electricity is supplied by a portable generator through a dedicated cable that connects the generator to an inlet box which supplies power to the switch.
Safe Emergency Power
The reason for a transfer switch is simple. A manual or automatic transfer switch isolates the home from the utility lines when power is supplied by the generator. Without a transfer switch, it is quite possible to accidentally feed the utility lines with a generator. The transformer that supplies the house will convert that generator power from 240 volts to as much as 69,000 volts.
More than enough voltage to kill or seriously injure a utility worker.
If you accidentally backfeed a utility line with your generator and your actions cause injury or death to a utility worker, you will be held responsible for those actions. Never backfeed your home and you won’t accidentally backfeed the utility lines.
Manual Transfer Switches
A manual transfer switch is exactly what its name states. It is a manual device that requires a human to throw the switch from utility to generator. When that happens, the circuits supplied by the generator are isolated from the utility lines and connected to the generator lines. Returning the switch to the utility reverses the action and reconnects utility power.
When a power outage occurs, the homeowner moves the portable outside to a predetermined location that won’t gather standing water or allows deadly exhaust to enter the home. The dedicated power cable is plugged into the generator panel and into the inlet box. After starting the generator and allowing it to warm up, the generator’s main breaker is turned to on, and then the manual transfer switch is moved to the generator position.
Power is now supplied to the circuits connected to the manual transfer switch.
When the utility restores power, the process is reversed. The manual transfer switch is returned to utility mode to restore power to the home. The main breaker is turned off, which removes power from the cable and receptacle panel. Finally, the generator is turned off, allowed to cool, and put away.
Extension Cord Size
Only use outdoor extension cords with the correct gauge wire. Size extension cords based on the current that the generator receptacle is capable of supplying. If a receptacle has a 20-amp circuit breaker, then it could supply 20 amps of current, and a 12-gauge extension cord is the minimum size.
A common mistake is to size the cord by the appliance requirement. For instance, using a 16-gauge extension cord to run a 10-amp appliance off a 20-ampere generator receptacle. If someone plugs another appliance into the cord, the cord could overheat and cause a fire.
Keep extension cords on hand that will supply the maximum amount of current that might be drawn through the cord. Don’t rely on guesses or that no one will make a mistake.
Dedicated cables connect a 240/120-volt generator outlet to the inlet box. Distributor or manufacturer supplied cables have the correct connectors for the amount of current they can handle. A 30-amp cord has connectors rated at 30 amps, and will only connect to 30-amp receptacles. The same is true of 50-amp cables.
The cables have four wires configured in similar way to an electric dryer or electric range cable. Two wires each carry 120 volts for a total of 240 volts. Another wire serves as a neutral or return for the 120-volt wires. The fourth wire a ground and connects to the generator’s metal chassis and to the ground bus in the manual transfer switch.