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galvanic isolator


Feeby100

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However, it does not seem to have any indication of correct functioning and I can't see the maximum fault current it can handle and for how long. It may or may not be reliable but any fault on the boat's mains circuit(s) might either stop the isolator working so you risk hull corrosion or the isolator might fail open circuit which puts anyone on board at risk of electrocution.

 

GIs and any other mains equipment are not things to skimp on or buy on price. In my view unless you know how to and regularly test the isolator you need some LEDs or a meter. For peace of mind it needs to handle fault currents in four figures.

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3 minutes ago, Feeby100 said:

do you recommend one please ? 

Victron VDI-16 is suitable for the typical inland marina 16A supply. Not much more expensive than the one you were looking at. Victron generally know their stuff, so blue boxes are usually a safe bet. This will need installing inside the boat.

Jen

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10 minutes ago, Tony Brooks said:

However, it does not seem to have any indication of correct functioning and I can't see the maximum fault current it can handle and for how long. It may or may not be reliable but any fault on the boat's mains circuit(s) might either stop the isolator working so you risk hull corrosion or the isolator might fail open circuit which puts anyone on board at risk of electrocution.

 

GIs and any other mains equipment are not things to skimp on or buy on price. In my view unless you know how to and regularly test the isolator you need some LEDs or a meter. For peace of mind it needs to handle fault currents in four figures.

I would want one that has some form of monitoring on it and conforms to the AAYC specification. If you can't find one doing that the one having a fault current rating of over a thousand amps for perhaps 10 seconds. Any that meet those specs will do the job.

 

 

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Just by way of explanation, the one you link to will most likely do a good job of protecting the boat from mains earth induced galvanic corrosion. The reason for the hesitation is that some of these devices may not be sufficiently resilient to cope with a live to earth short circuit on the boat. If this were to happen, a few thousand amps can momentarily flow before the bollard breaker operates. Although momentary, it can damage the diodes inside the GI and render them either short circuit (so you subsequently lose the galvanic protection) or open circuit, (so the boat becomes un-earthed).

 

This is the difference between a random cheap GI and an expensive certified one - the latter can tolerate very high fault currents without any risk of going open circuit, and they often have some means to monitor for correct operation.

 

so I suppose it depends on how risk averse you are. The chances of a live to earth short are pretty slim if your wiring is in reasonably good condition - in 11 years with a lot of time being spent on shore power, we have never had such a fault.

 

But it COULD happen and the fatalists will use that to justify getting a more expensive one that meets the ABYC standard.

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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.

 

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I have a 70amp non-ABYC compliant GI with a remote status monitor from safeshore marine. It's been on my boat for over 15 years and it's still working fine. It has a status monitor but you still need to check it from time to time. Sterling do a GI with a bypass capacitor I think. I'm not sure if that's ABYC compliant. There are only one or two units marketed in the UK that are and from what I've seen the diodes go into circuit at just over 1v which isn't great in terms of preventing RFI currents from activating the diodes. The diodes on mine go into circuit at 2.4v. if you want an ABYC compliant unit one of the contributors here should actually recommend a model rather than just saying "ABYC..." which isn't very helpful.

 

This sterling unit is compliant and if it falls it will fail closed circuit, however it has no status monitor so you won't know anything about it and your boat will be susceptible to galvanic currents.

 

https://www.visionmarine.co.uk/sterling-power-50-amp-zinc-saver-eu.html

 

This one meets ABYC standards and also has a status monitor, although if you install it in an engine space which is where most mains cables enter the boat then you probably won't see it very often in which case the monitor is rendered useless. You need to install it where you're likely to see it. It's also only good for 16amp supplies which is ok but it only blocks currents up to 1.1v meaning RFI currents might cause the diodes to conduct. At least you'd see it on the status monitor I suppose.

 

https://chandlery.biz/product/aquafax-galvanic-current-isolator-16a-with-indicator/?gclid=Cj0KCQjw9YWDBhDyARIsADt6sGY7oVFt75Br_jMPdj4bZn5z76bH-AVX8JnvNiT953zBJsoJCtX0XpgaAvv2EALw_wcB

 

 

Edited by blackrose
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6 hours ago, blackrose said:

I have a 70amp non-ABYC compliant GI with a remote status monitor from safeshore marine. It's been on my boat for over 15 years and it's still working fine. It has a status monitor but you still need to check it from time to time. Sterling do a GI with a bypass capacitor I think. I'm not sure if that's ABYC compliant. There are only one or two units marketed in the UK that are and from what I've seen the diodes go into circuit at just over 1v which isn't great in terms of preventing RFI currents from activating the diodes. The diodes on mine go into circuit at 2.4v. if you want an ABYC compliant unit one of the contributors here should actually recommend a model rather than just saying "ABYC..." which isn't very helpful.

