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RCD TRIPPING


SEPTEMBER MORN

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Hi I live on a narrowboat moored in a marina

I have recently bought a ‘suitcase’ Stanley SIG 2000, (1600W continuous), inverter generator for when out on the cut.

When out on the cut, when I start up the generator and plug it into the socket, (where I would normally plug my landline to when in the marina), it trips the 30mA RCD box that is wired in between the landline socket and the inverter, (a sterling ‘pro-combi pure sine 2500W - The inverter has a toggle switch with power saver auto position  / an off position / a Power saver off position).

The inverter is earth bonded to the hull and I have tried both earth bonding the gen-set ‘floating earth’ to the same point and not using the floating earth at all – But the RCD still trips.

Does this mean that I should take off the RCD and replace it with a manual changeover switch at the point where the RCD is?  If yes, can anyone recommend what to buy?

(PS: Yes, the cable that I made to plug into the generator and socket is wired correctly to the plugs at each end of the cable).

I look forward to any advice that you can offer.

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I don’t think your generator earth should be connected to the boat earth.

 

On mine, inside the plug that plugs into the genny, I have a short wire which connects neutral and earth, which is what Wotever is suggesting above. This should sort out your RCD tripping issue.... but the cable with the earth/neutral connected must NEVER BE USED TO CONNECT SHORE POWER TO THE BOAT.... THAT’S NEVER!!

 

I have a separate short cable that I use for the genny. If I was ever to connect to shore power, I would not use the short cable.

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1 hour ago, Richard10002 said:

the cable with the earth/neutral connected must NEVER BE USED TO CONNECT SHORE POWER TO THE BOAT.... THAT’S NEVER!!

Because it will trip the shore side RCD if the shore socket has the phase correct, and will trip the shore side MCB if the shore socket has the phase reversed. Neither of which is a very good idea. 

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RCDs only sense what is on the output side so does it trip with everything on the O/P side switched off and preferably disconnected? If you add things back in one at a time what causes it to trip?

Secondly some RCD are AC/DC sensing and the generator could be creating DC which is then being passed through the RF protection of the Sterling to ground causing it to trip. 

Can you post a close up picture of the RCD so the type can be determined.

 

For those that think I am talking cr@p about DC try reading the attached file!

 

 

Techpub-17.pdf

Edited by Loddon
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But the Stanley SIG2000 is a simple single phase inverter-generator. It isn’t a three phase frequency converter (as commonly used for motor control in industrial applications), so what relevance does the above pdf have?

 

If the generator is outputting DC then it’s broken, easily established by plugging something like an electric drill into its output. 

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27 minutes ago, WotEver said:

But the Stanley SIG2000 is a simple single phase inverter-generator. It isn’t a three phase frequency converter (as commonly used for motor control in industrial applications), so what relevance does the above pdf have?

 

If the generator is outputting DC then it’s broken, easily established by plugging something like an electric drill into its output. 

It can happen with single phase units but being pulsed a normal RCD should pick this up.

If its fine on shore power and only trips on the genset I cant see how anything on the input side apart from some kind of interference  created by the genset would cause an RCD to trip.

 

The PDF was the first one I found to try and explain my thoughts. Would still like to know the type of RCD (AC, A,B)

 

Type AC. Ensures tripping for residual a.c. currents,

Type A Ensures tripping for residual a.c. currents and pulsating d.c. currents,

Type B Ensures tripping for residual a.c. currents, pulsating d.c. currents and smooth d.c. currents.

Edited by Loddon
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7 minutes ago, Loddon said:

I cant see how anything on the input side apart from some kind of interference  created by the genset would cause an RCD to trip.

Me neither. I can’t even see how interference could do it. All an RCD does is to have a simple comparator to compare the current through live & neutral. With a floating output from a genny it can’t possibly be different on the two legs. 

 

So... let’s start from basics. If OP plugs something into the genny directly does it work?

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It's very simple. There is no neutral/earth bond at the generator. There is at the boat. Consequently where a "proper" supply has the neutral unable to rise above zero volts, on this both poles are cycling plus and minus 110V. consequently when one of the poles hits the neutral/earth bond on the boat it's earthed and current flows in that conductor which is not matched in the other and the RCD trips. If like WotEver says one pole is bonded to earth at the generator end it then becomes neutral and the RCD will be happy.

OH! FOR GOD'S SAKE DON'T CONNECT THE FLOATING EARTH AT THE SAME TIME.

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This could be my fault. I've got a knitted effigy of a suitcase generator which I stick pins in to make myself feel better when someone is running one of the damned things within earshot.  I didn't think to take the pins out the last time I put it away because I didn't think it would really work!  I'll take the pins out later this week when I get back onboard and if the OP's generator starts to work correctly we'll know for sure. :D

 

 

(I'll take pre orders for "effigies by post" now, but no payment please until we definitely know it works) ;)

 

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1 hour ago, Sea Dog said:

This could be my fault. I've got a knitted effigy of a suitcase generator which I stick pins in to make myself feel better when someone is running one of the damned things within earshot.  I didn't think to take the pins out the last time I put it away because I didn't think it would really work!  I'll take the pins out later this week when I get back onboard and if the OP's generator starts to work correctly we'll know for sure. :D

 

 

(I'll take pre orders for "effigies by post" now, but no payment please until we definitely know it works) ;)

 

Just stick a mooring pin through the real genny and see if your knitted effigy writhes in pain :D

 

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On ‎18‎/‎09‎/‎2018 at 16:36, Richard10002 said:

I don’t think your generator earth should be connected to the boat earth.

 

On mine, inside the plug that plugs into the genny, I have a short wire which connects neutral and earth, which is what Wotever is suggesting above. This should sort out your RCD tripping issue.... but the cable with the earth/neutral connected must NEVER BE USED TO CONNECT SHORE POWER TO THE BOAT.... THAT’S NEVER!!

 

I have a separate short cable that I use for the genny. If I was ever to connect to shore power, I would not use the short cable.

Hi, Richard 10002,  I have been told that this is what I should do but was a little concerned.  Do I also need to link the earth and neutral to the socket that plugs into the boat?

 

Also, what about the floating earth on the genset?  (I know that I will use it when working on the tow path and plugging - say a drill - straight into the genset etc), but what about when I have the genny plugged into the boat?

 

The cable I have made for the gen set is just for the genset and will never be use to connect shoe power to the boat, (but thanks for the warning anyway).

 

For the rest of you guys who have offered their thoughts - Thanks.

 

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35 minutes ago, SEPTEMBER MORN said:

Do I also need to link the earth and neutral to the socket that plugs into the boat?

No. Just at the plug that plugs into the genny. 

37 minutes ago, SEPTEMBER MORN said:

what about the floating earth on the genset? 

What about it?  It’s 99.99% certain to be connected to the earth pin on the output socket. If it isn’t then it should be. 

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I want to clarify this.

 

I think the idea is that the earth pin in the generator plug is left disconnected and the earth wire in the cable is connected to the neutral pin in the plug together with the neutral cable itself. I think that bridging between the earth pin and neutral pin (that is NOT leaving the earth pin disconnected) would be likely to short out one half of the generator .

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1 hour ago, Tony Brooks said:

I want to clarify this.

 

I think the idea is that the earth pin in the generator plug is left disconnected and the earth wire in the cable is connected to the neutral pin in the plug together with the neutral cable itself. I think that bridging between the earth pin and neutral pin (that is NOT leaving the earth pin disconnected) would be likely to short out one half of the generator .



I had heard of this as well and it seems logical and really, was going to try this until I decided to come and ask on this forum.  Now the question is: link between the two or join earth and neutral wire into the neutral pin on the plug.  (Still unsure about if I need to earth bond the gen-set via it's 'floating earth' to the boat though whilst in use.

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On ‎18‎/‎09‎/‎2018 at 19:19, WotEver said:

Me neither. I can’t even see how interference could do it. All an RCD does is to have a simple comparator to compare the current through live & neutral. With a floating output from a genny it can’t possibly be different on the two legs. 

 

So... let’s start from basics. If OP plugs something into the genny directly does it work?

yes

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10 hours ago, Tony Brooks said:

I want to clarify this.

 

I think the idea is that the earth pin in the generator plug is left disconnected and the earth wire in the cable is connected to the neutral pin in the plug together with the neutral cable itself. I think that bridging between the earth pin and neutral pin (that is NOT leaving the earth pin disconnected) would be likely to short out one half of the generator .

That would only happen if the genny output is CT earthed. If it IS centre tapped then nothing unusual need be done because it will work perfectly well with the boat’s RCD as it is and gives no explanation for OP’s problems. 

 

As it’s an inverter generator then it’s far more likely to be floating output. The only way to know for sure would be to wire a 60W bulb between Live and Earth and see if it lights up. If it doesn’t then try the same between neutral and earth. If neither of those connections light the bulb up then the generator output is indeed floating and should have earth and neutral connected together within the plug. 

9 hours ago, SEPTEMBER MORN said:

yes

Then the next check is as outlined above. If you don’t feel confident in doing it then get assistance because mains voltages can kill. 

9 hours ago, SEPTEMBER MORN said:

Still unsure about if I need to earth bond the gen-set via it's 'floating earth' to the boat though whilst in use.

If you’ve connected earth to neutral then it’s no longer floating and is already connected to the boat via the cable from genny to boat. 

Edited by WotEver
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Just now, TheBiscuits said:

That's the genny cable - because you (and others) rightly told him never to use that one as a shorepower cable ...

Whatever. It’s the cable he uses to connect the genny to the boat. I’ll edit my previous reply. 

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On 18/09/2018 at 18:36, Richard10002 said:

I don’t think your generator earth should be connected to the boat earth.

 

On mine, inside the plug that plugs into the genny, I have a short wire which connects neutral and earth, which is what Wotever is suggesting above. This should sort out your RCD tripping issue.... but the cable with the earth/neutral connected must NEVER BE USED TO CONNECT SHORE POWER TO THE BOAT.... THAT’S NEVER!!

 

I have a separate short cable that I use for the genny. If I was ever to connect to shore power, I would not use the short cable.

 

I'm not quite sure what you mean in your first sentence Richard? If you're bonding N-E on the cable then you should also be connecting the chassis of the generator to earth using the generator's earth stud. 

Edited by blackrose
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2 hours ago, blackrose said:

 

I'm not quite sure what you mean in your first sentence Richard? If you're bonding N-E on the cable then you should also be connecting the chassis of the generator to earth using the generator's earth stud. 

I wasn’t sure what Richard meant either. However I’m also not sure what you mean. If N-E are bonded at the generator end and if the boat is correctly wired (earth bond to hull from consumer unit) then the generator chassis will be connected to the boat hull via the hook-up cable.

 

The chassis earth terminal on a generator is connected to the generator’s earth pin on the output socket. I’ve never come across one that isn’t. 

Edited by WotEver
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