Using an inverter, where to put fuse & or trip switch for the 230v side?

[ambulancekidd]

We've recently bought two new batteries for the moho & they're usually hooked up to the inverter & or the 12v side of things.
What I don't know is where to put a fuse from the batteries to the inverter & an MCB on the 230v side?
I'm going to pop in a few dedicated 230v sockets which will be powered only by the inverter. I want to know that I have proper protection on that side of things, is it acceptable/recommended to install a separate MCB box.

At the moment I simply disconnect the batteries & inverter when they're not in use.
I still have the original hab battery which will eventually be removed.

The diagram below shows the way I have the batteries configured.

 

[pappajohn]

12v mega fuse close to the batteries. Size depends on inverters max output.
MCB (if the inverter has no inbuilt overload protection) before any 230v outlet sockets.

 

[Lenny HB]

If you are going to fit an RCD on the 240v side of the inverter you need to ground one side as inverter outputs as invertor outputs are isolated so just fitting an RCD won't work.

 

[pappajohn]

If you are going to fit an RCD on the 240v side of the inverter you need to ground one side as inverter outputs as invertor outputs are isolated so just fitting an RCD won't work.

He said MCB Lenny

 

[DBK]

He said MCB Lenny

I suspect that's a typo, why would you want to fit a circuit breaker? An RCD seems to recommended these days and as Vanbitz suggest you want a latching one, so it doesn't need to be reset every time the inverter is turned off. The inverter link in my signature below leads to the one I fitted.

Lenny's grounding advice is good and mirrors what happens in normal domestic systems where neutral is grounded at the local sub-station.

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[pappajohn]

I suspect that's a typo, why would you want to fit a circuit breaker? An RCD seems to recommended these days and as Vanbitz suggest you want a latching one, so it doesn't need to be reset every time the inverter is turned off. The inverter link in my signature below leads to the one I fitted.

Lenny's grounding advice is good and mirrors what happens in normal domestic systems where neutral is grounded at the local sub-station.

Must admit I did wonder as most inverters have inbuilt overload protection, may be basic but its there.

 

[Lenny HB]

He said MCB Lenny

As he said protection I assumed he meant RCD for his own protection Also an MCB would be too slow to save an inverter from frying.

 

[pappajohn]

As he said protection I assumed he meant RCD for his own protection Also an MCB would be too slow to save an inverter from frying.

MCB isn't there to protect the source Lenny, its to protect the wiring and to an extent, the appliance.
After all, its only a mechanical fuse.

 

[Lenny HB]

MCB isn't there to protect the source Lenny, its to protect the wiring and to an extent, the appliance.
After all, its only a mechanical fuse.

Yet alright I've been on the red water with dinner.

 

[autorouter]

RCDs and MCBs are normally separate units because usually one RCD and several MCBs are fitted. If you just want one RCD and one MCB, you could use an RCBO which combines both functions in a single device. Saves space but more expensive than two separate devices.

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[Stealaway]

I have one of these plugged into my inverter. All the other 240v sockets are fed from this.

 

[Lenny HB]

I have one of these plugged into my inverter. All the other 240v sockets are fed from this.

View attachment 304952

Have you got one side of the inverter output earthed if not it will just look pretty and have no useful function.

 

[Stealaway]

Have you got one side of the inverter output earthed if not it will just look pretty and have no useful function.

Do you know Lenny I've never thought to test it! I used to have special plug with a resistor in it I'd copied from somewhere that worked a treat.
Must find the link and make another one. You might remember?

 

[Lenny HB]

Do you know Lenny I've never thought to test it! I used to have special plug with a resistor in it I'd copied from somewhere that worked a treat.
Must find the link and make another one. You might remember?

That's a good idea, take your RCD apart and see what restitor is connected to the test button. I would have thought around 2.4k 1 W resistor as that would give a 100 ma, load that should trip a 60 ma RCD.

 

[autorouter]

I think an RCD will protect you from shock even if there is no earth connection anywhere. It works on the principle that to give you a shock, the current usually flows through you to earth. If you touch a mains connection, either it will try to pass a large current, or it will just tie one side to earth without much current flow. In the first case, the RCD will trip. In the second case, it won't trip, but there's no danger anyway.

The test button won't cause a trip because the earth pin is not connected to anything.

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[jp11]

Sorry to pick up this thread after such a long period, but it was mentioned in a recent similar thread. Am I not correct in saying that an RCD operates by comparing the current in both the live and neutral wires? And if it detects even a small difference it trips. I don't know (or understand) how the internal wiring of an inverter works, especially in relation to "earth", but I do know that my own inverter has an "earth" cable attached to the van body.