Cruisers Forum
 


Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on Cruisers Forums. Advertise Here
 
Thread Tools Search this Thread Rate Thread Display Modes
Old 20-12-2018, 10:52   #1
Registered User

Join Date: Jul 2015
Location: cape coral
Boat: Pearson 424
Posts: 109
grounding thu hull fittings . ??

ive been reading alot about grounding. some books reccomend putting a ground wire on . all the thru hulls and some say do not ground them . whats the best advice . ??
shadowdancer is offline   Reply With Quote
Old 20-12-2018, 11:06   #2
Registered User

Join Date: May 2014
Location: USA
Boat: 41' yawl
Posts: 1,187
Re: grounding thu hull fittings . ??

Through-hulls are already "grounded" in that they are sitting in seawater.

I think a lot of folks "bond" their through-hulls (wire them all together, and also to a submerged zinc) to help with corrosion prevention.

The only problem with this is if you are at a marina, docked, and there's a problem with the wiring somewhere causing some current to go through the water (apparently not uncommon, and another good reason to avoid swimming off a marina dock) that current might run through your boat, in one throughhull, along the bonding wiring, and out the other, and apparently cause rapid and dangerous corrosion to the throughhulls.

My boat's through hulls are all bonded to a big, submerged zinc plate. It was that way when I bought the boat, and I keep her on a mooring far from those stray currents, so I'm comfortable with it. Not sure how necessary it is since they are all beefy and bronze, it's likely an unnecessary complexity.
chris95040 is offline   Reply With Quote
Old 20-12-2018, 11:32   #3
Registered User

Join Date: Jul 2014
Location: Crete , Greece
Boat: Beneteau first 26
Posts: 670
Re: grounding thu hull fittings . ??

Mine are not grounded, never had an issue the boat is from.1984 , and the other boat from.1979 .
gmakhs is offline   Reply With Quote
Old 20-12-2018, 11:48   #4
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,429
Images: 22
Re: grounding thu hull fittings . ??

Seems to an American thing. I only have the rudder shaft and P bracket bonded to the hull anode. Prop shaft has its own anode. All seacocks are independent of any bonding.

Pete
Pete7 is offline   Reply With Quote
Old 20-12-2018, 18:30   #5
Registered User
 
Orion Jim's Avatar

Join Date: Dec 2008
Location: Noank, Ct. USA
Boat: Cape Dory 31
Posts: 3,170
Images: 8
Re: grounding thu hull fittings . ??

My seacocks/thru hulls, stern tube, and engine block were all bonded to a sintered bronze ground plate by the manufacturer when my boat was built in 1984.
They also provided lightning protection per ABYC specifications. This included bonding the mast, mast step, stays, shrouds, engine, fuel tank, and fuel filler cap to a sintered bronze plate.
I can’t prove that they work but I can attest that this boat has certainly not suffered any adverse effects in the 34 years since the bonding system was installed.
Orion Jim is offline   Reply With Quote
Old 21-12-2018, 09:29   #6
Registered User
 
Smokeys Kitchen's Avatar

Join Date: Aug 2015
Location: Back in Mexico cruising the northern part of Sea of Cortez
Boat: 1999 Pacific Seacraft 40
Posts: 716
Re: grounding thu hull fittings . ??

My thru hulls are not bonded. I believe that was/is a design decision by the particular manufacturer - in this case Pacific Seacraft
Smokeys Kitchen is offline   Reply With Quote
Old 21-12-2018, 09:45   #7
Registered User

Join Date: Oct 2018
Posts: 571
Re: grounding thu hull fittings . ??

Replaced last 4 original thru hulls last year.
45 years old, not bonded.
All were solid and negligible corrosion present.
From those facts I can't think of a reason to bond any of my thru hulls......but that's just how my thought process works.
Allied39 is offline   Reply With Quote
Old 21-12-2018, 10:11   #8
Registered User

Join Date: Oct 2015
Location: Minnesota / Florida
Boat: Westerly Fulmar 32
Posts: 475
Re: grounding thu hull fittings . ??

i'm glad this thread started this subject has been bothering me for a while, my 'new to me' boat has zinc's on the prop shaft only. the shaft was isolated from the engine by the rubber doughnut that attaches it to the engine. so basically nothing was grounded / bonded. my plan is to add a zinc to the iron keel and bond the through hulls to it, and connect the prop to the engine with a ground strap. the boat was kept on a mooring most of its life but the previous owner did say that he had problems keeping the paint on the keel... boat is 1983 vintage. i currently have no intention of using shore power but that could change.

