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Connecting a Portable Generator to Your Home Safely and Effectively

10 June 2011 5,803 views 2 Comments


You have two options when connecting your portable generator to your home. You can use extension cords to power each appliance or use a transfer switch.

man-connecting-generator-cords

Portable generators can be a lifesaver when a storm hits and your family is faced with an extended blackout. Today’s portable generators are easy to set up and use and are very efficient at powering a wide variety of appliances in your home. When you first look for a generator you need to know what your power requirements are before you buy. I’ve put together a Buying Guide that talks about choosing a portable generator that can help you assess your power needs based on the wattage of some common household appliances.

Smaller generators (under 5,000 watts) are excellent for powering a few essential appliances and are great to take out camping or tailgating. For machines of this size you can simply use several extensions cords to power everything. For medium and larger size generators that produce wattage from 5,000 to 15,000 watts I recommend you invest in a transfer switch. Here is a breakdown of the two connection choices you have; extension cords or a transfer switch.


Using Multiple Extension Cords

Every year for Christmas I pull out the lights and extension cords along with the decorations that go all over the house. It can be a chore, but if the whole family chips in, we can get it done and have the house looking beautiful for the season. The one thing that I really hate though is trying to untangle all of the lights and extension cords. I try to pack these up very organized and neat at the end of the season but inevitably they still seem to get tangled (by the tangle elves I suppose). Now try to imagine dealing with five or six extension cords in the dark after the power goes out. Sounds like a real pain right? Well it can be, but not horribly so if you are organized.

For your portable generator you’ll need to connect extension cords from the generator to each appliance in your home. Safety requirements mandate that you set up your generator outside your home at least 15 feet away to prevent any chance of carbon monoxide poisoning. So you’ll need some long extension cords. But not too long as power can drop as it travels along the cord and damage your appliances or the generator. To stay organized try keeping a couple cords wrapped nicely hanging near the generator in your garage or storage shed where you can access them easily during a blackout.

Most generators will have 5 or 6 receptacles to plug in the extension cords. So you can run multiple cords from the generator to each appliance you want to use, or you can buy a 25 foot, 30 amp gen-cord. A gen-cord is basically an extension cord with either a three or four prong plug on one end, and a box of three or four 120 volt outlets on the other end. You simply plug the gen-cord’s 3 or 4 prong plug into your generator’s most powerful outlet (typically 30 amps). Then run the cord from the outside into your house through a window and plug the household appliances you want to use into the 120 volt box at the end. You can also plug in additional extension cords. Just make sure you don’t exceed the wattage capacity of your generator.

Don’t put any of the cords under rugs because they can build up heat and cause a fire. Also make sure they aren’t too much in the way because they’re easy to trip over.

Extension cords are pretty inexpensive (Gen-cords start at around $80) and easy to use. They are perfect if you have a smaller generator and only need to power a few appliances. If you want to power more, including items that are hardwired to your house like a furnace, electrical stove or central air, then you’ll need to upgrade to a transfer switch.

This video from Popular Mechanics talks about operating your portable generator, connecting it to your home, and provides some additional safety tips.


Power Management

One important thing to remember when starting or stopping your generator is to never turn it on or turn it off with electrical devices plugged in or turned on. To ensure that your generator has a long life and to protect your appliances and electric devices you need to follow these steps when adding electrical load.

  1. Start the generator with no devices or extension cords plugged in.
  2. Let the engine stabilize by running it for a few minutes.
  3. Plug in the device that has the largest load or power demand.
  4. Turn the first device on.
  5. Let the engine stabilize so that it runs smoothly.
  6. Plug in the next device you want to run and turn it on.
  7. Let the engine stabilize again.
  8. Keep repeating the steps until you have everything plugged in that you want to run. Be sure not to exceed the maximum running wattage of your portable generator.

When you want to stop the engine follow these simple steps.

  1. Turn off and unplug all of your electrical devices.
  2. To stabilize the internal temperature of the generator and its engine you should let it run with nothing plugged in (no load) for a few minutes.
  3. Turn the ignition switch or button off.
  4. Some portable generators will also require you to turn the fuel valve to the off position as well.


Using A Transfer Switch

A transfer switch is a device that connects to your main circuit breaker for your house. To use it you simply run one extension cord from the generator to the transfer switch. The switch is used to power all of the hardwired items in your home including electrical sockets. It also prevents any back feed from your generator into the electrical grid outside your home. Back feed is extremely dangerous for power crews working on the lines as well as your neighbors.

transfer-switch-garage-installation

I recommend having the transfer switch professionally installed by a certified electrician. The actual transfer switch and installation should run you about $600 total and take a couple of hours of the electrician’s time. If your main circuit breaker is in your garage the installation and setup are fairly easy. You’ll just need to run a 25 foot extension cord from the portable generator into the garage and connect it to the transfer switch.

If your main electrical panel is in your basement it’s easier to have a power inlet box installed (about $50) outside of your house where you’ll be using your generator. A power inlet box is hardwired directly to the transfer switch in your basement and costs around $50. Then you can plug your extension cord into the inlet box and you won’t have to worry about running long cords into your basement through a window to your main circuit breaker.

transfer-switch-basement-installation

You can pick and choose which circuits you want running on the transfer switch by simply flipping the switches. Keep track of what you are using so that you don’t overload the circuits by trying to get more power than your generator is capable of. It’s also important to match the transfer switch to the wattage of your generator. For example, a six circuit switch works best with a 5,000 watt generator and a 10 circuit switch matches up well with a 7,500 watt unit.

One final thing you should do to make sure you have everything connected correctly is to conduct a test run. Turn off your power at the circuit breaker and turn on your generator. If you’re using just extension cords plug them in and see how your generator works. If you’re using a transfer switch then flip on the circuits you want to power up, plug in some appliances and check to see if everything is in working order. This type of Power Loss Preparedness Drill will help make sure you’re ready when a real blackout occurs.



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2 Comments »

  • Jeff said:

    Thanks for the information. You make no mention of circuit protection when using say, a 30Amp socket on a portable generator. Home wiring is protected from overloads and shorts by the 15Amp or 20Amp circuit breakers in the box. But if I use the 30Amp socket on my 3500 watt generator there is no protection for any wiring between the generator and the use point. Wouldn’t you prefer to see the homeowner use some form of in-line circuit breaker between the generator and the use point?

  • Lou said:

    Regarding the transfer switch – I have some friends who recently operated their generators safely by connecting a 240V line from the generator to a 220V receptacle in their homes. They cut off power to/from the house by throwing the main circuit breaker, then flipped on only those circuit breakers in the house that they needed…just like a transfer switch. Since they hooked up to the 220V line, they had the flexibility to run both 220V and 110V circuits. You don’t list this a third option. Is it because it carries some sort of risk or because there is some other flaw in this method?

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