Thank you for a good episode. I have a Mastervolt isolating transformer in my 40 foot sail boat. I am wondering if I have to worry about reverse polarity.
I have looked around but have not found a 30amp shore power device that goes between the dock pedestal and your shore power cable. This device would be plugged in first to test the circuit before you plug in your boat and also have a 30amp gfci built in so you are not relying on the docks circuit breaker. Some of the docks we have been on, the power pedestals are very old and look very suspect. The dock we are at now only has a plug, no pedestal. Seems like it should be readily available, maybe I just dont know the proper description to search for...
Here's how i test my shorepower connection. First disable all AC breakers, including the double main breaker before connecting shore power. Once shorepower is connected, only turn on the double pole main breaker and make sure that the voltage is adequate and that the reverse polarity light is not illuminated. Once those checks are done, i'll energize the AC breakers.
Oh man, I have had that light on forever at different marinas so the problem is in my boat! Where do you think the problem is most likely to be??? Could this be why my portable honda generator doesn't charge at all when contected??? Help please! 😪😪
Out of no where my AC RP light came on and it hasn’t done this before how do I fix this I am on mooring using my generator and have been for months and now one day all of a sudden it’s on how do I fix this
Might be good to remind viewers from the outset that an AC circuit is not like your boat’s 12V where Red is Always positive and Black is Always negative. Your shore power 120 V reverses 60 times per second so the 120V is pushing both ways. However the Hot rises to 120 above Neutral then instantly reverses to 120 below Neutral. Neutral stays where it is. On a home circuit the neutral is also directly attached to Ground - the green wire. In that situation reversed polarity would immediately blow a fuse or breaker.
Great episode Jeff. Love the show. I was also a network engineer before I retired, so I get a kick out of that little connection. Just one thing to add about reverse polarity. People often get that light when using a "suitcase" generator as those often have a floating neutral. I don't think the suitcase gennys are a good idea on boats but they are popular. I haven't tested them but they are supposed to safe to use that way. What has your experience been in that situation?
Just had a very bizarre incident on my boat whereby a reverse polarity situation occured out of the blue. I only noticed it when one of my appliances tripped. The bizarre thing was that before the marina service guy could check the breakers, the situation resolved itself. Any clues what could cause a temporary reverse polarity situation that resolves itself??!
Sometimes, the reverse polarity light can be dimly visible if the AC ground and AC neutral are not properly connected and you have a small voltage differential (e.g. 5 - 10 volts).
Misinformation in the video: Appliances don't "run backwards" due to reverse polarity. AC is alternating current so it does not matter. DC is a different story.
Hi Jeff, thanks for such an important subject selection. I would like to run some tests in my AC instalation to verify (reasonably) that AC circuits are mostly safe in my boat. Can you suggest at least two or three tests or verifications that should be done? This is something i have been worried about for some time. The shown tester, i have it, at least it did not showed anything wrong in my all outlets… Thanks!!!
Installing and using an ELCI on your boat main AC shorepower connection is a good way to make sure the boat the hot and neutral are well balanced and that very little current is using the AC grounding (green wire in North America).
If I have an outlet wired in reverse will it trigger my reverse polarity light? My reverse polarity light comes on only when I turn on my hot water heater
Not sure if this applies but... I had a situation in an old house once where a 240 volt water heater was causing the neutral to be energized. It turned out, one of the hot legs was disconnected and this caused the electricity to back feed into the neutral.
@@williamSailingWindDragon thanks to the input. This one is 120v on my boa. I reversed the hot and neutral at my panel and no change. Next I'll crawl back and check the heater. It works fine. Just not sure why it makes the light come on.
If you don't know if anything is wired correctly and your doing this yourself get at the very least a non- contact voltage sensor and multi-meter. A plug in socket tester. If your nutral connection is poor it is possible to light the reverse polarity light while using power. All power use off no light, assuming.
My first marina was always a scene on power. Wires in the water from broken conduit. They would 'work' on it till even my batteries and ups would run out. One well house I went into found the metal conduit carrying as the negative, sparks between boxes when it turned on. Wasn't allowed to fix it.
Is this not only a problem if your ac circuit breakers only disconnect one wire, and not both? In europe this practice is highly discouraged. On boats however sometimes amatours does project without enough knowledge. Had it been on a house electric wiring, it's would be against the law not having a certified electrician doing the work. Cheers.
Besides the main AC breaker, which is double-pole, the other AC circuits only need to have a single pole. My understanding that commercial vessels, will have a double pole breaker for all AC circuits. Anyone else can shine some light on this.
@@PacificYachtSystems In Norway only a few regions have TN configuration grid with H and N, most of the national grids is IT net with L1, L2 and Ground (two live wires and ground, no neutral). I recently bought a project boat and freaked out when I discovered single pole breakers on the panel. Panel is gotta go, installing new dual pole breakers with eart fault protection on the main breaker. And the DC system has «room for improvement» too, I have a lot to do. Designing new DC now, I find your web-resources very valuable. Yes, Im an engineer.
Great episode. Love the really informative info. Thanks for helping keeping us all safe. Best electrical channel for boating by far.
Much appreciated!
Always bringing relevant content. Just dealt with this on my bass boat. Thanks Jeff!
Thanks SoCal.
Great info on location for reverse polarity light
Glad it was helpful!
Nice information Jeff, Safety first.
Right on
Thank you for a good episode. I have a Mastervolt isolating transformer in my 40 foot sail boat. I am wondering if I have to worry about reverse polarity.
if it is wired correctly then it will correct the polarity for you. and the light at the panel would never come on.
