I’ve bought a home generator because of the rinky dink power company that feeds electricity to my area. I’ve been convinced to have a transfer switch installed at my fuse box, and I have a licensed electrician scheduled for the installation next Saturday. A few years ago, during what turned out to be a four day blackout, a neighbor brought home a generator from work, to power up his house. It was winter, and he offered the generator to me for a few hours, to get the heat going, refrigerators going, and let the well pump kick in so we could take showers, etc. It worked out well, we survived for another 24 hours. My question (the neighbor moved, so I can’t ask him) I seem to remember that all he did was plug the generator into an electrical outlet in my garage. How did that work? The juice was going the wrong way, no? What were the consequences if the rinky dink company had finally fixed the outage problem, and their power began feeding me again? I’m thinking only bad things here, am I right? What, if anything, would have been a better way to hook in the generator, safely, without a transfer switch?
First of all, NEVER plug a generator into a power outlet. You could give a lineman a rather deadly shock.
From what I’ve seen on various DIY shows, the procedure is to wire the generator into your system, and when a power outage is detected, the generator kicks in. I’m sure you could have it wired so that you can do it manually.
I’d go for the automatic switchover.
Also, you will want to test the generator a few times a year to make sure it’s functioning properly. The middle of a bad storm is not the time to have to call a repairmen.
In theory, it would work to simply plug your generator into an outlet, but there are many problems with this, including safety. And I doubt your generator is big enough to handle all the heavy loads, safety aside. Plus, when the power did come back on, who knows how your generator would handle it.
I would opt for a manual switch because of cost. When the power is down, you can go to your switch and flip it to generator mode and startup your generator. It is smart to have an electrician to do this, because when you start getting into your breaker box, that’s right where the mains come in and they pack a whallop of power.
Your electrician will probably install a switch that will switch the input lines of your circuits to your generator. This way you are either in one mode or another. He may also make a large cable that will go from the generator to the switch, enough to carry the load. Not sure how big your generator is, but you may have to be selective in what you power (i.e. an a/c or electric water heater might be too much for the generator, and may need to be disabled). You could do this at the circuit breaker level.
If you plug a generator into an outlet you need to turn off the main breaker at the panel. That’s the big breaker mounted all by itself at the top of the panel. That way when the power comes back on you won’t burn up your generator and maybe start a fire.
As other have said, this isn’t the best way and you will be limited as to the current you can supply. Say you have a 5 KVA generator. It can supply amost 50 amp. at 110 V. or 25 amp at 220 V. and if you plug it into a line that is breakered at 15 amp. that’s all you can provide. In addition, pluging it into an outlet only energizes one side of the panel. Appliances on the other side can’t be used. In order to energize the whole panel you need to plug it into the electric stove or dryer outlet or some other 220 V. outlet and you need a 220 V. generator.
Your electrician will no doubt wire it properly and according to code. In any case you have to have a switch to disconnect the power line when you are using the generator and the generator when you are using the power line. Connecting a generator to the power line requires some specialized equipment and skill that most people lack. And it’s a foolish thing to do because the power company doesn’t need your help and if your little generator engine quits for any reason you have a problem requiring your attention toute damned suite.
Your power is AC, which means that 60 times a second (50 in some places) it switches direction anyway, so it doesn’t really care where you feed it from. The real danger here is that the entire house is now being fed from one branch that probably has wire that’s only rated for 15 amps. Ditto to what all the previous posters have said about having a pro hook this up.
This is pretty much how generators on the power system are hooked up. They are all just conncted in parallel across the lines. However, the power company uses a thing called a synchroscope, where they wait until the generator and the rest of the power system are all at exactly the same point in the AC cycle, before they connect the generator to the lines. In your case, you are randomly connecting your generator to the power grid. The chances of hitting it close enough in the AC cycle that you don’t cause severe problems is fairly small. There’s even a chance your generator could come flying apart in a rather spectacular display of broken bits and pieces. If you get lucky, the generator will sync up with the line quickly enough not to cause some major damage, but it’s not something I would recommend trying.
Turning off the main breaker (as David Simmons said) should have been done, otherwise you were taking severe risks with your neighbor’s generator.
Once you get your generator in sync with the rest of the power system, it’s kinda interesting. No matter what you do it will stay locked at exactly the same frequency as the rest of the grid. If you use the generator’s engine to try and speed it up, it will supply power to the grid. If you slow down the generator’s engine and try and slow it down, then your generator starts to act like a motor and draws power from the grid.
I’ve heard of people plugging a 220 VAC generator (with center tap) into their clothes dryer receptacle. In theory this should be safe, since each leg is protected by a dedicated CB. But I wouldn’t use it for a permanent configuration.
Remember that even if you back feed the service from a generator (like the OP did with the neighbors or like Crafterman suggested) and you turn off the main breaker there is still a potential for some activity on the nuetral that goes out to the transformer on the pole. This could cause a dangerous situation for a Lineman who may be working on the lines nearby.
A transfer switch should disconnect the nuetral from the primary source as well as the hot legs. You would need to have a sound ground grid in and around your house as well as the professionally installed transfer switch. Make sure the electrician checks your ground rods and other points of bonding for your service.
Er, doesn’t that break some things on 110V circuits?
Oh, no, because the 110V circuits are two “halves” of the 220V circuit. Never mind…
Another danger with plugging the generator into an outlet is that in order to do so, you have to wire it up with a male plug; hot male terminals are a big no-no because the risk of accidental electocution or shorting is greatly increased.
There isn’t a better way to hook up your entire house without a transfer switch (also called “double throw switch,” IIRC). I had a dedicated circuit panel and dedicated plug installed in my garage when I bought our generator. It cost about $400 and works like a charm. Spring for it and get it installed by a licensed electrical contractor.
Why would you have to disconnect the neutral? It’s connected to earth ground, usually at multiple locations. I don’t see much danger in keeping the neutral connected.
I agree. However, as long as the generator is not referenced to earth ground, you’d have to touch both hot legs at the same time. (Touching one leg, even if you’re grounded, should not pose much of a risk. As long as the generator is not grounded.) At any rate, I agree there is some danger involved.
Not really. After all, the branch circuit the generator is plugged into has a circuit breaker which won’t allow more current to flow through the wiring than it can tolerate safely. Whether it’s sufficient to run everything that needs to be run is another matter.
Couple things. I believe that your typical residential transfer switch is a three pole switch, hot, hot, and nuetral. You are now operating an optional standby system and you have also created a seperately derived system.
The depths the NEC goes into is more than we shall cover here. Too many variables. However, the neutral must be opened to have a separately derived system and meet all the code requirements.
My only concern is that if you’ve lost the ground at your service for whatever reason, you’ll be using the nuetral up the service drop back to the transformer as the ground. Unlikely but slightly possible. I’ve heard lineman discuss this on job sites before as a potential hazzard. Whether it’s a legit concern or not is open to debate.
I’ve seen services that only have one ground bonding point in the panel and if that wire gets loose, corroded, cut, or disconnected then you’re only left with the nuetral. ?