Hull-earth bond protection

[blackrose]

Does anyone smear anything over their mains hull-earth bonding point to protect it from corrosion? In some damp engine spaces the connection to the bit of bare steel hull could become corroded over time and if you forget about it the hull-earth bond could be compromised.

 

So I just wondered if after cleaning the bonding point and the terminal I should smear the assembled connection with silicone grease to keep moisture out? I wouldn't want the grease seeping into the connection over time though.

 

Presumably copper grease isn't conductive enough to put between the joint and that wouldn't be a good idea?

Edited April 4, 2021 by blackrose

[Tony Brooks]

Interesting its the 240V bond you are concerned about and not the 12/24 V one. I can see that one would be more lethal if it failed but if the 12/24V did the same all sorts of odd symptoms might occur. I think as long as the bond pint is bright metal when the bond is made and a suitable washer is put above the terminal to spread the load then once you got it nice and tight and pant over it a couple of times the steel will be fairly well sealed against water ingress. Given that I would be more concerned about corrosion inside any crimped joints. I don't know the resistance of rust but I  expect 240V would make short work of passing enough current 15 or 30 mA through it to trip the RCD. More than happy to be told this is wrong.

 

If it turns out to be a real, known problem then it becomes a regular maintenance point.

[Alan de Enfield]

The only RCD Requirements I can find are :

 

 

11.5 Metals used for terminal studs, nuts and washers shall be corrosion-resistant and galvanically compatible with the conductor and terminal. Aluminium and unplated steel shall not be used for studs, nuts or washers in electrical circuits.

 

and

 

11.7 All conductors shall have suitable terminals installed, i.e. no bare wires attached to stud or screw connections.

[blackrose]

Thanks. I've seen plenty of corrosion on the mild steel plate underneath stainless nuts and bolts. Painting over it all is one option but then you really can't see what's going on and taking it apart to inspect it becomes something you'd rather not do, which is why I thought silicone grease would be better as long as it's properly cleaned off before the connection is put back together if it is inspected. Yes, it's the 240v earth bond that I'm concerned about because if you lose the connection at this point and one day your hull goes live, then that's the one that could to kill someone.    

[Phoenix_V]

you could weld the stud to the hull?

 

[canalboat]

2 hours ago, Alan de Enfield said:

The only RCD Requirements I can find are :

.........................  unplated steel shall not be used for studs, nuts or washers in electrical circuits.

 

And Tony Brooks said "Given that I would be more concerned about corrosion inside any crimped joints."

 

OK - that's for a RCD which (as I understand the differing advice to be found on a search of the forum) is to be found in a consumer unit from which my earth must go to the rather expensive Galvanic Isolator that has just arrived and which is fitted with steel studs, bolts and washers.

And to add to my continuing confusion about how to bond an earth to the hull, other forum advice specifically states use of crimped joints rather than wind the wire around the stud under the washer! 

Then of course there is the advice to use grip washers to get a good connection to the hull and the conflicting advice to use 4mm earth wire whilst another recommends 10mm.

And whilst saying you make the bond to the hull, advice on here seems to say make the bond to a bulkhead?

I promise that when  (IF) I get the definitive answer to how to earth the electrical system on a steel boat, I will put it on the forum for the benefit of the hundreds of boaters out there who are as confused as me.

 

OH NO - now I've got to weld a stud to the hull.......................

Edited April 4, 2021 by canalboat
response to comment whilst writing mine

[Alan de Enfield]

13 minutes ago, blackrose said:

Thanks. I've seen plenty of corrosion on the mild steel plate underneath stainless nuts and bolts.

 

 

We had some huge problems with Stainless steel and Zinc coated mild steel cable tray offshore (particularly in the splash zone)

Sets up a 'cell' and corrodes it away. Crevice corrosion.

 

We ended up having to supply the stainless steel fixings with a Macropol (Flame resistant UL 94 Vo rated) Polyester coating to insulate the tray from the fixings.

[Alan de Enfield]

24 minutes ago, canalboat said:

OK - that's for a RCD which

 

No you are misunderstanding ...........

 

The RCD (Recreational Craft Directive) is the specifications to which a leisure boat must be built and there are 1000's of requirements that must be met to ensure conformity.

The electrical section includes everything from the size and type of cable that must be used, to the installation, to the earthing, the 'pull off' forces for crimp terminals, and the 'fuse boxes' etc etc

 

I believe you are thinking of the Residual Current Device

 

 

 

Edited April 4, 2021 by Alan de Enfield

[David Mack]

Vaseline or battery terminal grease?

[blackrose]

12 minutes ago, Phoenix_V said:

you could weld the stud to the hull?

 

 

Yes but that doesn't stop the plate underneath the terminal corroding in a damp environment. I think I'll just put some silicone grease on mine as it's in a cruiser stern engine bay and it can get damp down there.

5 minutes ago, David Mack said:

Vaseline or battery terminal grease?

 

Yes that would also work.

[canalboat]

1 hour ago, Alan de Enfield said:

 

No you are misunderstanding ...........

 

The RCD (Recreational Craft Directive) is the specifications to which a leisure boat must be built and there are 1000's of requirements that must be met to ensure conformity.

The electrical section includes everything from the size and type of cable that must be used, to the installation, to the earthing, the 'pull off' forces for crimp terminals, and the 'fuse boxes' etc etc

 

I believe you are thinking of the Residual Current Device

 

 

 

No - I was trying (clumsily) to point out that the experienced and obviously knowledgeable electrical folk on here are not necessarily good at teaching, with liberal use of Initials that can mean more than one relevant thing.  Now I need to know how to measure a "Pull off force".   

Believe me, if I could find a proper qualified canalboat electrician,  I would have them do the work but how do you know what one looks like and where they are to be found? The electrical company that wired in the electric shore post certainly had no idea about boats or either version of the RCD.  

[GUMPY]

30 minutes ago, canalboat said:

Believe me, if I could find a proper qualified canalboat electrician, 

Does such a being exist? Somehow I doubt it.

 

Edited April 4, 2021 by Loddon

[Alan de Enfield]

 

50 minutes ago, canalboat said:

Now I need to know how to measure a "Pull off force".   

 

You can use something as crude as a spring balance, these are the figures you need to achieve :

 

There are a number of UK / EN specifications referred to in the RCD so all you need is to read up (or use an electrician who has read them) and you are 'good to go'.

 

1 Newton is almost 1/4 of a pound.

Attach / clamp your terminal

Attach your wire (a short length away from the terminal) to your spring balance, pull to the correct 'poundage' for one minute, if it holds it passes.

 

Or, clamp the wire and hook your spring balance over the terminal and 'pull'.

 

I wonder if all those 'self certifying' their boats to the RCD  are actually complying or fraudulently signing compliance and potentially signing their life away' ?

 

 

 

Edited April 4, 2021 by Alan de Enfield

[canalboat]

You have a fine sense of humour sir Alan.

I suppose its just a decision to be made between whether life's just too short or a short may lessen life.