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Wrong polarity from Generator


RufusR

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Ok so we bought a Honda 2.2eui genny got this one as was advised by our marine engineer that it has a very clean output and therefore is about the only one that will work properly with our victron charge inverter which is apparently notoriously fussy about the input . Started using it and it works great through the victron and every thing works on the boat apart from the immersion but will come back to that later . 

 

However the box fitted in the electrics cupboard presumably by the boat fitter has a red light on it which indicates incorrect polarity . Spoke to boat engineer and he said he has seen this with generators elsewhere but since the everything was working it “probably was not a problem “ I trust him as he is well known and very experienced but he admitted this was not an area of expertise. anyone any thoughts about what is occurring. ?

 

back to the immersion ours it 1kw so should work fine with Honda which is a2.2 but when I went to turn it on it tripped out the victron , Honda didn’t stall so wonder if this has something to do with polarity issue ?

 

any boat leccies out there can help ?

 

 

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Well to start with, an A.C. output from a genny can only be 'wrong polarity' in relation to something else, e.g. earth. If the terminal arbitrarily selected to be 'neutral' is connected to the earth terminal and the other terminal in the boat is selected as 'neutral' then I'd say this is a really BIG problem and needs resolving before someone gets electrocuted.

 

But I know little about 'lectrics. Mebbe Nick or Tony or someone will put me straight....

 

 

Just posting to get discussion started.

 

 

 

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1 minute ago, RufusR said:

I can’t see how it can be wired wrong . 

 

Well I can, which is what I just explained. But I'd rather expect it to trip something rather than carry on working.

 

Do you connect the genny to the Victron via a galvanic isolator?

 

 

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The reverse polarity indicator works by putting a (normally) neon lamp between neutral and earth. If neutral is in fact live, the bulb lights up.

 

However what is happening here is that the generator neutral is not connected to earth as it should be. Commonly known as NE bonding. Without NE bonding, the RCD won’t trip if there is a short between N and E or L and E. In other words, it’s a safety issue. That your boat engineer doesn’t understand this means he is very incompetent regarding mains electrics.

 

It’s likely that the L and N are both floating at around 1/2 the voltage relative to earth, so the light will come on which ever way you wire it.

 

Only thing to be careful of is that the genny can tolerate NE bonding. Have a look at the Smartgauge website, it has a treatise on this point. If the genny in fact has a centre-tapped type output, don’t connect NE otherwise you’ll blow it up! With centre tapped output, the RCD will still work even though the light will remain on unfortunately. But I doubt it is centre tapped.

 

Presuming it’s OK, you need to have a special lead for connecting genny to shore power inlet, that has N and E connected together. Don’t use this lead for a shore bollard, else you’ll trip the bollard RCD.

Edited by nicknorman
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Hi  Nick 

 

many thanks for for your reply and sorry i am such a dunce on the matter . So you are saying ineffect I have the incorrect lead for a gennie ? This would make sense As the one I have was for shoreline towers . Where do I get such a lead ? 

 

To to be fair to eng he doesn’t purport to be a boat electrician more engines etc hence why I am asking here . 

 

I will check smart gauge re Honda 2.2eu but would think would be ok as appears to be used alot on boats .  

 

Again in thanks for the help ?

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I’m not sure you can get such a lead ready made. But it is simply a matter of dismantling the plug at either end of the lead, and connecting a very short piece of wire between the N and E terminals. Then mark the lead as suitable for generators only.

Edited by nicknorman
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Hi Nick 

 

i am no electrician would any spark be able to do this ? Also can’t find that guide on smart gauge very busy and technical website , as said electrical dunce , do you have a quick link you could post . Sorry to be a pain 

 

regards 

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Yes anyone with any electrical competence could easily do it. The thing from Gibbo I’m thinking of may not be on the SG site, it may be on here, I’ll have a look. If Tony Wotever comes on, he’ll probably know where it is.

Edited by nicknorman
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3 minutes ago, RufusR said:

Hi Nick 

 

i am no electrician would any spark be able to do this ? Also can’t find that guide on smart gauge very busy and technical website , as said electrical dunce , do you have a quick link you could post . Sorry to be a pain 

 

regards 

As a time served electrician I can say you may have a problem finding a standard sparky to sort that for you. I for one wouldn't make a lead for you like that but I would look at neutral bonding the genny itself, I would suggest a lot of standard sparkies wouldn't have a clue. 

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1 minute ago, ditchcrawler said:

As a time served electrician I can say you may have a problem finding a standard sparky to sort that for you. I for one wouldn't make a lead for you like that but I would look at neutral bonding the genny itself, I would suggest a lot of standard sparkies wouldn't have a clue. 

If you are a house electrician, yes I’d agree. But any competent boat electrician should be familiar with the concept of NE bonding generators. After all, even if you plug this lead into a shore bollard, all that will happen is that the RCD will trip. Which is not dangerous.

 

Yes you could bond it at the genny but that is more difficult because you have to take the genny apart to get access.

Just now, RufusR said:

Ok thanks . Where do I go from here just want to use the generator safely now not sure what to do ?

