Inverter earth

[pwl]

The survey report on our prospect has highlighted that the 230V side of the 1.8KW inverter has no earth connection. This is one part of boat electrics I am not familiar with. This raises two questions in my mind

 

1) Should there be a full earth circuit in the 230V supply on a narrowboat?

 

2) If you 'ground' earth via the hull what does that do to the hull? Increased anode degradation?

 

P

[NB Willawaw]

Does that mean that your current AC wiring is a 2-wire circuit; just live and neutral ??

 

Are you just using the inverter or do you have a shore supply connection as well ??

[chris w]

The survey report on our prospect has highlighted that the 230V side of the 1.8KW inverter has no earth connection. This is one part of boat electrics I am not familiar with. This raises two questions in my mind

 

1) Should there be a full earth circuit in the 230V supply on a narrowboat?

 

2) If you 'ground' earth via the hull what does that do to the hull? Increased anode degradation?

 

P

 

You need to supply an earth from your inverter to the earth pins in all the mains outlets.

 

Secondly you also MUST connect inverter earth and inverter neutral together or else your RCD will not trip in the event of a mains fault and, further, you will not have a neutral and live at the mains sockets, unless you do this, but two lives floating above earth.

 

Some inverters have neutral and earth prewired together when you buy them for this very reason (eg: my 1800W Sterling inverter)

 

Thirdly, you must also ground your hull to the main battery negative point AND you MUST ground your hull to any shore mains earth you use. Doing the latter does leave you open to galvanic corrosion from neighboring boats who are also connected to the same shore line BUT this corrosion can be eliminated entirely by the fitting of a galvanic isolator or isolation transformer on the boat.

 

Chris

Edited December 20, 2007 by chris w

[pwl]

Does that mean that your current AC wiring is a 2-wire circuit; just live and neutral ??

 

Are you just using the inverter or do you have a shore supply connection as well ??

 

The 230V circuit is 3 wire but the earth is cut at the insulation and so not connected. There is no shore supply.

 

P

[NB Willawaw]

What model inverter is it ??

Does it have an earth connection or is it double insulated ?

[pwl]

You need to supply an earth from your inverter to the earth pins in all the mains outlets.

 

Secondly you also MUST connect inverter earth and inverter neutral together or else your RCD will not trip in the event of a mains fault and, further, you will not have a neutral and live at the mains sockets, unless you do this, but two lives floating above earth.

 

Some inverters have neutral and earth prewired together when you buy them for this very reason (eg: my 1800W Sterling inverter)

 

Thirdly, you must also ground your hull to the main battery negative point AND you MUST ground your hull to any shore mains earth you use. Doing the latter does leave you open to galvanic corrosion from neighboring boats who are also connected to the same shore line BUT this corrosion can be eliminated entirely by the fitting of a galvanic isolator or isolation transformer on the boat.

 

Chris

 

The inverter is a 1800W Sterling but I don't know the model number. The unearthed circuit only powers the hair dryer which is coming out anyway but it sounds like one more job on the list if we are able to agree a good price.

 

Thanks

 

P

[NB Willawaw]

I'm not that familiar with Sterling - I guess you got the 1800W modified sine wave (MSW) one ?

Is it the red one (Pro Power Q) or the silver one ??

[chris w]

The Sterling 1800W has the earth and neutral internally bonded together. You MUST connect the inverter earth to boat earth otherwise you are putting yourself, your family and/or friends at risk of a fatal electric shock in the event of an earth fault.

 

Chris

[pwl]

The Sterling 1800W has the earth and neutral internally bonded together. You MUST connect the inverter earth to boat earth otherwise you are putting yourself, your family and/or friends at risk of a fatal electric shock in the event of an earth fault.

 

Chris

 

Thanks Chris. As I said, one more thing on the list if we get her. It keeps getting longer! Boat = hole in water <- money/time :-)

 

P

[NB Willawaw]

There is apparently a grounding terminal on both the 1800W models I mentioned according to Sterling, so yes the inverter should be connected from this

terminal to the Crafts AC Ground Point. If the boat doesn't have the latter, it will need one - not a big job.

I recommend you put the output through a Residual Current Device before going on to any sockets, etc that you might wish to install.

 

You mention that you are only using a hairdryer at the moment and thats coming out. Does that mean that you plan to use the

inverter for other purposes like feeding sockets for general purpose use ??

