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Old 23-06-2013, 13:11   #46
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Re: GFIC WIRING

I'm glad you got an answer to your question. Remember, starting a thread is like starting a conversation - you don't get to control what others say. And you might have learned something extra here. Most cruisers should be considering additional electrical equipment, be it isolating transformer, galvanic isolators, and yes, ELCIs.

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Old 23-06-2013, 13:32   #47
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Re: GFIC WIRING

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You obviously don't see boats built in Europe. My 10 year old boat has a RCBO as the main breaker from the factory.
(snip)

False trips? They do trip for a reason, but it may be one that isn't discernible.
+1 on that.
I know that in the US false tripping is cited as the reason why you cannot use a single RCD to cover the whole house/boat, but I am afraid reality gets on the way of this nice theory because there are whole countries where every house has a 30mA whole-house RCD and false tripping is a non-issue . By the way, using a single RCD lets you buy an RCD that works reliably for ages, unlike the cheap outlet-mounted RCDs used in the US.

C
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Old 23-06-2013, 18:14   #48
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Re: GFIC WIRING

At least DOT Dun is thinking, whereas some are just parotting house wiring

AN invertor is a isolated mains power generator, just like a isolating transformer, onboard diesel generator etc.

Yes convention has it that protective ground is connected to neutral at the source of mains generation , this true for mains ( ie shorepower) or onboard generating systems.


HOWEVER ( and lets not parrot codes) . The primary purpose that a protective earth wire was introduced was to blow the fuse ( not a GFCI) if the hot , ie fused supply came in contact with a ground return , that didnt have a good connection with earth. Ie say the case of an appliance, on rubber feet, since the case is connected to the protective earth wire ,if the case inadvertently goes hot, a path for short circuit current is available and the fuse blows and the appliance is rendered safe.

In teh case however of a path to earth ground, ie a human standing on a concrete floor, who comes in contact with a hot wire ( that has not triggered protective earth) , there is a path back to the generator via the earth, not the earth wire the physical earth itself, this is because by design mains AC is earth referenced, ie it is not isolated.

Hence the user gets a shock as teh current passes through him to the earth ( planet).

enter the GFCI ( which is now more correctly called a RCB, ) One poster is correct in that it does not require the presence or connection of an earth wire to work.

It does however require a ground path via the planet, for a GFCI or RCD to work, the current must flow for a RCD to trip , therefor there must be a circuit. no circuit no fault current, no shock.

So with an isolated generator, since there is no particular earth connection ( ie to planet earth) then RCDs ( GFCIs) have limited use, since a fault cuurent may never flow that will trip them. One could argue that with an isolated supply even the protective earth wire to teh generator neutral isnt needed, as again since there isnt a planet return path , you cant get a shock from holding the live ( hot) wire of an isolated mains source.

However the protective earth does have a limited use in such situations as it provides a fault path back to the generator ( which is why its tied to its neutral) and therefor acts as a trip mechanism for a fuse, CB, etc to warn the user that an appliance connected to the earth protective wire has gone hot ( even though you cant get a shock from it)

This is why I put out the point that GFCIs on an isolated supply have little protective function.

You might argue that if the neutral made a good low resistance connection to earth and you also happened to make a good low resistance connection to earth with your body , then GFCIs might provide some protection, but that is in essence destroying the very advantage of isolated supplies and also providing a source of impressed current corrosion.

dave
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Old 23-06-2013, 18:58   #49
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Re: GFIC WIRING

Quote:
Originally Posted by goboatingnow View Post
HOWEVER ( and lets not parrot codes)... dave
I stand corrected. Thank you, sir.
Please forgive me for quoting the ABYC codes here on the forum.

But one little question, if I may...

Situation: the insurance company requires a recent survey, and then the hired surveyor writes down that the vessel has no GFCI(s) installed and needs them to meet code.

What would you recommend, that the owner install the GFCI units or just lie about doing so to the insurance company?
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Old 23-06-2013, 19:21   #50
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Originally Posted by svmariane View Post

I stand corrected. Thank you, sir.
Please forgive me for quoting the ABYC codes here on the forum.

But one little question, if I may...

Situation: the insurance company requires a recent survey, and then the hired surveyor writes down that the vessel has no GFCI(s) installed and needs them to meet code.

What would you recommend, that the owner install the GFCI units or just lie about doing so to the insurance company?
This would only be a requirement should the boat be built to ABYC specs and that the insurer mandates the vessel must so comply , since there are many European boats that are not built specifically to ABYC but to EU RCD standards and I don't believe US customers have any trouble with insuring them. Since aBYC has no statutory basis anyway , how can an insurer force compliance.


The fact is ABYC AC electrical practice in the face of whole boat Residual current devices , is flawed as its now a mis-match of pre and post RCB practice and does not sit well with on board AC generation ( by invertor, generator , or isolating transformer ) Calder gives some thought to this issue in his book on the subject


Dave
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Old 23-06-2013, 19:21   #51
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Re: GFIC WIRING

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Originally Posted by goboatingnow View Post
At least DOT Dun is thinking, whereas some are just parotting house wiring

AN invertor is a isolated mains power generator, just like a isolating transformer, onboard diesel generator etc.

Yes convention has it that protective ground is connected to neutral at the source of mains generation , this true for mains ( ie shorepower) or onboard generating systems.


HOWEVER ( and lets not parrot codes) . The primary purpose that a protective earth wire was introduced was to blow the fuse ( not a GFCI) if the hot , ie fused supply came in contact with a ground return , that didnt have a good connection with earth. Ie say the case of an appliance, on rubber feet, since the case is connected to the protective earth wire ,if the case inadvertently goes hot, a path for short circuit current is available and the fuse blows and the appliance is rendered safe.

In teh case however of a path to earth ground, ie a human standing on a concrete floor, who comes in contact with a hot wire ( that has not triggered protective earth) , there is a path back to the generator via the earth, not the earth wire the physical earth itself, this is because by design mains AC is earth referenced, ie it is not isolated.

Hence the user gets a shock as teh current passes through him to the earth ( planet).

enter the GFCI ( which is now more correctly called a RCB, ) One poster is correct in that it does not require the presence or connection of an earth wire to work.

It does however require a ground path via the planet, for a GFCI or RCD to work, the current must flow for a RCD to trip , therefor there must be a circuit. no circuit no fault current, no shock.

So with an isolated generator, since there is no particular earth connection ( ie to planet earth) then RCDs ( GFCIs) have limited use, since a fault cuurent may never flow that will trip them. One could argue that with an isolated supply even the protective earth wire to teh generator neutral isnt needed, as again since there isnt a planet return path , you cant get a shock from holding the live ( hot) wire of an isolated mains source.

However the protective earth does have a limited use in such situations as it provides a fault path back to the generator ( which is why its tied to its neutral) and therefor acts as a trip mechanism for a fuse, CB, etc to warn the user that an appliance connected to the earth protective wire has gone hot ( even though you cant get a shock from it)

This is why I put out the point that GFCIs on an isolated supply have little protective function.

You might argue that if the neutral made a good low resistance connection to earth and you also happened to make a good low resistance connection to earth with your body , then GFCIs might provide some protection, but that is in essence destroying the very advantage of isolated supplies and also providing a source of impressed current corrosion.

dave
Dave,

your argument sounds all good until, you stop and think about it, the generator nor the inverter are isolated from mother earth. They are both bonded to SHIPS GROUND, or at least they should be.

In salt water the bond is a fairly low resistance path to mother earth, in fresh water it's a high resistance path to mother earth, but still a bond to mother earth.

Now we know the electric ions always follow the path of least resistance. But what what most don't consider is that those ions follow all paths to mother earth.

Again anything above 5 mA across the heart is enough to cause de-fib in certain sections of the population.

Lloyd
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Old 23-06-2013, 19:38   #52
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Re: GFIC WIRING

Quote:
Originally Posted by goboatingnow View Post
Since aBYC has no statutory basis anyway , how can an insurer force compliance.
Naive much? Ever tried to get passage insurance for an ocean crossing without 3 experienced crew? No statutory basis there either. Insurance companies frequently tell their customers what they can and cannot do, at the risk of losing (statutorily required) insurance. I hate the loss of freedom, but that is the reality.

Greg
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Old 23-06-2013, 19:41   #53
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Originally Posted by FlyingCloud1937 View Post

Dave,

your argument sounds all good until, you stop and think about it, the generator nor the inverter are isolated from mother earth. They are both bonded to SHIPS GROUND, or at least they should be.

In salt water the bond is a fairly low resistance path to mother earth, in fresh water it's a high resistance path to mother earth, but still a bond to mother earth.

