Inverter grounding and other details

Jose Venegas

 I am installing BB lithium batteries and a new 5000 VA 24-240 v 50 hz Victron inverter.  I decided to avoid the temptation of installing an Inverter/charger because of the 50 to 60 Hz issues when using it in the Americas.  
I plan is to pass the 220 V 50 Hz cable from the inverter to the engine compartment and add a third outlet to the box that has the 220 V and 110 to 220V  transformed outlets.  This will allow me to power all 220 V outlets of the boat, plus air conditioning, microwave oven, washing machines, and water maker (obviously not all at the same time).  without having to rewire the 220 circuits. Also obviously, I will not be turning on the battery charger while the inverter is ON. 
With this approach, I expect that the system will switch automatically to the generator, as it does when the boat is running on shore power.  Yesterday I tested that the water maker was able to run under shore power without circuit breakers going off which suggests me it will be able to run with the inverter.  How much current will it draw and how long will the batteries be able to run it will have to be determined.

I found on this group a long discussion about the independence of AC and DC grounds in the SM Amel and long discussions about installing inverter/chargers but  I STILL HAVE A FEW QUESTIONS:

1) Is there something wrong with this approach? have I missed something?  For example, do the sudden shut down of the inverter AC output by the relay switch at the start of the generator damage the relay switch, the inverter, or the lithium batteries. Of course, to be safe I could turn off the inverter and or disconnect its AC output from the box before turning on the generator but it would be good to know is something is fundamentally wrong with this approach..    

2)   What to do with the AC "ground" 220 V connection from the inverter?  The inverter has the metal case connected to the ground of the 220 cable output and allows this ground to be connected to the neutral.  I have disconnected this and am not planning to connect the case to the bonding since that would connect the AC ground to the DC bonding that I have read is a NO-NO.  Alternatively, I could have the case connected to the DC negative or completely disconnected from everything.

3)   Any ideas where to pass the 220V cable from the battery compartment to the engine room.  There are several DC battery cables running through what looks like epoxy resin to prevent water from flowing between the two compartments.  Have anyone drilled a new hole along and above these cables?  If so, was it started from the engine compartment to avoid damaging of tubes and cables in the engine compartment?

4) I am planning to connect the DC cables from the inverter to the large DC switches from the batteries.  Are these switches large enough to handle the current if one does not use heavy current DC motors such as the bow thruster while running the inverter at full power?   The 5000 VA inverter requires a 400 amp fuse. 

Any thoughts or suggestions will be greatly appreciated.

Jose Venegas
Ipanema  SM2K 278



Hi Jose,
We installed a 63 amp, 660V, 3 position rotary switch.  The left position connects all 3 wires coming from the autoswitch that will give you shore power or generator, the middle position has no connections of the 3 wires and the right position switches all 3 wires coming from the inverter. The 3 wire output goes directly to the input terminals of the "white box" AC panel above the sink.

Earlier I had posted a full explanation of the installation and the advantages of it.  The Amel posting also has links to pics of the installation---,,,20,0,0,0::Created,,kaimi,20,2,0,46195362

A link to photos of the installation are in the posting--   The old link to eBay for the switch itself is no longer valid but here is a current link

Even though I had the parts and a plan, and the tools, we had the installation completed using a marine technician at Manoel Island Boatyard in Malta.  In my opinion having an professional expert involved is worth it for safety reasons.  He required an RCD installed immediately after the 220V exited the inverter (even though it went only about 3 feet to the "white box" AC which also has an RCD.  The installation also required an appropriately sized DC breaker just before the inverter (ABYC requirement which you can Google).

Let me know if you have questions.

Bob, KAIMI  SM 429

Jose Venegas

Hi Bob,
Thank you for your replay.  I think your approach is OK, particularly for a small inverter.  However, for a 5KW inverter, I also want to run pretty much all the 220V devices in the boat (obviously not at the same time). The inverter will be located next to the battery bank to minimize the distance to the batteries and make sure the inverter is in a dry place.  I already had the experience of having a saltwater leak which sprayed over the desalinator high-pressure pump (which shortly after died) the battery chargers and most of the pumps. I plan to place a Plexiglas barrier protecting the battery chargers similar to that which will be used to protect Kamela Harris tonight from the vice-president Corona virus spary ;). 

  Also, by connecting the inverter 220V output to an outlet identical to those used by the two shore power outlets, it will be connected to all the 220V devices that are run with shore power and generator without having to modify any of the AC wirings of the boat and will use the RCD of the "white box".  I find it unnecessary to add a second RCD at the outlet of the inverter for the same reason that there is no RCD between the shore power and the "white box".  With this approach, I can manually change the plug between any of the two shore power outlets (as currently possible) or the inverter outlet that will be installed in that box.  In addition, while I was charging the current AGM batteries with shore power and monitoring the current into the batteries, I turned on the generator and observed that the charging current went temporarily to zero before it restarted with the generator. This means that the relay switch does exactly what your 3 position switch.  It disconnects the power input to the "white box" before turning on the power from the generator.   Obviously, I will not be using the battery chargers while the plug is connected to the inverter outlet (the new outlet I plan to add to the "white box") but I could be using any of the other devices inadvertently.  In case I want to charge the batteries with the generator I will be turning off the inverter before I turn on the generator. and then turn on the battery chargers.  This will prevent that I inadvertently leave the battery chargers running on inverter power after I turn off the generator by forcing me to make sure the battery chargers are off any time I turn on the inverter.

I want to clarify that I will be installing an inverter and NOT and inverter charger which brings other complications to the problem, particularly when using shore power with 60 Hz.

Still, I what to know what people have done with the AC grounding of the inverter. (leave it disconnected or connected to the battery negative cable

I will be adding pix once I have concluded and tested the new system

Jose Venegas
Ipanema SM 278