electrickery

[Emerald]

Hi guys,

you may have seen another post I created that led to some lively debate regarding my boats electrics? In order to learn more from your vast knowledge and to follow up from that I thought I would post another to say that I have traced the earth connections from the engine rail into the wiring loom. Incidentally there are a number of earth connections made to the rail(engine earth etc) and I take on board what others have said regarding the rail being mounted on rubber mountings, however all of these connections ultimately end up back at the negative post of the batteries. The mains earth I traced back to the galvanic isolator(see the second picture)and ultimately to the shore earth.

 

I have read up in an attempt to educate myself on this wizardry and cannot see that there is anything wrong with this? I am sure someone will be around to say otherwise and advance my education?

 

 

Edited March 10, 2012 by Escape

[by'eck]

The mains earth I traced back to the galvanic isolator(see the second picture)and ultimately to the shore earth.

 

 

The galvanic isolator should sit between the shore power earth & the boat AC earth which should include a single strap to the boat hull, effectively isolating the two. If that is the case then all should be well in that area.

[Emerald]

The galvanic isolator should sit between the shore power earth & the boat AC earth which should include a single strap to the boat hull, effectively isolating the two. If that is the case then all should be well in that area.

 

Thanks for the reply. I understand the purpose of the isolator when using mains hook up but don't get the purpose of the boat hull earth? Are we saying that when the invertor is creating AC, should a fault condition occur then the hull sat in water and ground acts as the protection?

Edited March 10, 2012 by Escape

[MoominPapa]

Thanks for the reply. I understand the purpose of the isolator when using mains hook up but don't get the purpose of the boat hull earth? Are we saying that when the invertor is creating AC, should a fault condition occur then the hull sat in water and ground acts as the protection?

No. The reason for connecting the boat hull to the AC system earth is that many/most faults will either connect an AC conductor to the hull, or connect an AC conductor to a person who is touching the hull. In both cases the RCD breaker on the AC supply works better if the AC supply earth/neutral is connected to the hull.

 

MP.

[by'eck]

Deleted due double post

Edited March 10, 2012 by richardhula

[by'eck]

Thanks for the reply. I understand the purpose of the isolator when using mains hook up but don't get the purpose of the boat hull earth? Are we saying that when the invertor is creating AC, should a fault condition occur then the hull sat in water and ground acts as the protection?

 

No that is not what is being said. Its all about providing firm conditions for the RCD to detect an imbalance in live & neutral currents and so trip the instant the hull becomes live in a fault situation, before there is any danger to persons.

 

To explain further and add perspective to MoominPapa's reply, if the boats AC earth is not connected to the boat hull and there is a short from AC live to the hull when on shore power, its possible the RCD protection will not trip as the fresh water its floating in may not give an adequate earth.

 

This will leave the hull live to anyone passing by or stepping onto the boat, since they will have earth contact through the ground they are standing on, and any other part of their body on contact with the hull will complete a circuit

 

Of course the RCD should then trip, but do you want to take the risk ?

 

A similar risk to people on board will exist if the AC source is an isolated feed from onboard generator or inverter. Its for this reason that AC neutral and earth are required to be connected together and to the hull with such equipment, allowing the RCD to detect an imbalance & trip in a fault situation.

Edited March 11, 2012 by richardhula

[Roger Crown]

Hi guys,

you may have seen another post I created that led to some lively debate regarding my boats electrics? In order to learn more from your vast knowledge and to follow up from that I thought I would post another to say that I have traced the earth connections from the engine rail into the wiring loom. Incidentally there are a number of earth connections made to the rail(engine earth etc) and I take on board what others have said regarding the rail being mounted on rubber mountings, however all of these connections ultimately end up back at the negative post of the batteries. The mains earth I traced back to the galvanic isolator(see the second picture)and ultimately to the shore earth.

 

I have read up in an attempt to educate myself on this wizardry and cannot see that there is anything wrong with this? I am sure someone will be around to say otherwise and advance my education?

 

 

Hi again, from the information you have provided it appears my initial concerns are well founded.

 

I see you have done some research but cannot see a problem, I would strongly recommend you get your boat inspected by a professional A.S.A.P. to verify the hulls bonding arrangement and to ensure the Rcd will operate under fault conditions.

 

Regards

Roger

[bottle]

ps. pushing the yellow buttons is not an electrical test just mechanical.

 

It does not prove they will work in a fault situation.

[MoominPapa]

ps. pushing the yellow buttons is not an electrical test just mechanical.

 

It does not prove they will work in a fault situation.

But dropping the end of the extension lead in the water whilst using a sander on the roof is. Don't ask me how I know this.......

 

 

 

MP.

[Emerald]

I would strongly recommend you get your boat inspected by a professional A.S.A.P.

Regards

Roger

 

Thanks for your advice and everyone else's contributions for that matter. Someone is coming to have a look at the boat later in the week (it has a twelve month warranty).

BTW I got talking today to someone in our marina who is quite knowledgable and he also confirms your findings.

[Keith M]

Thanks for your advice and everyone else's contributions for that matter. Someone is coming to have a look at the boat later in the week (it has a twelve month warranty).

BTW I got talking today to someone in our marina who is quite knowledgable and he also confirms your findings.

 

 

I would strongly advise that you are happy that the person inspecting your boat is competent to carry out the inspection

Has your engineer passed a BMET exam?

 

If your boat has been built so that in complies with the RCD do you have copies of the schematic wiring diagrams and electrical test certificates?

 

Keith

[Emerald]

Hi again, from the information you have provided it appears my initial concerns are well founded.

 

I see you have done some research but cannot see a problem, I would strongly recommend you get your boat inspected by a professional A.S.A.P. to verify the hulls bonding arrangement and to ensure the Rcd will operate under fault conditions.

 

Regards

Roger

 

 

Roger,

many thanks for casting a critical eye on the wiring on my boat. The earth bonding has now been sorted and a lesson learnt that even with a new boat not to expect everything to be perfect. Thanks again.

[Roger Crown]

Roger,

many thanks for casting a critical eye on the wiring on my boat. The earth bonding has now been sorted and a lesson learnt that even with a new boat not to expect everything to be perfect. Thanks again.

 

You are welcome, hope you have many years of happy and safe boating,

Roger