Regards Steven
Steven UK is offline   Reply With Quote
Old 21-12-2018, 10:15   #9
Registered User

Join Date: Nov 2009
Location: State of Washington
Boat: Tayana 37 Pilot House
Posts: 153
Re: grounding thu hull fittings . ??

Chris makes a good point of stray currents in a marina causing accelerated corrosion of thru-hull fittings/seacocks that are bonded to the vessels bonding system via a grounding plate. To add to this problem, when bonding these underwater parts together, they become a potential path for a lightening strike to turn them into underwater torpedoes, allowing the vessel to sink. This is also more than a theoretical possibility for the grounding plate as well, as many have been blown off or loosened from the hull during lightening strikes.



Having thru-hull fittings & seacocks made from silicon bronze, the ball valve which is made from a ss alloy and is the only part subject to rust, but most of these seem to hold up pretty well for up to about twenty years or so. If one chooses not to bond and were to expend the extra cash for the Groco in-field serviceable type of seacock and carry a spare kit for the replaceable seals and ball, then one has all the bases covered. Also, the non-conductive Marelon fittings & seacocks are an option, though they ought to be opened & closed periodically, because when the valve body gets crusted and frozen from disuse, at least to me, its molded-on valve stem seems to be vulnerable to breaking from any excessive torque needed to open it.



I think most if not all marine surveyors now see the thru-hull/seacock, to bond vs. not to bond, as an informed personal choice. But, in lightening strike prone areas such as Florida, I would hope they would warn the owner not to bond. I am in a slip in a marina that is not known for excessive electrical field stray currents or lightening strikes. Still, I have removed all of my thru-hull bonding wires.
Taipe is offline   Reply With Quote
Old 21-12-2018, 12:11   #10
Registered User

Join Date: Sep 2017
Location: Langley, WA
Boat: Nordic 44
Posts: 2,501
Re: grounding thu hull fittings . ??

Go with plastic through hulls and seacocks. Eliminate all potential electrolysis.
stormalong is offline   Reply With Quote
Old 21-12-2018, 12:23   #11
Moderator
 
Pete7's Avatar

Cruisers Forum Supporter

Join Date: Aug 2009
Location: Solent, England
Boat: Moody 31
Posts: 18,429
Images: 22
Re: grounding thu hull fittings . ??

Quote:
Originally Posted by Steven UK View Post
i'm glad this thread started this subject has been bothering me for a while, my 'new to me' boat has zinc's on the prop shaft only. the shaft was isolated from the engine by the rubber doughnut that attaches it to the engine. so basically nothing was grounded / bonded. my plan is to add a zinc to the iron keel and bond the through hulls to it, and connect the prop to the engine with a ground strap. Regards Steven
Steven, you might be creating a problem that doesn't currently exist. I have two cast iron keels, they rust. Each year I grind the small rust spots, slap on some rust killer followed with Primocon, then antifoul paint. Finally go sailing

As Taipe said, bonding all together creates a path for those stray amps.

Quote:
Originally Posted by stormalong View Post
Go with plastic through hulls and seacocks. Eliminate all potential electrolysis.
Indeed, we did the heads seacocks this summer and will work our way around the others bit by bit.
Pete7 is offline   Reply With Quote
Old 21-12-2018, 13:30   #12
Registered User

Join Date: Jul 2014
Location: Crete , Greece
Boat: Beneteau first 26
Posts: 670
Re: grounding thu hull fittings . ??

Quote:
Originally Posted by Pete7 View Post
Steven, you might be creating a problem that doesn't currently exist. I have two cast iron keels, they rust. Each year I grind the small rust spots, slap on some rust killer followed with Primocon, then antifoul paint. Finally go sailing

As Taipe said, bonding all together creates a path for those stray amps.



Indeed, we did the heads seacocks this summer and will work our way around the others bit by bit.
My keel is covered with iron putty , no rust spots every year
gmakhs is offline   Reply With Quote
Old 21-12-2018, 14:28   #13
Registered User
 
CarinaPDX's Avatar

Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,270
Re: grounding thu hull fittings . ??

