GFCI operation question



On top of that, consider open neutral events. How many electricians have been injured or died from miswired milti-wire branch circuits? How many homes have had devices wiped out from open neutral between the transformer and main panel?
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| | |> If you think a neutral wire is safe, then I'll let you be the one to |> try it. Stand barefoot on a wet concrete floor at ground level, and |> lick a bare neutral wire with your tongue :-) I certainly would not |> ever do that. |> | | On top of that, consider open neutral events. | How many electricians have been injured or died from miswired milti-wire | branch circuits? | How many homes have had devices wiped out from open neutral between the | transformer and main panel?
I've seen 2 open neutral events in homes. I lived in one, and we were lucky enough to not lose anything except the evening dinner. My mother thought it was funny that the light over the bar opening would go up and down in brightness as she turned burners on the stove on and changed their setting. I was 14 at the time, but I knew what an open neutral could do and immediately recognized it. Turns out that light had been tapped from the stove circuit, and was the only thing like that. But it got some other wiring issues in the house fixed up in a hurry, like the open split bolt splice hanging on nails on a wooden board that fed the stove. At first I thought that was where the neutral was open. But as it turns out, it was open in the fuse box. But the electrician got it all cleaned up that day, finally. The other even I saw was in a neighbor's house. I never found out where it was caused from, but she did complain to my dad that the clock built in to her stove had quit working and was smoking. We got her disconnected, but she did have to get a new stove as a result.
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ASSuming they are qualified and have a little experience, I would think the answer would be damn few.

Likely, quite a few. It's happen to me. But as far as I could determine I didn't lose anything important. Some of the expensive stuff seems to be pretty resistant to over voltage damage (computer power supplies and electronics) or has thermally protected motors or whatever. Most of the interior lamps are CFs but in any case I didn't find a large numbr of burned out lamps of any type.
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Even among the experienced, there is still the risk of miswired circuits. Even measuring the current before opening the neutral can fail if the load is intermittent, like a water cooler or other thermostatic controlled device.

If it gets anywhere near the full 240V possible, not many consumer electronic devices can take that.
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| If it gets anywhere near the full 240V possible, not many consumer | electronic devices can take that.
OTOH, autoranging switch mode power supplies seem to have no trouble. the just have short switch-on times for the higher voltage, up to the voltage they are rated for breakdown, which for international units is going to be at least 250 volts as found in China. There may even be a chance they can work on 277 volts in the USA (though not officially rated at such because who would ever need to do that).
I have heard that some of the switch mode supplies that have the switch to change between voltages (usually marked as 110/220 or 115/230) are not really change a transformer between series and parallel, but rather are just changing some component values in the circuitry to operate better at the selected voltage (maybe to reduce harmonics or improve the power factor at that voltage).
The more such power supplies we can encourage electronics and appliance manufacturers to use, provided the harmonics and power factor issues are not a problem, the better off we are.
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wrote:

More than one IT equipment manufacterer has started to produce special supplies for China / India. Those supplies will work on US 277 V. Off label, but within specs for most of them. I don't think any of the "special" ratings are published.

Yep, autorangers have no problem. I have used them on 240V or 480V with a control power stepdown to 120V because it gives such a good margin for overvotlage - double input is OK
Autorangers are common on laptops, cell phone chargers, battery chargers, or other devices that may be used internationally. They tend to be in the lower power rated supplies.
120/240 supplies switch the rectifier type depending on input voltge. In the 240V position, they are a full wave rectifier. In the 120V position they are configured as voltage doublers. Either way, the bus voltage is supposed to be around 280V to 350V. In the 120V position, 240V will take them out. Most PC supplies are this type. Some are autoswitching, but a sudden increase from 120V while operating can take them out.
Consumer electronics are often 120V only. This is because their high volume and NA unique requirements (NTSC, ATSC, frequency alocation) make it cost effective to use 120V only supplies. With these also, 240V will wipe them out.
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volume
Quite possible. But if you are just living "normally" when the neutral goes out you end up with some light VERY bright and some very dim.
And, from my experience, the dropped neutral (from the service drop) doesn't take out much (if anything).
Of course, when the service drop neutral goes there is still the earth path between the power company ground (which "around here" is said to be 'zero ohms') and whatever ground that is bonded to neutral in the panel and meter base.
Another thing I had going for me is that I have a metalic connection from my deep well right up through my water tank to the household grounding wires. If you included the water heater ground there is the equivalent of a #10 wire between the well metalics and the panel ground. The negative is that the power company ground is 400' away from my meter box.
More urban folks may not have such a good house ground and urban low voltage distribution may not ground as effective as the rural providers do.
When in comes to a three wire 240/120 load circuit, of course, a lifted neutral might, for example, power a TV set and a toaster. When the neutral goes the TV would likely see no voltage. When someone decides to use the toaster the TV may become toast!

