Backfeed generator through dryer outlet?

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Incredibly stupid discussion. A service transformer steps voltage down from say, 7,200 volts to 240/120 volts. Backfeed 240 volts through the transformer, and 7,200 volts goes back out through the line. Anyone toucing the line can be killed at those voltages with very little current (milliamps in fact). It can and does happen, so stop using your limited knowledge to reach dangerous conclusions.
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JoeSixPack wrote:

Um, it only take milliamps to kill you at 120/240 volts as well. The only difference between 120/240 and 7,200 is amount of insulation required to protect you.
Pete C.
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Exactly right. It only takes milliamps to kill you, but the greater the voltage, the more milliamps are driven through your skin and into your body.
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JoeSixPack wrote:

More milliamps does not equal more dead. Dead is dead and once you're past the threshold the voltage is irrelevant.
Pete C.
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wrote:

The difference is whether you can have an open coffin, closed casket or instant cremation.
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snipped-for-privacy@aol.com wrote:

Indeed, but dead is still dead.
Pete C.
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wrote:

Last outage we had here, we lost a 13.8kv fuse on the main highway. My house and 10 others in the development. Happened during the day, with not many folks home. I'm pretty sure a 5kw generator would have energized the line for more than just a few seconds.
Folks have to remember that the load on the grid segment is highly variable. During the day, a house might only have a hundred watts or so unless the fridge kicks on. Add a thermostat for the furnace and you might have 300 watts (furnace blowers don't connect across the line until you energize the line). So a 5kw generator could conceivably *energize* 10 or more houses. And that would have made 13.8kV on the downstream side of that fuse out by the main highway (some 300 yards away from my neighbor's generator).
Do you *really* want to rely on how many lights the neighbor has switched on? Sure if there is a lot of loads turned on at the moment, your generator would stall out/smoke very quickly. But if all the lights are off (and the TV/computer shut off when the power goes off, so they won't come back on), then a house isn't always the same load and the generator may survive a bit longer.
I remember hurricane Frederick, back in '79. Power was out for weeks to some areas. But when the utility started powering up sub-stations, they would overheat because the long outage had effectively synchronized everyones load demand. Equipment is normally sized based on a certain amount of diversity factor between you and your neighbor's A/C, 'fridge, etc... Leave the power off long enough and when it comes back they *all* want to start at once. Ka-BOOM!!! goes the sub-station.
Predicting the amount of load drawn by a small group of houses can be a bit tricky.
daestrom

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refrigerator and freezer came on at the same time. 10 houses? 2 houses would be extraordinary.
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: : > So a 5kw generator could conceivably *energize* 10 or more houses. : > : Yes, but for the third time, it is 2kw. It tripped once when both the : refrigerator and freezer came on at the same time. 10 houses? 2 houses : would be extraordinary. : : And less than one's enough to kill someone.
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Toller wrote:

So you have some sort of radar/GPS/RFID system to determine the location of lineman?
But lets say you don't and consider other scenerios. Suppose the primary is knocked down (ice storm etc) leaving you on a deenergized segment. So you thoughtfully engergize the secondary and hence the primary (7 Kv in my area) which may be laying on the ground or otherwise accessable.
And my point being you can't possibly know about every condition and scenerio and that is why you install a disconnect so you don't have to.
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No, you thoughtfully throw the main breaker.
Nick
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snipped-for-privacy@ece.villanova.edu wrote:

Apparently, thinking is not a highly held attribute among many posters to this newsgroup.
Here's a simple solution: http://www.aecc.com/be-prepared/standby-generator /
Here is another: http://www.outbackmarine.com.au/MasterPages/TypeDetail/TypeDetail.asp?TypeID )9#74
--
Steve Spence
Dir., Green Trust, http://www.green-trust.org
  Click to see the full signature.
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snipped-for-privacy@ece.villanova.edu wrote:

Yes, thoughfully was tongue in cheek and should have been "thoughtfully".
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George wrote:

