Galvanic Isolator Installation, How?

[Thomas C King]

Hi,

 

I have a really basic question. We are new boaters, and we were going to get a galvanic isolator installed, but in light of recent events the planned work was cancelled and I can't find anywhere to do it for us.

 

I have bought a Sterling 30amp Galvanic Isolator and I'm getting a bit confused about what seems like a simple job - installation.

 

This video suggests that I just cut the cable in the boat near the shoreline power inlet, and install the galvanic isolator inline - https://www.youtube.com/watch?v=d35KxA8qmAc

However, the manual for the Sterling 30amp Galvanic isolator says that I connect the boat's bonding system and the AC inlet's ground to the isolator. Isn't the bonding system just a way to connect earth to the hull in some way? These seem like two completely different methods.

 

Excuse my ignorance, I'm not an electrician, and thank you if you can help.

 

P.s., I will buy a multimeter to test the installation...

[nicknorman]

Just find the back of the shore power inlet socket (make sure it is unplugged from the shore!), identify the earth wire (green / yellow), cut it and insert the GI between the two ends of the wire.

 

Separately, it is a good idea to check that the earth wire is connected to the hull somewhere within the boat, for that you need a multimeter on ohms range. It should already be connected, but in the world of boating electrics nothing is certain until tested!

[WotEver]

59 minutes ago, nicknorman said:

Separately, it is a good idea to check that the earth wire is connected to the hull somewhere within the boat, for that you need a multimeter on ohms range. It should already be connected, but in the world of boating electrics nothing is certain until tested!

That is of course the boat side of the GI. The shore side of the GI should not connect to the hull when you have a GI installed. 
 

 

Edited April 5, 2020 by WotEver
No superheroes intended.

[Jen-in-Wellies]

12 hours ago, Thomas C King said:

Hi,

 

I have a really basic question. We are new boaters, and we were going to get a galvanic isolator installed, but in light of recent events the planned work was cancelled and I can't find anywhere to do it for us.

 

I have bought a Sterling 30amp Galvanic Isolator and I'm getting a bit confused about what seems like a simple job - installation.

 

This video suggests that I just cut the cable in the boat near the shoreline power inlet, and install the galvanic isolator inline - https://www.youtube.com/watch?v=d35KxA8qmAc

However, the manual for the Sterling 30amp Galvanic isolator says that I connect the boat's bonding system and the AC inlet's ground to the isolator. Isn't the bonding system just a way to connect earth to the hull in some way? These seem like two completely different methods.

 

Excuse my ignorance, I'm not an electrician, and thank you if you can help.

 

P.s., I will buy a multimeter to test the installation...

Some questions for the OP:

• Are you staying on the boat at the moment, or is it mostly unoccupied?
• Is the boat currently (see what I did there!) connected to a shore outlet?
• Does the boat have any solar panels on top charging the batteries?

If the boat isn't connected to a shore line, or if you are not living on board, especially if there are panels to keep the batteries topped up, then wait until either a boat electrician can come, or civilisation collapses in to a Mad Max dystopia, whichever. ?. The galvanic isolator can wait as it isn't desperately needed.

If the boat is on a shore lead and you are living on board, then, if the boat hasn't been affected by galvanic corrosion up till now, then it is unlikely that a month or two wait for a sparky to visit will make much difference.

If galvanic corrosion is a worry to you and you are using mains and your boat has an inverter, the disconnect the shore lead and rely on engine charging and any solar panels there to keep the batteries topped up, as cruising boaters do, until a sparky can come. It will be expensive in diesel, compared with the cost of shore power, but the corrosion worry will be gone.

If doing it yourself, then you are messing about with mains. It is possible to kill yourself, or others by leaving the boat in an unsafe state. It is an easy DIY project, but you need to have some electrical understanding. From the questions you've asked, I'd respecfully suggest this isn't the project to learn on.

 

Jen

 

Edited April 6, 2020 by Jen-in-Wellies

[nicknorman]

Well yes but in the specific case of fitting a GI, it is as straight forward and safe as they come. A good task to cut ones teeth on. When our boat was built by “professionals” the GI was incorrectly installed (hull earth connected to shore side) so having it done professionally just means you pay for it, not necessarily that it is done correctly.

11 hours ago, WotEver said:

That is of course the boat side of the GI. The shore side of the GI should not connect to the hull when you have a GI installed. 
 

Yes, I probably should have been more precise.

[canalboat]

If you have a shoreline but it is not earthed to the boat i.e. a rather permanent extension lead, do I still need to fit a GI?

 

Edited April 6, 2020 by canalboat

[WotEver]

4 minutes ago, canalboat said:

If you have a shoreline but it is not earthed to the boat i.e. a rather permanent extension lead, do I still need to fit a GI?

Assuming that you haven’t connected the extension lead earth to the boat hull then no, you don’t need a GI, you’re simply risking the life of any passerby instead. 

[nicknorman]

1 minute ago, WotEver said:

Assuming that you haven’t connected the extension lead earth to the boat hull then no, you don’t need a GI, you’re simply risking the life of any passerby instead. 

... including yourself when you get off and on the boat.

