Reverse Polarity Challenge
- Thread starter tadslc
- Start date
Stu Jackson
C34IA Secretary
Yes, sounds right. Often folks put in three prong receptacles into old two prong boxes to avoid having to find the adapter. Happened to us in our old house, all over the place. Some was old knob & tube wiring!
Going back to my discussion with Dave, he's right (as an electrical engineer he should be!). While the RP light is connected between the neutral and the ground, as he says, the only point I was trying to make, and was done poorly, is that the RP (wired as it is) is actually TELLING you that the hot and neutral are reversed.
Going back to my discussion with Dave, he's right (as an electrical engineer he should be!). While the RP light is connected between the neutral and the ground, as he says, the only point I was trying to make, and was done poorly, is that the RP (wired as it is) is actually TELLING you that the hot and neutral are reversed.
mherrcat
Contributing Partner
I brought my tester down to the boat this weekend and was surprised to find my boat outlets also tested as "open ground." The outlets on the dock box tested the same. So the AC power on the dock is apparently ungrounded as well?How does this affect the AC and DC ground being combined on the boat?
jreddington
Member III
Unplug and Step Away From the Boat and
Get Off the Dock!
Unplug Your Neighbors Too
This is a very serious and dangerous condition.
The neutral and the ground need to be tied together back at the panel (and a common ground) which supplies this pedestal.
Power pedestals on floating docks are "daisy chained" together. Hot, ground, and neutral are wired to th 1st pedestal. Then the 2nd pedestal is wired to the 1st, etc.
If you lose a connection on one pedestal, all the ones downstream of it will lose it too. Lose the hot, and everyone downstream knows it immediately because the power goes out.
Lose the ground connection and it's not so immediately noticeable. Yo u're reverse polarity indicator is showing you have a voltage between neutral and ground which means the neutral is "floating". Heavy loads like A/C will cause this foating voltage to fluctuate. If it is floating high enough to light the reverse polarity indicator, the problem is serious.
Even worse, if it's an open neutral, on a 120/240 circuit, the hot voltages will be floating and you're looking at possible equipment damage or fire.
Notify the marina, IMMEDIATELY to confirm and correct. While it's never a good idea to swim in a marina area with power due to stray currents, it is especially important to keep everyone out of and not touching water until this is corrected. Open the breaker feeding power to this dock. The life or boat you save may be your own.
Get Off the Dock!
Unplug Your Neighbors Too
This is a very serious and dangerous condition.
The neutral and the ground need to be tied together back at the panel (and a common ground) which supplies this pedestal.
Power pedestals on floating docks are "daisy chained" together. Hot, ground, and neutral are wired to th 1st pedestal. Then the 2nd pedestal is wired to the 1st, etc.
If you lose a connection on one pedestal, all the ones downstream of it will lose it too. Lose the hot, and everyone downstream knows it immediately because the power goes out.
Lose the ground connection and it's not so immediately noticeable. Yo u're reverse polarity indicator is showing you have a voltage between neutral and ground which means the neutral is "floating". Heavy loads like A/C will cause this foating voltage to fluctuate. If it is floating high enough to light the reverse polarity indicator, the problem is serious.
Even worse, if it's an open neutral, on a 120/240 circuit, the hot voltages will be floating and you're looking at possible equipment damage or fire.
Notify the marina, IMMEDIATELY to confirm and correct. While it's never a good idea to swim in a marina area with power due to stray currents, it is especially important to keep everyone out of and not touching water until this is corrected. Open the breaker feeding power to this dock. The life or boat you save may be your own.
Electricity and Water
http://www.abycinc.org/lucas_ritz.pdf
Mr. Ritz has conducted marine wiring seminars at our club. Death from "stray current" is very real and also generally underreported.
:0
LB
http://www.abycinc.org/lucas_ritz.pdf
Mr. Ritz has conducted marine wiring seminars at our club. Death from "stray current" is very real and also generally underreported.
:0
LB
jreddington
Member III
Yes, I thought of Kevin, just when I put together what symptoms Mark was describing. I'm on the ABYC Accident Investigation Certification committee and he is putting together the course syllabus. Kevin is an excellent example of someone who has turned a tragedy into an effective pursuit to prevent this from happening to others.
I'm an Electrical Engineer, Fire Investigator, and ABYC Certified Technician. I've investigated fires from open neutrals even in my home port town. I still got caught in the trap of thinking the problem was on the boat.
Mark,
If you are not at the marina, get down there to let them know or give them a call.
My boat has always been on a mooring and I don't think I've plugged in anywhere for over a dozen years. The more I learn about marina systems the less I want to plug in. That is not to disparage well run marinas since dock electrical systems, if designed, installed, monitored, and maintained properly are safe systems. But even a safe system can be compromised both in safety and galvanic protection by a problem on just one boat.
Moral of the story, while traveling, NEVER blindly trust the dock power system. I had not thought of this, but Mark's input makes me think of a new recommendation I'll be making to fellow sailors. Buy one of those relatively inexpensive circuit testers and keep it on the boat. When at a transient marina, test an outlet on the dock before plugging in. Then test one of your on board outlets once you plug in. And keep an eye on that RP indicator. Check frequently at your home marina.
