galvanic isolator

[blackrose]

Thanks, yes I have to be here to see if the LEDs illuminate but surely you have to be there to see the needle move? The LEDs in mine stay illuminated if the diodes are in circuit.

 

The LEDs are either on or off, but if they're off then the dual set of diodes are blocking anything so I'm not sure why I'd need to know more than that. It sounds like your single set of diodes are right on the edge if the needle is deflecting.

 

Also why don't you think AC leaks are anything to worry about? If the diodes are forced into conduction by an AC leak then wouldn't any small DC currents also be able to pass?

Edited March 31, 2021 by blackrose

[robtheplod]

I know folks on here aren't keen on vlogs, but i thought this might be of use as its the GI thats been recommended and how its fitted. Please excuse the quality - hope it helps??

 

(3) #14 Replace shoreline socket & Galvanic Isolator - YouTube

[blackrose]

That's a good video for the OP. You need to make sure that the earth bond connection is on the boat side of the GI, otherwise as the guy in the video says, the GI will be doing nothing.

 

Posted October 5, 2018 (edited)

Put simply...

Shore power earth to GI.

[Boat side] GI earth along with shore power L & N to Consumer Unit

4mm² cable from Consumer Unit earth busbar to hull bonding point. 

Edited October 5, 2018 by WotEver

 

On my boat the connection is made from the boat side of the GI to the hull bonding point simply because that was easier. It's the same thing.

 

Remember to unplug the shore power cable first!

Edited March 31, 2021 by blackrose

[Feeby100]

Thank you great info there 

[cuthound]

6 hours ago, blackrose said:

Thanks, yes I have to be here to see if the LEDs illuminate but surely you have to be there to see the needle move? The LEDs in mine stay illuminated if the diodes are in circuit.

 

The LEDs are either on or off, but if they're off then the dual set of diodes are blocking anything so I'm not sure why I'd need to know more than that. It sounds like your single set of diodes are right on the edge if the needle is deflecting.

 

Also why don't you think AC leaks are anything to worry about? If the diodes are forced into conduction by an AC leak then wouldn't any small DC currents also be able to pass?

 

People used to worry about high frequency harmonic conduction, when switched mode power supplies became common (phone chargers etc). However as Nick Norman has already explained, most no longer use the earth connection.

 

So the only AC conduction that should now occur is during a fault of mains powered equipment, which is what the GI is designed to do.

[blackrose]

47 minutes ago, cuthound said:

So the only AC conduction that should now occur is during a fault of mains powered equipment, which is what the GI is designed to do.

 

Yes, so my point was if that's happening and your GI's diodes are conducting then surely you'd want to know about it? What's the point of a status monitor that only tells you certain fault conditions and not others? 

[cuthound]

40 minutes ago, blackrose said:

 

Yes, so my point was if that's happening and your GI's diodes are conducting then surely you'd want to know about it? What's the point of a status monitor that only tells you certain fault conditions and not others? 

 

You would know about it, both the shoreline and the boats protective devices would trip.

[blackrose]

15 minutes ago, cuthound said:

 

You would know about it, both the shoreline and the boats protective devices would trip.

 

Isn't it possible that a minor or partial AC fault could cause the diodes to conduct but the breakers wouldn't trip?

[cuthound]

4 minutes ago, blackrose said:

 

Isn't it possible that a minor or partial AC fault could cause the diodes to conduct but the breakers wouldn't trip?

 

Unlikely, as the diodes will conduct at around 2-3 volts (assuming 2 in series) and under fault conditions will create a live to earth fault, which will trip the breakers. 

[blackrose]

Ok thanks for everyone's help. That's it then, I've finally gone for an upgrade! I called aquafax who said the status monitor was well sealed and would be fine in my engine bay.

Edited March 31, 2021 by blackrose

[Feeby100]

What one did you go for ?

[blackrose]

18 hours ago, Feeby100 said:

What one did you go for ?

 

The Aquafax 16 amp one. MEC Marine, £121 including VAT and postage.

 

Seems to be £127 on their website but I've definitely paid £121.06 all inc.

 

https://www.mecmarine.co.uk/shop/galvanic-current-isolator-16a-with-indicator/

 

My boat has 16 amp breakers so there's no point paying for the 32 amp version. Even if I plug the boat into a 32 amp supply I can't draw more than 16 amps.

 

Edited April 1, 2021 by blackrose

[Theo]

On 30/03/2021 at 00:02, blackrose said:

Make sure your boat's mains system is hull-earth bonded too. If it isn't your hull is already isolated from earth so you'd be wasting your time with either a galvanic isolator or isolation transformer.

 

If you're wondering why a boat's mains earth is bonded to the hull when this introduces the problem of galvanic corrosion, it's because the problem of a live steel hull, electrocution and death is much worse.

 

A good indication of this sort of fault is dead fish and human swimmers floating about near your boat, and possibly a sharp tingle as you get on or off.

