Generator Grounding

[BargeeSpud]

Hi,

 

This is a follow up to a previous posting debate I had on another thread.

 

I have had a recurring problem with my 240V banging out when a load is applied via my landline socket & generator. It was suggested on that thread that my generator probably needs grounding & I can now confirm that my Honda 20i needs to be grounded when I use equipment that is itself grounded. Now to the nub of my question which might seem a bit dumb in some quarters, but I just need to understand properly the physics of it & whether my thinking is on the money.

 

As my 240V is earthed to the hull, can I take it that any equipment with an earth connection that I use on the circuit is considered to be grounded & that by grounding the generator, it & boat are grounded due to the fact that the boat is connected to the generator grounding via the water? I.e, hull - water- bankside - generator ground?

 

Also, if that is correct, would it be OTT to attach an earthing lead from the hull to the generator grounding pin?

 

Cheers.

Edited November 19, 2012 by Spuds

[Proper Job]

I've got a Honda EU20 that I use for battery charging via Sterling charger and the odd occasional use of a 240 appliance.

 

The only time it's every 'tripped' is when it gets overloaded

 

I've never earthed the generator when in use

[BargeeSpud]

I've got a Honda EU20 that I use for battery charging via Sterling charger and the odd occasional use of a 240 appliance.

 

The only time it's every 'tripped' is when it gets overloaded

 

I've never earthed the generator when in use

In my case, I can plug into the boat's 240V the same drill that works on the generator & it'll trip, so I don't think it can be an overload. I can see it being a wiring problem with the 240, but not an overload.

[Proper Job]

What trips? The generator or the the boats consumer unit?

[BargeeSpud]

What trips? The generator or the the boats consumer unit?

Sorry! The main 240V circuit breaker in the boat's consumer unit.

[Hawkmoth]

Sorry! The main 240V circuit breaker in the boat's consumer unit.

It seems to me that you've probably got your 240V L N or E wrong way around some how. I'd get out the multimeter and bell through all the wires from the boat input plug right through to the consumer unit, and maybe beyond that to be thorough.

I am assuming that the trip is the main o'load and not just the RCD.

[BargeeSpud]

It seems to me that you've probably got your 240V L N or E wrong way around some how. I'd get out the multimeter and bell through all the wires from the boat input plug right through to the consumer unit, and maybe beyond that to be thorough.

I am assuming that the trip is the main o'load and not just the RCD.

That was my original thought, that my wiring was wrong, but I've checked & it doesn't seem to be, from the diagrams I've seen. But then the diagrams I've seen don't actually show the connections, only the wires entering the box & not how they're wired inside it. So I'm non the wiser really.

 

The breaker that trips out is the main or master isolation RCD/circuit breaker, not the individual circuit RCD.

Edited November 19, 2012 by Spuds

[GUMPY]

Neutral/Earth linked or crosswired

You need to physically check the wiring not look at diagrams

[BargeeSpud]

Neutral/Earth linked or crosswired

You need to physically check the wiring not look at diagrams

That sounds a distinct possibility & I only mentioned the diagrams because I've yet to find a proper wiring diagram that clearly shows EXACTLY how you connect up a 240V consumer unit on a boat, & so its impossible for me to accurately check whether mine is wired properly or not. Regretably, Ive not yet been able to physically confirm how the unit is wired, which will make solving the problem a shedload easier if I can give out that info to everyone.

[Paul C]

That sounds a distinct possibility & I only mentioned the diagrams because I've yet to find a proper wiring diagram that clearly shows EXACTLY how you connect up a 240V consumer unit on a boat, & so its impossible for me to accurately check whether mine is wired properly or not. Regretably, Ive not yet been able to physically confirm how the unit is wired, which will make solving the problem a shedload easier if I can give out that info to everyone.

 

Its no different from how any other consumer unit is wired - or at least it should be no different! The only differences due to it being on a boat, MIGHT be if its used with an inverter or generator which didn't have a N-E bond, someone might have created this bond within the consumer unit. Also when a consumer unit in a home is wired up and the earth point is to a pipe/etc, on a boat it must be connected to a hull grounding point near to (but not the same as) the negative ground strap from the 12V DC side.

[ditchcrawler]

That sounds a distinct possibility & I only mentioned the diagrams because I've yet to find a proper wiring diagram that clearly shows EXACTLY how you connect up a 240V consumer unit on a boat, & so its impossible for me to accurately check whether mine is wired properly or not. Regretably, Ive not yet been able to physically confirm how the unit is wired, which will make solving the problem a shedload easier if I can give out that info to everyone.

I would suggest that you get a professional electrician to check it out for you, 230 volts from a generator can be as deadly as that from the mains.

[Gibbo]

I smell an electric shock in the pipeline

[jelunga]

I smell an electric shock in the pipeline

Frying tonight!

(sorry. Quote from kenneth williams. )

[by'eck]

Its no different from how any other consumer unit is wired - or at least it should be no different! The only differences due to it being on a boat, MIGHT be if its used with an inverter or generator which didn't have a N-E bond, someone might have created this bond within the consumer unit. Also when a consumer unit in a home is wired up and the earth point is to a pipe/etc, on a boat it must be connected to a hull grounding point near to (but not the same as) the negative ground strap from the 12V DC side.