 

This sterling unit is compliant and if it falls it will fail closed circuit, however it has no status monitor so you won't know anything about it and your boat will be susceptible to galvanic currents.

 

https://www.visionmarine.co.uk/sterling-power-50-amp-zinc-saver-eu.html

 

This one meets ABYC standards and also has a status monitor, although if you install it in an engine space which is where most mains cables enter the boat then you probably won't see it very often in which case the monitor is rendered useless. You need to install it where you're likely to see it. It's also only good for 16amp supplies which is ok but it only blocks currents up to 1.1v meaning RFI currents might cause the diodes to conduct. At least you'd see it on the status monitor I suppose.

 

https://chandlery.biz/product/aquafax-galvanic-current-isolator-16a-with-indicator/?gclid=Cj0KCQjw9YWDBhDyARIsADt6sGY7oVFt75Br_jMPdj4bZn5z76bH-AVX8JnvNiT953zBJsoJCtX0XpgaAvv2EALw_wcB

 

 

Thank you for taking the time and info 

you sent 

 

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12 hours ago, blackrose said:

I have a 70amp non-ABYC compliant GI with a remote status monitor from safeshore marine. It's been on my boat for over 15 years and it's still working fine. It has a status monitor but you still need to check it from time to time. Sterling do a GI with a bypass capacitor I think. I'm not sure if that's ABYC compliant. There are only one or two units marketed in the UK that are and from what I've seen the diodes go into circuit at just over 1v which isn't great in terms of preventing RFI currents from activating the diodes. The diodes on mine go into circuit at 2.4v. if you want an ABYC compliant unit one of the contributors here should actually recommend a model rather than just saying "ABYC..." which isn't very helpful.

 

This sterling unit is compliant and if it falls it will fail closed circuit, however it has no status monitor so you won't know anything about it and your boat will be susceptible to galvanic currents.

 

https://www.visionmarine.co.uk/sterling-power-50-amp-zinc-saver-eu.html

 

This one meets ABYC standards and also has a status monitor, although if you install it in an engine space which is where most mains cables enter the boat then you probably won't see it very often in which case the monitor is rendered useless. You need to install it where you're likely to see it. It's also only good for 16amp supplies which is ok but it only blocks currents up to 1.1v meaning RFI currents might cause the diodes to conduct. At least you'd see it on the status monitor I suppose.

 

https://chandlery.biz/product/aquafax-galvanic-current-isolator-16a-with-indicator/?gclid=Cj0KCQjw9YWDBhDyARIsADt6sGY7oVFt75Br_jMPdj4bZn5z76bH-AVX8JnvNiT953zBJsoJCtX0XpgaAvv2EALw_wcB

 

 


We have the aquafax one. After 10 years of being plugged into shore power for 90% of that time, we didn’t find any sign of galvanic corrosion  so I think it must work! We also have a lot of electronics on board, there doesn’t seem to be an issue with rf voltages on the earth line and I think this is a bit of a myth, as these days such things as phone chargers are not connected to earth at all (They have a plastic earth pin)

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14 hours ago, blackrose said:

This one meets ABYC standards and also has a status monitor, although if you install it in an engine space which is where most mains cables enter the boat then you probably won't see it very often in which case the monitor is rendered useless. You need to install it where you're likely to see it. It's also only good for 16amp supplies which is ok but it only blocks currents up to 1.1v meaning RFI currents might cause the diodes to conduct. At least you'd see it on the status monitor I suppose.

https://chandlery.biz/product/aquafax-galvanic-current-isolator-16a-with-indicator/?gclid=Cj0KCQjw9YWDBhDyARIsADt6sGY7oVFt75Br_jMPdj4bZn5z76bH-AVX8JnvNiT953zBJsoJCtX0XpgaAvv2EALw_wcB

 

I have one of these (slightly cheaper on ebay) but before it gets fitted and I plug in to a shore line, I understand I need to have the electric circuit on board earthed to the hull. What is the best /proper / easiest way to do this please.

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23 hours ago, Tony Brooks said:

I would want one that has some form of monitoring on it and conforms to the AAYC specification. If you can't find one doing that the one having a fault current rating of over a thousand amps for perhaps 10 seconds. Any that meet those specs will do the job.

 

 

Do you mean 10 milliseconds?

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7 hours ago, nicknorman said:


We have the aquafax one. After 10 years of being plugged into shore power for 90% of that time, we didn’t find any sign of galvanic corrosion  so I think it must work! We also have a lot of electronics on board, there doesn’t seem to be an issue with rf voltages on the earth line and I think this is a bit of a myth, as these days such things as phone chargers are not connected to earth at all (They have a plastic earth pin)

 

I'm not sure if EMI/RFI can reasonably be described as "a myth" as it definitely exists. If anyone is in doubt just do a Google search. What happens on one boat isn't necessarily a measure of what will happen on all boats. If you haven't seen any evidence of galvanic corrosion on your boat that could be the result of a few factors: a) no RFI currents were emitted. b) RFI currents were emitted but blocked by your GI. c) RFI currents forced your GI into conduction but any galvanic currents between your boat and any dissimilar earthed metals in the vicinity were too weak to do any damage. 

