mlts22 wrote:
There are a few ways to skin this cat and be up to code standards:
1: A circuit breaker interlock. This puts the incoming generator at the top right breaker, a device that only allows the main switch or the generator switch to be on, never both, and the top right breaker goes to a -male- connector on the outside. No widow maker cable needed, ever.
2: A sub-panel as mentioned above.
3: A manual transfer switch.
4: An automatic transfer switch. This is the easiest because one can just fire up the generator, let it warm up, plug it in, and the ATS takes over from there. When power comes back on, the ATS swaps back to mains lines.
I like the sub-panel or transfer switches because it is a lot more idiot-resistant than the interlock (as the interlock can fall off), but all of these are generally approved by electrical code in all areas.
Of course, one can run extension cords from the generator inside the house as well.
Backfeeding isn't a good idea. Those step-down transformers by the house? They will step up the voltage down the power lines when backfed.
This post by mlts lists all the options. I'll add some comments about cost. Option 4 (the ATS) is the most expensive, but it's also the most automatic. Personally, I don't mind turning some switches to save that expense. An ATS may have some maintenance requirements that manual switches avoid.
Option 3 is a transfer switch located between your home and the incoming power from the power lines. You throw the transfer switch and your home is disconnected from those power lines and connected to the gen. This is the safest for power company workers. It's expensive to install for two reasons. The first is that the TS needs to be rated for your home power. If you have a 200A service, then that 200A is passing through the new TS at your service entrance. High power, service entrance rated is expensive and you need that high power rating, even if you are only installing a 16A generator. The second cost comes from the fact that to install it at the service entrance, you need to have the power company turn off your power during installation. Your electrician can't do this alone. These costs also apply to option 4.
Option 2 is the most widely used. Basically, it's a simple sub panel. You move the breakers for a selected set of circuits hyou want to use during a power outage into that new subpanel, or you buy new ones. You need space to install the new subpanel. You need to move the wires that currently go to from your main panel to the various rooms in your house from your main panel into the new subpanel. Some may not be long enough, and they may need to be extended. The good news is that your electrician can do all this work without calling the power company. You are limited to powering only the circuits you select. If you decide you don't need to power the garage, or run the fan in the guest bathroom, then during the outage, you need lights in the garage, or want that fan, you are out of luck.
Then there is option 1. It is by far the cheapest. Electrically, it is nearly identical to the "suicide cord" and "dryer plug backfeed" that is universally illegal, except it is approved by the National Electrical Code (NEC and most local codes. The differences are subtle, but critical for safety. First, it requires an interlock so the main breaker (connecting your home to the power company)) can never be on when the generator breaker is on and vice-a-versa. Second, it needs a new breaker for the generator instead of using the dryer breaker. Often, that new breaker will be identical to your dryer breaker. Third it requires a new generator connection point socket (with male pins) instead of using the dryer receptacle so that your generator doesn't use a suicide cord. It uses a normal extension cord having a female end, so you don't have exposed pins when the gen is on. All of the options above need this new generator socket.
If the new generator socket was replaced with a dryer receptacle, and the interlock was removed, you'd have a normal dryer receptacle (or a second one, if you already had one.) Electrically, this type of installation is otherwise identical to backfeeding through the dryer plug, but it's done safely and according to the applicable electrical codes.
People are often surprised that it is legal to "backfeed" through a normal dryer circuit breaker when an interlock is installed, but this practice has been legal for many decades, and has often been used in industry. Almost all circuit breakers are rated for backfeeding. They must be specially marked if they are not, and all those sold by Home Depot that I've seen can be used in this type of legal backfeeding installation as long as a legal interlock is also used.
The cost advantages of option 1 are multiple, which is why I went with that option. I had no space for the new subpanel. My circuits wouldn't reach to where it would have to be installed, so I would have needed to extend all of them.. Plus, I wanted to be able to power everything in my home - not all at once - but I wanted to be able to turn on any circuit breaker and know I could send power out that circuit.
edit: I didn't list it, but one other subtle difference is that the generator breaker needs to be held down with additional clamps. Their cost is minor and they are often included with the interlock kit.
