Shore Power

[jonlaw]

I have a little Honda suicase generator, if I connect it to my boats shore connection, the lights on the shore panel indicate 'incorrect polarity'.
It is definately connected correctly, any ideas ?
Could it have anything to do with the fact that the gen is not earthed ?
Thanks

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[ccscott49]

The genny should be earthed through the shorepower connection to the boat system. I know you say it's definitely connected properly, but have you tried reversing the polarity, if so does it say the same thing, ie, polarity reveresed?

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[MainlySteam]

It will cause an incorrect polarity indication.

They also do not have the neutral and earth bonded at the generator as is required by codes for marine installations for the case that the generator is plugged into the boat's electrical distribution system, rather than just powering a single appliance as that generator is actually designed to do.

John

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[gtmoore]

I recently asked a question here regarding connecting a genny to a shorepower socket and got some very useful replies. The thread is here:

<A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=385705&page=&view=&sb=&o=&vc=1>http://www.ybw.com/cgi-bin/forums/showflat.pl?Cat=&Board=pbo&Number=385705&page=&view=&sb=&o=&vc=1</A>


<hr width=100% size=1>Gavin

 

[Alex_Blackwood]

Agree you don't have a grounded neutral on the Generator. You are in fact working between phases as opposed to phase and neutral as supplied by normal shore supply installations.
As it is your own private supply I am not sure it has to comply with regs for shore installations? The difference with working between phases is that if you go between one phase and earth you will only get a shock of 110volts. With phase and neutral you will get a 220 volt shock. In other words with your generator you would have to hang on to both wires to get a 220 volt shock.
Your boat is probably made of an insulating material anyway, unless it is steel, so the only way you can touch an earth is via the engine and transmission or by sticking some part of your body in the water. Or of course via the earth wiring for your system. BUT. Where is that connected when you are running the generator?
Even if the generator is ashore it may not be bonded to earth.
In short the Incorrect phase indication is not really important and the generator will power your system up to its rated loading. However I would want to look very seriously at how you can bond your system and the generator to earth.

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[MainlySteam]

Alex - All marine codes I am aware of require earth to neutral bonding at the point of supply. Another risk with them is that residual current protection devices may not work correctly - there was some discussion on that in the thread gtmoore has referred to.

In the end, if there is a fuel or electrical accident, ones insurer may not respond as the generator is being used for a purpose for which it was not designed.

John

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[tgalea]

Hi

I've been thinking about buying one of these units. Any comments ? Are they worth the price ?

Thanks

Tyrone

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[Alex_Blackwood]

John.
Yes I agree about the RCD's not being as effective with a non-earthed neutral system. (It may have been me who raised the point previously).
I will not get into an discussion about the marine codes as you know more about it than I do. However I suspect that the codes are written to cover the provision of shore power from marinas using the national grid system.
It is certainly the case on large ships for the electrical system to be of the insulated neutral type. (Apart from High Voltage systems ie 1000volts+). I am not sure how you would be covered using an onboard generator. I do agree that the insurance companies would know doubt find an excuse not to cover in the event of an accident. As far as the generator design is concerned I would think that it could be used for any purpose, if connected by the correct plugs, sockets and safety devices and the total load did not exceed the generators capacity.
Having said all that I am not at all in favour of portable generators being used for shore supply on small craft. The safety implications regarding fuel, electrical connections ( Insulated neutral etc) The need to keep watch on it and the noise would to me outweigh any advantages over plugging in to a supply on the jetty.
Jon could also get some advice on the use of portable generators and earthing requirements etc. if he has a local tool hire firm who deal in generators. They are usually very good with advice.

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[jonlaw]

I paid about £650 for mine 2 or 3 years ago, I think the price has come down some since.
I think its great, very quiet and very portable, mine is 700 watts, but if buying again would go for the 1000 or 2000 watt version.
It starts at the first pull and hasn't given me any trouble (touch wood)

Jon

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[Guest]

Purpose not designed ....

A portable genny is designed for portable electrical power. I don't remember seeing any instruction or other that says a portable genny is for a particular electrical job etc. or only one job.

I have been on, inspected many boats that have genny's tucked away .....

I am not an electrical specialist but consider that as long as the genny is not overloaded and working within capacity sensibly and all relevant instructions / connections carried out as per manuals etc. - then why is it so wrong.

Anyway I would consider that the genny is a useful item away from true shore power - as long as its quiet and away from annoying others.