 

The point is that without a proper study there are too many variables to know exactly what's happening. Likewise I can't say that my non-ABYC compliant GI will never stop working due an earth fault despite it working fine and protecting my boat for the past 15 years.

 

 

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1 hour ago, blackrose said:

 

I'm not sure if EMI/RFI can reasonably be described as "a myth" as it definitely exists. If anyone is in doubt just do a Google search. What happens on one boat isn't necessarily a measure of what will happen on all boats. If you haven't seen any evidence of galvanic corrosion on your boat that could be the result of a few factors: a) no RFI currents were emitted. b) RFI currents were emitted but blocked by your GI. c) RFI currents forced your GI into conduction but any galvanic currents between your boat and any dissimilar earthed metals in the vicinity were too weak to do any damage. 

 

The point is that without a proper study there are too many variables to know exactly what's happening. Likewise I can't say that my non-ABYC compliant GI will never stop working due an earth fault despite it working fine and protecting my boat for the past 15 years.

Well obviously RFI a isn’t a myth, my point was that it being an issue for a GI is I suspect no longer the case. In the early days of switch mode power supplies designers sometimes put capacitors to the earth line to shunt away switching noise. However decades ago this became disallowed for CE stuff at least. If you look at your average charger with a SMPS it doesn’t even have a connection to earth - plastic earth pin. Or it comes with multiple plug options of which some (USA) don’t have any sort of earth pin.

 

So any phone /laptop  charger or other such stuff built within say the last 20 years is very unlikely to put any RF onto the earth line.

 

Of course this doesn’t stop certain manufacturers gaining advert brownie points by installing a few pence of shunt capacitors in the GI and charging £20 extra for it.

 

If I was concerned, I would fit my own capacitor across the GI terminals for a few pence, but I’m not.

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Fair enough, you know more about electrics than me. Where do you have your GI installed. Is that GI suitable for installation in an uninsulated (potentially damp) engine space? If I replaced mine that's where it would have to go. I wouldn't be concerned about the solid state diodes but I was just wondering about the status monitor.

 

 

 

7 hours ago, canalboat said:

I have one of these (slightly cheaper on ebay) but before it gets fitted and I plug in to a shore line, I understand I need to have the electric circuit on board earthed to the hull. What is the best /proper / easiest way to do this please.

 

Search hull-earth bonding. It's likely that it's already done but you should check that it has been.

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1 minute ago, blackrose said:

Fair enough, you know more about electrics than me. Where do you have your GI installed. Is that GI suitable for installation in an uninsulated (potentially damp) engine space? If I replaced mine that's where it would have to go. I wouldn't be concerned about the solid state diodes but I was just wondering about the status monitor.

 


Ours is installed right at the back in the engine bay, but of course we have a trad stern so it is a much nicer environment than the engine bay of a cruiser stern. I think you are probably right to be concerned about having that meter in a potentially fairly damp environment, although it does look reasonably well made. I’ll have a closer look tomorrow to see how well sealed it is.

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2 hours ago, Feeby100 said:

How about this one ? 
 

C0BE9C9E-84C8-44EE-91B9-327A2DF7DCD9.png

 

Try this supplier too

 

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

13 minutes ago, nicknorman said:


Ours is installed right at the back in the engine bay, but of course we have a trad stern so it is a much nicer environment than the engine bay of a cruiser stern. I think you are probably right to be concerned about having that meter in a potentially fairly damp environment, although it does look reasonably well made. I’ll have a closer look tomorrow to see how well sealed it is.

 

Thanks. The status monitor on the aquafax GI only shows DC current leaks, is that correct? What about AC current leaks, how would you know if the GI was conducting that? I think mine is supposed to show both. 1 led or 2 LEDs.

 

Edited by blackrose
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7 hours ago, blackrose said:

Thanks. The status monitor on the aquafax GI only shows DC current leaks, is that correct? What about AC current leaks, how would you know if the GI was conducting that? I think mine is supposed to show both. 1 led or 2 LEDs.

 

 

Yes the meter only shows dc leaks. But IMO AC leaks are not something to worry about. The meter has the advantage of showing how close to conduction you are, whereas the LEDs only show that it is conducting - and of course you have to be there to see the LEDs illuminating.
We mostly plug in at the marina, where the meter moves a barely noticable amount, giving me confidence that we are a long way from conduction. Other places we have plugged into give a varying amount of needle deflection, though I have never seen it close to the limit. The meter is thus useful for getting an idea of the “quality” of the earth.

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