Robert_in_MS
Member
- Location
- Madison, MS
- Occupation
- Mechanical Engineer
Hi Folks,
I’m in leadership, and have a small boat, at a local marina. We recently had new piers installed and there were issues with the electrical panels and pedestals which first showed up because I was getting a reverse polarity indication (RPL for brevity) in my 1981 vintage trawler. I checked and there was 7.45V between Neutral and Ground when the RPL was on. I then found big problems with the panels and wiring because I do have a good bit of experience with electrical systems and panels, I was a plant engineer at a manufacturing company for years. It was quite a mess, and I was asked to help, so we worked with the same professional electrical engineer to get the drawings revised and same contractor to get everything corrected. I have read thoroughly y’all’s Intro to Article 555 and a detailed article on ABYC Electrical Standard (by Jim? Gilwellbear, Mike is linked in it) which were very helpful in getting everything straightened out. I did search and read thru the forum but could not find enough information to fully help me with my continuing problem.
The system is 120V with 30A Shore Power (and 20A GFCI) receptacles fed from a main panel on land, then some 400 ft to a sub-panel in a boathouse, then to a sub-panel on the pier, then to the International Dock Products pedestals. Both before the redo of the panels and wiring, and now, I’ve confirmed that the 30A receptacles were/are wired properly, so my RPL is not actually reversed polarity in the wiring.
After everything was corrected and working fine for a number of days, last week my RPL came on again which prevents the AC power from operating in the boat. To troubleshoot, using an adapter, I plugged my shore power cable into an extension cord (I know that’s a nono) into the boathouse and found no RPL. Leaving the boat unplugged to talk to folks about what may have changed. I noticed the big boat next to me had their AC running again, evidently, they had an electrician fix something b/c that boat had been tripping their GFCI breaker (there was not a GFCI breaker before the panel was redone, when I got the 7.45V with their AC running). The next day when I plugged back into the pedestal, miraculously no more problem.
I did not have my meter last week so I could not test the voltages. Testing last night, serendipitously, I think I found part of the problem.
- With the AC running on the boat next to me I got:
N-G 5.63 V
L1-N 119.1 V
L1-G 113.8 V
- BUT when the AC turned OFF on the boat next to me I got:
N-G 1.84 V
L1-N 120.6 V
L1-G 118.8 V
I know that the N-G voltage should be zero or certainly less than 1V and I suspect what is tripping my RPL is N-G high voltage (it would be nice to understand why this is). I tried to talk to the EE about this, but he basically blew me off and said 5-7 volts N-G is normal. Well of course it is not, so I need some help determining if there is something amiss with the pier wiring/bonding? and if it that is related to my neighbors AC running causing the N-G voltage to double. I want to get it fixed before somebody potentially gets shocked and have an intelligent conversation with the EE, contractor and boat neighbor. I realize I’m more of an “end user” but given my responsibilities and experience, I hope y’all will indulge in helping me.
Link to 4 photos:
https://www.dropbox.com/scl/fo/vlmu...ey=rjp8lmsua4yrqkr17aovazmq3&st=p4z6b8hs&dl=0
Thanks so much, ROBERT
I’m in leadership, and have a small boat, at a local marina. We recently had new piers installed and there were issues with the electrical panels and pedestals which first showed up because I was getting a reverse polarity indication (RPL for brevity) in my 1981 vintage trawler. I checked and there was 7.45V between Neutral and Ground when the RPL was on. I then found big problems with the panels and wiring because I do have a good bit of experience with electrical systems and panels, I was a plant engineer at a manufacturing company for years. It was quite a mess, and I was asked to help, so we worked with the same professional electrical engineer to get the drawings revised and same contractor to get everything corrected. I have read thoroughly y’all’s Intro to Article 555 and a detailed article on ABYC Electrical Standard (by Jim? Gilwellbear, Mike is linked in it) which were very helpful in getting everything straightened out. I did search and read thru the forum but could not find enough information to fully help me with my continuing problem.
The system is 120V with 30A Shore Power (and 20A GFCI) receptacles fed from a main panel on land, then some 400 ft to a sub-panel in a boathouse, then to a sub-panel on the pier, then to the International Dock Products pedestals. Both before the redo of the panels and wiring, and now, I’ve confirmed that the 30A receptacles were/are wired properly, so my RPL is not actually reversed polarity in the wiring.
After everything was corrected and working fine for a number of days, last week my RPL came on again which prevents the AC power from operating in the boat. To troubleshoot, using an adapter, I plugged my shore power cable into an extension cord (I know that’s a nono) into the boathouse and found no RPL. Leaving the boat unplugged to talk to folks about what may have changed. I noticed the big boat next to me had their AC running again, evidently, they had an electrician fix something b/c that boat had been tripping their GFCI breaker (there was not a GFCI breaker before the panel was redone, when I got the 7.45V with their AC running). The next day when I plugged back into the pedestal, miraculously no more problem.
I did not have my meter last week so I could not test the voltages. Testing last night, serendipitously, I think I found part of the problem.
- With the AC running on the boat next to me I got:
N-G 5.63 V
L1-N 119.1 V
L1-G 113.8 V
- BUT when the AC turned OFF on the boat next to me I got:
N-G 1.84 V
L1-N 120.6 V
L1-G 118.8 V
I know that the N-G voltage should be zero or certainly less than 1V and I suspect what is tripping my RPL is N-G high voltage (it would be nice to understand why this is). I tried to talk to the EE about this, but he basically blew me off and said 5-7 volts N-G is normal. Well of course it is not, so I need some help determining if there is something amiss with the pier wiring/bonding? and if it that is related to my neighbors AC running causing the N-G voltage to double. I want to get it fixed before somebody potentially gets shocked and have an intelligent conversation with the EE, contractor and boat neighbor. I realize I’m more of an “end user” but given my responsibilities and experience, I hope y’all will indulge in helping me.
Link to 4 photos:
https://www.dropbox.com/scl/fo/vlmu...ey=rjp8lmsua4yrqkr17aovazmq3&st=p4z6b8hs&dl=0
Thanks so much, ROBERT