Just get someone to put a 2” bit of insulated wire between N and E on the lead plug. Don’t listen to the house-trained naysayers!  Anyway, I found what I was thinking about from Gibbo here:

 

 

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4 minutes ago, nicknorman said:

If you are a house electrician, yes I’d agree. But any competent boat electrician should be familiar with the concept of NE bonding generators. After all, even if you plug this lead into a shore bollard, all that will happen is that the RCD will trip. Which is not dangerous.

 

Yes you could bond it at the genny but that is more difficult because you have to take the genny apart to get access.

Just get someone to put a 2” bit of insulated wire between N and E on the lead plug. Don’t listen to the house-trained naysayers!  Anyway, I found what I was thinking about from Gibbo here:

 

 

Ok thanks . Where do I go from here just want to use the generator safely now not sure what to do ?

 

thanks again nick . Not sure where to find said boat electrician but will look around I am sure Honda is not central tapped as probably most common gennie on the cut . Is it ok to use in the meantime ?

 

 

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2 minutes ago, RufusR said:

Ok thanks . Where do I go from here just want to use the generator safely now not sure what to do ?

 

thanks again nick . Not sure where to find said boat electrician but will look around I am sure Honda is not central tapped as probably most common gennie on the cut . Is it ok to use in the meantime ?

 

 

Where are you?

 

There might be a forum member near you who understands what Nick is advising. 

 

 

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28 minutes ago, RufusR said:

Marsworth 

Rufus, I had a Honda EU20i and now have an EU10i. Had the same issue as you when I got the 20i second hand in 2011. When I discovered the issue, did the same bit of research and fitted my own short wire in the plug. If you can wire a house plug, you can do this yourself.

 

In the manual that came with the new 10i a few weeks ago, I’m pretty sure it describes this issue, along with the solution. If yours is new, I’d guess it has a similar section in the manual, but you would have to read every page to find it :) 

 

Im fairly sure the genny is safe to use, but it won’t trip your RCD/consumer unit if a fault develops.

  • Greenie 1
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4 minutes ago, David Mack said:

None of the above discussion addresses why using the immersion heater trips the Victron. I would have thought it should all have worked fine (if not entirely safely) with or without the NE bond.

Maybe the generator is live earth bonded hence the light and there is a neutral earth fault on the immersion heater and then maybe not. Or even if the genny has a floating earth there could be a live earth fault bring on the invers supply lamp and an earth neutral fault on the immersion heater.

Edited by ditchcrawler
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17 hours ago, RufusR said:

Hi Nick 

 

i am no electrician would any spark be able to do this ? 

 

I'm no electrician either but we're only talking about linking N-E in the plug of your shoreline cable that goes into the generator.

 

I don't think there's any particular advantage of N-E bonding the generator itself as opposed to the cable and there are quite a few disadvantages, but as previously mentioned you must label the cable for generator use only and I'd also advise putting some flexible conduit over the cable because as far as I'm aware it's not electrically protected itself until the supply has passed through the boats breakers. That's the same whether you N-E bond the cable or the generator.

 

My only concern here is that what you're effectively doing is changing the generator from a floating earth to neutral-earth bonded (just like the mains) and my understanding is that the chassis or case of anything N-E bonded must also be bonded to earth. I run my generator on my boat (which is frowned upon mainly because of the risk of petrol fumes getting into the engine bilges or into the boat, and also the carbon monoxide risk). However I'm on a big widebeam and the generator is far enough away and separated from the rest of the boat. I wouldn't do this on a narrowboat as it's simply too confined.

 

Anyway, the point I'm trying to make is that the chassis of my generator is connected to the boat's hull, so it's effectively connected to earth (unpainted base plate). If you're running a N-E bonded generator on the bank as you should, then shouldn't it be run in conjunction with an earth spike connected to the generator's chassis?

 

Sorry to complicate things further but electrical safety is paramount and I'm really wondering whether anyone running a generator on the bank should be messing about with the generator's floating earth system unless they are going to do it properly.

 

 

Edited by blackrose
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The OP has a suitcase generator so the “chassis” is plastic. Apart from the exhaust outlet which it might be possible to touch if you really tried, I don’t think there is anything metal that could be touched.

 

But anyway, the generator earth is connected to boat hull via the lead, which as you say is a reasonable earth (depends on the water quality) so I’m not clear what additional safety having an earth spike would give for a metal framed genny.

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2 hours ago, nicknorman said:

The OP has a suitcase generator so the “chassis” is plastic. Apart from the exhaust outlet which it might be possible to touch if you really tried, I don’t think there is anything metal that could be touched.

 

But anyway, the generator earth is connected to boat hull via the lead, which as you say is a reasonable earth (depends on the water quality) so I’m not clear what additional safety having an earth spike would give for a metal framed genny.

I go along with that. No one ever suggested earthing your helicopters and they had generators or even if you have an inverter or travel power. the important thing is that your protection system works. It could be argued that no earth at all is safer in some circumstances. 

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2 minutes ago, ditchcrawler said:

I go along with that. No one ever suggested earthing your helicopters and they had generators or even if you have an inverter or travel power. the important thing is that your protection system works. It could be argued that no earth at all is safer in some circumstances. 

...or in the International Space Station!

 

Yes we had 115v 400Hz 3 phase alternators. 115v phase voltage which gave a line voltage of 200v. Enough for an ouch moment!

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