[Tony Brooks]

2 minutes ago, WotEver said:

Assuming that you haven’t connected the extension lead earth to the boat hull then no, you don’t need a GI, you’re simply risking the life of any passerby instead. 

or even yourself as you step on or off the boat

 

SNAP

Edited April 6, 2020 by Tony Brooks

[blackrose]

8 minutes ago, canalboat said:

If you have a shoreline but it is not earthed to the boat i.e. a rather permanent extension lead, do I still need to fit a GI?

 

No, but you have much bigger problems (potentially life-threatening)

[Alan de Enfield]

2 minutes ago, WotEver said:

Assuming that you haven’t connected the extension lead earth to the boat hull then no, you don’t need a GI, you’re simply risking the life of any passerby instead. 

Its another example of the BSS 'inconsistency' in application of safety.

The requirements are only 'advisory', surely they should be mandatory with 'extension leads' not allowed.

 

Advisory Only :

 

Are all a.c. shore‐power and battery charging lead inlet connections of the correct type in good condition, and suitably protected from the weather?

Check the type, condition and
location of all a.c. shore‐power and
battery charging inlet connections
where they can be seen.

Shore‐power and battery charging inlet connections must be of
suitable proprietary manufacture and must be a plug (male) type.
Shore‐power and battery charging inlet connections must be:
• securely fitted;
• free of missing components; and,
• free of signs of damage or deterioration.
Shore‐power and battery charging inlet connections not obviously
splash‐proof must not be located where they are likely to be subject
to the weather or splashing.

 

Shore‐power and battery charging leads must be fitted with
a female type socket at the end which connects to the
vessel’s inlet connection.
Alternating current leads within the vessel used to connect
individual power sources to the vessel’s alternating current
distribution system must be fitted with a male type plug (or
be permanently connected) at the end which connects to
the power source, and a female type socket at the end
which connects to the distribution system.

[WotEver]

3 minutes ago, Alan de Enfield said:

The requirements are only 'advisory', surely they should be mandatory with 'extension leads' not allowed.

I’ve never before noticed that those requirements were advisory. That’s nuts!  But if you have your alternator bypassing the isolator that’s a fail?  

[Markinaboat]

All of the above.

 

As mentioned, try and find the cable coming into the boat from the shoreline connector (unless the connector is already in the boat as is sometimes the case). The insertion point of the isolator should, ideally, be as close to the shore connector as possible. However, as long as the isolator is anywhere inline between the input from the shore connector and the cables first point of contact/connection in the boat, then this will be fine (i.e. the earth coming into the boat must not have been connected to anything else before the isolator). The only slightly awkward bit is using a nice sharp Stanley or craft knife to carefully split the outer cable insulation to expose enough cable to allow the earth to be shortened (without actually cutting into the earth/live/neutral wires!) and then connected to either end/terminal of the isolator. The remaining live and neutral wires can then be neatly wrapped in insulating tape to protect from chaffing etc.

Edited April 6, 2020 by Markinaboat
additional info

[David Mack]

1 hour ago, canalboat said:

If you have a shoreline but it is not earthed to the boat i.e. a rather permanent extension lead, do I still need to fit a GI?

 

 

Belfast is currently moored in a boatyard with no shore power connection. But there are trailing extension leads running over the cabin top to boats moored further out. Movement of the boats has already led to enough chafing to have worn through the paint and exposed the steel on the corner of the cabin (I have since moved the cable, but can't now check during lockdown). How worried should I be?

[ditchcrawler]

1 hour ago, Alan de Enfield said:

Its another example of the BSS 'inconsistency' in application of safety.

The requirements are only 'advisory', surely they should be mandatory with 'extension leads' not allowed.

 

But how do you not allow something that is completely portable and may or maynot be there at the time of inspection. Think of all the people with petrol generators, I bet they don't all drain and dry the tanks before takinging them onboard and store their petrol in a suitable place. If they do I can't see how they manage to run them on cruiser decks under the canopy.

 

[Tony Brooks]

16 minutes ago, David Mack said:

 

Belfast is currently moored in a boatyard with no shore power connection. But there are trailing extension leads running over the cabin top to boats moored further out. Movement of the boats has already led to enough chafing to have worn through the paint and exposed the steel on the corner of the cabin (I have since moved the cable, but can't now check during lockdown). How worried should I be?

I would suspect the boatyard owner has a duty of care to you if they are allowing that sort of thing to go on. A line (live) cable chaffed through onto a steel boat would make that boat live and that gives the potential to electrocute someone stepping form steel jetty onto the boat. Much depends upon the resistance of the water and how well insulated the hull is from the jetty. It would also lead to hull corrosion. I think a polite phone call/email/letter to the owner pointing out the dangers would not go amiss.

[BEngo]

40 minutes ago, David Mack said:

 

Belfast is currently moored in a boatyard with no shore power connection. But there are trailing extension leads running over the cabin top to boats moored further out. Movement of the boats has already led to enough chafing to have worn through the paint and exposed the steel on the corner of the cabin (I have since moved the cable, but can't now check during lockdown). How worried should I be?

