Just about to install a new Victron Inverter & wondering where I should connect the Chassis to ground connection on my steel boat??

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

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Lazzz said..
Just about to install a new Victron Inverter & wondering where I should connect the Chassis to ground connection on my steel boat??

I could be wrong, but I think chassis grounding is a land thing, detailed for hard wired installations. I put a dedicated fuse on the battery 400a just to cover my butt.

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woko said..

Lazzz said..
Just about to install a new Victron Inverter & wondering where I should connect the Chassis to ground connection on my steel boat??

I could be wrong, but I think chassis grounding is a land thing, detailed for hard wired installations. I put a dedicated fuse on the battery 400a just to cover my butt.

Again, I don't know what model you have and what you're connecting it to, but the manual for the Victron MultiPlus-II 230V, (see link in previous post) says (Section 4) [bolding added]:

! Warning GROUNDING INSTRUCTIONS - This marine unit should be connected to a grounded, metal, permanent wiring system; or an equipment-grounding conductor should be run with circuit conductors and connected to equipment-grounding terminal or lead on unit. Connections to unit should comply with all local codes and ordinances

...suggests to me grounding isn't only a land thing.

Manual also has a table of DC battery fuse ratings and battery cable sizes depending on run length, by model and battery Ah.

Must admit I skipped thru your 1st post and missed the marine thing. The instructions are definitely for hard wired insulation though. I'm confident lazz will come back with an explanation

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

bottom 2 text boxes:

This of any use? While it is a specific implementation, it shows ground going to negative busbar, which is in turn connected to the BMS which in turn is shown as grounded to common earth. My guess is that still leaves you with the question as to whether to connect the 'ground' to your hull. Do you ground anything/everything else to your hull?

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.

Sorry, amended/added to my post before I saw your reply.

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

Excellent!!
I missed the light green wire in the diagram (colour blind!!) but this sorts the problem for me.

Thanks all for your help. I was hoping you'd chime in Shagster!! :)

It was Chat GPT that was steering me in the wrong direction!!

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?

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Yara said..
.............. but do we really need complex electronics to enjoy sailing?

Happy wife - happy life!!

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Lazzz said..

Yara said..
.............. but do we really need complex electronics to enjoy sailing?

Happy wife - happy life!!

Ah! Say no more....

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shaggybaxter said..
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

thanks a informative post. I can deal with inverter chassis ground to dc neg, I can deal with inverter chassis ground to steel hull/ engine. But after decades of being schooled to not using the hull as neg for dc like in a car / any machine, I find it difficult to conceptualise dc Neg to vessel/ motor. I'm sure you're correct but my poor little brain is struggling !

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.

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woko said..

shaggybaxter said..
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

thanks a informative post. I can deal with inverter chassis ground to dc neg, I can deal with inverter chassis ground to steel hull/ engine. But after decades of being schooled to not using the hull as neg for dc like in a car / any machine, I find it difficult to conceptualise dc Neg to vessel/ motor. I'm sure you're correct but my poor little brain is struggling !

Hiya Woko,
In principle, there is nothing fundamentally wrong with floating (isolated) DC systems, aircraft still use this for example.
I'm struggling to explain this properly (my fault, not yours) as earthing can be an absolute %$#@ to simply qualify.
I need to spend some time on how best to explain it succintly, do you mind if I come back to you?

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

My contribution (I have just completed a lot of IEC60601 Medical Device Safety work). Feel free to correct me if anyone can explain better.

The original idea of an "Earth" was to "Earth" the metal case of an electric device. The idea being that if an electrical short circuit occurred between the Active wire inside (the dangerous one) the metal case the current would be safely diverted to Earth rather than the metal case being "Live" (connected to the active wire because of a fault) which might then hurt or kill a person who then touched that metal case while at the same time being connected to the real Earth causing the fault current to go through him.

Then double insulation came along. If the device doesn't have a metal case (ie power tools, TVs etc), then the Earth is redundant. Thats why many devices have two pin mains plugs.

In the case of a 240VAC inverter on a boat. I personally always bought 12V appliances. A bit of salt water around 240VAC and danger danger, way too scary for me. But if you did have one....

The Inverter will internally highly likely have small capacitors for noise suppression connected from its Active output pin to its Earth output pin. Also from its Neutral output pin to its Earth output pin. They conduct electrical noise from those pins to Earth. The more metal everywhere on the boat that is connected to this Earth pin will reduce the EMI from the Inverter (which hurts your VHF reception etc). So its a great idea to connect it to the the hull of a metal boat but ......