Hopefully, we can get the industry moving to a point where Residual Current Devices (RCDs), essentially whole boat GFCIs, are factory installed on boats by standard, and/or all dock pedestals are built with them. I believe this is the current standard in Australia.
Mark, Let us know what you find.
I'm an Electrical Engineer, Fire Investigator, and ABYC Certified Technician. I've investigated fires from open neutrals even in my home port town. I still got caught in the trap of thinking the problem was on the boat.
Mark,
If you are not at the marina, get down there to let them know or give them a call.
My boat has always been on a mooring and I don't think I've plugged in anywhere for over a dozen years. The more I learn about marina systems the less I want to plug in. That is not to disparage well run marinas since dock electrical systems, if designed, installed, monitored, and maintained properly are safe systems. But even a safe system can be compromised both in safety and galvanic protection by a problem on just one boat.
Moral of the story, while traveling, NEVER blindly trust the dock power system. I had not thought of this, but Mark's input makes me think of a new recommendation I'll be making to fellow sailors. Buy one of those relatively inexpensive circuit testers and keep it on the boat. When at a transient marina, test an outlet on the dock before plugging in. Then test one of your on board outlets once you plug in. And keep an eye on that RP indicator. Check frequently at your home marina.
Hopefully, we can get the industry moving to a point where Residual Current Devices (RCDs), essentially whole boat GFCIs, are factory installed on boats by standard, and/or all dock pedestals are built with them. I believe this is the current standard in Australia.
Mark, Let us know what you find.
Maine Sail
Member III
ELCI's/RCD's are already part of ABYC E-11, as of last July it became effective. Still at the last boat show only about 15% of the builders were following the standards and installing them. Some even proudly displayed the ABYC logo while also ignoring this important advancement in safety...
Reversed polarity.
All, Does a reverse polarity condition mean that one could get un-electrocuted by touching the wires? ; - ) Glyn
All, Does a reverse polarity condition mean that one could get un-electrocuted by touching the wires? ; - ) Glyn
Tom Plummer
Member III
I appears from your posts that plug that you have tested with your tester has an open ground. I would strongly suggest if you haven't already that you test your tester on a known good ckt. before doing anything else.
mherrcat
Contributing Partner
I didn't have my multimeter with me at the boat this weekend but just used it to test the outlets at home on the chance that the hardware store tester might be faulty. It seems it may be. Here are the results:
Hot+Gnd = 120+ volts
Hot+Neutral = 120+ volts
Neutral+Gnd = 0 volts
This is as it should be, correct? If the ground were "open" I should get 0 volts from hot to ground, correct?
Vagabond39
Member III
Open Neutral
Mark, that is correct.
Several areas of the country have had thieves, cutting and removing the Neutral wire from power lines, to sell as scrap for the copper. As long as all the laods are balanced no problem, If one side draws more load than the other, its voltage drops, and the light load gets excessive voltage.
The use of a tester and a voltmeter is necessary.
Mark, that is correct.
Several areas of the country have had thieves, cutting and removing the Neutral wire from power lines, to sell as scrap for the copper. As long as all the laods are balanced no problem, If one side draws more load than the other, its voltage drops, and the light load gets excessive voltage.
The use of a tester and a voltmeter is necessary.
Tom Plummer
Member III
I think you need to take the tester back it appears to be faulty.
I agree with Tom. The tester is probably bad. The testers with 3 indicators are relatively simple.
The Red indicator is connected between Ground and Neutral. It lights when there a is voltage difference between them, typically a reverse polarity condition.
One of the remaining two is connected between Hot and Neutral. Under normal conditions, with the hot at 120V and Neutral at 0V, it should be lit. When the Hot or Neutral is open, this indicator is off.
The other remaining indicator is connected between Hot and Ground. Under normal conditions, with the hot at 120V and Ground at 0V, it should be lit.
When the Hot or Ground is open, this indicator is off.
Since you measure 120 v between Hot and Ground (with a multimeter),and also between Hot and Neutral, both indicators should be lit. And since a multimeter trumps a cheap tester, The Hot-Ground Indicator on the tester is probably bad.
Dave
The Red indicator is connected between Ground and Neutral. It lights when there a is voltage difference between them, typically a reverse polarity condition.
One of the remaining two is connected between Hot and Neutral. Under normal conditions, with the hot at 120V and Neutral at 0V, it should be lit. When the Hot or Neutral is open, this indicator is off.
The other remaining indicator is connected between Hot and Ground. Under normal conditions, with the hot at 120V and Ground at 0V, it should be lit.
When the Hot or Ground is open, this indicator is off.
Since you measure 120 v between Hot and Ground (with a multimeter),and also between Hot and Neutral, both indicators should be lit. And since a multimeter trumps a cheap tester, The Hot-Ground Indicator on the tester is probably bad.
Dave