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[LadyInBed]

Also see this thread:
<A target="_blank" HREF=http://www.ybw.com/cgi-bin/forums/showthreaded.pl?Cat=&Board=pbo&Number=383738&page=&view=&sb=&o=&vc=1#Post383738>http://www.ybw.com/cgi-bin/forums/showthreaded.pl?Cat=&Board=pbo&Number=383738&page=&view=&sb=&o=&vc=1#Post383738</A>

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[MainlySteam]

Alex - I think your summation in your second to last paragraph is excellent.

For the sake of others, if they follow the referred to threads they will see that I am not opposed to the use of such generators, just that the increased risk from using them is not often pointed out. Those are risks that I personally would not take on a boat. Others accept them or, most frequently, are unaware of them.

John

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[LadyInBed]

Re: advantages over plugging in to a shore supply

Shore supplies with RCD's are great - if you have access to them.
If you are out on a swinging mooring or on a trot somewhere and need to use several different power tools your options are:
- Generator
- Inverter
- Up sticks and book into a Marina
The generator is for me the most viable and versatile option, as I can also charge batteries with it.
Carrying petrol for it is a risk, but many boats already carry petrol for their outboard.
Earthing: Many power tools are 'double insulated' and have 'two wire' connectors, so there is no earth connection.
Marine codes: I agree, not really relevant to Joe Bloggs working on his own boat.
Insurance: Mine has no exclusions re using a mains generator.

Anything can be dangerous, especially if it isn't used properly, and safe if used with care and consideration of the risks involved.

I didn’t realise that I felt so strongly about the subject!


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[Alex_Blackwood]

Re: advantages over plugging in to a shore supply

If your worry is power tools, what about battery operated power tools. Very safe.
The RCDs Refered to were ones fitted to equipment in the boat and in use when the generator was running, you only get about 80-90% protection when you use these devices with an insulated neutral system.
I fully appreciate your comments about isolated moorings etc. and like MAINLYSTEAM I am not opposed to the use of portable generators but think that if you use them you must be aware of the dangers and if you are in a situation where there is a supply available I just cannot see the point of using a portable geny. The risk involved compared to "Plugging in" are just not acceptable.
Getting back to the original question. Yes you will get incorrect polarity indication because of the insulted neutral arrangement of the generator. The generator will run your system. However, you MUST ensure that your electrical system is somehow bonded to earth. If you are not sure of this consult a qualified electrician. Remember there are no shortcuts to safety!
You must also remember that an insulated neutral system will carry ONE (1) earth fault with no effect. However TWO (2) faults will blow fuses etc.
As I pointed out previously if you happen to grab one phase of the insulated system and go to earth you will only get a 110 volt shock. however if there is another fault on the system you will get 220 volts. You cannot rely on earth leakage (RCD) circuit breakers to protect you with this system.
An earthed neutal system will trip safety devices with ONE (1) fault.
I am not 100% certain but I believe the developement of double insulated tools came about because of the use of the insulated neutral system in portable generators used on building sites.
As I mentioned previously advice on the use of these machines can be obtained from your local tool hire centre. The people in there are, due to the nature of their job, well up on the use, regs, and limitations of these machines.
Consider my wrists severly slapped! I didn't mention the obvious. With a Phase and neutral system (Earthed neutral) you only have protection - fuses etc. on the Phase line. With an insulated neutral (Phase to Phase) you need protection on both lines (Douple pole switching and fuses in both lines).
The system in boats, and domestic supplies, is earthed neutral so if you connect up to a generator and under fault conditions you blow a fuse, or trip a breaker, you can still have one side of your supply and system live. This is because the boats neutral is now a phase and will be at 110volts with respect to earth. So what can appear to be a DEAD system still has one side LIVE. BEWARE!
<hr width=100% size=1><P ID="edit"><FONT SIZE=-1>Edited by Alex_Blackwood on 17/09/2003 11:37 (server time).</FONT></P>

 

[MainlySteam]

Re: advantages over plugging in to a shore supply

And users should be aware that if the vessel's DC negative is bonded to the AC ground, as is commonly the case, then with an insulated neutral system, getting between the neutral and any DC chassis or negative will result in a shock accident just as getting between the phase and the DC negative would.

John

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[Guest]

Seconded -

I'm lucky I sit in a marina - but many a time I have wanted a genny - being stuck where there is no power.


<hr width=100% size=1>Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !