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davidc

Galvanic Isolators

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My boat does not have either a Galvanic Isolator or Galvanic Transformer

As the transformer cost in the region of 800 pounds plus Ive decided to go with a isolator.

 

My question which is the better make Sterling or Victron or another make .

 

What is the forums considered opinion.

Edited by davidc

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My boat does not have either a Galvanic Isolator or Galvanic Transformer

As the transformer cost in the region of 800 pounds plus Ive decided to go with a isolator.

 

My question which is the better make Sterling or Victron or another make .

 

What is the forums considered opinion.

What size of transformer are you contemplating fitting? Quality boxes for about £200 ish are available that will meet your shore power loadings.

 

Edit:- Well done Loddon. Beat me to it!

Edited by Taslim

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Still a lot more, and a lot bulkier than a GI, and no safer intrinsically.

 

I would get a GI with status indication, LEDs preferably, or a meter.

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Still a lot more, and a lot bulkier than a GI, and no safer intrinsically.

 

I would get a GI with status indication, LEDs preferably, or a meter.

Was thinking the same there seems no consensus on what is better so will go with GI (where is Gibbo when you need him).

 

So what model do you have.

 

Have to say on the survey there was min pitting and, the steel had lost no thickness on the hull.

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Still a lot more, and a lot bulkier than a GI, and no safer intrinsically.

 

 

Maybe true if you KNOW the GI has been built to a given standard but as far as I know a UK/EU standard for GIs has not yet been completed so you are in the hands of the manufacturer to fit adequate diodes and those diodes require a far higher rating than many people think.

 

Having indicator LEDs may help but according to Gibbo, as I understood him, they are not as foolproof as may be thought.

 

I think the answer for the OP is one that has been built to meet the ABYC standard.

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Was thinking the same there seems no consensus on what is better so will go with GI (where is Gibbo when you need him).So what model do you have.Have to say on the survey there was min pitting and, the steel had lost no thickness on the hull.

I have the Aquafax one, with a meter as opposed to LEDs. This is just the one that came with the boat, I didn't select it. The meter deflects slightly when on shore power in our marina, so I know its doing some good!

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Maybe true if you KNOW the GI has been built to a given standard but as far as I know a UK/EU standard for GIs has not yet been completed so you are in the hands of the manufacturer to fit adequate diodes and those diodes require a far higher rating than many people think.

 

Having indicator LEDs may help but according to Gibbo, as I understood him, they are not as foolproof as may be thought.

 

I think the answer for the OP is one that has been built to meet the ABYC standard.

Thank you for that info was not aware of the standard

can I ask do you have one and if so what model

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Maybe true if you KNOW the GI has been built to a given standard but as far as I know a UK/EU standard for GIs has not yet been completed so you are in the hands of the manufacturer to fit adequate diodes and those diodes require a far higher rating than many people think.

 

Having indicator LEDs may help but according to Gibbo, as I understood him, they are not as foolproof as may be thought.

 

I think the answer for the OP is one that has been built to meet the ABYC standard.

Yes, I agree that one built to ABYC would seem sensible.

 

However, let's consider the consequences of one with inadequate diodes. All is well until there is a short from live to hull. The return path is through the GI diodes and they blow (open circuit) before the breakers can trip. Now we have a live hull. However, if the bollard has an RCD, return current is flowing back via exposed metal (baseplate, prop etc), the water and shore to the wrong side of the bollard RCD and so it will trip if the current exceeds 30mA or so. Unless the water is very pure I think its likely the current would exceed 30mA. If the water is very pure, the breaker will only trip if somebody assists the current flow by bridging between the hull and the ground, but it will still trip to protect the human.

 

It is only if there is no RCD on the bollard that a blown GI will cause a dangerous situation. But then, that would also mean (even with an intact GI) that any flaw in the shore power lead could be fatal, or even dropping the live end into the water, plugging in with wet hands and water in the cable connectors etc.

 

So if you have no RCD on the bollard, I think that having an under-rated GI is the least of your worries! If you do have an RCD on the bollard, blowing the GI diodes is not a critical failure.

 

Please feel free to pick holes in my logic...

Edited by nicknorman

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You are wrong Nick

There is no guarantee that an RCD will trip relying on a return path through fresh water.

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You are wrong Nick

There is no guarantee that an RCD will trip relying on a return path through fresh water.

Well I think I covered that point. Isn't the point that < 30mA through a human body is considered not fatal? Therefore if less than 30mA is leaking through the water (although I maintain this is unlikely with the impurities in most canals) its not fatal, and if a human helps to bridge the water the current will exceed 30mA and trip the RCD. If a human can't withstand 30mA than RCDs seem a bit pointless.

