ordkhntr

Shore power installation question

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I am going to be installing shore power on our boat and am having a hard time finding an answer to one question. Well, actually I have found lots of answers, just not sure which is correct. 

The boat is Ranger 26, has an outboard with an alternator. DC system is what is called ( I think ) floating. One deep cycle battery, small dc breaker panel, nav lights, cabin lights,  instruments, VHF. 

AC will be 30 amp with 2 15 amp circuits, one for a battery charger and one in the cabin for heat and maybe a dehumidifier. 

My question has to do with the grounding of the AC coming on board. Everywhere I have read it says to ground to the inboard engine. We don't have one, just the outboard, and when it's not running it's tilted up out of the water.  The other options I have seen are to ground it to a thru hull (I have 2 brass and 2 instrument thru hulls) or ground it to the main DC ground. Right now my DC is incredibly basic and doesn't have a "main ground".  The third option was to let the AC system float as well (which does not sound correct at all). I don't have Calder's book but I have Casey's book and have also read the ABYC guidelines and can't find which route I should follow. 

Thanks, 

RJ

 

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Common misconception is that a boat is "grounded" like your house thru the water. Bad things happen when the water is part of the circuit so the ground is there to serve as a fault path if something goes wrong. A boat like that will most likely be set up with the AC ground and the DC negative being tied together at ONE point on the boat (often the engine negative terminal or its bus). 

If you have a bonding system, your underwater components are tied together (by a green wire just to confuse things) and that all ties together at a bus as well and ultimately tied to the DC grounding bus. That is to keep all the components at the same electrical potential and not cathodically melt.

AC neutral and AC ground are NEVER tied together on the boat as you would commonly see in a household panel.

Put in a reverse polarity indicator or else you'll need to have double poll breakers on your AC panel.

ELCI is required within 10' of the shore power inlet.

So far I haven't seen someone building pre-made all inclusive panels like what you're specing out.

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2 hours ago, mtn_matt said:

AC neutral and AC ground are NEVER tied together on the boat as you would commonly see in a household panel.

Not really correct. Mains supply via shore power will have earth and neutral bonded to allow a RCD/ELCI's to operate and prevent electrocution particularly say someone in the water in the event of a onboard fault. On board AC generation via say a generator or inverter can either be floating or earth/neutral bonded depending on the equipment.

2 hours ago, mtn_matt said:

If you have a bonding system, your underwater components are tied together (by a green wire just to confuse things) and that all ties together at a bus as well and ultimately tied to the DC grounding bus. That is to keep all the components at the same electrical potential and not cathodically melt.

Highly unlikely this vessel has a bonding system for exposed metallic components below the water line and seldom done anymore on GRP vessels. Alloy materials such as legs, saildrives etc are most at risk. The largest threat of electrolysis is stray DC currents in the water finding their way ashore and completing the circuit is via the AC safety ground. The best way to prevent that is to block that path using either a isolating transformer (expensive) or a decent galvanic isolator (AC safety/ground path ok in the event of a fault,  but blocks small DC currents) located at shore power inlet.

Blue Seas make neat AC/DC panels with breakers, polarity alarms etc.

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The panel I am looking at is a blue sea and it has a main breaker and 3 or 4 separate circuits. It also has a reverse polarity indicator. It's a small boat so it will be easy to place within 10 feet (probably more like 3) of the shore power connection. 

Eta, no bonding system and I will most likely be adding a galvanic isolator.

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25 minutes ago, ordkhntr said:

It's a small boat so it will be easy to place within 10 feet (probably more like 3) of the shore power connection. 

I doubt the board will have provision for a RCBO/ELCI only CB's. It (not the board) should be close to shore power inlet. Put it in a IP rated DIN rail mount enclosure. 

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3 hours ago, jack_sparrow said:

Not really correct. Mains supply via shore power will have earth and neutral bonded to allow a RCD/ELCI's to operate and prevent electrocution particularly say someone in the water in the event of a onboard fault. On board AC generation via say a generator or inverter can either be floating or earth/neutral bonded depending on the equipment.

Agreed... coffee hadn't set in yet. Gensets, inverters and iso transformers each have N-G connections on board.

Highly unlikely this vessel has a bonding system for exposed metallic components below the water line and seldom done anymore on GRP vessels. Alloy materials such as legs, saildrives etc are most at risk. The largest threat of electrolysis is stray DC currents in the water finding their way ashore and completing the circuit is via the AC safety ground. The best way to prevent that is to block that path using either a isolating transformer (expensive) or a decent galvanic isolator (AC safety/ground path ok in the event of a fault,  but blocks small DC currents) located at shore power inlet.

I figured it was a long shot it was bonded, but green wires throw folks off when they see them running all over the boat.

Blue Seas make neat AC/DC panels with breakers, polarity alarms etc.

They definitely have the closest thing to a single SKU electrical system like what ordkhntr wants.

Geesh... just when I thought I could provide something useful. oh well.

There's a reason Al Bundy is my avatar.

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I thought the ELCI was only required on new manufactured boats.  Would an ELCI change how the AC should be grounded on the boat? 

