Pants
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What has been your experience with reverse wiring in AC receptacles?
Does it seem to cause damage to equipment?
Does it seem to cause damage to equipment?
reverse polarity AC....bad?
- Thread starter Pants
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Do you mean swapping live and neutral?
What sort of equipment? Does it have a ground/earth connection?
Generally, no, it won't do any damage, especially not with equipment that is 'double insulated' or that has no ground/earth connection. Such equipment will even happily operate with reversed live and neutral connections, usually without any issues. However, neutral is effectively the same potential as ground/earth of course (unless we're talking about isolated AC), so it could cause damage to some equipment that form ground/earth circuits with the chassis, though that's fairly unusual with modern equipment.
What sort of equipment? Does it have a ground/earth connection?
Generally, no, it won't do any damage, especially not with equipment that is 'double insulated' or that has no ground/earth connection. Such equipment will even happily operate with reversed live and neutral connections, usually without any issues. However, neutral is effectively the same potential as ground/earth of course (unless we're talking about isolated AC), so it could cause damage to some equipment that form ground/earth circuits with the chassis, though that's fairly unusual with modern equipment.
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citizensmith
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??
Doesm't the fuse go in the Live side or am I missing the point here????
Doesm't the fuse go in the Live side or am I missing the point here????
Pants
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yah was talking about swapping the hot and neutral. It sounds like it's not a simple queation to answer. Someone here mentioned something about some brand new systems going bad and it was discovered later that there was reverse wiring.
Pants
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My new battery backup's warranty will be voided if there is damage from being plugged into an ungrounded outlet. I'm sure most if not all UPSes will void the warranty in that case...Anyway, If the battery backup is designed to recognize that the hot wire is the small prong, and the neutral wire is the larger prong (where earth ground is tied to), it will not recognize that there is an earth ground...there will be no green light indicating that there is a ground present and in the event of a surge, the unit and/or attached devices could be damaged.
I know that this wouldn't be direct damage from reversed hot and neutral, but more indirect damage, however. Maybe that's what happened in other scenarios.
I know that this wouldn't be direct damage from reversed hot and neutral, but more indirect damage, however. Maybe that's what happened in other scenarios.
jbartlett323
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No, it does not matter on Alternating Current. The name implies it all, it alternates direction, therefore it runs both ways on both lines, hot and neutral.
Pants, your ground is the third, round pin. Not the neutral. If your ground is tied to neutral you will blow the breaker, as power is going straight to ground.
If ya all remember the electrical devices from the way back, they never had a "large" or "small" plug. Wall worts don't either to this day. This was because it didn't matter which way you plugged in. The only reason it matters is if you have a fuse in-line, you want that on the hot side so as to blow before sending all power to ground, frying anything in its path. And also so people didn't ask this question (literally, that's why in most cases).
So moral of the story, If in the US, don't cut off the round ground pin to flip you plug over, just use it how it was made. If your UPS is not recognizing ground, its very possible your not on a grounded outlet. Remove the outlet and check for 3 wires (white, black, green/copper). If all there, go to your breaker panel and check for them. It is not uncommon to not find the ground in the box, however it should run *someplace*, so find your ground point (it'll be close to the ground, seriously). Its also not uncommon for shady builders to put in 3 wire, connect all wires at the outlet, then not connect ground to anything so that when an inspector checks it looks ok, unless they dig, which they don't usually.
And remember, ALL electronics run on DC power. A PSU converts AC to DC, transforms it to proper voltage, and splits to proper rails. Doesn't give a lick which wall wire is hot or neutral anymore than your wall wort does. The UPS only cares for protection purposes.
Pants, your ground is the third, round pin. Not the neutral. If your ground is tied to neutral you will blow the breaker, as power is going straight to ground.
If ya all remember the electrical devices from the way back, they never had a "large" or "small" plug. Wall worts don't either to this day. This was because it didn't matter which way you plugged in. The only reason it matters is if you have a fuse in-line, you want that on the hot side so as to blow before sending all power to ground, frying anything in its path. And also so people didn't ask this question (literally, that's why in most cases).
So moral of the story, If in the US, don't cut off the round ground pin to flip you plug over, just use it how it was made. If your UPS is not recognizing ground, its very possible your not on a grounded outlet. Remove the outlet and check for 3 wires (white, black, green/copper). If all there, go to your breaker panel and check for them. It is not uncommon to not find the ground in the box, however it should run *someplace*, so find your ground point (it'll be close to the ground, seriously). Its also not uncommon for shady builders to put in 3 wire, connect all wires at the outlet, then not connect ground to anything so that when an inspector checks it looks ok, unless they dig, which they don't usually.
And remember, ALL electronics run on DC power. A PSU converts AC to DC, transforms it to proper voltage, and splits to proper rails. Doesn't give a lick which wall wire is hot or neutral anymore than your wall wort does. The UPS only cares for protection purposes.