 

N

[nicknorman]

1 hour ago, blackrose said:

 

The Aquafax 16 amp one. MEC Marine, £121 including VAT and postage.

 

Seems to be £127 on their website but I've definitely paid £121.06 all inc.

 

https://www.mecmarine.co.uk/shop/galvanic-current-isolator-16a-with-indicator/

 

My boat has 16 amp breakers so there's no point paying for the 32 amp version. Even if I plug the boat into a 32 amp supply I can't draw more than 16 amps.

 

Well no, you misunderstand. Under normal circumstances, none of the 16A flows through the GI. So the 16A doesn’t relate to any specific current rating of the device. However if there is a live to earth short, in the few milliseconds before the breaker contacts open enough to quench the arc, probably 1000s of amps flow through it. It is that very short duration but very high current that the GI diodes have to be able to tolerate. The difference with a 32A bollard is that its peak current under short circuit conditions will likely be higher than for a 16A bollard - thicker wiring from source to bollard etc. So it is not about the breaker value inside your boat, it is about the ability of the source to deliver a higher if extremely short duration current.

 

But anyway, if you mostly plug into a 16A bollard I wouldn’t worry about it.

Edited April 1, 2021 by nicknorman

[blackrose]

44 minutes ago, nicknorman said:

Well no, you misunderstand. Under normal circumstances, none of the 16A flows through the GI. So the 16A doesn’t relate to any specific current rating of the device. However if there is a live to earth short, in the few milliseconds before the breaker contacts open enough to quench the arc, probably 1000s of amps flow through it. It is that very short duration but very high current that the GI diodes have to be able to tolerate. The difference with a 32A bollard is that its peak current under short circuit conditions will likely be higher than for a 16A bollard - thicker wiring from source to bollard etc. So it is not about the breaker value inside your boat, it is about the ability of the source to deliver a higher if extremely short duration current.

 

But anyway, if you mostly plug into a 16A bollard I wouldn’t worry about it.

 

Ok thanks, so with this 16amp GI fitted one shouldn't plug into a 32 or 64 amp supply?

 

I'm a bit confused now because a technical support guy at Aquafax told me that as I had a 16amp breaker in my boat I'd be wasting my money on the 32amp GI. You seem to be suggesting otherwise?

 

I'd assumed my board was 16amp, but looking at it now I can't tell. I see 25A and C16. Why isn't it clearly stated so that those who aren't electrically trained can see exactly what they're plugging into?

 

Edited April 1, 2021 by blackrose

[Feeby100]

24 minutes ago, nicknorman said:

Well no, you misunderstand. Under normal circumstances, none of the 16A flows through the GI. So the 16A doesn’t relate to any specific current rating of the device. However if there is a live to earth short, in the few milliseconds before the breaker contacts open enough to quench the arc, probably 1000s of amps flow through it. It is that very short duration but very high current that the GI diodes have to be able to tolerate. The difference with a 32A bollard is that its peak current under short circuit conditions will likely be higher than for a 16A bollard - thicker wiring from source to bollard etc. So it is not about the breaker value inside your boat, it is about the ability of the source to deliver a higher if extremely short duration current.

 

But anyway, if you mostly plug into a 16A bollard I wouldn’t worry about it.

Ok thanks so what one should I go for 16 or 32 ?

[blackrose]

26 minutes ago, Feeby100 said:

Ok thanks so what one should I go for 16 or 32 ?

 

? ❓❓❓ confusing init. I thought I understood it. Must be a nightmare as a newbie.

Edited April 1, 2021 by blackrose

[nicknorman]

1 hour ago, blackrose said:

 

Ok thanks, so with this 16amp GI fitted one shouldn't plug into a 32 or 64 amp supply?

 

I'm a bit confused now because a technical support guy at Aquafax told me that as I had a 16amp breaker in my boat I'd be wasting my money on the 32amp GI. You seem to be suggesting otherwise?

 

I'd assumed my board was 16amp, but looking at it now I can't tell. I see 25A and C16. Why isn't it clearly stated so that those who aren't electrically trained can see exactly what they're plugging into?

 

The 2 things labelled 25A are rcd breakers. They trip on earth leakage, not on overcurrent. The 25A is just the maximum current they can cope with without  overheating etc.

 

Then you have 2 breakers of 16A each. These are probably for sockets etc. And then you have a 6A breaker which is probably for lighting.

 

It could be that all that lot are in parallel making a theoretical maximum continuous current of 38A. That would be bad because the inlet socket is only rated at 16A. Of course the 16A socket should only be connected to a 16A bollard which will be protected by a 16A (max) breaker. If you make up a lead that has a 16A fitting on one end and a 32A on the other end, so that you can plug your 16A socket into a 32A bollard, that is naughty!

