TechTip#74 Shore Power Grounding & Isolation w/Nigel Calder
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- เผยแพร่เมื่อ 18 พ.ย. 2022
- Tech Tip with Nigel Calder!
This was harder and longer than we thought, but we got it done. Check out CruisersCollege.org for the “Quick Reference Guide” and many others. Our goal is to have technicians onboard your vessel that can quickly evaluate the shore power ground for safety and isolation to prevent corrosion. Since most of them don’t do this very often, the reference guides are great for refreshing the testing procedures and keeping us efficient, a must when shop rates are now well over $100/hr with some hitting $150/hr!!
I was editing this on an airplane and didn’t have access to my ABYC standards, the 11.1.1.1. in the video is referring to:
Neutral ground connections at a source of power E-11.5.3.2 Grounded Neutrals
E-11.5.3.3.2 AC grounds connected to DC negative
CruisersCollege.org
Shore Power Grounding Isolation: Quick Reference Guide
cruiserscollege.org/links/
boathowto.com/
Boatowners Mechanical and Electrical Manual 4/E
boathowto.com/books/
Please leave us a comment, we’ll keep producing these videos!
As always, if you or someone you know is interested in the program, check us out!
More information: www.skagit.edu/marinetech
Take a Virtual Tour of our Campus - future technicians wanted, we can train you!
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If you have questions about the program contact:
Michael Beemer
Department Chair
Skagit Valley College
Marine Technology Department
Mike.Beemer@skagit.edu
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This was harder to put together than I thought! But always fun to hang out and problem solve with Nigel. Great material for our technicians & the BoatHowTo students!
Regarding the capacitor required for new galvanic isolators, I presume those are to allow even low voltage AC current from a short to ground a low impedance path back to the shore ground. Is that capacitor as simple as a third branch, in parallel with the two diode branches?
I'm not sure, I think just in parallel. I've chopped up a bunch of old non-compliant units for students, but not one with a capacitor. I'll put it on my to-do list!
I hope you see this. Can you have an isolation transformer and an auto transformer being inverted on a vessel?
Or can you have a vessel powered by dock power with an autotransformer feed by a combination inverter/charger?
Yes, you can have a iso trans on 240 VAC shore, then go to an auto-trans to pickup the neutral for 120V and balancing. Yes on inverter, but a lot of different situations....
Hello guys, I have a Charles model 93 transformer wired with Charles method 1 (isolation). Which Blue Sea SMS ELCI should I get for the secondary? SMS 3120 is two pole only with no polarity sensing. SMS 3119 is three pole with neutral switching and polarity sensing. Old school favors not switching the neutral, especially just after the transformer. I also am concerned about abrupt total open circuit at the secondary. Perhaps it matters “where” the neutral-to-ground is? Can you comment on these concerns and which ELCI might better serve the situation?
Best practice and ABYC is we only break the nuetral on the incoming, before a transformer or main shore power with reverse polarity light. Once we've done that, you only need to break the hots. After your TX you only need a double breaker. ELCI are on the feed side.
Cheers!
Better to use a two pole voltage tester and proving unit to prove ‘dead’, rather than a voltstick
Good thoughts, I'll have to think about this. 2-pole are very reliable!
At minute 8:13, the training tool made from a cardboard box, do you have a schematic on how it is made. This would be a great to use in my Advanced Marine Electrical class.
John, for sure! Where do you teach at? I made the temporary cardboard box last year when students were struggling with this topic. The video was also hard to put together. I think I can give you the plans in 4 sentences, but if you want a drawing or photo of inside, let me know. We are switching to a plastic box with cord grips for the next year knowing it works! Here are the 4 scenarios, I just put them in random order with numbers and the students fill in a lab sheet (part of there lab book).
#1: Wire goes straight through. Shore power, safe, no isolation
#2: Wire passes through, but ground is cut - unsafe!
#3: Wire passes through Hot/Neutral but with a galvanic isolator installed in green wire
#4: Two pieces of wire to simulate transformer not connected at all, the Neutral/Ground connected on the boat side
The box is labeled boat/shore
Hope that helps
I teach at Cape Fear Community College, Advanced Marine Electrical. We are currently using Boatowner's Illustrated Electrical Handbook by Charlie Wing, that was the text that was being used prior to me taking up the class. My goal is to teach by ABYC standards so that the students can have a leg up in getting ABYC certified if they want to. I am working on getting some decent teaching tools that will be easy for the students to understand. Thank you for the description of the box, I showed your video to the class the other day and it seemed to click for some of them, but a hands-on demonstration would be much better.
Informative, any subject matter that educates boaters safety wise can prevent accidents. I would recommend not calling it electrocution, this is a word originally derived from execution better to use electric shock death or accident or in addition electric shock drowning.
Thanks for the notes! We want everyone to know
If I told someone that I'd have to spend 5mins explaining what it meant and another 5+ defending the new term. Why worry about an obscure past of some word that 99.99% of people are unaware of? Do you mention that slave originated from slav and discuss that aspect of the slave trade every time you use the term? How about terms like 'taken aback' or '3 sheets to the wind' - "well, taken aback hearkens back to the days of square rigged vessels and ..." or "well, a sheet is a piece of rope used on a boat to trim the sails and ..." If someone were to object to me using the term I'd make it a point to just avoid them. Who has that kind of time to be a part time politician when engaging in conversation?
shop rates are hitting $240/ hr in some locations
I know - considered taking my tool bag back down the docks! But, it far too rewarding training new technicians
If any of them head to Florida for work I know a few places looking....
I have never before left a negative comment to a you tube video.
However I am very fortunate to have a basic understanding of galvanic isolation and boat electrics safety as I’m afraid that this was a very confusing video.
I would suspect that a script would have reduced this.
To fumble around with various cables and saying that “this should beep” and it didn’t or vice versa really didn’t have the desired effect of passing on critical information.
And, like the court lawyer says, something cannot be unsaid.
If I was a newbie to the subject, by eight minutes in I would have been hopeless confused.
I personally consider Nigel Calder to be an invaluable source of brilliant information and am somewhat disappointed with this offering.
This is intended as positive criticism - I have no desire to be a keyboard warrior and giving grief for the sake of it.
I have enjoyed many other of your videos.
Thanks.
Mark K
Mark - yes, after this I worked on a reference guide. 1 page to make it clearer how to check a shore power connection for safety and isolation. Under resources at my website cruiserscollege.org. We got too much on our plates and hurried a bit.