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Was thinking the same there seems no consensus on what is better so will go with GI (where is Gibbo when you need him).

 

So what model do you have.

 

Have to say on the survey there was min pitting and, the steel had lost no thickness on the hull.

 

Please read the information by using the link below.

 

http://www.smartgauge.co.uk/galv_tran.html

 

Keith

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Yes, I agree that one built to ABYC would seem sensible.

 

However, let's consider the consequences of one with inadequate diodes. All is well until there is a short from live to hull. The return path is through the GI diodes and they blow (open circuit) before the breakers can trip. Now we have a live hull. However, if the bollard has an RCD, return current is flowing back via exposed metal (baseplate, prop etc), the water and shore to the wrong side of the bollard RCD and so it will trip if the current exceeds 30mA or so. Unless the water is very pure I think its likely the current would exceed 30mA. If the water is very pure, the breaker will only trip if somebody assists the current flow by bridging between the hull and the ground, but it will still trip to protect the human.

 

It is only if there is no RCD on the bollard that a blown GI will cause a dangerous situation. But then, that would also mean (even with an intact GI) that any flaw in the shore power lead could be fatal, or even dropping the live end into the water, plugging in with wet hands and water in the cable connectors etc.

 

So if you have no RCD on the bollard, I think that having an under-rated GI is the least of your worries! If you do have an RCD on the bollard, blowing the GI diodes is not a critical failure.

 

Please feel free to pick holes in my logic...

 

This is why the latest ABYC compliance requires the GI to be able to withstand 5000 amps peak (on a 30 amp system) for a full mains cycle (previously around a half cycle) allowing adequate time for safety trip to work. A beefy diode system is need to comply.

 

Latest compliance also requires GI monitoring. The Sterling system sends a signal down the neutral wire and looks for it returning (via local substation where the strap is made) back on the boats earth cable after GI.

Edited by by'eck

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Thank you for that info was not aware of the standard

can I ask do you have one and if so what model

 

I will simply not have anything to do with a shoreline. I have a 12V boat with a very small inverter for charging a hand held Hoover, visitors' phones that do not use one of the 12V adaptors we have, the PWM radios and rechargeable battery charger. All plugged directly into the inverter (150 watts).

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You are wrong Nick

There is no guarantee that an RCD will trip relying on a return path through fresh water.

One data point. I've dropped the end of a live extension lead into canal (well, actually Middle Level) water and the RCD tripped very promptly.

 

MP.

Edited by MoominPapa

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My boat does not have either a Galvanic Isolator or Galvanic Transformer

As the transformer cost in the region of 800 pounds plus Ive decided to go with a isolator.

 

My question which is the better make Sterling or Victron or another make .

 

What is the forums considered opinion.

Worth a look too at the Safeshore Marine ones (google), they specialise in them and offer models with an LED status monitor which can be very useful. I think a few people on here have them.

 

One data point. I've dropped the end of a live extension lead into canal (well, actually Middle Level) water and the RCD tripped very promptly.

 

MP.

 

That is very much my experience too, can't see otherwise unless you moor in a marina full of de-ionised water. :)

 

cheers, Pete.

~smpt~

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One data point. I've dropped the end of a live extension lead into canal (well, actually Middle Level) water and the RCD tripped very promptly.

 

MP.

 

 

The connector has L N & E all close together a very short path so lowish resistance going through the water/soil bank etc back to the supply is a much higher resistance path.

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The connector has L N & E all close together a very short path so lowish resistance going through the water/soil bank etc back to the supply is a much higher resistance path.

Set against that, the longer the path the lower the potential gradient within the water will be. A swimmer etc is shocked because he stretches along a region of potential gradient - ie his head is in water at a different potential from his toes. Therefore if its a long path to earth, the potential gradient will be shallow and not harming. If its very short, the resistance will be low and will trip the RCD. Its the middling case I am not sure about - can there be sufficient separation between live and earth so as not to trip the RCD, whilst their being sufficient potential gradient in the length of a human to be harming. Dunno! But being taller than most, I guess I am at most risk. Eeek!

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I've just fitted the transformer Loddon links to above. No idea yet whether it works but I can say it was very easy to fit. It comes with no instructions and no holes in the case, which foxed me for a bit. I used the wiring diagrams on the smartguage site to connect it up. I was swayed by the smartguage site advice which seemed to me to be saying there was a balance in favour of the transformer over the GI both for effectiveness in preventing electolysis and in safety. It is more expensive but I thought it worth the extra.

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Please read the information by using the link below.

