Hull Earth Bond

[Doorman]

Pitting isn't always the result of galvanic action.

 

Edit: as I see you discovered yourself.

Quite true.

 

I recall Dominic Miles telling me about a fairly new boat that came onto his listings down at Rugby, that had a badly pitted hull and it had never been near a shoreline or marina. There's a stretch of canal near us on the Midlewich Branch of the Shroppie that is alleged to be quite brackish and prone to eating hulls.

 

All you can do is try and protect your hull within the boundaries of your budget, but the knowledge gleaned on here is of great assistance.

[clbrof]

HI again everyone. I have bought a Sterling Power Galvanic Isolator, I am hoping its brand name will protect me better than ones I saw without a name?

[blackrose]

HI again everyone. I have bought a Sterling Power Galvanic Isolator, I am hoping its brand name will protect me better than ones I saw without a name?

 

Strictly speaking, the GI is designed to protect your boat (while connected to shore power), not you. Which model did you buy?

Edited August 14, 2013 by blackrose

[clbrof]

Prosave E ZS16A

[Richard10002]

OK! I haven't done any of the multimeter tests but it just so happens I bought a cheap plug in tester with lights on the back to tell you a variety of things.

Plugged it in to a few mains sockets this morning, when th genny was running via the shore power socket - it goes through the inverter charger, then into a consumer unit with RCD and MCB before supplying the boat 240v supply - the tester showed 2 red lights indicating no earth.

Shut down the genny, so nothing via the shore power socket. Left the inverter running,msupplying the boat with 240v and, lo and behold, the tester showed 3 lights, indicating all is well, and there is an earth.

So.... It looks like thet is no earth when the genny is running, which kind of suggests there is no route back to the generator negative for the earth. Does this suggest no neutral-earth bond at the genny? How to resolve? Do I connect the earth to neutral in the plug which goes into the genny, or is there some other solution - I probably know enough to be dangerous at the moment, but I'm probably not far from getting it right with a bit of guidance.

Can I bump this again? I'd guess that a few people may have the same issue with their generators and no earth, so I think it will be a welcomed answer.

 

Having googled a bit, there is one suggestion that a second plug is plugged into the second socket, and that this second plug, which is powering nothing, has its neutral and earth connected - cant get my head around how that might work?

[ditchcrawler]

Can I bump this again? I'd guess that a few people may have the same issue with their generators and no earth, so I think it will be a welcomed answer.

 

Having googled a bit, there is one suggestion that a second plug is plugged into the second socket, and that this second plug, which is powering nothing, has its neutral and earth connected - cant get my head around how that might work?

Especially if the generator is center tap earthed.

[blackrose]

Prosave E ZS16A

 

I'm sure it will be fine.

 

I prefer a GI with led status monitor. Mine is the Safeshore 70 amp

[Richard10002]

Especially if the generator is center tap earthed.

It's a Honda EU20i. How can I tell?

[ditchcrawler]

It's a Honda EU20i. How can I tell?

I have no idea what he has, that's the problem with so many questions on here. You don't know at a distance what you are dealing with.

[blackrose]

It's a Honda EU20i. How can I tell?

 

Honda EU portable generators have a floating earth. I don't know exactly how that works but it's not N-E bonded. Strictly speaking I think floating earths are designed for running one or two power tools rather than an entire AC system through a consumer unit with multiple outlets. But most people don't realise this and just use it as it is to run the AC system on their boats. However, there may be an issue that the consumer unit's RCD or RCBO won't work in the event of of a fault because it needs the AC supply to be N-E bonded to work.

 

You have a couple of different options:

 

1) N-E bond the generator at the outlet socket and label this on the generator. Connect the chassis earth connector on the generator to your hull's (AC) earth stud. Label the generator clearly to state that it has been N-E bonded and must only be used through the boat's consumer unit (because you have disabled the floating earth and if you run a power tool from it direct you will have no protection at all.)

 

2) N-E bond the cable used to connect the generator to the boat at the socket that plugs into the generator. Label the cable Cable N-E bonded. Only for use with Honda EU20i Generator through (name of your boat) consumer unit. Connect the chassis earth connector on the generator to your hull's (AC) earth stud. The only problem with this option is that the cable used to connect the generator to the boat is unprotected by the boat's RCD/RCBO and now has no floating earth protection either.

 

3) Leave it as it is but be aware that you are relying on the generator's floating earth for protection rather than your boat's RCD/RCBO.

Edited August 17, 2013 by blackrose

[Doorman]

It's a Honda EU20i. How can I tell?

Contact a guy called Peter at: www.petepower.co.uk

 

He is an expert on Honda generators and will be happy to answer any queries that you have in mind.

[by'eck]

It's a Honda EU20i. How can I tell?

 

I doubt the Honda EU20i and other similar inverter generators use a centre-tapped earth.

 

Googling the subject it seems many people with safe incoming mains warning lights which show incorrect earth among other things, have cured the fault indication by using a dedicated lead (never to be used with shore connection) with earth and neutral connected within one end of the lead. I would get a qualified opinion before trying this though.

 

If the generator was centre tap earthed this would have put a direct short on one leg of the output, so I conclude the earth must be floating wrt live and neutral.

 

BTW my Kipor IG2600 causes the mains warning light to show more than one fault dependent on load which would also suggest it has a floating earth. In all other respects it works fine though.

[Richard10002]

Contact a guy called Peter at: www.petepower.co.uk

He is an expert on Honda generators and will be happy to answer any queries that you have in mind.

Thanks for that. Email sent.

[Richard10002]

Contact a guy called Peter at: www.petepower.co.uk

He is an expert on Honda generators and will be happy to answer any queries that you have in mind.

Here is Pete Powers response:

 

"Hello Richard,

 

 

it is true that most generators have floating live and neutral. This means

that there is no connection between neutral and earth. The effect of this is

that when you measure between live and neutral you see 230v but between

neutral and earth or live and earth it could be anything from 0 to 230v.

Domestic supplies are almost always referenced to earth ie neutral and earth

connected.

 

The difference is significant if you have equipment that looks at the live

to earth voltage. Some washing machines do this and some charger systems. If

you do find it necessary to reference to earth then its important to mark

the generator to let anyone using it know that this has been done and to

ensure that you have a good earth connection to the generator. It's a wise

precaution to have a good earth connection anyway. Even with an EU20i that

has the plastic casing there are still a few metal parts like the control

panel that come into contact with the user.

 

When a generator is referenced to earth if a fault puts live to the frame of

the genny, it will definitely present the full 230v. That is why it's doubly

important to make sure that the operator is not the only route to ground.

 

Generally speaking if the floating earth situation is not causing a problem

then its probably best left alone.

 

Regards Pete"

 

To be honest, his answer leaves me just as confused, and much of it has "whooshed" over my head.

 

My current conclusion is that it's probably best left alone.... Everything works, and nobody has died?

 

However, this might be because there haven been any faults where something has become live, with a person/dog becoming the route to earth. So what actually happens with this system when there is a fault? Presumably the RCD on the consumer unit won't trip?

 

Does the stray power find its way back the the floating earth of the genny? Does the genny then become live? Could a person/dog then become the path to earth from the genny control panel? Therefore, should the genny earth stud be connected to the Hull Earth point?

 

etc. etc. etc.

[nicknorman]

If the genny output is left floating, it means that you can touch either live or neutral and not receive a shock, or even notice. So in some ways it could be considered a good thing, as perhaps Peter is implying. However it also means that a fault that connects live to earth won't be noticed and it might persist for a long time (years) before another fault ties neutral to hull, and then you have some bits of the system lethal.

 

If you are just plugging in a device into the genny, say a power drill (which is probably double insulated anyway) for occasional use, there is no point in an NE bond and without an RCD this in any case would be bad idea (since it means that touching live would give a shock).

 

However for permanently installed equipment such as a mains distribution system running various appliances, and with an appropriately rated MCB and RCD, the balance shifts to make having an NE bond the safer option. That way, something will trip with the first fault, as opposed to having the first fault potentially present for years awaiting a second fault to make a big problem. Therefore, if you are plugging the genny into your boat's electrical distribution system, which already has an RCD &MCB, having an NE bond on the genny is the way to go.