 

P.S You shouldn't get any problem with anodes if you have no shore line.

Edited December 20, 2007 by NB Willawaw

[pwl]

There is apparently a grounding terminal on both the 1800W models I mentioned according to Sterling, so yes the inverter should be connected from this

terminal to the Crafts AC Ground Point. If the boat doesn't have the latter, it will need one - not a big job.

I recommend you put the output through a Residual Current Device before going on to any sockets, etc that you might wish to install.

 

You mention that you are only using a hairdryer at the moment and thats coming out. Does that mean that you plan to use the

inverter for other purposes like feeding sockets for general purpose use ??

 

P.S You shouldn't get any problem with anodes if you have no shore line.

 

The second circuit is connected to a socket in the galley but nothing is connected. Probably intended to run a toaster or a microwave. If we get her, dont think I will use the 230V until I have gone through it fully. One question. Chris W indicated that the battery negative should be connected to the hull (no idea if it is). I assume that the AC ground point is also the hull?

 

P

Edited December 20, 2007 by pwl

[NB Willawaw]

Okay, I stand by what I said last.

If you want to add a shore supply at any stage, you will need some more bits.

 

If the guy who fitted the inverter didn't know what he was doing, it might also be worth checking

to see if the inverter supply lines are thick enough and presuming they are connected directly to the

inverter from the battery, fused.

[chris w]

The second circuit is connected to a socket in the galley but nothing is connected. Probably intended to run a toaster or a microwave. If we get her, dont think I will use the 230V until I have gone through it fully. One question. Chris W indicated that the battery negative should be connected to the hull (no idea if it is). I assume that the AC ground point is also the hull?

P

 

Correct.

 

Also, you'll need a 300A fuse (fitted in the negative battery cable to the inverter) for an 1800W inverter to give enough overhead to cope with start-up surges.

 

BTW, never use your hull as a return wire because you will get massive corrosion issues if you do. Always use a 2-wire system (ie: out & return) for any 12v or AC stuff (including earth wires). The exception is the single hull bond of battery negative and AC earth.

 

Chris

[PeterF]

Also, you'll need a 300A fuse (fitted in the negative battery cable to the inverter) for an 1800W inverter to give enough overhead to cope with start-up surges.

 

Chris

Chris,

 

Can you explain why the fuse is in the -ve cable, my boat came with a 600W unit without any fuses and I am chaning it for 1800W. I have bought heavier cables, an isolation switch so I will take a separate feed direct from battery bank and a Mega fuse but would have put it in the +ve so your post has come at just the right time before I get around to doing this over the Christmas hols.

 

Cheers,

 

Peter.

[chris w]

Chris,

 

Can you explain why the fuse is in the -ve cable, my boat came with a 600W unit without any fuses and I am chaning it for 1800W. I have bought heavier cables, an isolation switch so I will take a separate feed direct from battery bank and a Mega fuse but would have put it in the +ve so your post has come at just the right time before I get around to doing this over the Christmas hols.

 

Cheers,

 

Peter.

 

It could go in either cable in terms of overcurrent protection but putting it in the negative will blow it IF you happen to connect the inverter the wrong way round to the batteries (+ve to -ve).

 

Chris

[smileypete]

Can you explain why the fuse is in the -ve cable

 

I would put the fuse in the +ve cable as near to the battery or isolator as possible.

 

Reason: If the fuse is in the -ve cable, and the +ve cable to the inverter falls off and shorts to the hull - BANG!

 

cheers,

Pete.

[chris w]

I would put the fuse in the +ve cable as near to the battery or isolator as possible.

 

Reason: If the fuse is in the -ve cable, and the +ve cable to the inverter falls off and shorts to the hull - BANG!

 

cheers,

Pete.

 

The positive cable cannot be removed from the Sterling 1800W inverter - it is integral to the unit therefore it can never fall off.

 

But to be fair, I notice in the latest website instructions they do indeed say to install in the +ve lead. My manual (for the previous model) showed the -ve lead

Chris

Edited December 20, 2007 by chris w

[Guest]

Shoot me down if I am talking crap, but I thnk that some part of the world, maybe USA?, requires a fuse in the negative. Possibly someone has followed the wrong instructions.

