Portable Backup Generator

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Old 07-27-10, 10:53 AM
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Portable Backup Generator

I'm about to buy a Generac XG8000E portable generator. It's rated at 8,000 watts (33.3a) continuous and 10,000 watts (41.7a) max/surge.

During power outages, I'm looking for an easy(inexpensive) way to use this generator to make my breaker panel live.

My home once had a hot-tub w/ a dedicated 60a 240v circuit in the breaker panel and still has the exterior junction box on the outside of the house. I was considering connecting a power inlet box to the old hot-tub circuit on the outside of the house as a location to plug in the generator. This would supply 240v to my home breaker panel through the old 60a hot-tub breaker. I know of course I'd have to turn off the line power to the breaker panel before connecting the generator and always make sure that both were never allowed to make the panel live at the same time.

I'm pretty certain this is against code, but I can't see any reason it wouln't work. I would be the only person operating the generator and I would never leave this setup if I ever sold the house.

Thoughts?
 
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Old 07-27-10, 11:24 AM
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That would be fine as long as the feed to the hot tub had 4-wires (H-H-N-G) and you use a mechanical interlock in your main panel such as Generator InterLock Kit
Not much to spend to do it right.
 
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Old 07-27-10, 11:26 AM
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Well...Until the Pro's answer...DON'T DO IT! There are some panels that can use an interlock device, where the main breaker HAS to be off before the generator breaker can be on...but some are not approved locally....and many electricians refuse to use them.

A transfer switch is not really that expensive and if your area is prone to outages will be a selling point when you do leave.

That said...you are correct..it probably could be made to work...but it's a really bad bad idea...and illegal.
 
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Old 07-27-10, 11:46 AM
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Yes, the hot tub was HHNG.

Thanks for the info... I wasn't aware such a device as a mechanical interlock existed. That would be a nice idiot proof safety. I would be the only one hooking the generator up and turning it on, but the interlock would make me feel safe if my wife wanted to switch back to city line power to see if the power had come back on yet.

One thing I don't understand about transfer switches is this. Why do they have breakers in them... like a miniature breaker panel? All I want to do is switch back and forth between city and generator power.
 
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Old 07-27-10, 06:22 PM
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Most transfer switches don't have the breaker panels built into them, but Generac makes some for residential use that are easy to install and mostly pre wired. Maybe what you need is a 2 pole double throw switch instead of a Generac transfer switch.
 
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Old 07-27-10, 06:55 PM
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I think you realize already the potential danger....if you or a subsequent owner energized the line leaving your property, that has the potential to kill a lineman working on a line that is supposed to be dead. SO, the requirement for absolutely foolproof interlocks just makes sense, legally and otherwise!
 
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Old 07-28-10, 01:25 AM
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Originally Posted by bajafx4 View Post
One thing I don't understand about transfer switches is this. Why do they have breakers in them... like a miniature breaker panel? All I want to do is switch back and forth between city and generator power.
Transfer SWITCHES do not have circuit breakers but transfer PANELS do. The reason is that the interconnecting wiring must also be protected from short circuits and overloads. A typical transfer panel has a single-pole, double-throw switch for each circuit it can transfer. One side of the switch is fed from the Service panel's branch circuit breaker and the other side of the switch is fed from the branch circuit breaker assigned to the generator output. The circuit itself connects to the center pole of the switch.

In my particular case I have a transfer switch that connects to both my Service panel and a separate "standby" circuit breaker panel. My standby panel is a standard MLO (Main Lugs Only) circuit breaker panel and it has the individual circuits (furnace, TV, Internet and some lighting) that I want to be able to power from my generator. The transfer switch is similar to a double-pole, double-throw switch in that it has the feed from the Service panel to one side of the switch (via a 60 ampere circuit breaker) and the feed from the generator inlet mounted outside my house to the other side of the switch. The standby circuit breaker panel is connected to the center poles of the transfer switch thereby precluding any possibility of the generator power being routed to the utility.
 
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Old 07-31-10, 07:25 AM
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Originally Posted by bajafx4 View Post
II know of course I'd have to turn off the line power to the breaker panel before connecting the generator and always make sure that both were never allowed to make the panel live at the same time.

I'm pretty certain this is against code, but I can't see any reason it wouln't work. I would be the only person operating the generator and I would never leave this setup if I ever sold the house.
Just to make this 100% clear: You have to have a transfer mechanism of you could kill somebody. It's not a question of you making sure, or not letting anyone else operate it... it's if your house catches on fire, are you going to go turn off the generator, or leave it running and maybe kill the emergency responder who is supposed to kill your electricity in order to do their job?

A proper transfer switch setup has to disconnect the mains. Anything less is a potential hazard, no matter how careful you are. It doesn't have to be expensive though... I really like the looks of that interlock kit. Simple and elegant solution, as long as the backfed breaker is in the right physical spot.
 
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Old 07-31-10, 09:37 AM
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It's not a question of you making sure, or not letting anyone else operate it... it's if your house catches on fire, are you going to go turn off the generator, or leave it running and maybe kill the emergency responder who is supposed to kill your electricity in order to do their job?
This is a whole different issue. A transfer switch or generator interlock at the main panel is not the same as a disconnect on the outside of the house.
 
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Old 07-31-10, 09:32 PM
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A few things.. First of all, I am not advocating backfeeding without a transfer switch or interlock AT ALL by saying this, but the idea that your little generator wouldn't instantly trip its breaker as it attempts to power up your entire neighborhood is ridiculous. Even if the breaker didn't trip and magically the windings didn't instantly burn out, the backfed power would not kill any lineman who knows what he is doing. Because any lineman knows that he has to ground any wire he is about to work on. If he gets killed, it was because he didn't follow the standard safety protocol.

That said, a proper transfer DOES NOT have to disconnect the main. In fact, I am not a fan at all of using main breaker interlocks, because you get absolutely no indication of when the power is back on. And as was already mentioned, they are not made for all panels, and they are not a code accepted transfer method.

It is not difficult at all to install a transfer panel, and it is not much more expensive than the interlock kits. A transfer panel comes pre-wired, and installs right next to the breaker box. Each circuit has a double throw center-off switch, and two wires that go to the breaker box. You unhook the desired circuit wire from its breaker, wirenut it to the OUT wire from the transfer panel, then connect the IN wire back to the breaker.



I installed one of these. You can use a power inlet outside the house instead of the inlet right on the front. It comes with a blanking plate if you go this way.

If you're going to do it, do it right.
 

Last edited by JerseyMatt; 07-31-10 at 10:17 PM.
 

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