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| 120/240 supplies switch the rectifier type depending on input voltge. In | the 240V position, they are a full wave rectifier. In the 120V position | they are configured as voltage doublers. Either way, the bus voltage is | supposed to be around 280V to 350V. In the 120V position, 240V will take | them out. Most PC supplies are this type. Some are autoswitching, but a | sudden increase from 120V while operating can take them out.
But autoswitching is NOT the same as autoranging, correct?
So the autoswitchers are best switched only from a power coming on state?
Can the autorangers function for any voltage in between 120 and 240?
The impression I got from the designs I saw for a switch mode power supply, which was not really complete info, is that on a higher voltage the time the current flowed was shorter, and for a lower voltage it was longer. But maybe that was just for some brownout handling. I have seem power go completely out for an instant, long enough for the lights to go all the way out and even for clocks to lose time, and yet, my computers stayed up. I guess the capacitors have enough reserve and I'm not loading them up on the DC side too much.
| Consumer electronics are often 120V only. This is because their high volume | and NA unique requirements (NTSC, ATSC, frequency alocation) make it cost | effective to use 120V only supplies. With these also, 240V will wipe them | out.
As long as a single voltage supply has a cost lower than a dual voltage by an amount greater than the savings of having only one type of supply being manufactured and in inventory, then I guess we wil continue to see them, and have damages.
So why are PC supplies pretty much all dual voltage or autoranging? I can see that for laptop external power converters, as they may be used in some other country. But for towers that don't move around much?
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wrote:

Autoswitching and autoranging usually mean the same thing.
Wide range is the term you are looking for.

Wide range can.
One place where autorange or manual switched 120 /240 designs can get into trouble is 208V feed. The supplies that include 90V for Japan are OK. Supplies for 120V or 240V only with a lower limit of 102V/204V get into trouble becuase there is not enough margin on 208V.

Wide range supplies under 90W will have just a straight rectifier on the input. When supplied with 240V, they have a large ride through because the ride through is based on minimum voltage. At 2.5 X the minimum input, the cap has 6.25 times as much energy.
Over 90W, and the supplies have power factor correction. They boost the AC to 380V DC, regardless of input voltage. This makes them invariant of input voltage for ride though time.

