can utility power jump main power cutoff switch?

as the subject says, have had an interesting discussion that goes something like this.
assume the main power utility line is dead, that is, the local power utility is "down" and your service line is dead.
turn off your house main switch, right next to your utility service meter (also called "the can").
if the power utility turns power back on the line, this energizes the "can" (but keep in mind that the main switch is still OFF), the claim is that despite the main switch being turned off, you can still have 120v (not 240v) leaking through to your breaker panel and if there is a generator feeding power, it can cause a shutdown or worse.
can this be even remotely true?
if not, can the condition occur somehow due to the way the power utility has wired the neutral line connection from the main line to the house?
the main question here is: Does the house remain safe, ie. power off, if the Main switch is Off, even if the main utility line is restored to power?

Tom wrote:

as the subject says, have had an interesting discussion that goes something like this.
assume the main power utility line is dead, that is, the local power utility is "down" and your service line is dead.
turn off your house main switch, right next to your utility service meter (also called "the can").
if the power utility turns power back on the line, this energizes the "can" (but keep in mind that the main switch is still OFF), the claim is that despite the main switch being turned off, you can still have 120v (not 240v) leaking through to your breaker panel and if there is a generator feeding power, it can cause a shutdown or worse.
can this be even remotely true?
if not, can the condition occur somehow due to the way the power utility has wired the neutral line connection from the main line to the house? the main question here is: Does the house remain safe, ie. power off, if the Main switch is Off, even if the main utility line is restored to power?

Of course. With the main switch off, the power stops at the switch and goes no further.
daestrom

On Fri, 4 Jul 2008 22:02:17 +0300, "Tom" wrote:

as the subject says, have had an interesting discussion that goes something like this.
assume the main power utility line is dead, that is, the local power utility is "down" and your service line is dead.
turn off your house main switch, right next to your utility service meter (also called "the can").
if the power utility turns power back on the line, this energizes the "can" (but keep in mind that the main switch is still OFF), the claim is that despite the main switch being turned off, you can still have 120v (not 240v) leaking through to your breaker panel and if there is a generator feeding power, it can cause a shutdown or worse.
can this be even remotely true?

No

if not, can the condition occur somehow due to the way the power utility has wired the neutral line connection from the main line to the house?

No

the main question here is: Does the house remain safe, ie. power off, if the Main switch is Off, even if the main utility line is restored to power?

Yes.
It is remarkable the amount of absolutely idiotic stuff that gets written about utility service, meters and entrance panels. Almost as bad as all that over-unity energy crap.
The main breaker is just a switch with an overload trip capability. No more, no less. The power on the breaker is the same 120/240 volts that goes out to every branch circuit.
The power here in the mountains is so unreliable that one might think that a slow motion flasher was installed somewhere upstream. I spend a good deal of time on generator power.
I do the manual transfer thing, turning the MAIN breaker off and the generator breaker on. The only way that I know when the utility power is back on is when the two neon pilot lights that I installed in my panel ahead of the main breaker come back on.
JOhn
-- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN I like you ... you remind me of me when I was young and stupid.

On Sat, 05 Jul 2008 10:37:34 -0400, hubops wrote:

Of course. With the main switch off, the power stops at the switch and goes no further. daestrom
I wonder if he is talking about the momentary situation - when a phase conductor is re-energized, after a trip, while in contact with the neutral ?

No, this idiocy started a couple of years ago when someone who knew just enough to be dangerous ran his mouth. His allegation was that the utility power could come back 180 deg out of phase with the generator power (true, so far) and that the main breaker could have a differential voltage across it of 480 volts (also true). The idiocy starts with his next claim, that since the main breaker is only "rated for 240 volts", the double voltage could flash over. I mean, after all, "480" is a much larger number than "240", right? Sheesh.
This guy was totally ignorant of what kind of impulse tests such apparatus has to withstand to get the UL and other stamps of approval. I don't recall the exact numbers but the voltage is in the thousands of volts. Dissecting even the cheapest stuff on the market like Murray breakers quickly shows just how much arc/creep distance there is inside.
I thought that we beat this one down pretty well when it made the Usenet rounds but it sounds like this same idiot is now promoting his zany idea in the fora world.
John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN If stupidity hurt then there'd be Aspirin in the salt shakers.