Much depends on what is on the shore ends of the cables.  If they are correctly fused/breakered and the outlets protected by RCD or RCBO  as they should be according to the electrical regs marina code of practice then, if the cable insulation chafes away to expose the conductors and the conductors contact Belfast or another boat either the fuse/breaker should  trip or the RCD/RCBO should trip.  Which one goes will depend on which conductor contacts the boat.

This would be one of the situations that the IET was thinking of when it  wrote the CoP.

If the shore end is not properly protected a potentially dangerous situation could arise where Belfast, or another boat is 'live'.

 Long, trailing, mechanically unprotected extension cables are always bad practice.  Sometimes they are not easily avoidable.  That is why site power is usually 110V centre tapped so as to reduce the risk.

N

[Tony Brooks]

8 minutes ago, BEngo said:

Much depends on what is on the shore ends of the cables.  If they are correctly fused/breakered and the outlets protected by RCD or RCBO  as they should be according to the electrical regs marina code of practice then, if the cable insulation chafes away to expose the conductors and the conductors contact Belfast or another boat either the fuse/breaker should  trip or the RCD/RCBO should trip.  Which one goes will depend on which conductor contacts the boat.

This would be one of the situations that the IET was thinking of when it  wrote the CoP.

If the shore end is not properly protected a potentially dangerous situation could arise where Belfast, or another boat is 'live'.

 Long, trailing, mechanically unprotected extension cables are always bad practice.  Sometimes they are not easily avoidable.  That is why site power is usually 110V centre tapped so as to reduce the risk.

N

I would suggest that in clean water (low conductivity) with the boat insulated from a metal mooring or against a wooden or plastic mooring then there is no guarantee the RCD will trip. Hopefully it would trip if you made a circuit between boat and metal mooring but i would not like to risk it. Basically I tend to distrust marina RCDs because of the abuse they can be subject to.

[Alastair]

1 hour ago, David Mack said:

 

Belfast is currently moored in a boatyard with no shore power connection. But there are trailing extension leads running over the cabin top to boats moored further out. Movement of the boats has already led to enough chafing to have worn through the paint and exposed the steel on the corner of the cabin (I have since moved the cable, but can't now check during lockdown). How worried should I be?

Either those cables should be re-routed (so they don't pass over your boat), or they need to be put in some casing. Hosepipe works quite well - slit it in a spiral, fit over the  cable (you can add the odd cable tie to ensure it doesn't come off). 

 

[David Mack]

2 minutes ago, Alastair said:

Either those cables should be re-routed (so they don't pass over your boat), or they need to be put in some casing. Hosepipe works quite well - slit it in a spiral, fit over the  cable (you can add the odd cable tie to ensure it doesn't come off). 

 

There isn't any practical rerouting that wouldn't involve the risk of cables trailing in the water. And encasing the cable in hosepipe won't stop it chafing my paintwork.

[TheBiscuits]

1 minute ago, David Mack said:

There isn't any practical rerouting that wouldn't involve the risk of cables trailing in the water. And encasing the cable in hosepipe won't stop it chafing my paintwork.

Secure the able to your boat so it doesn't rub, and allow enough slack either side so the boats can move.

 

Failing that build an overhead gantry to carry the cables.

[ditchcrawler]

19 minutes ago, Tony Brooks said:

I would suggest that in clean water (low conductivity) with the boat insulated from a metal mooring or against a wooden or plastic mooring then there is no guarantee the RCD will trip.  

One day I am going to test this. My gut feeling even in clean canal water it will trip

[Alastair]

You said 'clean canal water'. Where is this?

[ditchcrawler]

8 minutes ago, Alastair said:

You said 'clean canal water'. Where is this?

OK any canal water

[canalboat]

7 hours ago, Alan de Enfield said:

Its another example of the BSS 'inconsistency' in application of safety.

The requirements are only 'advisory', surely they should be mandatory with 'extension leads' not allowed.

 

Advisory Only :

 

Are all a.c. shore‐power and battery charging lead inlet connections of the correct type in good condition, and suitably protected from the weather?

Check the type, condition and
location of all a.c. shore‐power and
battery charging inlet connections
where they can be seen.

Shore‐power and battery charging inlet connections must be of
suitable proprietary manufacture and must be a plug (male) type.
Shore‐power and battery charging inlet connections must be:
• securely fitted;
• free of missing components; and,
• free of signs of damage or deterioration.
Shore‐power and battery charging inlet connections not obviously
splash‐proof must not be located where they are likely to be subject
to the weather or splashing.

 

Shore‐power and battery charging leads must be fitted with
a female type socket at the end which connects to the
vessel’s inlet connection.
Alternating current leads within the vessel used to connect
individual power sources to the vessel’s alternating current
distribution system must be fitted with a male type plug (or
be permanently connected) at the end which connects to
the power source, and a female type socket at the end
which connects to the distribution system.

I should have explained that mine complies with the above and although advisory, the examiner did examine the wire and sockets, the RCD on the boat and the RCD on the shore into which it plugs, and state they were safe so I am left alarmed by the accusations of potentially killing passers by and myself!