Electrical RCD consumer units onboard

[Arvor250]

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Hi,
I’m hoping to install a ip65 4 way consumer unit RCD 6amp 16amp MCB with separate shore power , this consumer unit is for the inverter I’m fitting can you or anyone help in the earthing of this please ? Regards

 

[PaulRainbow]

Hi,
I’m hoping to install a ip65 4 way consumer unit RCD 6amp 16amp MCB with separate shore power , this consumer unit is for the inverter I’m fitting can you or anyone help in the earthing of this please ? Regards

Inverters, when connected to the boats onboard systems, are usually wired through a two pole changeover switch, or are you planning to install a separate consumer unit, with circuits dedicated to the inverter ?

If it's a separate system, what do you intend to run from the inverter ?

Exactly what make and model of inverter are you intending to install ?

I assume a 6a RCD was a typo ?

 

[rogerthebodger]

My boat mains setup has mains inputs from shore power, inverter or generator.

I select the input by using a 2 pole 4 position selector switch , the extra position is an OFF position.

Earthing an inverter depends on the exact type of inverter which is why Paul as the question and it is very important to know the type before any advice can be given.

Earthing of the shore power input also depends on the exact arrangement. Do you have an isolation transformer as the earthing will be different if you have one or not.

 

[st599]

Is it not better to have double pole breakers to deal with both UK and EU power supplies?

 

[JumbleDuck]

I’m hoping to install a ip65 4 way consumer unit RCD 6amp 16amp MCB with separate shore power

I assume a 6a RCD was a typo ?

I assume s/he means a standard garage consumer unit with an RCD feeding 6A (lighting) and 16A (power) MCBs.

 

[PaulRainbow]

I assume s/he means a standard garage consumer unit with an RCD feeding 6A (lighting) and 16A (power) MCBs.

Ah yes, i see what you mean

 

[superheat6k]

My boat mains setup has mains inputs from shore power, inverter or generator.

I select the input by using a 2 pole 4 position selector switch , the extra position is an OFF position.

Earthing an inverter depends on the exact type of inverter which is why Paul as the question and it is very important to know the type before any advice can be given.

Earthing of the shore power input also depends on the exact arrangement. Do you have an isolation transformer as the earthing will be different if you have one or not.

If I had three supplies I would prefer a five position switch so there is a full off between each power source position, so no chance of inadvertently having two sources of supply connect together, as they would almost certainly be out of phase at the moment they connected.

 

[rogerthebodger]

If I had three supplies I would prefer a five position switch so there is a full off between each power source position, so no chance of inadvertently having two sources of supply connect together, as they would almost certainly be out of phase at the moment they connected.

Point taken but its unlikely in my setup the I would have the inverter and/or generator running at the same time.

Also my switch is a break before make so unless the switch fails again unlikely to 2 phases connecting together

I also have a RCD for each supply connected before the selector switch of the is also an isolator before the selector switch.

 

[Arvor250]

My boat mains setup has mains inputs from shore power, inverter or generator.

I select the input by using a 2 pole 4 position selector switch , the extra position is an OFF position.

Earthing an inverter depends on the exact type of inverter which is why Paul as the question and it is very important to know the type before any advice can be given.

Earthing of the shore power input also depends on the exact arrangement. Do you have an isolation transformer as the earthing will be different if you have one or not.

Thanks for the information I need to check inverter spec, as I have shore power separate to their on sockets and staying that way ! Cheers

 

[VicS]

Thanks for the information I need to check inverter spec, as I have shore power separate to their on sockets and staying that way ! Cheers

If you insist on a duplicate systems of consumer units, sockets and wiring for the inverter and shorepower ............ (but Lord knows why you want to do that) ...... earth both system to the same point together with the incoming shorepower ( hopefully incorporating a galvanic isolator in this), anodes etc and the DC negative, provided it is not an isolated DC system.

Be aware that many/ most portable inverters have something resembling a centre tapped AC output. which if earthed would mean that your inverter fed sockets do not have neutral and line connections but rather two live connections each 115 volts relative earth potential. The RCD may not work as intended with this ??? and single pole mcbs and swiches will leave one conductor ( the one you'd expect to be neutral) at 115 volts relative to earth and therefore the whole appliance possibly 115 volts relative to earth,
Ideally you should install an inverter which is already wired to provide line and neutral or which can be wired externally to do so.

This is why you have been asked to identify make and model of inverter.

 

[PaulRainbow]

If you insist on a duplicate systems of consumer units, sockets and wiring for the inverter and shorepower ............ (but Lord knows why you want to do that) ...... earth both system to the same point together with the incoming shorepower ( hopefully incorporating a galvanic isolator in this), anodes etc and the DC negative, provided it is not an isolated DC system.

It is certainly questionable as to why installing the inverter on a separate system. I would normally be connected to the onboard systems or used stand alone.

Ref Earth, there must be continuity between the inverter, the anode/underwater metalwork/hull (if metal). There is no requirement to connect DC negative.

There is actually no requirement to connect the shore power Earth to the above, if it's currently not so connected. But, it would be good practice to do so, in which case a galvanic isolator is a must.

I still wouldn't want to give any specific advice without knowing more about the inverter.

 

[rotrax]

If I had three supplies I would prefer a five position switch so there is a full off between each power source position, so no chance of inadvertently having two sources of supply connect together, as they would almost certainly be out of phase at the moment they connected.

I dont have an inverter but do have an 8KW Westerbeke genset.

Shore power/genset has a very complicated OE system of sliding blocks/switches which stop both being selected at the same time. I decided not to use this.

I used a KISS* method. I just connect the shorepower lead to the boats 240 inboard socket when I want shorepower.

For genset use I disconnect and plug in the genset output.

Only one can be used, not possible to make a mistake.

I have seen a 'blow out' when phases dont match.............................

* KISS - Keep it simple stupid..............................