I am a bit surprised that no one here has yet grasped what bonding is about. Bonding the thru-hulls and other underwater metal is done to protect against an electrical short of the hot "line" causing a dangerous electrical field in the water (especially fresh water). This is important in the US because the "neutral" current-carrying wire is attached to ground (at the transformer) so leakage from the "line" wire is a shock hazard to any ground. (With bonding a short is likely to trip the breaker, or at least provide a safe path.) Elsewhere both current-carrying wires are floated so a leak from one does not find a return path to the other through ground; the standards differ with country. This is thus a safety issue; people die in the U.S. every year from ESD (electro-shock drowning) which usually could have been prevented with bonding.

Leaving each thru-hull isolated is the best way to avoid galvanic corrosion; as soon as they are bonded together a sacrificial zinc should be attached to protect against dissimilar metals causing loss of the least noble (in seawater). Stray currents are a different problem, and again are eliminated if the thru-hulls are isolated; stray current corrosion is an effect of DC currents, not AC. Boats should have either isolators or isolation transformers on the AC inlet to protect against these DC problems.

The bottom line is that isolating the thru-hulls would be the best way to protect against loss of metal if safety were not an issue - but it is: life is more valuable than your boat! Once bonded a zinc will be necessary to protect against loss of metal. Also an isolator, or especially an isolation transformer, will further reduce the potential for metal loss. The iso transformer also has safety benefits.

Greg
CarinaPDX is offline   Reply With Quote
Old 21-12-2018, 16:29   #14
Registered User

Join Date: Jun 2015
Location: New Zealand
Boat: Custom sailing catamaran
Posts: 183
Re: grounding thu hull fittings . ??

Quote:
Originally Posted by shadowdancer View Post
ive been reading alot about grounding. some books reccomend putting a ground wire on . all the thru hulls and some say do not ground them . whats the best advice . ??

Article on this in Wooden boat some time ago, from a very experienced yacht surveyor.


In wooden hulls the current from bonding skin fittings seriously degraded the timber around them, while having little effect on how long bronze alloy fittings, last. You see the same effect on iron or steel fastened, "nail sick" hulls.

Cannot really comment on US, electric system specs. However if a fitting is not connected to the electrical ground, it cannot become part of the mains circuit, when a power supply shorts to ground.
KJThomas is offline   Reply With Quote
Old 21-12-2018, 16:53   #15
Registered User
 
CarinaPDX's Avatar

Join Date: Jan 2010
Location: Portland, Oregon, USA
Boat: 31' Cape George Cutter
Posts: 3,270
Re: grounding thu hull fittings . ??

Quote:
Originally Posted by KJThomas View Post
However if a fitting is not connected to the electrical ground, it cannot become part of the mains circuit, when a power supply shorts to ground.
Not really correct, if the neutral is connected to ground at the transformer (i.e. not floating). If there is a short from the hot "line" lead to a thru-hull or underwater fitting it can make its way back through seawater and earth to the neutral ground at the transformer. With fresh water the potential (voltage) across the water can drive lethal current through a body in the water, because the salt in the body makes it a better conductor than fresh water and hence the preferred path.

Returns of current back to the transformer outside of the neutral wire are "leakage currents". This is why we use GFCIs in outlets to detect that some current is returning outside of the neutral wire. Whole boat ELCIs (RCDs), now required by ABYC, do the same thing.

One advantage of an isolation transformer is that it can be used to float the AC electrical system, although this is a violation of the ABYC standards. The only way to get shocked then is if there is a path on or near the boat from its "line" to its "neutral", much less likely.

I recommend buying an iso transformer with dual voltage for world cruising. In addition to the safety and metal loss issues it can convert from the local voltage, to say 120VAC, if needed.

Greg
CarinaPDX is offline   Reply With Quote
Reply

Tags
hull

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
through hull grounding point on Lancer 45 spav350 Electrical: Batteries, Generators & Solar 0 26-05-2017 07:06
DC Negative Grounding to grounding plate - Isolated shaft Thistle1969 Electrical: Batteries, Generators & Solar 17 27-09-2015 04:51
SSB grounding on a steel hull nofacey Marine Electronics 18 06-04-2014 17:04
Hull/Rigging Grounding Plates... Christian Van H Construction, Maintenance & Refit 4 30-04-2011 19:14
Grounding IC802 to Steel Hull Okiwi Marine Electronics 2 30-12-2009 16:01

Advertise Here


All times are GMT -7. The time now is 08:08.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.