as the subject says, have had an interesting discussion that goes something like this. assume the main power utility line is dead, that is, the local power utility is "down" and your service line is dead. turn off your house main switch, right next to your utility service meter (also called "the can"). if the power utility turns power back on the line, this energizes the "can" (but keep in mind that the main switch is still OFF), the claim is that despite the main switch being turned off, you can still have 120v (not 240v) leaking through to your breaker panel and if there is a generator feeding power, it can cause a shutdown or worse. can this be even remotely true? if not, can the condition occur somehow due to the way the power utility has wired the neutral line connection from the main line to the house? the main question here is: Does the house remain safe, ie. power off, if the Main switch is Off, even if the main utility line is restored to power?

Of course. With the main switch off, the power stops at the switch and goes no further. daestrom

I wonder if he is talking about the momentary situation - when a phase conductor is re-energized, after a trip, while in contact with the neutral ? John T

On Sat, 05 Jul 2008 01:40:30 -0400 Neon John wrote:
| On Sat, 05 Jul 2008 10:37:34 -0400, hubops wrote: | | |>>Of course. With the main switch off, the power stops at the switch and goes |>>no further. |>>daestrom |> |> |> I wonder if he is talking about the momentary situation - |>when a phase conductor is re-energized, after a trip, |>while in contact with the neutral ? | | No, this idiocy started a couple of years ago when someone who knew just | enough to be dangerous ran his mouth. His allegation was that the utility | power could come back 180 deg out of phase with the generator power (true, so | far) and that the main breaker could have a differential voltage across it of | 480 volts (also true). The idiocy starts with his next claim, that since the | main breaker is only "rated for 240 volts", the double voltage could flash | over. I mean, after all, "480" is a much larger number than "240", right? | Sheesh.
That depends on where the flashing is expected to take place. Assuming the neutrals are already connected (e.g. the switch does not disconnect neutral) then as the utility has +240 (x sqrt 2) volts and the generator has -240 (x sqrt 2) volts, there would be a difference of 480 volts (x sqrt 2).
This is assuming a 240 volts relative to ground system (e.g. UK, AU).
| This guy was totally ignorant of what kind of impulse tests such apparatus has | to withstand to get the UL and other stamps of approval. I don't recall the | exact numbers but the voltage is in the thousands of volts. Dissecting even | the cheapest stuff on the market like Murray breakers quickly shows just how | much arc/creep distance there is inside.
Of course the tests already take into account the (x sqrt 2). So a test for 240 volt AC is a test for 340 volts peak. A test for 480 volts AC is a test for 680 volts peak.
It is quite normal for UL tests to test for voltages at least double that for which the device insulation is to be rated, and perhaps well more than that.
| I thought that we beat this one down pretty well when it made the Usenet | rounds but it sounds like this same idiot is now promoting his zany idea in | the fora world.
Sounds like he is wrong. But it is more a social question than a technical question that he is wrong about. If UL had done tests exactly for 240 volts AC (340 volts peak) and no more than that, and the device under test was designed for the minimal capability that would pass, it could be that such a device could fail a little above 240 volts AC.
Fortunately, UL is not so foolish. At least I hope not.
But that begs the question of manufacturing tolerance. If the device is tested at merely a 480 volt AC (680 volt peak) level, variations of say 10% in manufacturing could result in some devices that could break down at 432 volts AC (612 volts peak). Such a device would work to protect a 240 volts circuit under normal circumstances, yet fail when faced with the scenario described wherein 480 volts AC (680 volts peak) is applied to the terminals of the breaker pole.
I just don't know at what level the UL actually tests these breakers, and what aspects the tests apply to. For example, it might test for two times the voltage between conductors and the frame outside the breaker (e.g. the voltage withstand of the breaker casing) and test for four times the voltage between terminals (e.g. the contact gap). UL testing procedure documents are available, but have a high cost, so I have not purchased them. If you really want to know for sure, you will have to part with some coin to see.
I'm far less worried about double voltage jumping across an open breaker contact than I am about the idiots that might close the breaker when the utility linemen are working on the wires. The scenario of double voltage across an open breaker should not be allowed to be possible, regardless of whether the breaker can withstand it or not.
-- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