Pants
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If ground is not tied to neutral, then is the following article wrong?
http://www.allaboutcircuits.com/vol_1/chpt_3/8.html
Sure looks like it's tied to neutral, to me.
http://www.allaboutcircuits.com/vol_1/chpt_3/8.html
Sure looks like it's tied to neutral, to me.
jbartlett323
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Nope, its perfectly correct! For DC Circuits. You UPS is worried about ground on its AC Circuit...
DC only runs 2 wires, hot and ground. They refer to ground as neutral, which is technically ok, but very confusing.
AC runs 3 wires: Hot (black), Neutral (white), and Ground (green/copper). Neutral is always neutral in an AC Circuit, while ground is not required.
You need to start here: http://www.allaboutcircuits.com/vol_2/chpt_1/1.html
DC only runs 2 wires, hot and ground. They refer to ground as neutral, which is technically ok, but very confusing.
AC runs 3 wires: Hot (black), Neutral (white), and Ground (green/copper). Neutral is always neutral in an AC Circuit, while ground is not required.
You need to start here: http://www.allaboutcircuits.com/vol_2/chpt_1/1.html
Pants
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Here you go: http://hyperphysics.phy-astr.gsu.edu/hbase/electric/hsehld.html
Diagram also illustrates that neutral is tied to ground in household wiring AC
jbartlett323
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Ok, yes, that is one way of tying in the ground. And while it does allow the neutral to be "At ground Potential" it does not ground the neutral wire.
So what are you trying to get at though? Wasn't the question related to if you would damage a UPS by plugging into a non-grounded circuit? Or was the question how to wire a grounded circuit, cause for that I'd recommend an electrician. And the blurb at the bottom of that diagram answers the question of if you can plug in either way:
So what are you trying to get at though? Wasn't the question related to if you would damage a UPS by plugging into a non-grounded circuit? Or was the question how to wire a grounded circuit, cause for that I'd recommend an electrician. And the blurb at the bottom of that diagram answers the question of if you can plug in either way:
Pants
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My reference to the UPS
So what I was getting at is, if the UPS is designed to recognize that hot wire as the small prong, and the neutral wire as the larger prong, it's probably looking for the ground wire on the larger (neutral) prong...and the UPS won't know where to find the ground if the wiring in the AC receptacle is reversed. So, the reversal of the wiring does not directly effect the unit, it's the fact that the unit is designed to see the ground wire on the neutral prong, which it can't find because the wiring is reversed. ...So when it's said that "reverse wiring can damage equipment", which there seems to be some debate about, perhaps it's because the unit cannot find the ground when it's needed.
So what I was getting at is, if the UPS is designed to recognize that hot wire as the small prong, and the neutral wire as the larger prong, it's probably looking for the ground wire on the larger (neutral) prong...and the UPS won't know where to find the ground if the wiring in the AC receptacle is reversed. So, the reversal of the wiring does not directly effect the unit, it's the fact that the unit is designed to see the ground wire on the neutral prong, which it can't find because the wiring is reversed. ...So when it's said that "reverse wiring can damage equipment", which there seems to be some debate about, perhaps it's because the unit cannot find the ground when it's needed.
Pants
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I discovered recently in my house that one of our surge protectors' ground light was not coming on...After a closer look I realized that it was because the wiring was reversed, so I corrected it....Now I got a green light on the surge protector.
Pants
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As a matter of fact, Cyber Power hints to something those lines on their own site about this possible scenario.
http://www.cyberpowersystems.com/support/faqs/faq_surge.html
http://www.cyberpowersystems.com/support/faqs/faq_surge.html
Mercenary Roadie
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Neutral and Ground are bonded at the main panel.
To answer the OPs original question. I depends on the equipment. Reversing phase and neutral can cause damage to equipment and injury to people. A correctly wired receptacle is required to safely operate equipment plugged into it.
The correct answer is to insure that all receptacles are wired correctly to meet Code Requirements. An incorrectly wired receptacle is an accident waiting to happen.
To answer the OPs original question. I depends on the equipment. Reversing phase and neutral can cause damage to equipment and injury to people. A correctly wired receptacle is required to safely operate equipment plugged into it.
The correct answer is to insure that all receptacles are wired correctly to meet Code Requirements. An incorrectly wired receptacle is an accident waiting to happen.
Exactly!
Here's another safety issue to consider when it comes to wiring protocol. Lets say you have to rewire a simple 2 wire table lamp with a switch on the power cord, no ground. The lamp will work whether or not the Hot and Neutral wires are reversed.
But think about this. If the switch is on the Neutral (wrong) wire and its open (light off) the lamp socket is still energized. If someone goes to change the bulb there is the potential to get a shock. I like catching a buzz as much as anyone but not that kind!
If the switch is on the Hot (correct) lead the socket is not energized when switched off. The circuit is broken before the appliance which is what the code wants.
When you strip a length of lamp cord both conductors are usually copper colored. How do you tell which lead is Hot or Neutral? Look close at the wire jacket. One side will be smooth (Hot) and the other will be ribbed (Neutral). On the socket the hot screw will be gold or bronze colored. The neutral screw will be silver or chrome colored.