 

Isn't the Honda's output balanced with a centre tap on its output winding leaving 120 volts between each leg and its earth? If so beware of any neutral-earth bond on your boat as mentioned above.

[GUMPY]

I would suggest that you get a professional electrician to check it out for you, 230 volts from a generator can be as deadly as that from the mains.

Now where could you find one of those locally that would be prepared to take the job and that has experiennce with boats and generators?

Edited November 20, 2012 by idleness

[DandV]

Isn't the Honda's output balanced with a centre tap on its output winding leaving 120 volts between each leg and its earth? If so beware of any neutral-earth bond on your boat as mentioned above.

This is quite common arrangement for portable generators as their predominate task is as portable power sources for small appliances. This arrangement halves the maximum voltage to earth, still nasty if you are the conductor, and also means for the manufacturer, minimal modification between US 110v x 2 60hz units and 230v x1 50hz units. Speed change and outlet plugs only. We had the same problem with our off grid solar powered weekender house. Advice was that I could snip the star point to earth star point connection on the genny which I was not brave enough to do so, but found a 2.5kw isolating transformer to connect the genny to the house neutral earth bonded reticulation. The generator has its own remote driven earth separate from the house earth. I still would be careful though about the effect on electrolytic corrosion. Seek competent advice.

 

Don

[Chris Pink]

Member Blackrose has converted a Honda (an Honda?) to neutral earth bonding. It's a complete red herring in this situation, the lack of bonding is not causing/ would not cause the breaker to trip.

 

Seek competent advice.

[Gibbo]

Very few generators use a centre tapped output. The only current one I'm aware of is the Travelpower which isn't a normal generator.

 

To check, do the following:-

 

Put a 60 watt lightbulb, in turn, between each of the two outputs and ground.

 

If it lights up when connected between one output and ground, but not the other output and ground, the unit is already neutral earth bonded.

 

If it does not light up on either, it is not neutral earth bonded, but it is safe to add the bond.

 

If it lights up at half brightness on each, it is centre tapped. Do not attampt to neutral earth bond it.

 

Note I say "one output" and "the other output". This is because without a neutral earth bond, there is no such thing as live or neutral. They are just two outputs with nothing to differentiate between them.

 

But, as Pinky says, this all has got nothing whatsoever to do with the circuit breaker tripping.

[BargeeSpud]

I'm knocking this one on the head for now.

 

I've not put across my query properly because I haven't given you the complete picture regarding how my current set up is actually wired. Until I do that, we aren't going to get anywhere, so I'll go away & come back with as complete a description of my set up as possible so that you might fully understand where my problem could be. My apologies for the confusion.

 

Thanks for all the comments so far, they might not have pin pointed the problem, (well, they might have but we simply don't know it) they've never the less been extremely useful.

 

Cheers.

Edited November 20, 2012 by Spuds

[by'eck]

Member Blackrose has converted a Honda (an Honda?) to neutral earth bonding. It's a complete red herring in this situation, the lack of bonding is not causing/ would not cause the breaker to trip.

 

Seek competent advice.

 

Is it the breaker tripping though? Read Spuds post #7 where he mentions the main RCD/breaker (RCBO?) tripping. Since the RCD part is the most sensitive of the two I would suspect its causing the trip.

 

Also in his post #3 he mentions a drill causing tripping through the boats wiring but not when run directly from generator.

[smileypete]

Hi,

 

This is a follow up to a previous posting debate I had on another thread.

 

I have had a recurring problem with my 240V banging out when a load is applied via my landline socket & generator. It was suggested on that thread that my generator probably needs grounding & I can now confirm that my Honda 20i needs to be grounded when I use equipment that is itself grounded. Now to the nub of my question which might seem a bit dumb in some quarters, but I just need to understand properly the physics of it & whether my thinking is on the money.

 

As my 240V is earthed to the hull, can I take it that any equipment with an earth connection that I use on the circuit is considered to be grounded & that by grounding the generator, it & boat are grounded due to the fact that the boat is connected to the generator grounding via the water? I.e, hull - water- bankside - generator ground?

 

Also, if that is correct, would it be OTT to attach an earthing lead from the hull to the generator grounding pin?

 

Cheers.

You could try a socket tester, might shed some light on the problem, and a useful thing to have around:

 

http://www.amazon.co.uk/Mains-Socket-Tester-Correct-Wiring/dp/B001SIE5DQ/ref=sr_1_3?ie=UTF8&qid=1353417663&sr=8-3

http://www.amazon.co.uk/Green-Mains-Socket-Safety-Tester/dp/B003337BLM/ref=cm_cr_pr_sims_t

 

Has the boat worked OK on a shoreline without the RCD tripping?

 

RCD tripping under load points to a neutral-earth short somewhere downstream of the RCD, but the socket tester won't find that, it's a multimeter job.

 

cheers, Pete.

~smpt~

Edited November 20, 2012 by smileypete