 

http://www.smartgauge.co.uk/galv_tran.html

 

Keith

thank you I stand corrected

I've just fitted the transformer Loddon links to above. No idea yet whether it works but I can say it was very easy to fit. It comes with no instructions and no holes in the case, which foxed me for a bit. I used the wiring diagrams on the smartguage site to connect it up. I was swayed by the smartguage site advice which seemed to me to be saying there was a balance in favour of the transformer over the GI both for effectiveness in preventing electolysis and in safety. It is more expensive but I thought it worth the extra.

Also after reading the smartguage web site I am going to splash out and get a transformer

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Set against that, the longer the path the lower the potential gradient within the water will be. A swimmer etc is shocked because he stretches along a region of potential gradient - ie his head is in water at a different potential from his toes. Therefore if its a long path to earth, the potential gradient will be shallow and not harming. If its very short, the resistance will be low and will trip the RCD. Its the middling case I am not sure about - can there be sufficient separation between live and earth so as not to trip the RCD, whilst their being sufficient potential gradient in the length of a human to be harming. Dunno! But being taller than most, I guess I am at most risk. Eeek!

When I was an apprentice it was a thoroughbred stallion with his front hoof on the earth rod and high earth loop impedance.

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I will simply not have anything to do with a shoreline. I have a 12V boat with a very small inverter for charging a hand held Hoover, visitors' phones that do not use one of the 12V adaptors we have, the PWM radios and rechargeable battery charger. All plugged directly into the inverter (150 watts).

 

I take it you do not live onboard then? It's easy to decry something that one doesn't need. I know many liveaboards don't have shore power, but I'd guess the vast majority who don't wish they did - especially in winter.

I have the Safeshore GI70sm. I'm not sure if it complies with ABYC regs but surely a 70amp isolator on a 16amp supply is ok?

 

http://www.safeshoremarine.com/assetts/specification%20sheet.pdf

 

http://www.safeshoremarine.com/Which%20isolator%202012.pdf

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I take it you do not live onboard then? It's easy to decry something that one doesn't need. I know many liveaboards don't have shore power, but I'd guess the vast majority who don't wish they did - especially in winter.

 

No, I do not live aboard but have spent fairly long periods board during the winter months - without feeling the need for a shoreline.

 

Also I did not decry anything or anyone. I simply answered a question in which the questioner seemed to assume most boats have shoreline hookups so need a GI or IT.

 

The basic human needs of shelter, warmth and food can all be easily met without the need for a large inverter or shoreline - I do not see that many CCers with shorelines and generators. It all depends upon what one considers vital on the boat. I would like my wife to have a mains hair dryer to make life easier for her but we both recognise that it is not practical. I suppose we would both like a iron but the same applies.

 

Be content with a simple life need there is no need for a shoreline. Doing without one is even easier now than it was because of solar and LED lighting.

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The basic human needs of shelter, warmth and food can all be easily met without the need for a large inverter or shoreline - I do not see that many CCers with shorelines and generators. It all depends upon what one considers vital on the boat. I would like my wife to have a mains hair dryer to make life easier for her but we both recognise that it is not practical. I suppose we would both like a iron but the same applies.

 

Be content with a simple life need there is no need for a shoreline.

 

Says the person who doesn't live aboard... laugh.png

 

My life is already simple enough. I've been living on a boat for 10 years and don't have a house to go back to when I feel like it. It just seems a bit rich for someone who lives in a house and also owns a boat, to tell people who live aboard permanently that they should be living the simple life!

 

We all know that there is no need for a shoreline. I lived aboard for 3 years without it. However, some of us choose to have shore power because it makes life a bit easier.

 

Edit: In a country full of decadent consumers I don't see why liveaboard boaters are the ones who are expected to "live the simple life"? It reminds me of a non-boater who once told me I shouldn't have my small (Honda EX650) generator onboard my 45ft Springer and should use solar panels instead because it would be more environmentally friendly. Then she drove off in a 4x4 back to her comfortable house (with mains electricity)!

Edited by blackrose
  • Greenie 1

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I find your comments extremely rude and doubt that you actually read and UNDERSTOOD my replies. In both the latter cases I responded to questions directed to myself specifically giving my personal choices and in no way suggested that anyone should do without a shoreline. You have no idea how long I spend on my boat so have no grounds for comment.

 

Unlike your implied opinion I do not think it is my place to tell anyone how they ought to live their life anymore than you should.

 

If you want mains a lot of mains power then that is your choice and it is not up to you to try to foist that choice on others. I have never wanted a lot of mains power on a boat but again I can not try to foist that choice on others. I am not the idiot in the 4 x 4 so do not try to imply I have similar views.

 

If you could see my "postbag" over the years you should soon see why I have made the choices I have, but then just maybe you would not understand what I was being told/asked.

 

If you can not add anything to the OPs question do not try to pick a fight with those who have.

  • Greenie 2

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