Installing inverter - MCB+RCD single RCDO

[gregcope]

I am installing an inverter (Mutilplus-II 12 3000 120-32). I want to add a breaker between the Shore power hookup/socket and the inverter. I have an existing consumer unit that has breakers for the charger/water heater and 230V socket ring. This existing cabling will be used on the output of the inverter.

I plan on input current limiting the inverter to 16A from 32A as I imagine most shore power connections are limited to this value.

As this needs only one way to break/protect between the shore power and inverter as the inverter is the only load. I was looking to fit a 32A MCB and similar RCD (30mA). This will take three ways in a DIN box. Alternatively can I fit a single 32A 30mA RCDO. This takes one way in DIN box.

Thoughts?

 

[PaulRainbow]

I'd fit the correct RCBO

 

[dankilb]

Why not a 16amp breaker? I’m thinking of doing the same thing, for same reasons, but was thinking I’d want the beaker in the boat to trip if we accidentally exceeded 16A.

I was therefore planning to source a 16A RCDO (of the right curve etc.).

 

[gregcope]

@PaulRainbow I assume you mean correct as in a 16A 30ma RCBO as opposed to an RCD+MCB combo and my 32A initial write up?

@dankilb Good point. I had not thought that all the way through. I need to this breaker somewhere simple to reset if it trips!

 

[dankilb]

On ours the shore power socket luckily comes in the transom opposite a large lazarette so that’s where I’d planned to locate the breaker.

We’re replacing a bodgey old installation so starting from scratch.

I thought the aim was to get the breaker as close to the inlet as possible (so it ‘protects the wire’)? In our case that is mercifully accessible.

The Victron also allows you to set a limit to the amps it draws. Hopefully the breaker shouldn’t trip in normal service with your Multiplus doing its thing.

The above is all sheer speculation via my novice reading of the instructions and relevant threads, I should add. Haven’t even installed ours yet and would only ever defer to the pros on electrics in general.

 

[Alex_Blackwood]

Something like this:-
Axiom Mini RCBO B Type 16A 30mA | Toolstation

 

[PaulRainbow]

@PaulRainbow I assume you mean correct as in a 16A 30ma RCBO as opposed to an RCD+MCB combo and my 32A initial write up?

@dankilb Good point. I had not thought that all the way through. I need to this breaker somewhere simple to reset if it trips!

I would fit an RCBO because it's simpler and neater.

If your current setup has a 32a inlet and suitable cables, fit a 32a RCBO, even if your present marina supply is only 16a. You can use 32a to 16a adaptor cable unless 32a is available.

If your current setup has a 16a inlet, fit a 16a RCBO. Good call on limiting the multiplus current to 16a, otherwise you'll spend a lot of time resetting the marinas breaker.

Current standards dictate that you should have a RCD or RCBO within 1 metre of the inlet socket. That's not always easily achievable, but it should be as close as possible as it is there to protect anything between the inlet and the consumer unit, or, in your case, the inverter.

You should then have an RCD or RCBO close to the inverter, for the outlets. The Mulitplus has 2 outlets, each one that you use has to have it's own RCD/RCB and suitable MCBs for the circuits it supplies. You can do this in two ways, either, fit 2 consumer units, one for each outlet, or, fit a split consumer unit.

Whilst you are fitting the initial RCBO, you must fit a galvanic isolator between it and the shore power socket. Pay particular attention to the grounding requirements that need to be made, as they may differ from your current setup.

 

[gregcope]

@PaulRainbow i do not appear to have a galvantic isolator on the present install (that i can see). Got any resources or recommendations for such a thing?

 

[Trident]

Next day from Amazon and a well respected brand
https://www.amazon.co.uk/Marine-gal...0883035&sprefix=galvanic+isol,aps,165&sr=8-11

 

[Tranona]

I have just fitted one of these force4.co.uk/item/Sterling/Galvanic-Isolator/T7R

 

[PaulRainbow]

@PaulRainbow i do not appear to have a galvantic isolator on the present install (that i can see). Got any resources or recommendations for such a thing?

If your boat is more than a few years old it's likely that there is no connection between the shore power Earth and the water, in which case no need for a GI.

Your inverter has to have a connection to the water, so you'll need to make a connection from the boats Earth circuit to a ground plane, anode or something else that gives a sound electrical connection to the water to provide a secondary Earth. At present, you have no Earth when you disconnect from shore power, no problem without an alternative AC supply, but fit an inverter, generator etc and you don't have an Earth, hence the need for the connection.

Either of the GI's in posts #9 and #10 will be OK

 

[William_H]

OP wrote "I plan on input current limiting the inverter to 16A from 32A as I imagine most shore power connections are limited to this value."

