Association Forum - AC GROUNDS TO ??

Assn Members Area · Join

Home.

Association Forum

Ships Store

Cruising

Racing

Technical Tips

Photo Gallery - New

Boat Search - Updated

Manuals & Brochures

Swap Meet

Links

Officer Flag Line & Staff

Bylaws & Constitution

Members Area

Join the Association

Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.

Association Forum

Username:	Password:
Save Password
Forgot your Password?

All Forums

Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

AC GROUNDS TO ??

New Topic

Topic Locked

Printer Friendly

Author

Topic

kiko
1st Mate

Member Avatar

USA
69 Posts

Initially Posted - 07/17/2015 : 14:36:41

So just finished reading Don Casey's Sailboat Electrics simplified before I rewire the complete AC system.

Question is, in the book, Don explains that you ground system to the motor.

But doesn't mention what to do if it's a trailer sailor with an outboard.

So is ground wired back to the dock?

I.e. hot to hot, neutral to neutral and ground to ground?

thanks!

Wiring this via the original catalina 25 three prong cord inlet, to a blue sea systems AC 30 amp main only circuit breaker panel to a gfci and four outlets.

1979 C-25 SR/SK/Dinette
14' Hobie Cat
Sunfish

Voyager
Master Marine Consultant

Members Avatar

USA
5231 Posts

Response Posted - 07/17/2015 : 20:35:08

Wow! This is a highly charged subject (I could not resist - doh!)
AC power should be isolated completely. Think of it like this: you're running an extension cord from the dock to your microwave oven. For DC power, there's the positive side and the negative side. There's no real "ground" in this system.
And never connect the AC system to the DC system. One place this could happen is through an AC powered battery charging system. That's where galvanic isolation comes in to play.
I think of it, and have wired my boat in that manner, to prevent galvanic corrosion and to prevent "hot" power accidentally being connected to the water in the local marina. This can be one of the most dangerous things you can do. It makes the water, especially in fresh-water marinas, deadly. It'll also eat your prop pretty quickly.
So if you want to "ground" anything - think again.
Oh, yeah - you might want to add a grounding plate to ground your mast for lightning - and ONLY your mast - but that's an entirely different electrifying controversy...

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Edited by - Voyager on 07/17/2015 20:49:09

kiko
1st Mate

Members Avatar

USA
69 Posts

Response Posted - 07/18/2015 : 01:25:32

AC and DC systems are completely seperate. Just wondering if ground can be routed back to shore power with no issues to anyone in the water...

But I will admit, wanting to ac power a WM battery charger.

any advice on this would be helpful.

1979 C-25 SR/SK/Dinette
14' Hobie Cat
Sunfish

Edited by - kiko on 07/18/2015 01:30:59

islander
Master Marine Consultant

Members Avatar

USA
3992 Posts

Response Posted - 07/18/2015 : 06:36:19

quote:
So is ground wired back to the dock?

I.e. hot to hot, neutral to neutral and ground to ground?

For the shore power, yes. The shore power post on the dock is grounded so your AC boat ground goes to it or if you ran an extension cord from your house to the boat AC your house AC has the ground. Your boat has two electrical systems. A 12V and a 120V. They must be kept separate.

Scott-"IMPULSE"87'C25/SR/WK/Din.#5688
Sailing out of Glen Cove,L.I Sound

Edited by - islander on 07/18/2015 06:41:39

kiko
1st Mate

Members Avatar

USA
69 Posts

Response Posted - 07/18/2015 : 22:57:52

thanks for your 'shocking' advice islander :)

Going to research a bit more on the battery charger.

1979 C-25 SR/SK/Dinette
14' Hobie Cat
Sunfish

dmpilc
Master Marine Consultant

Members Avatar

USA
4593 Posts

Response Posted - 07/19/2015 : 16:33:44

We have a new rule at our marina, may be new federal law, NO swimming within 100 yards of the docks!

DavidP
1975 C-22 SK #5459 "Shadowfax" Fleet 52
PO of 1984 C-25 SK/TR #4142 "Recess"
Percy Priest Yacht Club, Hamilton Creek Marina, Nashville, TN

Edited by - dmpilc on 07/19/2015 16:34:15

Stinkpotter
Master Marine Consultant

Members Avatar

Djibouti
9013 Posts

Response Posted - 07/19/2015 : 20:49:29

Good rule--especially in fresh water. There, the body's high salinity makes it a better conductor than the water is, so stray current will tend to go through the body. In salt water, stray current is somewhat less dangerous. I haven't heard of any federal action, but some states are working on requiring inspections and warnings...

To reiterate on AC/DC, neither should be "grounded" directly to an engine. AC is the issue, and at the dock is grounded through the third wire to the shore power outlet. The AC ground wire only carries current when there's a fault somewhere that electrifies the component, which should immediately trigger a Ground Fault Circuit Interrupter (GFCI) at the outlet to cut off the shore power (hot and neutral sides). If you have an inverter to convert DC to AC while not at a dock with shore power, a ground can go to the engine if the drive system is in the water (as with an inboard), but it should be through a specific type of isolator, and should include a GFCI in that line to cut off the inverter in the event of a current.

DC is just positive and negative (no "ground"). Some diagrams and instructions refer to a "common ground" or "ground bus" in the DC system--that's a misnomer for a common negative connection point. It does not go to "true ground"--it goes to the negative side of the battery.

The only relationships between the AC and DC systems should be a battery charger and/or an inverter.

IMHO, an AC system, especially, in a boat should be installed by a licensed marine electrician following ABYC standards. Terrible things happen every year because of amateur installations and modifications--people die in the water, things corrode away, and boats burn.

Curmudgeon out.

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 07/19/2015 21:04:40

Voyager
Master Marine Consultant

Members Avatar

USA
5231 Posts

Response Posted - 07/20/2015 : 09:27:50

Dave
I agree completely with your last statement (and the one before that too...) That goes back to a question from "Kiko": Installing a battery charger. Many folks wire their battery chargers into the AC circuits, and hopefully they connect the "hot" (black), neutral (white) and ground (green) polarities correctly. In line with Dave's advice, its best to get a licensed electrician to do this. Also hopefully, the dock's power is wired correctly. It is not inconceivable that some shore power outlets can be set up wrong. That's why GFCIs onboard or outlet testers are a good idea to have.

Others purchase a plug-in battery charger. Some come with two lead non-polarized plugs, some with polarized plugs and some with three prong grounded plugs.
The first type (probably > 20 years old) will allow connection of the "hot" AC side to DC + or -. This is very bad. These should not be used.
The second type will prevent reversal of hot and neutral in most cases, however some polarized outlets may unintentionally be reversed. This would also be bad.
Three-prong polarized plugs are your best bet for a plug-in battery charger.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Voyager
Master Marine Consultant

Members Avatar

USA
5231 Posts

Response Posted - 07/20/2015 : 09:35:52

DavidP
Last weekend I was at the marina and it was pretty hot. I saw dozens of people diving off their boats into the harbor.
Now, in line with Dave B's comments, this is salty/fresh water - a tidal river - so perhaps the danger is less.
Nonetheless, I'm always concerned when I see people diving around the marina due to stray currents.
But just as bad, it's kinda like playing ball in the street! Harbors are busy traffic-wise and boats are moving in and out.
Accidents can and do happen.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Topic

New Topic

Topic Locked

Printer Friendly

Jump To:

Association Forum

Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.