[Guest]

If the genny output is left floating, it means that you can touch either live or neutral and not receive a shock, or even notice. So in some ways it could be considered a good thing, as perhaps Peter is implying. However it also means that a fault that connects live to earth won't be noticed and it might persist for a long time (years) before another fault ties neutral to hull, and then you have some bits of the system lethal.

 

If you are just plugging in a device into the genny, say a power drill (which is probably double insulated anyway) for occasional use, there is no point in an NE bond and without an RCD this in any case would be bad idea (since it means that touching live would give a shock).

 

However for permanently installed equipment such as a mains distribution system running various appliances, and with an appropriately rated MCB and RCD, the balance shifts to make having an NE bond the safer option. That way, something will trip with the first fault, as opposed to having the first fault potentially present for years awaiting a second fault to make a big problem. Therefore, if you are plugging the genny into your boat's electrical distribution system, which already has an RCD &MCB, having an NE bond on the genny is the way to go.

Nicely put. You wouldn't believe the trouble I have had trying to explain to people over the years about a floating earth, when it is possible to touch a phase without getting a shock. One was a bloke who had been an electrician all his life, and he didn't understand it. He claimed I was wrong. Frightening really.

My RCD failed on my RCD tester when I fitted it, and I quickly realised that the inverter was a floating earth (as was my genny) A suitable earth bond and a N_E link put things right. It is of course vital to check with the manufacturers before adding such a link.

[smileypete]

 

He also goes on to point out that those GI's with status monitors generally have a higher switch on theshold because they have more diodes and can offer better protection against this potential, but by no means certain problem

 

 

For the price of an IT you could buy a GI with status monitor, and one of those neat little £50 nano oscilloscopes, and have enough left over for quite a few beers.

 

Use the scope across the GI when you feel like it, to reassure there's no problem with SMPS noise across the GI. And if there is, post a piccy on here...

 

With inverters and gennys that have a floating earth, even if only using one appliance on them, it may still be a very good idea to use a plug in RCD. This would be to reduce the risk of electrocution from a fault path that returns though the exposed metal frame or case of the inverter/genny.

 

cheers, Pete.

~smpt~

Edited August 17, 2013 by smileypete

[Doorman]

For the price of an IT you could buy a GI with status monitor, and one of those neat little £50 nano oscilloscopes, and have enough left over for quite a few beers.

 

cheers, Pete.

~smpt~

You are right Pete, I've just sold ours on Ebay to generate some Guinness money for next weekend! :-)

 

The cheeky sod who bought it wanted me to leave the boat attached to the transformer for the price that I commanded.

 

With inverters and gennys that have a floating earth, even if only using one appliance on them, it may still be a very good idea to use a plug in RCD. This would be to reduce the risk of electrocution from a fault path that returns though the exposed metal frame or case of the inverter/genny.

 

cheers, Pete.

~smpt~

I invested in an earth rod to ground the frame on our Honda generator, if I can get past all of Mrs Doorman's flower arrangements on our mooring I'll drive it into the ground.

Edited August 18, 2013 by Doorman

[by'eck]

If the genny output is left floating, it means that you can touch either live or neutral and not receive a shock, or even notice. So in some ways it could be considered a good thing, as perhaps Peter is implying. However it also means that a fault that connects live to earth won't be noticed and it might persist for a long time (years) before another fault ties neutral to hull, and then you have some bits of the system lethal.

 

If you are just plugging in a device into the genny, say a power drill (which is probably double insulated anyway) for occasional use, there is no point in an NE bond and without an RCD this in any case would be bad idea (since it means that touching live would give a shock).

 

However for permanently installed equipment such as a mains distribution system running various appliances, and with an appropriately rated MCB and RCD, the balance shifts to make having an NE bond the safer option. That way, something will trip with the first fault, as opposed to having the first fault potentially present for years awaiting a second fault to make a big problem. Therefore, if you are plugging the genny into your boat's electrical distribution system, which already has an RCD &MCB, having an NE bond on the genny is the way to go.

 

Apologies for my last post #62 where I referred to floating earth as there can be no such thing on a generator connected via shore power lead and I was just jumping on the bandwagon. In such a situation the earth potential is fixed by connection of generator earth/chassis to earth pin on output socket and also the boat earth/hull via power lead. It is of course the main output live and neutral (although there is no difference) that are floating.