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i've got to add AC to my boat at some time - same reasons.

 

Who's got the schematic so I don't burn the boat down or kill someone?

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5 hours ago, ordkhntr said:

I thought the ELCI was only required on new manufactured boats.  Would an ELCI change how the AC should be grounded on the boat? 

I'm led to believe the US is the only 1st world country that doesn't mandate an RCD/ELCI at the shore point of recreational vessels. Spending $50 to potentially save a life seems pretty good value. And no it doesn't alter either safety or galvanic grounding approach.

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1 hour ago, Raz'r said:

Who's got the schematic so I don't burn the boat down or kill someone

Your local marine electrician who would also like to send his kids to college.

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4 hours ago, jack_sparrow said:

I'm led to believe the US is the only 1st world country that doesn't mandate an RCD/ELCI at the shore point of recreational vessels. Spending $50 to potentially save a life seems pretty good value. And no it doesn't alter either safety or galvanic grounding approach.

Thats a valid point. The ELCI is a bit more than 50 bucks but it's worth it and it's way easier to do it now. 

So back to the original question....if I install the ELCI and then route to a main A.C. breaker panel what is the correct way to run the ground in my situation? 

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^^ Galvanic Isolator goes on shore side of ELCI/GFCI/RCD and Shore Power Breaker combo (to protect wiring between inlet a switchboard) at shore power inlet with ground from Galvanic Isolator to your common AC Ground Bus.

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On 3/13/2018 at 8:53 PM, jack_sparrow said:

I'm led to believe the US is the only 1st world country that doesn't mandate an RCD/ELCI at the shore point of recreational vessels. Spending $50 to potentially save a life seems pretty good value. And no it doesn't alter either safety or galvanic grounding approach.

Under the EU Recreational Craft Directive, an RCD has been required for a long time with good success.

Since USCG has no regs on AC power installations on recreational boats, there's no law that says an ELCI needs to be installed.

ABYC requires one, but they are voluntary standards which are industry adopted with virtually no oversight.

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Hmm... BlueSeas now offers an ELCI main breaker (#3106) to retrofit their existing panels, but it's like, $150.

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We'll be using the Blue Sea System 8101. It has room for more breakers/circuits than we will use but it is a good price and gives us what we'll need. 

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On 17/03/2018 at 10:08 AM, toddster said:

Hmm... BlueSeas now offers an ELCI main breaker (#3106) to retrofit their existing panels, but it's like, $150.

Blue Seas and most marine panel makers only make traditional metal or proprietary panels suitable for front panel mounted breakers and ELCI's. They are a specialist product as opposed to mass produced and cheaper din rail style gear. That and they also being ignition protected (essential on gasoline boats), with appropriate approvals etc makes them expensive. 

A normal commercial ELCI/Breaker in a IP rated enclosure located at the shore power inlet is both cheaper and a better solution compared to mounting it remotely on the main board.

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Well, the main panel, is the nearest place to the inlet with any available volume. The intervening 24 inches may get by without protection. Unless someone were to make a compact inlet fixture or cable with built-in protection.

My marina was recently re-wired with ELCIs on the pedestal circuits.  As I understand it, the plan was to have 30 mA trip-level throughout the marina, identify problem boats, and disconnect them until brought up to snuff.  They have gradually been lowering the trip-level for the last couple of years, but last I heard, were still discovering problems with the marina itself.  Somewhat disturbing since it is a freshwater marina with lots of kids hanging out all summer.  

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Todster that is a worry..salt water you may be lucky, fresh guaranteed not. Why the US doesn't make RCD/ELCI's mandatory for recreational vessels is very puzzeling, particularly with your high fresh water boating population. 

Faulty Galvanic Isolators for those that have them can render Marina pole mount RCD/ELCI's useless. A lightening strike in a marina can produce a lot of those overnight and no one is the wiser.

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For some reason I thought I had seen an ELCI that was built into the boat side inlet by Hubble but now I can't find it. 

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Hubbell makes a blank bezel matching their shore power inlets that accept a northshore safety ELCI. Its a good alternative that gets the ELCI within that 10' requirement, but it involves drilling another hole in the boat.

http://ecatalog.hubbell-wiring.com/press/pdfs/MLD001.pdf

http://www.nssltd.com/pdfs/Layout for marine module cutsheet A.pdf

 

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Our marina was just emergency rewired with ELCI's on pedestals, power was off for a few weeks in the process. On our dock they measured 740 mA, in fresh water, which I gather is very far above the lethal level... and I had been swimming around our boat last summer. The problem was apparently in the marina wiring. 

I have two A/C sub panels on my Blue Seas panel, which I don't fully understand yet.  The boat has a Pathfinder inverter / charger on one panel, the other seems to have just galley and cabin outlets. What I find now is that I can switch on either of the A/C sub panels alone and I'm fine, but if I switch on both together the ELCI on the dock trips.  I haven't really looked at it enough to understand what might be happening. But if anyone has trouble shooting suggestions for where to start I'll enlist my wife, who is the electrical engineer in the family. I do have a galvanic isolator as well. 

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