One PC design can be shipped to anywhere in the world, with the only change being the power cord, keyboard, manual, software, and shipping carton. The tower doesn't change. So it makes sense to have a power supply that will work anywhere in the world.
Consumer electronics are either NA or ROW because of NTSC,ATSC,PAL,SECAM & frequency allocation. Here the box itself is specific to end user location, so a unique supply is cheaper.
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| wrote: |> |> | 120/240 supplies switch the rectifier type depending on input voltge. |> In |> | the 240V position, they are a full wave rectifier. In the 120V position |> | they are configured as voltage doublers. Either way, the bus voltage is |> | supposed to be around 280V to 350V. In the 120V position, 240V will |> take |> | them out. Most PC supplies are this type. Some are autoswitching, but |> a |> | sudden increase from 120V while operating can take them out. |> |> But autoswitching is NOT the same as autoranging, correct? |> |> So the autoswitchers are best switched only from a power coming on state? | | Autoswitching and autoranging usually mean the same thing. | | Wide range is the term you are looking for.
The specifications of some power supplies say 100-250 volts. So shouldn't that mean they could operate just fine on 150 volts? These say autoranging.
|> Can the autorangers function for any voltage in between 120 and 240? | | Wide range can.
So are the makers like Antec just trying to pull a fast one on people?
| One place where autorange or manual switched 120 /240 designs can get into | trouble is 208V feed. The supplies that include 90V for Japan are OK. | Supplies for 120V or 240V only with a lower limit of 102V/204V get into | trouble becuase there is not enough margin on 208V.
So what is the term to look for on the power supplies to get the right ones? And which manufacturers make them?
How would you select a power supply for a PC if you needed to connect them to a 208 volt power source? I assume if it were a 240 volt power source (e.g. single phase in the USA, L-L) you wouldn't have any trouble.
|> The impression I got from the designs I saw for a switch mode power |> supply, |> which was not really complete info, is that on a higher voltage the time |> the current flowed was shorter, and for a lower voltage it was longer. |> But maybe that was just for some brownout handling. I have seem power go |> completely out for an instant, long enough for the lights to go all the |> way out and even for clocks to lose time, and yet, my computers stayed up. |> I guess the capacitors have enough reserve and I'm not loading them up on |> the DC side too much. | | Wide range supplies under 90W will have just a straight rectifier on the | input. When supplied with 240V, they have a large ride through because the | ride through is based on minimum voltage. At 2.5 X the minimum input, the | cap has 6.25 times as much energy. | | Over 90W, and the supplies have power factor correction. They boost the AC | to 380V DC, regardless of input voltage. This makes them invariant of input | voltage for ride though time.
How do they boost the AC voltage regardless of input? Sounds like a nice trick a lot of things might like to do.
What do you mean by "ride though time"? Does that imply or mean there is a time limit?
|> | Consumer electronics are often 120V only. This is because their high |> volume |> | and NA unique requirements (NTSC, ATSC, frequency alocation) make it |> cost |> | effective to use 120V only supplies. With these also, 240V will wipe |> them |> | out. |> |> As long as a single voltage supply has a cost lower than a dual voltage |> by an amount greater than the savings of having only one type of supply |> being manufactured and in inventory, then I guess we wil continue to see |> them, and have damages. |> |> So why are PC supplies pretty much all dual voltage or autoranging? I can |> see that for laptop external power converters, as they may be used in some |> other country. But for towers that don't move around much? | | One PC design can be shipped to anywhere in the world, with the only change | being the power cord, keyboard, manual, software, and shipping carton. The | tower doesn't change. So it makes sense to have a power supply that will | work anywhere in the world. | | Consumer electronics are either NA or ROW because of NTSC,ATSC,PAL,SECAM & | frequency allocation. Here the box itself is specific to end user location, | so a unique supply is cheaper.
But the power supply is still a component. They either have to stock two different power supplies, or one, at the place where the whole electronics is manufactured. Why is it cheaper to have only one power supply design for computers but not so for TV sets?
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Another term used is universal range - I was grasping for the other term earlier and didn't remember until now.
If it's not speced as 2 descrete ranges, then it's likely wide range / universal range and should work anywhere in the whole range.

I think it may be a case of marketing types writing the spec sheet.

PC's are usually OK. They are designed for 90-140 on the low range and 180-280 on the high range. 180V is plenty of margin on a 208V supply.
The equipment I had trouble with were industrial power supplies.

Look Here: http://focus.ti.com/analog/docs/techdocsabstract.tsp?familyIdf2&abstractName=slua144 http://tinyurl.com/q22gh
TI is trying to sell the chip so it's written towards that aim, but it is one of the better (free) articles on PFC design.

Yep.
Look here:
http://www.powerstandards.com/itic.jpg
That is the current CBEMA standard. It once was 8.3ms. Way to many crashes from dips, so now it's 20ms.