"Neon John" wrote in message

On Sat, 05 Jul 2008 10:37:34 -0400, hubops wrote:
Of course. With the main switch off, the power stops at the switch and goes no further. daestrom
I wonder if he is talking about the momentary situation - when a phase conductor is re-energized, after a trip, while in contact with the neutral ?
No, this idiocy started a couple of years ago when someone who knew just enough to be dangerous ran his mouth. His allegation was that the utility power could come back 180 deg out of phase with the generator power (true, so far) and that the main breaker could have a differential voltage across it of 480 volts (also true). The idiocy starts with his next claim, that since the main breaker is only "rated for 240 volts", the double voltage could flash over. I mean, after all, "480" is a much larger number than "240", right? Sheesh.
This guy was totally ignorant of what kind of impulse tests such apparatus has to withstand to get the UL and other stamps of approval. I don't recall the exact numbers but the voltage is in the thousands of volts. Dissecting even the cheapest stuff on the market like Murray breakers quickly shows just how much arc/creep distance there is inside.
I thought that we beat this one down pretty well when it made the Usenet rounds but it sounds like this same idiot is now promoting his zany idea in the fora world.

Even the simple light bulb socket that I installed last weekend was rated for a maximum of 600 volts, while the most it will ever see is 125 volts unless lightning hits it.

On 6 Jul 2008 22:51:26 GMT, phil-news-nospam@ipal.net wrote:

It is quite normal for UL tests to test for voltages at least double that for which the device insulation is to be rated, and perhaps well more than that.

<snippity>

UL testing procedure documents are available, but have a high cost, so I have not purchased them. If you really want to know for sure, you will have to part with some coin to see.

So you know what is "quite normal for UL tests to test" and yet you've never actually seen a UL test procedure. Hmmmm. This is the perfect example of one of the more remarkable phenomena on the net - someone writing a wordy article on a topic about which he has absolutely no knowledge. In any other environment, most folks would simply keep the lip zipped, listen and learn.
Here's a suggestion, Phil. Look up what "Basic Impulse Load" (BIL) testing consists of. That'll give you an inkling of just how silly your writing really is. You don't have to buy a UL document to learn all about BIL testing. You can simply go to an instrument company's website like Biddle and download a BIL tester's manual. While you're at it, learn about "Hi-Pot" testing. The same companies that make BIL testers tend to also make Hi-Pot testers so that shouldn't be too challenging for you to learn about both.

I'm far less worried about double voltage jumping across an open breaker contact than I am about the idiots that might close the breaker when the utility linemen are working on the wires.

Damn, did someone just turn on the WayBack machine? I thought we pretty much beat this topic to death just last week.

The scenario of double voltage across an open breaker should not be allowed to be possible, regardless of whether the breaker can withstand it or not.

Really? Quite a few authorities such as UL and the NEC tend to disagree with you. Consider this fully approved gadget
http://www.interlockkit.com/intro2.htm
This is a purely mechanical gadget that prevents the main breaker and the generator input breaker from being closed at the same time. Has all the UL, CSA and other stamps necessary to make even the worst code nazi happy.
Now then. Let's consider what happens when the generator breaker is closed, the main breaker is open, the generator is supplying power to the house and the utility service comes back on. Since small generators rarely to never operate at precisely 60.0 hz (normal spec is 62 to 58 hz from 0 to full load), the phase angle between the utility service and the generator will be constantly rotating. A couple of times a second, plus or minus, the phases will align 180 deg out and there will be, guess what? That's right, double voltage across the main breaker.
How about that? Something that you believe should never be allowed to happen does indeed happen essentially every time one of these interlocks is used. How can that be? Well, one possibility is, again, that you don't know what you're talking about.
Which brings us around to:

|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. |

As if anyone cared?
John


-- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN If we aren't supposed to eat animals, why are they made with meat?