Now we know the electric ions always follow the path of least resistance. But what what most don't consider is that those ions follow all paths to mother earth.

Again anything above 5 mA across the heart is enough to cause de-fib in certain sections of the population.

Lloyd
Ok we're closing in on the nub. I see no reason for and several against any reason to ground reference to seawater, isolated mains supplies ( note isolated ) in fact in doing do you are destroying the very isolation. ( like in a isolation transformer ) that makes it safe in the first place.

I would cite European whole house 30mA which begs to differ with the 5mA argument and this is at 230 vac. !!!

Again why would you destroy the very useful isolating feature of onboard AC generating devices.


I'm not aware ABYC requires you to establish a local AC seawater earth. ( in fact in many jurisdictions elsewhere its specifically forbidden )

Dave
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Old 23-06-2013, 19:59   #54
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Re: GFIC WIRING

Quote:
Originally Posted by goboatingnow View Post
enter the GFCI ( which is now more correctly called a RCB, ) One poster is correct in that it does not require the presence or connection of an] earth wire to work.
That may be literally correct but misleading, because the RCD works differently in each of those two scenarios.

If there is a protective earth wire (connected to neutral at source and to the case of a double-insulated appliance as usual) then the RCD (if fitted) or the fuse/breaker (depending on the nature of the incident) will trip as soon as, or before, the case of the appliance acquires the potential to hurt you.

If there is no protective earth wire then an RCD will not trip until you touch the case of the appliance and get a nasty shock.

Using reasonably conservative assumptions (say a few thousand ohms or less between the floor and source neutral and 1000 ohms for your body) this applies to boats, oil platforms and houses. This is physics, it does not depend on codes. Therefore the protective earth wire does make a difference even if there is an RCD.
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Old 23-06-2013, 20:01   #55
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Re: GFIC Wiring

ABYC wiring diagrams clearly show the ship's side of an isolation transformer's neutral and ground connected "To Engine Negative Terminal or its Bus".

Greg
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Old 23-06-2013, 20:06   #56
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ABYC wiring diagrams clearly show the ship's side of an isolation transformer's neutral and ground connected "To Engine Negative Terminal or its Bus".

Greg
Yes bit no requirement I know of states the engine must be connected to seawater.

Dave
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Old 23-06-2013, 20:17   #57
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Re: GFIC Wiring

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Originally Posted by goboatingnow View Post
Ok we're closing in on the nub. I see no reason for and several against any reason to ground reference to seawater, isolated mains supplies ( note isolated ) in fact in doing do you are destroying the very isolation. ( like in a isolation transformer ) that makes it safe in the first place.
A generator even though isolated, is connected to mother earth, by the fact that it is sea water cooled, this is a high Resistance connection. So in a fault situation, where the unsuspecting touches a live fault in one hand an a better connection to mother earth in the other hand, an x mA across the heart is psooible.


Quote:
I would cite European whole house 30mA which begs to differ with the 5mA argument and this is at 230 vac. !!!
Euro is 50 cycle, and US is 60 cycle, 60 cycle is a perfect cause of de-fib, I heard rumor that's why Euro chose 50 cycle....but I serious doubt they were seriously considering the de-fib factor when they chose 50 cycle.

30 mA was choose to stop shore power nuisance tripping whole boat, but to be safe any load that potentially has a fault path to sea water, should be protected by a 5 mA leakage protection device.

Quote:
Again why would you destroy the very useful isolating feature of onboard AC generating devices.
because it's very likely that anything isolated is not, and now you have 2 problems. 1. Ions will find the path to ground, any path...ground=mother earth. 2. multiple pathes to ground set up the possibility for different potentials to ground and thereby circulating currents in the earth ground. which creates all manor of corrosion issues.

Quote:
I'm not aware ABYC requires you to establish a local AC seawater earth. ( in fact in many jurisdictions elsewhere its specifically forbidden )

Dave
Wow, giving advise

Lloyd
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Old 23-06-2013, 20:17   #58
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That may be literally correct but misleading, because the RCD works differently in each of those two scenarios.

If there is a protective earth wire (connected to neutral at source and to the case of a double-insulated appliance as usual) then the RCD (if fitted) or the fuse/breaker (depending on the nature of the incident) will trip as soon as, or before, the case of the appliance acquires the potential to hurt you.