 

It could also be that one of the 16A breakers is just after the inlet socket, and then it splits into two to feed the other 16A breaker (for sockets) and the 6A breaker (for lighting). The first breaker limiting the overall maximum to 16A. That would be good, but it doesn’t explain why there are 2 RCDs.

 

Anyway, it’s easy to find out - just pop the breakers (the C16 or C6 ones) one at a time and find out what stops working!

 

As an aside, you’ll notice the breakers have a rectangular box with 3000 or 6000. This is the maximum current breaking capability, which just goes to show that under fault conditions, thousands of amps can flow.

1 hour ago, Feeby100 said:

Ok thanks so what one should I go for 16 or 32 ?

Assuming this is an inland waterways boat, it will likely have a 16A socket and thus a 16A RCD will be fine. If you are near or on the coast or big tidal rivers with bigger boats, maybe the bollards are 32A in which case get the 32A one. But 99% of canal boats have 16A sockets and plug into 16A bollards

Edited April 1, 2021 by nicknorman

[blackrose]

Thanks, my bollard has 2 outlets so I assume they are 16 amp each.

 

Just to clarify, you shouldn't plug into a 32 amp bollard if you only have a 16 amp GI fitted?

[Feeby100]

1 hour ago, blackrose said:

 

? ❓❓❓ confusing init. I thought I understood it. Must be a nightmare as a newbie.

Tell me about it ha I’m more confused than before 

[nicknorman]

48 minutes ago, blackrose said:

Thanks, my bollard has 2 outlets so I assume they are 16 amp each.

 

Just to clarify, you shouldn't plug into a 32 amp bollard if you only have a 16 amp GI fitted?

Well in theory no, but in practice I would, especially if it was just now and again. There is only an issue if you get a dead short between live and earth and how often does that happen? And it will also depend on the resistance of all the wiring between the transformer/substation and the boat as to how much peak current you get. It’s not an exact science.

[Feeby100]

1 hour ago, nicknorman said:

The 2 things labelled 25A are rcd breakers. They trip on earth leakage, not on overcurrent. The 25A is just the maximum current they can cope with without  overheating etc.

 

Then you have 2 breakers of 16A each. These are probably for sockets etc. And then you have a 6A breaker which is probably for lighting.

 

It could be that all that lot are in parallel making a theoretical maximum continuous current of 38A. That would be bad because the inlet socket is only rated at 16A. Of course the 16A socket should only be connected to a 16A bollard which will be protected by a 16A (max) breaker. If you make up a lead that has a 16A fitting on one end and a 32A on the other end, so that you can plug your 16A socket into a 32A bollard, that is naughty!

 

It could also be that one of the 16A breakers is just after the inlet socket, and then it splits into two to feed the other 16A breaker (for sockets) and the 6A breaker (for lighting). The first breaker limiting the overall maximum to 16A. That would be good, but it doesn’t explain why there are 2 RCDs.

 

Anyway, it’s easy to find out - just pop the breakers (the C16 or C6 ones) one at a time and find out what stops working!

 

As an aside, you’ll notice the breakers have a rectangular box with 3000 or 6000. This is the maximum current breaking capability, which just goes to show that under fault conditions, thousands of amps can flow.

Assuming this is an inland waterways boat, it will likely have a 16A socket and thus a 16A RCD will be fine. If you are near or on the coast or big tidal rivers with bigger boats, maybe the bollards are 32A in which case get the 32A one. But 99% of canal boats have 16A sockets and plug into 16A bollards

Thank you

[blackrose]

Thanks for all the advice.

 

I've already bought the 16 amp GI so I'll just fit it when it arrives as I'm pretty sure my bollard is a 16amp supply. 

 

If I'm ever at a mooring with a bigger capacity supply then I'll change the GI back to my current 70amp safeshore unit.

Edited April 1, 2021 by blackrose

[nicknorman]

1 minute ago, blackrose said:

I've already bought the 16 amp GI so I'll just fit it when it arrives as I'm pretty sure my bollard is a 16amp supply. 

 

If I'm ever at a mooring with a bigger capacity supply then I'll change the GI back to my current 70amp safeshore unit.

I presume you realise that a 32A bollard socket looks quite different from a 16A one? So it’s not about some tiny writing somewhere, it’s about the general shape and size of the socket.

[Alan de Enfield]

10 minutes ago, nicknorman said:

I presume you realise that a 32A bollard socket looks quite different from a 16A one? So it’s not about some tiny writing somewhere, it’s about the general shape and size of the socket.

 

They are both colour blue and both very similar to look at but the 32A one is huge compared to the 16A one.

 

It may be 'naughty' but I have a 32A plug on a short lead to a 16A socket so if there is a 32 amp bollard available and no 16 amp ones I can still plug in.

More and more Inland marinas are offering 32 amp bollards as 'demands' from liveaboards increase.

 

 

Screwfix 32A and 16A Plugs

 

 

 

 

 

Edited April 1, 2021 by Alan de Enfield