Neon John wrote:

On 6 Jul 2008 22:51:26 GMT, phil-news-nospam@ipal.net wrote:
It is quite normal for UL tests to test for voltages at least double that for which the device insulation is to be rated, and perhaps well more than that.
snippity
UL testing procedure documents are available, but have a high cost, so I have not purchased them. If you really want to know for sure, you will have to part with some coin to see.
So you know what is "quite normal for UL tests to test" and yet you've never actually seen a UL test procedure. Hmmmm. This is the perfect example of one of the more remarkable phenomena on the net - someone writing a wordy article on a topic about which he has absolutely no knowledge. In any other environment, most folks would simply keep the lip zipped, listen and learn.
Here's a suggestion, Phil. Look up what "Basic Impulse Load" (BIL) testing consists of. That'll give you an inkling of just how silly your writing really is. You don't have to buy a UL document to learn all about BIL testing. You can simply go to an instrument company's website like Biddle and download a BIL tester's manual. While you're at it, learn about "Hi-Pot" testing. The same companies that make BIL testers tend to also make Hi-Pot testers so that shouldn't be too challenging for you to learn about both.
I'm far less worried about double voltage jumping across an open breaker contact than I am about the idiots that might close the breaker when the utility linemen are working on the wires.
Damn, did someone just turn on the WayBack machine? I thought we pretty much beat this topic to death just last week.
The scenario of double voltage across an open breaker should not be allowed to be possible, regardless of whether the breaker can withstand it or not.
Really? Quite a few authorities such as UL and the NEC tend to disagree with you. Consider this fully approved gadget
http://www.interlockkit.com/intro2.htm

Interesting device. The closest I've seen to that was a set of locks that threw bolts in front of breakers you should not operate. To make sure you could not operate two breakers in conflicting states, the key would stay captive in each lock depending on whether or not the bolt it threw was or wasn't blocking the circuit breaker paddle.
It may sound complex, but it was just a bunch of panel mount deadbolts attached to the face of the breaker panel, far far cheaper than some weird rotary switch.

"Neon John" wrote in message

Which brings us around to:
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. |

We usually agree John, but this part is not so stupid at all.
Since AOL dropped its Usenet service, all of the idiots seem to have migrated to Google Groups. Far worse, Google insists on accomidating spammers. Sometimes I think that Google is trying to kill the Usenet because it has no way of reliably collecting ad revenue from it. Since Google Mail does such a good job of blocking spam, there is no doubt that Google could do the same to Groups if it served their corporate plan. Since the Google spam seems to come in waves, I may or may not have Google blocked on any given week.
The Google idiots I can put up with, but spammers are the lowest form of sub-human life.
Vaughn

Really? Quite a few authorities such as UL and the NEC tend to disagree with you. Consider this fully approved gadget
http://www.interlockkit.com/intro2.htm

That's kind of neat....looks like a sideways version of the device on Manual Bus Transfer I remember from the Navy. Useful for those that don't know what they are doing.

Vaughn Simon wrote:

Since AOL dropped its Usenet service, all of the idiots seem to have migrated to Google Groups.