I have looked around but have not found a 30amp shore power device that goes between the dock pedestal and your shore power cable. This device would be plugged in first to test the circuit before you plug in your boat and also have a 30amp gfci built in so you are not relying on the docks circuit breaker. Some of the docks we have been on, the power pedestals are very old and look very suspect. The dock we are at now only has a plug, no pedestal. Seems like it should be readily available, maybe I just dont know the proper description to search for...
Easy to make, low demand would = overpriced.
Here's how i test my shorepower connection. First disable all AC breakers, including the double main breaker before connecting shore power. Once shorepower is connected, only turn on the double pole main breaker and make sure that the voltage is adequate and that the reverse polarity light is not illuminated. Once those checks are done, i'll energize the AC breakers.
Oh man, I have had that light on forever at different marinas so the problem is in my boat! Where do you think the problem is most likely to be??? Could this be why my portable honda generator doesn't charge at all when contected??? Help please! 😪😪
I would suggest having a electrician come take a look. AC is nothing to play with if you don't understand it.
Out of no where my AC RP light came on and it hasn’t done this before how do I fix this I am on mooring using my generator and have been for months and now one day all of a sudden it’s on how do I fix this
Might be good to remind viewers from the outset that an AC circuit is not like your boat’s 12V where Red is Always positive and Black is Always negative.
Your shore power 120 V reverses 60 times per second so the 120V is pushing both ways. However the Hot rises to 120 above Neutral then instantly reverses to 120 below Neutral. Neutral stays where it is. On a home circuit the neutral is also directly attached to Ground - the green wire.
In that situation reversed polarity would immediately blow a fuse or breaker.
Thanks for sharing Paul, appreciate your input.
Great episode Jeff. Love the show. I was also a network engineer before I retired, so I get a kick out of that little connection. Just one thing to add about reverse polarity. People often get that light when using a "suitcase" generator as those often have a floating neutral. I don't think the suitcase gennys are a good idea on boats but they are popular. I haven't tested them but they are supposed to safe to use that way. What has your experience been in that situation?
We share the same concern, suitcase generators have a floating neutral and general cause the reverse polarity light to get somewhat dimly lit.
Just had a very bizarre incident on my boat whereby a reverse polarity situation occured out of the blue. I only noticed it when one of my appliances tripped. The bizarre thing was that before the marina service guy could check the breakers, the situation resolved itself. Any clues what could cause a temporary reverse polarity situation that resolves itself??!
Sometimes, the reverse polarity light can be dimly visible if the AC ground and AC neutral are not properly connected and you have a small voltage differential (e.g. 5 - 10 volts).
@@PacificYachtSystems Nothing had been connected/disconnected for months!
Misinformation in the video: Appliances don't "run backwards" due to reverse polarity. AC is alternating current so it does not matter.
DC is a different story.
Brushed 'ac-dc' motors can be depends on specific design, diode placement if they use them. An AC designed motor correct no change.
Good point.
can a generator be the cause of rp?
Hi Jeff, thanks for such an important subject selection. I would like to run some tests in my AC instalation to verify (reasonably) that AC circuits are mostly safe in my boat. Can you suggest at least two or three tests or verifications that should be done? This is something i have been worried about for some time. The shown tester, i have it, at least it did not showed anything wrong in my all outlets… Thanks!!!
Installing and using an ELCI on your boat main AC shorepower connection is a good way to make sure the boat the hot and neutral are well balanced and that very little current is using the AC grounding (green wire in North America).
If I have an outlet wired in reverse will it trigger my reverse polarity light? My reverse polarity light comes on only when I turn on my hot water heater
Not sure if this applies but... I had a situation in an old house once where a 240 volt water heater was causing the neutral to be energized. It turned out, one of the hot legs was disconnected and this caused the electricity to back feed into the neutral.
@@williamSailingWindDragon thanks to the input. This one is 120v on my boa. I reversed the hot and neutral at my panel and no change. Next I'll crawl back and check the heater. It works fine. Just not sure why it makes the light come on.
If you don't know if anything is wired correctly and your doing this yourself get at the very least a non- contact voltage sensor and multi-meter. A plug in socket tester.
If your nutral connection is poor it is possible to light the reverse polarity light while using power. All power use off no light, assuming.
@@williamSailingWindDragon 240v water heater should not not be using a nutral. 2 hots and ground. Miswired homes every day.
My first marina was always a scene on power. Wires in the water from broken conduit. They would 'work' on it till even my batteries and ups would run out.
One well house I went into found the metal conduit carrying as the negative, sparks between boxes when it turned on. Wasn't allowed to fix it.
Is this not only a problem if your ac circuit breakers only disconnect one wire, and not both? In europe this practice is highly discouraged. On boats however sometimes amatours does project without enough knowledge. Had it been on a house electric wiring, it's would be against the law not having a certified electrician doing the work. Cheers.
Besides the main AC breaker, which is double-pole, the other AC circuits only need to have a single pole. My understanding that commercial vessels, will have a double pole breaker for all AC circuits. Anyone else can shine some light on this.
@@PacificYachtSystems
In Norway only a few regions have TN configuration grid with H and N, most of the national grids is IT net with L1, L2 and Ground (two live wires and ground, no neutral). I recently bought a project boat and freaked out when I discovered single pole breakers on the panel. Panel is gotta go, installing new dual pole breakers with eart fault protection on the main breaker. And the DC system has «room for improvement» too, I have a lot to do. Designing new DC now, I find your web-resources very valuable. Yes, Im an engineer.
Surely the biggest issue on AC& DC is that the circuit has no fuse protection
Surprisingly happens too often.