[chris w]

Shoot me down if I am talking crap, but I thnk that some part of the world, maybe USA?, requires a fuse in the negative. Possibly someone has followed the wrong instructions.

 

That right. It's the ABYC regulations.

 

Chris

[Keeping Up]

Secondly you also MUST connect inverter earth and inverter neutral together or else your RCD will not trip in the event of a mains fault and, further, you will not have a neutral and live at the mains sockets, unless you do this, but two lives floating above earth.Some inverters have neutral and earth prewired together when you buy them for this very reason (eg: my 1800W Sterling inverter)

Just one point to note is that on SOME inverters you cannot connect the neutral to earth because their earth is internally prewired to a point midway between live and neutral. Mine is like that; it is easy to identify because if you do connect the neutral to earth it stops working and indicates a "short circuit" warning condition. If you have one of these it is OK to operate it without a connection from neutral to earth, it will be safe and the RCD will operate satisfactorily, as long as the earth is properly bonded to the hull; on my inverter there is an internal connection from the earth to the battery negative but I have no way of knowing if it is adequate so I've bonded the ring-main earth to the hull as well.

That right. It's the ABYC regulations.

It would seem to make sense if it's either a battery charger or a combi, with multiple positive outputs (to multiple batteries) and a shared negative, one fuse serves all

[NB Willawaw]

Allan,

 

Understand your response to Chris' points.

I specifically and pedantically tried to pin down exactly what inverter pwl had on board, so we could advise him specifically

what was needed for the unit that he has. The Sterling inverter that pwl has is just an inverter, not a combi and its neutral is

connected to ground internally. It doesn't have a centre tapped output as some of the earlier Sterling's did as I believe these

do not comply with current legislation for the sale of new equipment (don't quote me on this last bit as I only normally get involved with

Mastervolt).

Its always very difficult on electrical matters because one answer often doesn't fit all and readers clipping responses out of context

and applying it to their situation can often result in problems.

[smileypete]

If the inverter handbook is available, I'd go with that regarding earthing and fusing.

 

Also if Gibbo is around I'm sure he can comment on +ve versus -ve fusing.

 

Does anyone have access to an up to date copy of the ABYC standards, to be 100% sure and not rely on speculation?

 

cheers,

Pete.

[NB Willawaw]

No, I refuse to pay for them when they have no relevance in Europe.

 

This is straight off the Sterling website:

 

QUOTE

 

Negative Fused externally (A.B.Y.C requirement)

Because the largest market for our products is in the USA, it is important to conform to European and USA standards. This is a requirement for the USA A.B.Y.C boat building code of practice, as a result some electricians were receiving electric shocks because they thought they were on the DC negative system when they were on the 110V AC system (guaranteed to wake you up first thing in the morning). As a result international regulation bodies are attempting to change the colour of the DC negative cables (which have been black) to yellow, this is already the case in the USA for ABYC and is under review in the UK. The negative cable in the new digital range comes as yellow and a gold fuse is supplied.

 

UNQUOTE

[Ray]

This could be where I show my ignorance (again).

 

We've a Mastervolt 2000 combi and, as far as I know I wired it as per instrctions, see previous thread about surveyor's concerns over size of cables between battery and combi. We also have a shore line which we connect when we're on the boat on our marina mooring.

 

I have a battery master switch between batteries and all uses thereof, so the connection to the Mastervolt is effectively from the non battery side of the switch. That is, the Mastervolt won't work when the master switch is turned off.

 

When the shore line is connected, the charger is pumping power into the non battery side of the master switch and thus powering all the 12v circuits on the boat, even though the master switch is off.

 

Have I overlooked something in the wiring?

 

Ray

Edited December 21, 2007 by Ray

[smileypete]

We've a Mastervolt 2000 combi and, as far as I know I wired it as per instrctions, see previous thread about surveyor's concerns over size of cables between battery and combi. We also have a shore line which we connect when we're on the boat on our marina mooring.

 

I have a battery master switch between batteries and all uses thereof, so the connection to the Mastervolt is effectively from the non battery side of the switch. That is, the Mastervolt won't work when the master switch is turned off.

 

When the shore line is connected, the charger is pumping power into the non battery side of the master switch and thus powering all the 12v circuits on the boat, even though the master switch is off.

 

Have you tried calling Mastervolt to see what they say? Mastervolt is a premium brand so they should have a good helpline.

 

cheers,

Pete.