To Ground or not to Ground. That is the question?

[K1MGY]

In this thread https://www.cruisersforum.com/forums...mg-279906.html you will read about my keel bolt adventure. My question is relevant here - it has to do with grounding. No, not the kind you run into when not paying attention - I mean grounding of the electrical kind.

Now that the keel bolts are installed (we removed all the ground leads) I feel it's important to connect up, and improve, the grounds to the bolts. I do not know if these ground connections meet boating/electrical standards, so I am starting over.

I confess electrical engineering as my latter profession, however my work was in development of Radon and Thoron measurement instrumentation, not the rough and tumble world of boats.

As I have gathered, it's important to provide a path to "ground" (parenthetical here as we can get into "what is ground?"), where ground may be best described in two nodes (1) the massive metal keel and (2) the engine. As I gather (and please correct me), the engine is the common DC node and the keel is a subsidiary node that provides a best path from the mast to the water. My Hunter 42 Passage of 1993 vintage is a deck-stepped mast system.

So the first thing I intend to do is improve the ground lead from the base of the compression post to the keel bolt ground connections. Good idea?

The next task is to connect the keel bolt "ground" to the engine DC ground (the body of the auxiliary engine, with "ground" extending out the shaft to the prop in the water. As she was on the hard for 2 weeks, we placed two sacrificial zincs on the propeller shaft, so all set there.

However, is my connection from keel bolts to engine "ground" the right move?

And what of AC ground?

I did a few measurements and found a 137 mA current between the keel and DC ground. This circuit shows 0.5v DC. On the AC side, I see about 8 mA in the same circuit.

There is a ground isolator installed between the AC mains inputs (there are two inputs, at 30A each) and the boat AC ground. I don't yet know if the AC and DC grounds are tied together or whether the isolator serves both AC buses. The AC supply here at my marina is substandard at best.. another concern.

Those with knowledge and well grounded wisdom? Please suggest a good approach here.

With thanks!!

[wholybee]

It might be good to try and find the ABYC standards appropriate to grounding and bonding. Especially if you have some electrical education and experience behind you to actually understand what they are talking about. You can join ABYC and get a free 2 weeks membership and access and download the documents, then just don't continue the membership.

Take advice you get here with caution, there is as much misinformation as there is good information, and that is especially true of this topic. It is complex. On boats you have DC ground, AC ground, AC neutral, possibly bonding(which is what your keel is probably part of), possibly lightning protection grounding(which your keel might be part of), and cathodic protection, and if you have SSB also an RF ground. These systems should not be arbitrarily connected together, even though loosely speaking they are all "ground."

[SailingHarmonie]

Originally Posted by wholybee

Take advice you get here with caution, there is as much misinformation as there is good information, and that is especially true of this topic. It is complex. On boats you have DC ground, AC ground, AC neutral, possibly bonding(which is what your keel is probably part of), possibly lightning protection grounding(which your keel might be part of), and cathodic protection, and if you have SSB also an RF ground. These systems should not be arbitrarily connected together, even though loosely speaking they are all "ground."

I can't agree more. Go to places with vetted information. Random strangers do NOT understand the various grounding issues on a boat. I KNOW there are a FEW people on here who do, but they tend to be drowned out by the people who do not know what they do not know, and more importantly, don't want to learn.

And seriously, on such a complex and involved issue expecting someone to write out the chapter length answer needed to explain it is more than a bit unrealistic.

Start with Caldor's book: Boatowners Mechanical and Electrical Manual Read it, and if you have specific questions after that (you shouldn't) come back.

[Bowdrie]

Originally Posted by K1MGY

So the first thing I intend to do is improve the ground lead from the base of the compression post to the keel bolt ground connections. Good idea?

The next task is to connect the keel bolt "ground" to the engine DC ground (the body of the auxiliary engine, with "ground" extending out the shaft to the prop in the water.

However, is my connection from keel bolts to engine "ground" the right move?

Compression post to keel bolt is a reasonable first step to provide some protection from a lightning strike, (allowing that there are devices that improve upon "just connected together").
You might want to learn a bit more before you just move along connecting up "grounds".
Keel bolts to engine?
Maybe, maybe not, it's not so simple, particularly if a lightning strike occurs.
It's not generally wise to mix-up the easy paths that lightning can and will follow with all kinds of interconnected "grounds" scattered around a boat.

[HeinSdL]

No expert here but trying to figure out the mechanics of it all. If all 'systems' (engine, keel, windlass) are connected to a common ground then any stray currents in the water (thinking berthed in a marina) will prefer to travel through the boat than through the water (into the keel out of the prop shaft/sd) and speed up corrosion tremendously, in excess of what any zincs can accommodate.

So on my boat both the engine + and - can be isolated from the battery. Came like that from the builder. I always wondered about that but am now concluding the saildrive should stick into the water, isolated. So only connect + and - to the engine when underway (the start battery is grounded to the service battery). And in any case to not use any common ground engine/keel/windlass or to connect thru hulls to any ground either.

But then again, maybe the regs say something quite different.

[Uncle G]

No one seems to agree. Should the electrical system be bonded to the hull or not?
SmartGauge Electronics - To bond or not to bond - Hulls and electrical earthing
SmartGauge Electronics - Galvanic Corrosion
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator? 1/2
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator 2/2

[K1MGY]

Originally Posted by Uncle G

No one seems to agree. Should the electrical system be bonded to the hull or not?
SmartGauge Electronics - To bond or not to bond - Hulls and electrical earthing
SmartGauge Electronics - Galvanic Corrosion
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator? 1/2
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator 2/2

Thanks for these citations. I will read tomorrow.