Pants
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Yikes. I think from now on I'm going to check all the AC outlets at each house we move into, before we use the outlets. I just don't trust the land lords. We lived in another house a couple years ago where the previous tenants rewired a couple of the kitchen outlets to 240. We burned up a toaster and a cordless phone charger using the outlets. Finally I got curious and check them out with a volt meter and realized that outlets were not putting out the correct voltages. Landlords had some electricians come out to fix it, but imagine if your lamp had been plugged into one of those!
LifelineIT
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I don't feel like your question was adequately answered---yes, your UPS (and any "ground tester" circuitry) is testing for continuity between neutral and ground, so yes reversed polarity is going to not have continuity, test will fail (but UPS will still function properly.) I'm not sure about the actual load protection side of the UPS, I'd IMAGINE that both sides are protected because things like lightning strikes will carry voltage down both wires, but I'm not sure about that. In two phase wiring, which is common residential, ground exists as a redundancy to carry shorted load back to earth in a more efficient path than across, say, your body.
Here's a random and uninvited story from my life the other day:
My parents asked me to come install 3 new light fixtures for them. The house is ~110 years old, massive, with ~3 wiring revisions in that time, the most recent being in the probably mid 80's. So I've got knob and tube in some places, cloth wrap in others, and nearly modern romex style in others. So I get two installed and it's no biggie. I'm using my non-contact tester to make sure that in fact some lunatic isn't breaking neutral at the switch before I go jumping into the outlet. I get to light number 3 in their kitchen, which has drop ceiling. If you're not used to a non-contact tester, it's an induction tester looking for the magnetic field generated by live AC, it chirps when you stick it in an outlet or right on energized wire. Awesome and necessary tool. Usually you have to be right up on the energized wire/piece to make it chirp. This time, I get the tester within about 8 inches of the old fixture, and it's chirping. The switch is OFF. So I turn the tester off, reset in a known live outlet, try again. Same result. Same result with switch on. So not only is the thing energized with the switch off, BUT it's seemingly leaking energy all over the place. So I run the tester along the ceiling...the entire kitchen ceiling is making the thing chirp within ~4-5" of the ceiling. What the HELL. So I step back and think about it, and I realize that the fixture itself is positioned on the X of two pieces of drop ceiling grid. Ok...so I'm shorting to grid. That explains why the fixture has been eating lightbulbs probably...but wtf do I do about it? Then I have an idea. I grab my multimeter and test for voltage between the hot side of one of the light sockets and the grid, understanding that the grid is painted and aluminum. I pick up ~2V. I test as far as I can with the meter, same thing, alternating between about .8V and 2V. I call up my buddy who is an EE and explain the situation to him and my suspicion, and he confirms it. Yes, there's an AC short to the grid, but a small one. Because of the nature of the grid though, it's creating a weak but large magnetic field across the whole grid, which is why my tester is freaking the hell out anywhere near the ceiling. I'll kill the breaker and pull the fixture later this week, but what a super unique experience.
Here's a random and uninvited story from my life the other day:
My parents asked me to come install 3 new light fixtures for them. The house is ~110 years old, massive, with ~3 wiring revisions in that time, the most recent being in the probably mid 80's. So I've got knob and tube in some places, cloth wrap in others, and nearly modern romex style in others. So I get two installed and it's no biggie. I'm using my non-contact tester to make sure that in fact some lunatic isn't breaking neutral at the switch before I go jumping into the outlet. I get to light number 3 in their kitchen, which has drop ceiling. If you're not used to a non-contact tester, it's an induction tester looking for the magnetic field generated by live AC, it chirps when you stick it in an outlet or right on energized wire. Awesome and necessary tool. Usually you have to be right up on the energized wire/piece to make it chirp. This time, I get the tester within about 8 inches of the old fixture, and it's chirping. The switch is OFF. So I turn the tester off, reset in a known live outlet, try again. Same result. Same result with switch on. So not only is the thing energized with the switch off, BUT it's seemingly leaking energy all over the place. So I run the tester along the ceiling...the entire kitchen ceiling is making the thing chirp within ~4-5" of the ceiling. What the HELL. So I step back and think about it, and I realize that the fixture itself is positioned on the X of two pieces of drop ceiling grid. Ok...so I'm shorting to grid. That explains why the fixture has been eating lightbulbs probably...but wtf do I do about it? Then I have an idea. I grab my multimeter and test for voltage between the hot side of one of the light sockets and the grid, understanding that the grid is painted and aluminum. I pick up ~2V. I test as far as I can with the meter, same thing, alternating between about .8V and 2V. I call up my buddy who is an EE and explain the situation to him and my suspicion, and he confirms it. Yes, there's an AC short to the grid, but a small one. Because of the nature of the grid though, it's creating a weak but large magnetic field across the whole grid, which is why my tester is freaking the hell out anywhere near the ceiling. I'll kill the breaker and pull the fixture later this week, but what a super unique experience.
