Need some help choosing RCD consumer box for the AC out from 375W inverter

Al's Shed

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Jul 15, 2017
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Hello,
I'm a little bit stuck on what size RCD or MCB to get for the AC side of my inverter output.

I've got a Victron energy 24V 375Winverter (off grid)and my load will be a maximum of about 150W. I need to connect a couple of pumps which operate underwater in the pond, so definitely need RCD protection. I also want to run the outside lighting and some lighting inside the shed.

I have been looking at different types of consumer units, however, many of them have 63A RCD with 6-16A MCBs.

One like this.

MK garage consumer unit

My concern is that the 63A rating on the RCD and the 16A rating of one of the MCBs are too high for the appliances I plan to run. Here the AC voltage is 240V. Since the maximum load i have measured on the AC side has been less than 150W, that's less than 1A at 240V.

Have i misunderstood something, or should I look for another consumer unit rated at a lower value??

Any advice on this would be great.

Thanks. Alex.
 
I wouldn't worry too much about the breaking voltage. If you want to add a little extra security by using a smaller breaker, put that after the victron, then feed the RCD from that one. The RCD will give you the water protection, and the smaller breaker will give you lower amps protection; however, finding a smaller breaker would be tough. Though, I think you'd be fine with just the RCD by itself. 16A is for the rating on the wire of the max it can handle, not the for the load. If the wires on the load end were to short, you'd definitely go over 16A and the RCD will pop.
 
You size the MCBs for the wires you use, not for the devices you are powering. They protect your wires from getting hot and potentially starting a fire. 16A isn't unusual as they are the standard for 230Vac household sockets.
As for the RCD, they are rated for a current, but this has nothing to do with their protective function. What you are looking for is their sensitivity, the difference between the current coming in and going out. This is usually 30mA or less when you want to protect people.
 
RCD is usually 300mA and the 30mA for "wet" rooms, outdoors,and appliances connected to water...
Make sure all your equipment is grounded.

But always check your local code for this.
 
Thanks for the comments people :)

The RCD in the MK one I'm looking at has a sensitivity of 30mA. I know the fuses protect the wire gauge. I think that's where I was getting confused though, all of the pond equipment has standard 13A plugs and I was thinking 63A going though those wires would be way too much...But that would never happen as the feed would be going through the 16A MCB, so that would protect the 13A cable.

Thinking about it, all of the wall sockets on the grid side are on 16A breakers.

I think I'm a little more clear on this now.

And yes, everything is earthed through a separate ground rod.
 
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