Those capacitors can fail and connect the Inverters Active output pin to its Earth output pin. This means any metal connected onto that Earth is now live. (Dangerous). So your toaster or VHF radio antenna cable might be a death trap. If you get connected between the metal of hull of the boat (easy in wet weather) and a damp connection to the inverters Neutral output pin you can be hurt or dead. You have added a big dangerous electrode to your boat.

Medical devices specify "Safety Capacitors" which are guaranteed not to fail in a short circuit condition. An inverter made in China may not have these.

If you dont connect the Inverter Earth output pin to anything (ie no hull connection) the Inverters entire wiring is kept isolated from all other boat wiring in theory you can only hurt yourself if you get connected between its Active Output pin of the inverter and its Neutral Output pin. Thats much harder to do than if the inverter is connected to the metal boat hull.

The two options I see:

1. Connect the Inverter Earth pin to the metal boat hull to reduce EMI. But now there is an electrical safety risk factor. It might also induce electrolysis. (Do it via a good RCD you can test). Only ever use double insulated appliances.

2. Don't connect the inverter Earth pin to anything. You may have higher EMI. Only ever use double insulated appliances.

I would go with option #2 if there was no EMI problem.

Others who understand this swamp please comment :-)

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.

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cammd said..
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.

Most of the Sparkys I have met have no idea about this complex stuff. The last one I dealt with didn't understand why the fuse needed to be at the battery end of a power cable not the load end.

There is still only option 1 or 2. Sparky or no Sparky.

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!

I bet lazz had no idea of the can of worms he was opening up ! I've had a look at the items I would/ do use the inverter for, wet&dry vac, battery tool charger, small blender, induction cooktop ( will start another thread) angle grinder all are double insulated ie 2 pin plugs no earth. It seems in this case earthing is a moot point, but of course you could plug in an earth pin item. It would be educational if a rep from Victron / Renogy etc could explain chassis earthing ... ( please note the use of the term earthing as opposed to grounding,grounding on boat is to be avoided !

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.

Sorry, but the can of worms is getting longer.... just to check my plan - if it was me - with a 240VAC inverter not to connect the Earth pin (ie in electrical terms create a floating power system) wasn't totally flawed I checked with the famous Chatgpt.

Notice the very last line. Also use RCDs everywhere.

Here are five boat types where the 240 VAC system is commonly electrically floating. (no bond between neutral and hull/earth on the vessel itself). This is standard practice to reduce corrosion risk and avoid marina earth-loop issues: Fibreglass sailing yachts GRP hull = electrically non-conductive Shore power earth is isolated from DC negative and hull Neutral is not bonded onboard (bonding only occurs ashore via the supply transformer) Catamarans (fibreglass or composite) Same principles as monohull GRP yachts Floating AC system reduces stray current corrosion between twin hulls Very common in cruising and charter cats Luxury motor yachts (GRP or composite hulls. Especially those with isolation transformers or gensets AC system typically floats with controlled bonding points Neutral-earth bond occurs only at generator or shore transformer, not the hull Wooden boats and classic wooden yachts Hull is non-conductive AC earth kept isolated from hull and DC system Floating systems reduce electrolytic damage to fastenings Offshore cruising yachts with inverter-based AC systems. Inverter output is floating when not connected to shore Neutral-earth bond often relay-switched only when required Very common in blue-water boats running solar + battery systems Key idea (important for safety & corrosion) Protection is provided by RCDs, isolation transformers, and proper bonding strategy not by tying everything to the hull This is exactly why many marine standards (ISO 13297, ABYC E-11) allow or prefer floating AC systems.

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.

Thanks very much Trek, I stand corrected. You can tell I didn't have much to do with Aussie builders, I appreciate you chiming in.
I'll still earth my DC systems, I don't believe in running the risk of peeps ever becoming an electrical pathway!

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!

Well, she's in & running!!

Thanks for all the feedback.

This might help some too from Nigel!!

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Lazzz said..
Well, she's in & running!!

Thanks for all the feedback.

This might help some too from Nigel!!

Wahoo! Go Lazz!

But wait there's more, RCD is good in an earthed system, like Lazz's lovely small ship system. In an isolated/ floating system a RVD is the option. In a system like my recent upgrade where the inverter is turned on to use a specific tool/ device then an inline RVD seems to be the safest option. Phew my brain still hurts !