This is what I am coming up with as well. I read the coverage that is provided in boatowners electrical and mechanical manual.. and can't reach any solid conclusion.

However...

Surely there are no leakage paths possible with unbonded through hull connected with non-conductive material to whatever it's servicing. So why be concerned with galvanic action?

So perhaps the best is to connect my compression post to the keel bolts, and avoid bonding these bolts to the DC ground?

[aberglas]

Be very careful about grounding your boat to the marina. You need a special isolator otherwise you can have severe corrosion issues.


For my fibreglass boat, I just leave the 240 ungrounded, with residual current circuit breakers. But the earths of all appliances are connected together, so you can not have two hot ones on active and neutral.



My 12 volt is unfortunately grounded in the engine to the prop.



For lighning, i have a thick cable that I can attach to the mast hand into the sea and hope it would take most of the current.

[Bowdrie]

The best scenario, (in an ideal world/boat,) is that every single electron that leaves a source, (batteries or shore power,) performs it's assigned work and then goes back to the source.
No stray ones running around thru various detours/paths.
We don't want any DC running loose to cause corrosion or eat-up the zincs, and we don't want any AC to shock anyone on board or in the water.
Engines/transmissions don't generally do so well if a lightning strike goes thru them seeking the water thru the shaft/prop.
We would like for the zincs on the shaft/prop to only do what they were intended to do, and that is to provide protection between the stainless shaft and the bronze prop, not to be a "Band aid" for loose electrons running amuck.

[aquarian]

Originally Posted by Uncle G

No one seems to agree. Should the electrical system be bonded to the hull or not?
SmartGauge Electronics - To bond or not to bond - Hulls and electrical earthing
SmartGauge Electronics - Galvanic Corrosion
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator? 1/2
SmartGauge Electronics - Isolation Transformers or Galvanic Isolator 2/2

Great info. Thanks for sharing

[K1MGY]

So I have read the NMEA stuff and also the magic in Nigel Calder's book. I'm still uncertain how to move forward.

I've discovered and fixed (this was dumb on my part) a reversed neutral and hot lead.

I also discovered that the galvanic isolator on my boat (Hunter passage 42, 1993) is wired AFTER the main AC breaker. The result being that my Victron inverter is connected before the isolator, thereby bonding the AC shore ground to the DC ground, eliminating the galvanic isolator entirely!!

So I am setting about to fix this problem, but am left with the keel bolts (and keel obviously) bonded to the mast, but NOT presently connected to the common ground (engine), which I believe should be internal (post-isolator) AC+DC ground.

Anyone out there with a similar Hunter? Are your keel bolts and mast tied to common ground?

And what about through hulls? I read two approaches: (1) leave these floating and (2) bond them together and connect to common ground. Approach 1 assures (provided there is no other path to ground) that the through hull will not be destroyed by galvanic current. Approach 2 gives the galvanic current a path to dissipate without destruction. So are both true? What does Hunter do?

[s/v Jedi]

Grounding electric systems is different from a bonding system.

I recommend bonding designed for lightning strike protection. This also serves as a “ground” for surge protectors.

That’s about it. I hate it that the engine etc. connects DC negative to the water, but a disconnect switch can fix that when the engine isn’t in use.

I find it upsetting that people connect electrical systems to the water but understand it’s the cheap way to have something. From an engineering standpoint it’s a bad design though.

So do not connect any electrical systems to a bonding system but instead invest in an isolation transformer that not only provides the best safety for life but also for the boat and underwater metals.

This means you can use shore power without really having shore power aboard. It only lives inside that blue Victron box where it creates a magnetic field that is galvanically isolated from everything else aboard.

Of course this means double pole circuit breakers as well. If you have an aluminum boat this is also needed for DC.

[DougR]

Interesting paper on yacht grounding written by Stan Honey, internationally known yacht racer, Volvo Race navigator, EE, found at “honeynav.com”.

Worth a look...

[Bowdrie]

I agree with the above post by Jedi.
I will add that having an isolated ground alternator and a "Drivesaver" is good practice.
Neither should the engine be used as a terminal block for a multitude of ground wires.

[deblen]

Just a personal observation.
Most EU boats go to great lengths to bond every underwater metal to each other with substantial "inside" bonding wire plus many use a "ground" plate.


Many N.American boats have none or little of this bonding.


Both EU & NA boats generally use shaft/prop/strut zincs.


In many years of reading "corrosion" posts,I detect no difference in performance of either system on fiberglas boats.

If a serious zinc/metal eating problem arises,it is usually found to be leakage of "hot" to the surrounding water,as opposed to DC bat negative or AC green wire earth to the water.


Earthing and/or connecting DC neg to the mast :
I have seen the results of a floating mast becoming DC hot,due to a lighting wire,or other 12V + source shorting to the mast.If the mast is DC neg connected,a fuse/breaker will blow. If it is floating,or only earthed to the water,current will flow thru any path it can find,back to DC neg. This will usually be the VHF ant. braid & radio and/or the water to the prop & shaft which are attd to DC neg at the engine.


I suggest any lightening earthing of the mast,etc., be thru a lightening spark gap,to prevent DC flow. I also suggest that the mast be connected to DC neg with #10 (or so).


I have personally seen no evidence of the need or benefit of bonding each or any proper thru hull fittings on a fiberglas boat.



Above are my personal observations & opinions only.
Cheers/Len