Electrical question

I assume you've got the installation instructions and the manual?

The manual for a Victron MultiPlus-II 230V (www.victronenergy.com/media/pg/MultiPlus-II_230V/en/safety-instructions.html#UUID-49c10f22-7174-f7f9-932c-8fd46d8eff2e) says as below (bold type is from the manual), but you should refer to the documents for your model.

1. IMPORTANT SAFETY INSTRUCTIONS - Save these instructions!
In general
Please read the documentation supplied with this product first, so that you are familiar with the safety signs and directions before
using the product.

This product is designed and tested according to international standards. The equipment should be used only for the designated
application.

! Warning - These servicing instructions are for use by qualified personnel only. To reduce the risk of
electric shock, do not perform any servicing other than that specified in the operating instructions
unless you are qualified to do so

!The product is used in combination with a permanent energy source (battery). A dangerous electrical voltage
can occur at the input and/or output terminals, even if the equipment is switched off. Always turn off the AC
power and disconnect the battery before performing maintenance.

The product contains no internal user-serviceable parts. Do not remove the front panel, and do not put the product into operation
unless all panels are fitted. All maintenance should be performed by qualified personnel. Internal fuses are not user-replaceable.
A unit with suspected blown fuses should be taken to an authorized service centre for evaluation.

Never use the product at sites where gas or dust explosions could occur. Refer to the specifications provided by the manufacturer
of the battery to ensure that the battery is suitable for use with this product. The battery manufacturer's safety instructions should
always be observed.

This appliance is not intended for use by persons (including children) with reduced physical, sensory or mental capabilities, or
lack of experience and knowledge unless they have been given supervision or instruction concerning the use of the appliance by
a person responsible for their safety. Children should be supervised to ensure they do not play with the appliance.

Installation
Read the installation instructions before commencing installation activities. Follow the local national wiring standards, regulations,
and installation instructions for electrical work. The installation shall be in accordance with the Canadian Electrical Code, Part 1.
The wiring methods shall be in accordance with the National Electrical Code, ANSI/NFPA 70.

This product is a safety class I device (supplied with a ground terminal for safety purposes).Its AC input and/or output
terminals must be provided with uninterruptible grounding for safety purposes. An additional grounding point is located
on the product's exterior. The ground conductor should be at least 4mm(2).If it can be assumed that the grounding protection
is damaged, the product should be taken out of operation and prevented from accidentally being put into operation again; contact
qualified maintenance personnel.

Ensure that the connection cables are provided with fuses and circuit breakers. Never replace a protective device with a
component of a different type. Refer to the manual for the correct part.

Do not invert neutral and phase when connecting the AC.

Check before switching the device on whether the available voltage source conforms to the configuration settings of the product
as described in the manual.

Ensure that the equipment is used under the correct operating conditions. Never operate it in a wet or dusty environment. Ensure
that there is always sufficient free space around the product for ventilation and that those ventilation openings are not blocked.
Install the product in a heatproof environment. Ensure that there are no chemicals, plastic parts, curtains or other textiles, etc. in
the immediate vicinity of the equipment.

This inverter is provided with an internal isolation transformer providing reinforced insulation

I have the manual, but my question is where I should connect the Chassis to ground connection on my steel boat.

Thanks for the wiring diagram Q!!
The trouble is that I'm getting conflicting information!!
The lower left info box on the above diagram "Important Information" says to connect the chassis Gnd to the Negative DC Busbar!!
Other info says to connect to the AC Gnd!!
Also, in the above diagram, the lower right "Important Information" info box is confusing.

I'll keep looking.

Hi Lazz,
Yes, connect the inverter chassis ground to neg busbar, which then connects to the boat's ground. This is the light green wire in Q's wiring diagram. Only use one ground connection from the neg busbar to the boat hull/engine, multiple grounds can be problematic.

The right hand information box has a statement " when operating in inverter mode, the neutral output must be connected to ground'.
I would reword this to say" The AC system must have a Neutral-Earth bond when the inverter is the supply source".

This is done internally in the Multiplus II. This is a safety thing and uses an internal Neutral-Earth relay. When you are connected to shore power it disconnects, so the shore power handles all the safety stuff (RCD). When you are off shore power and the inverter is the AC source, the internal relay kicks in to bond the Neutral-Earth, enabling RCD protection to work on the boat.

The boat earth is very high impedance compared to the neutral conductor, so AC current doesn't 'flow' through to the hull, just like current doesn't flow through the earth stake on your house. This simply ensures the hull and Neutral sit at the same voltage unless a fault occurs. In normal operation, think of the boat ground as a reference, not a current carrying circuit.

Ergo:
-- Do wire the Multiplus-II chassis ground to the boat's ground. That's it.
-- Do not wire any AC (L, N or PE) to your boat's ground.