Remember the "Always assume a downed power line is live"? Also the main breaker on your service panel *is* a disconnect.
The main thing here is the even if you, Joe Homeowner screw up and backfeed the mains, you have virtually zero chance of killing a lineman directly, only assisting a Darwin award candidate. Every report I've seen of a utility worker "killed by an improperly connected home generator" has shown that it was a perhaps overworked / over tired lineman who got careless and didn't follow procedures.
There are far more reports of utility linemen being killed or injured by other careless actions than by improperly connected generators. One report I read that springs to mind (the lineman survived this one) is where a drunk driver had plowed a pad mount transformer off the pad and tossed it a few hundred feet. The lineman arrived, walked over the the pad and saw that the high voltage cables with the "elbow" connectors looked to be in good shape so he picked one up, grabbed a rag from his pocket and proceeded to wipe some dirt out of the connector. He hadn't checked to see if things were still live and regained consciousness a short while later with the cops paying more attention to him than the drunk driver.
Pete C.
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Exactly! My, and many other's, point! Well said.
It is still advisabe to use transfer switches for generators. Take all the safety precautions you can. The nightmares and the legal fees may not be worth what could happen to you or another human being. Despite the bullshit the Electrical Utilities dish out to the simpleton public.

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Sooo, all that "data" means it's OK to kill someone that way as long as it's just a once in awhile thing, eh? "Snot my fault; he shouldn'ta been workin so tired trying to help all dem peoples!"
: George wrote: : > : > Toller wrote: : > > : > > Bull. In the last 5 years we have had 3 poweroutages where I used my : > > generator. There wasn't a lineman within 5 miles of me on any of them. My : > > 2kw generator is going to power up 80 square miles? Don't think so. : > > : > > : > : > So you have some sort of radar/GPS/RFID system to determine the location : > of lineman? : > : > But lets say you don't and consider other scenerios. Suppose the primary : > is knocked down (ice storm etc) leaving you on a deenergized segment. So : > you thoughtfully engergize the secondary and hence the primary (7 Kv in : > my area) which may be laying on the ground or otherwise accessable. : > : > And my point being you can't possibly know about every condition and : > scenerio and that is why you install a disconnect so you don't have to. : : Remember the "Always assume a downed power line is live"? Also the main : breaker on your service panel *is* a disconnect. : : The main thing here is the even if you, Joe Homeowner screw up and : backfeed the mains, you have virtually zero chance of killing a lineman : directly, only assisting a Darwin award candidate. Every report I've : seen of a utility worker "killed by an improperly connected home : generator" has shown that it was a perhaps overworked / over tired : lineman who got careless and didn't follow procedures. : : There are far more reports of utility linemen being killed or injured by : other careless actions than by improperly connected generators. One : report I read that springs to mind (the lineman survived this one) is : where a drunk driver had plowed a pad mount transformer off the pad and : tossed it a few hundred feet. The lineman arrived, walked over the the : pad and saw that the high voltage cables with the "elbow" connectors : looked to be in good shape so he picked one up, grabbed a rag from his : pocket and proceeded to wipe some dirt out of the connector. He hadn't : checked to see if things were still live and regained consciousness a : short while later with the cops paying more attention to him than the : drunk driver. : : Pete C.
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Oh dear! Whenever this subject comes up, we never fail to get the same fodder from the amateur Internet moralists. Nothing is fail safe, I point my car at hundreds of innocent people every day and there is nothing to keep me from accidentally killing them, save my (very average) driving skills.
Please save the moralizing and stick to the facts.
Vaughn
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Vaughn wrote:

Well, it amazes me that there are so many people that have so many excuses for not properly, and safely, connecting their generators to their electrical systems. They talk about safely using suicide cords, throwing main breakers and other hogwash such as using a sign to remind them to throw the breakers.
The fact that the NEC requires generators to be connected with isolation switches seems to go right over their heads. They apparently think it's ok for them to bypass code requirements because 'they know what they're doing' and neither them, nor someone else trying to use their generator will ever make a mistake! Pretty arrogant attitude if you ask me.
Bottom line - if you're going to use a generator to energize your home do it right! Use an isolation switch! The code requires it for the safety of everyone involved!
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Waldo wrote:

There is nothing improper or unsafe about a temporary generator hookup when done by a competent person. "Throwing the main breaker" is exactly what some approved transfer switches do, they have two very ordinary circuit breakers mounted opposite each other and a link bar between the handles. The only difference between this arrangement and the "turn off the main and back feed the dryer circuit" temporary connection is the link bar.
A competent person switches off and tags the main breaker before they even haul out the generator, double checks it again after turning off the dryer circuit breaker and connecting the "suicide cable", starts the generator and then finally reviews the main breaker once more before turning on the dryer circuit breaker to power the panel.

The NEC requires double throw transfer switches or approved equivalents for permanent generator installations. A temporary hookup of a portable generator in an emergency situation is not within the scope of the NEC. Nothing "arrogant" about not not following code that is not applicable.

It is asinine to claim that you should always install a transfer switch in order to connect a generator, transfer switches only make sense in permanent installations.
Pete C.
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Wow, there's so much bull here it's almost amazing.
.... : : There is nothing improper or unsafe about a temporary generator hookup : when done **by a competent person**. " ===> If that's the basis of your comments, it's silly - these posts aren't about a vague descrition of a "competent" person.
Throwing the main breaker" is exactly : what some approved transfer switches do, ===> No, it is not. They connect to or disconnect power from/to a predetermined path. The main breaker is not "thrown" by the transfer switch.
they have two very ordinary : circuit breakers mounted opposite each other and a link bar between the : handles. The only difference between this arrangement and the "turn off : the main and back feed the dryer circuit" temporary connection is the : link bar. ===> Guess you're making apoint here, but not sure what it is. : : A competent person ===> Meaningless term again. Vague, not useful or meaningful. You mean a licensed electrician or more from the sound of it.
switches off and tags the main breaker before they : even haul out the generator, double checks it again after turning off : the dryer circuit breaker and connecting the "suicide cable", starts the : generator and then finally reviews the main breaker once more before : turning on the dryer circuit breaker to power the panel. ===> Oh, but they don't notify/chase out the neighborhood kids, pets and others? : : > : > The fact that the NEC requires generators to be connected : > with isolation switches seems to go right over their heads. ===> No, I haven't seen much evidence of that. Pooly stated comment and not what I think you meant to say.
: > They apparently think it's ok for them to bypass code : > requirements because 'they know what they're doing' and ===> But, if they "know what they're doing", wouldn't that make them a "competent person"?
: > neither them, nor someone else trying to use their generator : > will ever make a mistake! Pretty arrogant attitude if you : > ask me. ===> Yabut, it sounds just like your attitude earlier in this post. : : The NEC requires double throw transfer switches or approved equivalents : for permanent generator installations.
A temporary hookup of a portable : generator in an emergency situation is not within the scope of the NEC. : Nothing "arrogant" about not not following code that is not applicable. ===> True, but ... there are a couple sections of the NEC you're apparently not familiar with, plus you totally ignore any local codes in that statement. : : > : > Bottom line - if you're going to use a generator to energize : > your home do it right! Use an isolation switch! The code : > requires it for the safety of everyone involved! ===> No, use a Transfer Switch. An "isolation" switch in this context is meaningless. : : It is asinine to claim that you should always install a transfer switch : in order to connect a generator, ===> No, it is assinine to make the ego-centric statements you've made, though. Something tells me you only -think- you are a "competent person". Else you wouldn't try to make most of these statements.
transfer switches only make sense in : permanent installations. ===> No, they make a tremendous amount of sense. They make it easy, quick to do, and about as close to foolproof as you can make the situation. If Mom's the only one home and the pipes are freezing, all she has to do is start the generator by pusing the button, then turn on the power with the transfer switch. We'd be up and running before your "competent" guy even found his cordsets. Our situation isn't quite as neat: Here, you first have to roll the generator out of the garage and over to the porch, about 5 feet from the garage door, and plug it into the house first. Quite a hardship, but ... it's reliable and works.
Ice Storm Survivor Pop
: : Pete C.
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