I am confused by this post /question. Input current limiting to the inverter at 16Amps seems reasonable that will give about .8 amp of AC from inverter on 12volt or 1,6 amp on 24v system. So very little relationship to AC mains input current rating.
I am guessing that OP wants a simple switching arrangement to connect inverter AC output to "ring main" AC supply outlets. This is no necessarily a good idea.
Firstly it is absolutely imperative that there is no way inverter (or generator) output can be connected to ring main when mains AC is connected. This is because any phase difference (almost inevitable) of the 2 x240v can in worst case look like 2x 240v DC connected in parallel so as to be 480v shorted. The 2 supplies will fight one another with inverter or generator sent to heaven. So if you want inverter connected to AC ring main in boat you must have a changeover switch with off in the centre.
The next problem with inverter on ring main is that most items you will use on shore power are just too power hungry for an inverter/batteries to supply. (even with a high powered inverter) You must be very selective about what items use inverter power and or how long.
I would suggest separate outlets for the inverter AC output and treat the mains connection (ring main) as normal with RCD over current protection and galvanic isolator. ol'will

 

[VicS]

OP wrote "I plan on input current limiting the inverter to 16A from 32A as I imagine most shore power connections are limited to this value."
I am confused by this post /question. Input current limiting to the inverter at 16Amps seems reasonable that will give about .8 amp of AC from inverter on 12volt or 1,6 amp on 24v system. So very little relationship to AC mains input current rating.
I am guessing that OP wants a simple switching arrangement to connect inverter AC output to "ring main" AC supply outlets. This is no necessarily a good idea.
Firstly it is absolutely imperative that there is no way inverter (or generator) output can be connected to ring main when mains AC is connected. This is because any phase difference (almost inevitable) of the 2 x240v can in worst case look like 2x 240v DC connected in parallel so as to be 480v shorted. The 2 supplies will fight one another with inverter or generator sent to heaven. So if you want inverter connected to AC ring main in boat you must have a changeover switch with off in the centre.
The next problem with inverter on ring main is that most items you will use on shore power are just too power hungry for an inverter/batteries to supply. (even with a high powered inverter) You must be very selective about what items use inverter power and or how long.
I would suggest separate outlets for the inverter AC output and treat the mains connection (ring main) as normal with RCD over current protection and galvanic isolator. ol'will

The inverter / charger in in question has two AC outputs about which the data sheet says.
"The main output has no break functionality. The MultiPlus-II takes over the supply to the connected loads in the event of a grid failure or when shore/generator power is disconnected. This happens so fast (less than 20 milliseconds) that computers and other electronic equipment will continue to operate without disruption. The second output is live only when AC is available on the input of the MultiPlus-II. Loads that should not discharge the battery, like a water heater for example, can be connected to this output. "

Doesn't the no break functionality suggest that it has its own internal change over switching.

 

[PaulRainbow]

Victron Mulitplus are inverter/chargers. The inverter is connected to the shore power supply and the two outputs connected to separate consumer units, each with their own RCB and MCBs (or RCBO and MCBs). If shore power is connected both circuits are live. If shore power is lost, one of the circuits stays live, the other does not. Heavy consumers, such as immersion heaters, towel rails etc would be connected to the circuit that's only live when shore power is present, so they do not impose a heavy load on the batteries.

The current limit feature limits how much power can be drawn from shore power. The OPs inverter supports a maximum of 32a, but he's on a 16a supply. Leaving the inverter on max means that he can switch on equipment that collectively use more than his 16a supply can support and trip the shore power MCB/RCBO, we've all been there, i'm sure. Limiting the current to 16a will stop this from happening.

With this inverter there is no need for change over switches. With respect, post #12 does not apply to this inverter, please disregard it.

 

[markspark7]

No point in fitting anything above 16a as in the event of overload you will simply trip the mcb in the pontoon pillar. Most pontoons are less than 16a to begin with, usually 10amp in my experience to reduce nuisance tripping on the main pontoon supply . Anything over a type B will still trip on the pontoon due to time characteristics.

 

[gregcope]

The current limit feature limits how much power can be drawn from shore power. The OPs inverter supports a maximum of 32a, but he's on a 16a supply. Leaving the inverter on max means that he can switch on equipment that collectively use more than his 16a supply can support and trip the shore power MCB/RCBO, we've all been there, i'm sure. Limiting the current to 16a will stop this from happening.

If I read the manual correctly the Multiplus II could supply the input current AND the inverter current to the protected AC-Out-1 circuit. For my example 16A+13A = 27A. This is the "PowerAssist" feature. I am not planning on using it. I am planning on current limiting the input to avoid the AC loads and Charger (120A at 12V!) tripping a 10A or 16A shorepower connection.

I rarely use short power being on a mooring or anchoring. When I am sailing... which has been interrupted by lack of working engine, but that is a different story...