Cheers!
SB

I shudder when I see that complex wiring diagram and think it is going to be installed on a boat.
Oh for the old days when sailing was a way to return to older, more simple ways of oil lamps and coastal navigation with compass bearings and a pencil on paper charts.
Sure a GPS is great, and some LED lighting is better, but do we really need complex electronics to enjoy sailing?

Well the way I look at it is that fibreglass boat does not have a "chassis ground" as such.

So you dont really need to tie anything to your vessels hull. Secondly you dont want current to be running into your steel hull normally or if you have a faulty electrical item. If current flows in your hull you are going to eat away your electrodes. However its difficult to avoid because technical your engine is mounted onto the hull through engine supports which may be insulated. The only reason you would want earth bonding to the hull is for "equi-potential bonding" for lighting or things like a HF radio to prevent interference. You dont want DC, RF or 240AC at different potentials. Its a hazard for shock, Lightning damage, RF problems and safety. So the ideal is to have one ground reference point for all systems and that does not require you to use your hull if you have a proper ground return bus bar that is not attached to your hull but is floating and not bonded.

When I had a steel boat I just had a heavy copper ground bar. This was my negative DC return and negative bond point for all dc circuits. I did have a switch that grounded this ground bar to the hull when lighting was around through a heavy duty switch. You will have some DC bonding to your hull through the HF antenna tuner, the negative is bonded to the mounting bracket which you will screw to your hull for RF ground. I did bond my tuner to the steel hull but the tuner was floating and not directly connected to the hulll. It was grounded through a RF choke for lightning and RF ground purposes but the choke blocked noise from other circuits interfering with the HF radio. At that time I was using Pactor email and did not want any noise.

The bottom line is that is ONE one ground in the electrical world, and you can call it what you want DC, RF or whatever its essentially the RF or DC current return path. On metal hull you want to be careful about electrolysis and dont currents running through the hull by design or accident like cars that use the cars body as a negative ground wire.

All good. I understand the concept, when living of grid with generators as 240v supply they where grounded for safety

Option 3 - engage an electrician to do the install

I am not sparky but I know enough to realise often bad wiring isn't discovered until a fault occurs. That is when it becomes a disaster, get it wrong and you could be planting a time bomb.

Earthing is one of those subjects that even intelligent engineers try to shy away from!
In undersea submarine cable systems, there is a electrically sealed undersea steel cylinder with 8 x amplifiers approx every 50 kms lying on the ocean floor. Each amplifier is powered by 12V DC/1 Amp. Over the span of a transocean cable, you might be running 10,000+ VDC/1 amp over that cable.
As it is DC, massive copper rods are installed that are connected to the cable landing station at either end of the cable. They are pile driven into the beach below the water table, similar to foundations on a 30 storey buiding. These are called the Sea Earths. The cable landing station would also have a normal(ish) earth stake, just like any other building. This is called the Station Earth.

When commissioning these systems, every now and then we would be chasing some weird non linear effect on the optical signal. We would sometimes switch from the multi squillion dollar Sea Earth to the piddly little Station Earth, resolve the issue, then switch back to the Sea Earth. Problem solved.

In what alternate reality does that even make sense???
That's earthing for you. Part engineering, part black magic!

It's worth mentioning that speaking with the yacht builders, not one uses a floating (isolated) DC system. Why?
Because:
- the standards (ISO etc) mandate it; and
- they dont want to get sued.
In a boat, an earthed system is MUCH safer than isolated. Maybe we should buy aircraft. Aircraft get away with it because the systems are in a controlled environment, they are rigorously maintained, stuff doesn't get added by twisting it into the closest power wire and.... they don't float in water.
Actually that's a bit harsh. They might float...just not for very long.

In Australia, standard AS/NZS3004.2 Electrical installations: Marinas and boats - Boats

Floating system is the normal requirement. For most boats, the AC system must be electrically isolated from the hull and DC system, meaning: Neutral is NOT bonded to earth onboard Earth is NOT bonded to the hull[ (for non-metal boats) The shore earth is carried onboard only for fault protection, not bonding The system is therefore floating with respect to the hull This applies especially to: Fibreglass boats Timber boats Composite boats Boats on marina shore power. Safety is achieved via RCDs and isolation, not by tying AC to the hull. RCDs are mandatory.

No worries Shaggy. I had a head start on the subject. For the last 12 months ensuring electrical safety of sensors attached to a laser going into peoples lungs to treat cancer. Much smaller space and tiny current 10uA instead of 10A but same principle :-)
In theory if Lazz connected the Ground pin on his inverter to the hull via one of these au.mouser.com/ProductDetail/KEMET/R474N31005001K?qs=MdJgNetHbfmbEG0LDSqYUg%3D%3D it should meet the floating standard and also let the inverter EMI filter continue to reasonably work. Its an X2 safety capacitor. Its guaranteed to fail open circuit not short circuit.
But I think hes probably fallen asleep after all this!