If there is no protective earth wire then an RCD will not trip until you touch the case of the appliance and get a nasty shock.

Using reasonably conservative assumptions (say a few thousand ohms or less between the floor and source neutral and 1000 ohms for your body) this applies to boats, oil platforms and houses. This is physics, it does not depend on codes. Therefore the protective earth wire does make a difference even if there is an RCD.
No I don't beleive you are right. , a double insulated appliance does not require a protective earth connection , hence you cannot get a shock by coming into contact with the live wire , you can only get a shock by inserting yourself into the circuit and in that case a RCD will not protect you. The reason is the power output of a double insulated device is an isolated mains supply and therefore protective earth plays no part in the fault circuit

Furthermore , you receive no noticeable shock effect in European wiring on triggering a 30 mA RCD device , in fact a local electricians party piece to disconnect the buildings wiring was to stick his finger in the live plug point to force a RCD disconnect ( warning dont try this at home kids )

If you were to follow the confused codes , in the case of an isolating transformer , on board being fed by shore power , creating a seawater connector to local ships earth wire and hence the output neutral of the transformer, would destroy the very thing the traffo was installed to do. ( ie both neutrals would be linked by a earth ground path !!)

Dave
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Old 23-06-2013, 20:25   #59
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Re: GFIC Wiring

Quote:
Originally Posted by goboatingnow View Post
This would only be a requirement should the boat be built to ABYC specs and that the insurer mandates the vessel must so comply , since there are many European boats that are not built specifically to ABYC but to EU RCD standards and I don't believe US customers have any trouble with insuring them. Since aBYC has no statutory basis anyway , how can an insurer force compliance.

The fact is ABYC AC electrical practice in the face of whole boat Residual current devices , is flawed as its now a mis-match of pre and post RCB practice and does not sit well with on board AC generation ( by invertor, generator , or isolating transformer ) Calder gives some thought to this issue in his book on the subject

Dave
Oops...Did I mention ABYC specs in the example? Let me check....

[QUOTE] Originally Posted by svmariane

I stand corrected. Thank you, sir.
Please forgive me for quoting the ABYC codes here on the forum.

But one little question, if I may...

Situation: the insurance company requires a recent survey, and then the hired surveyor writes down that the vessel has no GFCI(s) installed and needs them to meet code.

What would you recommend, that the owner install the GFCI units or just lie about doing so to the insurance company?
[QUOTE]

Hmmm... No. No mention of ABYC in the situation or question, nor EU, RCB or RCD. And so the question stands - well, side-stepped.

Maybe I'm just not much of a Viking. If the USCG says I need 6, or 16, or 66 red flares then that's what I put aboard. If the insurance company demands GFCI then that's what I install. {Mr. Calder and his non-legally binding thoughts aside.}

On the other hand, when the neighbors music gets too irritating I weigh anchor.
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Old 23-06-2013, 20:27   #60
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A generator even though isolated, is connected to mother earth, by the fact that it is sea water cooled, this is a high Resistance connection. So in a fault situation, where the unsuspecting touches a live fault in one hand an a better connection to mother earth in the other hand, an x mA across the heart is psooible.

Euro is 50 cycle, and US is 60 cycle, 60 cycle is a perfect cause of de-fib, I heard rumor that's why Euro chose 50 cycle....but I serious doubt they were seriously considering the de-fib factor when they chose 50 cycle.

30 mA was choose to stop shore power nuisance tripping whole boat, but to be safe any load that potentially has a fault path to sea water, should be protected by a 5 mA leakage protection device.

because it's very likely that anything isolated is not, and now you have 2 problems. 1. Ions will find the path to ground, any path...ground=mother earth. 2. multiple pathes to ground set up the possibility for different potentials to ground and thereby circulating currents in the earth ground. which creates all manor of corrosion issues.

Wow, giving advise

Lloyd
Fine Lloyd consider a air cooled generator , or a simple isolating transformer

50-60 cycles has nothing to do with de-fib. ( the decisions were based on the dominance of certain countries manufacturers of AC generator equipment in the late 1890s -1920

230vac has a greater shock risk, yet 30ma is considered adaquate.

As for your comments re anything isolated is not , this is electrical nonsense. If you generate a isolated supply ( by magnetic coupling ) you by definition do not have current flow to " ground" that's the whole point. The earth is not a return path.

Dave
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