Often the entire product design is a ROW of NA only, so there really isn't a case of two power supplies.
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| Another term used is universal range - I was grasping for the other term | earlier and didn't remember until now. | | If it's not speced as 2 descrete ranges, then it's likely wide range / | universal range and should work anywhere in the whole range.
I've seen them spec'd at "100-250", presumably the lowest (Japan) and highest (China) nominal home/office building distribution voltages. Hopefully there is some undervoltage and overvoltage margin in that.
|> |> Can the autorangers function for any voltage in between 120 and 240? |> | |> | Wide range can. |> |> So are the makers like Antec just trying to pull a fast one on people? | | I think it may be a case of marketing types writing the spec sheet.
Now there's an area where we could use some government intrusion and require some licensing. As it is now we have to depend on land sharks.
|> | One place where autorange or manual switched 120 /240 designs can get |> into |> | trouble is 208V feed. The supplies that include 90V for Japan are OK. |> | Supplies for 120V or 240V only with a lower limit of 102V/204V get into |> | trouble becuase there is not enough margin on 208V. |> |> So what is the term to look for on the power supplies to get the right |> ones? |> And which manufacturers make them? |> |> How would you select a power supply for a PC if you needed to connect them |> to a 208 volt power source? I assume if it were a 240 volt power source |> (e.g. single phase in the USA, L-L) you wouldn't have any trouble. | | PC's are usually OK. They are designed for 90-140 on the low range and | 180-280 on the high range. | 180V is plenty of margin on a 208V supply. | | The equipment I had trouble with were industrial power supplies.
The old "some places have 240 and some places have 208" for single phase supply (and even three phase) is a big annoyance sometimes.
|> How do they boost the AC voltage regardless of input? Sounds like a nice |> trick a lot of things might like to do. | | Look Here: | http://focus.ti.com/analog/docs/techdocsabstract.tsp?familyIdf2&abstractName=slua144 | http://tinyurl.com/q22gh | | TI is trying to sell the chip so it's written towards that aim, but it is | one of the better (free) articles on PFC design.
Could this chip be used to control a device that regulates the AC voltage (AC in, AC out) for a building on the order of 200 amps or more?
|> What do you mean by "ride though time"? Does that imply or mean there is |> a time limit? | | Yep. | | Look here: |
http://www.powerstandards.com/itic.jpg
| | That is the current CBEMA standard. It once was 8.3ms. Way to many crashes | from dips, so now it's 20ms.
OK, 5 cycles to 12 cycles in 60 Hz systems.
I've seen a PC stay up in around 400 to 500 millisecond outage. I saw an old Apple II (circa late 1970's) stay up in a 1.5 second long outage.
|> But the power supply is still a component. They either have to stock two |> different power supplies, or one, at the place where the whole electronics |> is manufactured. Why is it cheaper to have only one power supply design |> for computers but not so for TV sets? |> | | Often the entire product design is a ROW of NA only, so there really isn't a | case of two power supplies.
If the power supplies are built on the same floor as the end product, then I can see that being the case. But if the power supplies are sourced in, then I believe there would be economic advantage to have one model instead of two.
And if we start seeing single DC output voltage designs for PCs in the next generation of PC architecture, I think that will help to bring P/S costs even further down.
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All GFCIs today must detect a NG connection downstream, regardless of whether or not a load is connected. They inject current on BOTH the hot & neutral so things stay balanced with any load, as long as there is no additional return path that bypasses the neutral.
Ben Miller
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Benjamin D. Miller, PE
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wrote:

Uh, I thought the 'current injection' was on the groundED conductor. No need to inject a signal in the ungrounded conductor ('hot') as a fault there will be sensed immediately.
A 'current' signal is injected on the groundED conductor (neutral) so if it is connected to the groundING conductor downstream, the GFCI will trip *immediately*, not just when a load is connected (been there, done that :-(
daestrom
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It is on both hot and neutral, common mode. For N-G detection it is only required on the N as you say, but unless it is also applied to the hot in common mode form, it would also appear across all loads downstream, which would require a much more powerful current source in the first place.
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     snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) writes:

And just to correct myself, it's a voltage source, not a current source. Current only flows when there's a N-G fault.
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Andrew Gabriel

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Yes, the ones I have seen it's nothing more than a toroid core that the 'hot' and 'neutral' pass through, with a few turns of a second 'winding' that is fed from hot and neutral 'upstream' of both this toroid and the sensor one. Perhaps a resistor in series with this 'primary winding', can't remember now. The winding is fed from 'across the line', and the 'output' is a common-mode signal on groundED and ungrounded current carrying conductors.
daestrom
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snipped-for-privacy@ipal.net wrote:

What makes you so certain that a GFCI circuit breaker does not open the neutral? Have you checked with several manufacturers.
One reason why it might be OK for a breaker to leave the neutral alone is that it is far less likely and in fact rather difficult for a breaker to be revere wired. When a breaker type GFCI operates it will nearly always open the ungrounded conductor. There are a lot more ways a receptacle type of GFCI can be supplied with the ungrounded conductor controlled by the grounded conductor leg of the GFCI mechanism.
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Tom Horne

"This alternating current stuff is just a fad. It is much too dangerous
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On Sun, 01 Oct 2006 17:14:18 GMT, "Member, Takoma Park Volunteer Fire

Square D doesn't
http://members.aol.com/gfretwell/gfci.jpg
There is no real need for it in a breaker since you know which leg is hot.
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And it saves a little money. It's looks like the GFCI/CB doesn't have the extra coil that injects the signal to detect a Neutral/Ground cross. Is that true?
EMWTK
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