You still get the occasional WebTV one, and my, are they crackers !
Graham

On Sun, 6 Jul 2008 20:43:07 -0400 EXT wrote: | | "Neon John" wrote in message | |> On Sat, 05 Jul 2008 10:37:34 -0400, hubops wrote: |> |> |>>>Of course. With the main switch off, the power stops at the switch and |>>>goes |>>>no further. |>>>daestrom |>> |>> |>> I wonder if he is talking about the momentary situation - |>>when a phase conductor is re-energized, after a trip, |>>while in contact with the neutral ? |> |> No, this idiocy started a couple of years ago when someone who knew just |> enough to be dangerous ran his mouth. His allegation was that the utility |> power could come back 180 deg out of phase with the generator power (true, |> so |> far) and that the main breaker could have a differential voltage across it |> of |> 480 volts (also true). The idiocy starts with his next claim, that since |> the |> main breaker is only "rated for 240 volts", the double voltage could flash |> over. I mean, after all, "480" is a much larger number than "240", right? |> Sheesh. |> |> This guy was totally ignorant of what kind of impulse tests such apparatus |> has |> to withstand to get the UL and other stamps of approval. I don't recall |> the |> exact numbers but the voltage is in the thousands of volts. Dissecting |> even |> the cheapest stuff on the market like Murray breakers quickly shows just |> how |> much arc/creep distance there is inside. |> |> I thought that we beat this one down pretty well when it made the Usenet |> rounds but it sounds like this same idiot is now promoting his zany idea |> in |> the fora world. | | Even the simple light bulb socket that I installed last weekend was rated | for a maximum of 600 volts, while the most it will ever see is 125 volts | unless lightning hits it.
Then you could use it for these:
http://www.bulbs.com/eSpec.aspx?ID=11007&Ref=Base&RefId=24
if you could find a source of that right voltage.
-- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |

phil-news-nospam@ipal.net wrote:

On Mon, 07 Jul 2008 00:48:55 -0400 Neon John wrote: | On 6 Jul 2008 22:51:26 GMT, phil-news-nospam@ipal.net wrote: | | |>It is quite normal for UL tests to test for voltages at least double that for |>which the device insulation is to be rated, and perhaps well more than that. | | <snippity | |>UL testing procedure documents |>are available, but have a high cost, so I have not purchased them. If you |>really want to know for sure, you will have to part with some coin to see. | | So you know what is "quite normal for UL tests to test" and yet you've never | actually seen a UL test procedure. Hmmmm. This is the perfect example of one | of the more remarkable phenomena on the net - someone writing a wordy article | on a topic about which he has absolutely no knowledge. In any other | environment, most folks would simply keep the lip zipped, listen and learn.
Why don't you do some analysis, John. Or don't you know how? You could also post some specific facts if you are claiming to have them.
You sound like Matthew L. Martin in disguise. Another persona?
| Here's a suggestion, Phil. Look up what "Basic Impulse Load" (BIL) testing | consists of. That'll give you an inkling of just how silly your writing | really is. You don't have to buy a UL document to learn all about BIL | testing. You can simply go to an instrument company's website like Biddle and | download a BIL tester's manual. While you're at it, learn about "Hi-Pot" | testing. The same companies that make BIL testers tend to also make Hi-Pot | testers so that shouldn't be too challenging for you to learn about both.
I know what BIL is. Did I ever say I didn't? You seem to be jumping to (false) conclusions.
|>The scenario of double voltage |>across an open breaker should not be allowed to be possible, regardless of |>whether the breaker can withstand it or not. | | Really? Quite a few authorities such as UL and the NEC tend to disagree with | you. Consider this fully approved gadget
Then it needs to be specifically RATED at that double voltage ... 480 volts! It needs to SAY that so people know what they are getting.

Where do you keep coming up with 480 volts? Nobody in the US, where UL listed items are key has 240 volts from neutral coming into their home.
Split 240 service is 120 volts to neutral x2. A 240 volt breaker can handle that, even if you have 120 volts from the utility and generator cranking out another 120 volts, out of phase. There's no 480 volts anywhere.

