A Tri Fuel Portable Generator running on natural gas and connected to the home’s electrical system though an inlet box and manual transfer switch. The large heavy cord makes the inlet box connection. The red cord powers a load not included in the manual transfer switch.
Generator to Home Connections Through a Transfer Switch
If you use a portable generator for home backup, a manual transfer switch is the safest, easiest way to make the connection between the generator and your home’s electrical system.
Backfeeding your home’s electrical panel through an appliance outlet is dangerous and illegal. It has the potential to cause a fire and poses a risk of electrocution to your family, neighbors, and utility workers. Don’t backfeed your home with a generator.
The homeowner usually chooses the most important circuits to power with the generator. Common circuits to power include the furnace, refrigerator, sump pump, medical equipment, router, lights, well pump, and air conditioner.
A transfer switch can supply loads that require 120 volts, 240 volts, and 120/240 volts. Except for some very heavy loads, like multiple baseboard heating units, the manual transfer switch can power almost any circuit in your home.
How Does a Manual Transfer Switch Work?
The manual transfer switch distributes power from your generator the same way your main circuit breaker panel distributes power from the utility. During normal operation (utility power), a circuit breaker in the main panel feeds power to the manual transfer switch. Moving the switch to generator disconnects the breaker in the panel before it connects power from the generator. This effectively isolates the circuits in the generator from utility power until the homeowner moves the switch back to utility power.
In either case, utility or generator power, circuit breakers in the switch distribute power to the circuits chosen when the electrician installed the manual transfer switch.
An electrician can also balance the load on the two lines carrying power into the transfer switch. This is more important while operating on generator power than on utility power.
The circuits served by the manual transfer switch always get power through the switch whether regardless of the utility or generator switch position.
A Generator Transfer Switch is Essential for Home Backup
A power outage hits and has the potential to last for days. Thinking quickly, you make a trip to the home center and buy one of the few generators left on the shelf. It takes about twenty minutes to complete assembly. You add fuel and oil, and fire it up. Fast, Easy, Simple. Right?
One extension cord runs indoors to the refrigerator, then another down to the basement to run the sump pump. A few lights would be nice, so that’s another extension cord. (Have you run out yet of extension cords yet?) Maybe you use a CPAP at night, so at bedtime you run another cord from the lights to the CPAP. In the morning, someone will want to make coffee and toast, use a hair dryer, microwave breakfast and charge their laptop, phone, or tablet (or all three).
Related: Portable Generator Grounding
The weather report talks about freezing temperatures or a heat wave. That’s when you realize you have no way to run your hard-wired appliances like the furnace or air conditioner. With any luck, the power company will restore power before it gets too cold or too hot. Meanwhile, you have extension cords running everywhere. How long before someone accidentally kicks the refrigerator cord or trips over the cord for something else?
The generator + extension cords solution gets old fast. A generator transfer switch is a better, safer, and easier solution:
- Eliminates trip hazards.
- Can’t accidentally kick the refrigerator cord (or other cord) and disconnect the fridge
- Your most essential circuits have power.
- Furnace and air conditioner work.
- Medical equipment works.
- Lights work.
Just as important, setting up the generator is easier than before. A single generator cord runs from the generator to the transfer switch inlet box.
- Make one connection from the generator to the inlet box.
- Start the generator, give it a minute to warm up.
- Move the transfer switch to generator.
All the circuits served by the transfer switch have power.
Planning a Manual Transfer Switch Installation
A Manual Transfer Switch installation is not a job for the novice DIY homeowner.
This job requires:
- A building permit, which requires an approved plan.
- An inspection.
- Plan which circuits will receive power (Do This Yourself)
- Moving circuit breakers from the main panel into the transfer switch while balancing the circuits in the transfer switch.
- Adding a circuit breaker to the main panel
- Understanding your generator ground.
- Wiring the new breaker to the transfer switch.
- Wiring the inlet box to the transfer switch.
- Installing covers in the main panel door to cover the empty slots.
And before you decide you don’t need a permit or inspection, remember that your homeowner insurance policy probably has a clause that will void your policy if you make changes to your home that result in injury, death, or fire (or any other catastrophe). If you change the electrical system and the insurance company finds an error, they won’t accept liability (meaning, they won’t pay a claim.) However, an installation that passed inspection won’t void your homeowner’s insurance.
Complete Series: How to Install A Generator Transfer Switch
Unless you have a very good grasp of home wiring, don’t do this yourself. Hire a qualified electrician.
However, the electrician will need to know what circuits you want to power. Make a list. At a minimum include the refrigerator, the sump pump if you have one, a lighting circuit, a circuit for your medical equipment, the furnace, a kitchen circuit, bathroom circuit. Optionally, include the central air conditioner, but keep in mind it draws more power than almost anything else. Depending on the air conditioner’s size, you may need a larger generator.
Portable Generator Safety
Follow the rules for portable generator safety. Read the guidelines in the owner’s manual and obey all the safety decals on the generator.
Here’s a few important generator safety guidelines to follow:
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Never run a generator indoors, not even if it has carbon monoxide detector and shutoff. They only prevent misuse and do make it safe to run the generator indoors. Always place the generator outdoors, never in any enclosed space (including a garage with the door open), at least 20 feet from any doors, windows, or other openings. Remember to keep it away from your neighbor’s house too.
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Only use outdoor-rated cords with an amperage rating that meets or exceeds the generator outlet rating. A 20-amp outlet requires a 20-amp cord.
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Never refuel a generator while it is running. Always shut it down. Let it cool for five minutes (good time to check and top off the oil). Wipe up any spilled gasoline or oil before you start the engine.
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It’s a good idea to secure your generator from theft. Choose a level place in advance. An eyebolt set in concrete with a chain through the generator frame will deter all but the most determined thief.
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A portable generator tent protects from the weather. Always shield the generator from rain, snow, and ice.