 

I agree that strapping one leg (neutral pin) of the generator output to earth would allow RCD's to work with full safety, the question is how best to do this on a boat that also requires shore power hook-up. For this reason It can't be done permanently on the boat itself unless there is some automatic make/break of earth/neutral strap as with most Combi's. I guess a strap on the generator itself would be the most foolproof solution as I'm not really sure the dedicated power lead with internal strap, although used with success, is the best answer.

[Keith M]

I would just like to add an update on this subject

 

While conducting some testing on a craft within a mariner connected to the power supply

 

All it took to get the galvanic isolator to start conducting was just four items. All of which contained switch mode power supply's

 

As most boats these will easy have this number of power supply's on-board if you have up to date white appliances etc.

 

And don't forget most combi's will have at least 1 switch mode power supply as well

 

Keith

[blackrose]

I would just like to add an update on this subject

 

While conducting some testing on a craft within a mariner connected to the power supply

 

All it took to get the galvanic isolator to start conducting was just four items. All of which contained switch mode power supply's

 

As most boats these will easy have this number of power supply's on-board if you have up to date white appliances etc.

 

And don't forget most combi's will have at least 1 switch mode power supply as well

 

Keith

 

However, it also very much depends on which GI you were testing (See post 50). I had a lot more than 4 appliances connected when I did my test and could not force the GI to conduct. This was the Safeshore 70amp GI with status monitor. Which make and model of GI were you testing?

[smileypete]

I would just like to add an update on this subject

 

While conducting some testing on a craft within a mariner connected to the power supply

 

All it took to get the galvanic isolator to start conducting was just four items. All of which contained switch mode power supply's

 

As most boats these will easy have this number of power supply's on-board if you have up to date white appliances etc.

 

And don't forget most combi's will have at least 1 switch mode power supply as well

 

Keith

Interesting, a few questions if you don't mind....

 

Did the boat have a steel hull or not, was it tested for a proper hull earth bond, did it have a working RCD and exactly what GI and equipment was used???

 

If conduction IS a problem, one way round it is connect a suitable capacitor across the GI which will conduct AC but block DC. Normally a steel boat sitting in the water will act sufficiently as a capacitor to prevent conduction problems.

 

cheers, Pete.

~smpt~

Edited August 18, 2013 by smileypete

[blackrose]

Interesting, a few questions if you don't mind....

 

Did the boat have a steel hull or not, was it tested for a proper hull earth bond, did it have a working RCD and exactly what GI and equipment was used???

 

If conduction IS a problem, one way round it is connect a suitable capacitor across the GI which will conduct AC but block DC. Normally a steel boat sitting in the water will act sufficiently as a capacitor to prevent conduction problems.

 

cheers, Pete.

~smpt~

 

Chris W's GI has a capacitor built in. I think it's a Sterling model...

 

If I wanted to add a capacitor to my 70 amp GI, could you suggest a suitable one?

[by'eck]

 

Chris W's GI has a capacitor built in. I think it's a Sterling model...

 

If I wanted to add a capacitor to my 70 amp GI, could you suggest a suitable one?

 

Sterling use a bipolar (non-electrolytic) 25,000µF 2.5 volt capacitor although not cheap.

 

According to their sales blurb an ABYC requirement to have one fitted to GI's used on boats came into being this year. It is thought that Europe will follow with similar.

[Doorman]

Sterling use a bipolar (non-electrolytic) 25,000µF 2.5 volt capacitor although not cheap.

 

According to their sales blurb an ABYC requirement to have one fitted to GI's used on boats came into being this year. It is thought that Europe will follow with similar.

An interesting account regarding Electric Shock Drowning can be read on the ABYC site. This phenomena has only become apparent after a young American boy died in 1999, whilst returning to his father's boat after swimming in a fresh water river. Initially, it was believed that he had drowned, but his mother recalled that the boy's head was never submerged whilst he was in the water.

 

In fact he had been electrocuted because a nearby boat had faulty wiring and was leaking an electrical current into the water! Since the incident the boy's father has worked tirelessly to create awareness of this silent danger to an unsuspecting American public. I wonder whether we British are also aware of this potentially fatal phenomenon?

Edited August 19, 2013 by Doorman