On Mon, 07 Jul 2008 00:48:55 -0400 Neon John wrote: | On 6 Jul 2008 22:51:26 GMT, phil-news-nospam@ipal.net wrote: | | |>It is quite normal for UL tests to test for voltages at least double that for |>which the device insulation is to be rated, and perhaps well more than that. | | <snippity> | |>UL testing procedure documents |>are available, but have a high cost, so I have not purchased them. If you |>really want to know for sure, you will have to part with some coin to see. | | So you know what is "quite normal for UL tests to test" and yet you've never | actually seen a UL test procedure. Hmmmm. This is the perfect example of one | of the more remarkable phenomena on the net - someone writing a wordy article | on a topic about which he has absolutely no knowledge. In any other | environment, most folks would simply keep the lip zipped, listen and learn.
Why don't you do some analysis, John. Or don't you know how? You could also post some specific facts if you are claiming to have them.
You sound like Matthew L. Martin in disguise. Another persona?
| Here's a suggestion, Phil. Look up what "Basic Impulse Load" (BIL) testing | consists of. That'll give you an inkling of just how silly your writing | really is. You don't have to buy a UL document to learn all about BIL | testing. You can simply go to an instrument company's website like Biddle and | download a BIL tester's manual. While you're at it, learn about "Hi-Pot" | testing. The same companies that make BIL testers tend to also make Hi-Pot | testers so that shouldn't be too challenging for you to learn about both.
I know what BIL is. Did I ever say I didn't? You seem to be jumping to (false) conclusions.
|>The scenario of double voltage |>across an open breaker should not be allowed to be possible, regardless of |>whether the breaker can withstand it or not. | | Really? Quite a few authorities such as UL and the NEC tend to disagree with | you. Consider this fully approved gadget
Then it needs to be specifically RATED at that double voltage ... 480 volts! It needs to SAY that so people know what they are getting.
| http://www.interlockkit.com/intro2.htm | | This is a purely mechanical gadget that prevents the main breaker and the | generator input breaker from being closed at the same time. Has all the UL, | CSA and other stamps necessary to make even the worst code nazi happy.
That's fine. So you need to be using that WITH breakers that SAY they are rated to handle that ... and NOT be depending on the testing labeled for a lower voltage.
| Now then. Let's consider what happens when the generator breaker is closed, | the main breaker is open, the generator is supplying power to the house and | the utility service comes back on. Since small generators rarely to never | operate at precisely 60.0 hz (normal spec is 62 to 58 hz from 0 to full load), | the phase angle between the utility service and the generator will be | constantly rotating. A couple of times a second, plus or minus, the phases | will align 180 deg out and there will be, guess what? That's right, double | voltage across the main breaker. | | How about that? Something that you believe should never be allowed to happen | does indeed happen essentially every time one of these interlocks is used. How | can that be? Well, one possibility is, again, that you don't know what you're | talking about.
If you read my post (is your native language something other than English) then you can see that I do actually understand this. I did not describe the scenario where there is constant rotation. I shouldn't need to. I did describe that this double voltage scenario does exist. I did state what the voltage would be. So it must be that you have some reading disability or simply skipped over parts.
You sure do sound just like Matthew L. Martin.
I will stand by my statement that the scenario of 480 volts being applied to the opposing terminals of a breaker specifically rated for 240 volts should NOT be allowed. If the breaker really CAN withstand that voltage and is designed for it, tested for it, and listed for it, then it should have that as a rating. If NEC and/or UL want to say it is OK to have 480 volts applied across a 240 volt breaker, then that's just them being them and missing an opportunity for more safety.
And yes, I do prefer a genuine transfer switch over that of a pair of locked out breakers. That doesn't mean I consider the lockout setup unsafe when properly installed and maintained ... as long as the breakers involved are rated for the use.
BTW, even when the house is on utility power, the same issue can happen across the generator breaker when the generator is fired up for weekly exercise. Now I'm pretty sure you are aware of that. But if I had your attitude, I could go ahead and accuse you of being ignorant about that simply on account of you not having said you are.
| Which brings us around to: | |>|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | |>| by the abuse department, bellsouth.net is blocked. If you post to | |>| Usenet from these places, find another Usenet provider ASAP. | | | As if anyone cared? | | John | | | | | | | -- | John De Armond | See my website for my current email address | http://www.neon-john.com | http://www.johndearmond.com <-- best little blog on the net! | Tellico Plains, Occupied TN | If we aren't supposed to eat animals, why are they made with meat?
Like anyone would ever care.
So there. Back at ya.
-- |WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance | | by the abuse department, bellsouth.net is blocked. If you post to | | Usenet from these places, find another Usenet provider ASAP. | | Phil Howard KA9WGN (email for humans: first name in lower case at ipal.net) |