Safety trip for an inverter?

[Itsmcb]

Apologies if this has been answered before but I can't find anything specific.

I've picked up a Studer 1200watt inverter which I'm going to fit in my van to supply a separate run of sockets not linked to the existing EHU at all. The inverter has about 150mm of 230v 3core cable feeding a single extension socket. This cable includes an earth wire. I'm going to wire both my new sockets with 3 core cable as normal. My question is, is there a plug in type safety trip I can plug into the inverter outlet and then plug my new cable into that. Something like the ones used for electric lawnmowers?

 

[Richard n Ann]

Apologies if this has been answered before but I can't find anything specific.

I've picked up a Studer 1200watt inverter which I'm going to fit in my van to supply a separate run of sockets not linked to the existing EHU at all. The inverter has about 150mm of 230v 3core cable feeding a single extension socket. This cable includes an earth wire. I'm going to wire both my new sockets with 3 core cable as normal. My question is, is there a plug in type safety trip I can plug into the inverter outlet and then plug my new cable into that. Something like the ones used for electric lawnmowers?

The inverter can only supply about 5 amps so unless the mains 3 core is very thin it doesn't need fusing on the 230v side.

 

[NicM]

Yes you can get lawnmower safety plugs that will plug into a 3 pin socket then you plug into that.

 

[Itsmcb]

The inverter can only supply about 5 amps so unless the mains 3 core is very thin it doesn't need fusing on the 230v side.

Since it already has a fitted socket outlet my plan was to put a plug with a 5amp fuse on the end of my new 1.5mm three core cable which will supply the new sockets and just plug it in. What I would like is a plug in RCD or similar safety device, I'm just not sure what is suitable?

 

[Itsmcb]

Yes you can get lawnmower safety plugs that will plug into a 3 pin socket then you plug into that.

I appreciate that they are available but I'm just not sure if it's the best item to use in the case? Also I'm sure I've read about 'latching and non-latching' somewhere?

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[Stealaway]

I have one of these in my inverter - I'm not sure if it worthwhile in a van.
There are two types and because I turn my inverter of every night, I didn't want one you need to reset every time you turn the power off.
Mine doesn't but I don't know the name / type.

Edit --- Latching??

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[NicM]

So one like this… Amazon product ASIN B00STN8B1U its 13 amp but the safety side will work fine.

 

[Itsmcb]

I have one of these in my inverter - I'm not sure if it worthwhile in a van.
There are two types and because I turn my inverter of every night, I didn't want one you need to reset every time you turn the power off.
Mine doesn't but I don't know the name / type.

Edit --- Latching??

Resetting Rcd Socket for sale | eBay

Find great deals on eBay for Resetting Rcd Socket. Shop with confidence.

www.ebay.co.uk

I'm keen to fit something as one of the items to be used is a low power microwave () and it has a metal exterior and it's not double insulated.

Latching is the type you don't need to reset every time you turn off the power. Non-latching needs resetting every time. At least I believe that's correct.

 

[funflair]

I am no expert in electrickery so somebody cleverer than me is going to have to explain this, but I think it might be important

Note: An Inverter constitutes a voltage source independent from the grid and could be considered in the same way as a generator set. The voltage in between the phase and the neutral is 230V. An appropriate divisor establishes a 115V voltage in between neutral and earth, and between the phase and earth. According to the local prescriptions or particular requirement, (example: use of a ground fault detector) a true neutral may be established by connecting the neutral and the earth wire together (yellow - green and blue)

 

[Itsmcb]

I am no expert in electrickery so somebody cleverer than me is going to have to explain this, but I think it might be important

Note: An Inverter constitutes a voltage source independent from the grid and could be considered in the same way as a generator set. The voltage in between the phase and the neutral is 230V. An appropriate divisor establishes a 115V voltage in between neutral and earth, and between the phase and earth. According to the local prescriptions or particular requirement, (example: use of a ground fault detector) a true neutral may be established by connecting the neutral and the earth wire together (yellow - green and blue)

Yes I'm aware that there are issues with inverters and earthing hence my original question really. I would like to get the correct item for the job. I don't really want my lovely wife to get electrocuted when using the microwave if it develops an internal fault.

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[Itsmcb]

Incidentally, I've read this thread and I'm not really any the wiser.

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

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...

www.motorhomefun.co.uk

The posts all seem to contradict each other (unusually )

 

[Richard n Ann]

Inverters come with a floating earth, there is a connection terminal but it's not wired to anything from new.

An RCD will be useless in this instance because neither of the live outputs (yes they're both lives) will flow to earth.

In order to get a shock you'd have to touch both live outputs at the same time, which is very unlikely. It's safe as designed

 

[Itsmcb]

Inverters come with a floating earth, there is a connection terminal but it's not wired to anything from new.

An RCD will be useless in this instance because neither of the live outputs (yes they're both lives) will flow to earth.

In order to get a shock you'd have to touch both live outputs at the same time, which is very unlikely. It's safe as designed

Ok, I understand that but this particular inverter doesn't have an external earth post. It has a pre-fitted 3 core cable, 1 of these cores is an earth cable. I don't want to open the case to have a look if it's connected (or not). I have a socket tester, will this show if the earth is connected (in this situation)? Or plug in an RCD and see if trips on the tester button?

 

[Itsmcb]

 

[Richard n Ann]

Ok, I understand that but this particular inverter doesn't have an external earth post. It has a pre-fitted 3 core cable, 1 of these cores is an earth cable. I don't want to open the case to have a look if it's connected (or not). I have a socket tester, will this show if the earth is connected (in this situation)? Or plug in an RCD and see if trips on the tester button?

Yes a socket tester will usually show missing earth. If the inverter does have a live and neutral there will be continuity between neutral and earth on a multimeter. And in that case an RCD will work and protect the install

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[Richard n Ann]

View attachment 555068

That's a NICE inverter by the way

 

[Itsmcb]

That's a NICE inverter by the way

I couldn't believe it when I saw it on ebay with no bids on it. It's a bit heavy

 

[Richard n Ann]

I couldn't believe it when I saw it on ebay with no bids on it. It's a bit heavy

I bought the baby one, ex demo on ebay, 275w £200

Like yours the output is a flex, never tested the earth though

 

[Itsmcb]

I bought the baby one, ex demo on ebay, 275w £200
View attachment 555079
Like yours the output is a flex, never tested the earth though

Yes that is a BIT smaller .. If mine was only for hairdryer or straightener use I wouldn't be worried but that microwave concerns me a little. My wife insists that we need it so I need to make sure its safe. I'll test the earth and see if its connected but I do suspect that it is as its shown as an earth on the manual.

 

[Itsmcb]

Update and confusion . I couldn't find my socket tester so I went ahead and bought a RCD socket. I thought I would be professional and opted for a double pole latching socket so I could just plug in as required. I even stuck the information sticker on

I switched on the inverter and tried the test button on the RCD and it tripped. Excellent I thought, all is well. I then tried a little heat gun in The socket and that worked so I tried the microwave and that also worked . HOWEVER, this morning I found my socket tester and tried it only to find that it's reading as in the photo and the RCD test button on the tester does not trip the RCD socket. I've double checked all my connections so is it just the earthing system that's confusing the tester?

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[Pausim]

Regarding inverters it is worth remembering that the single pole switches supplied on UK sockets only switch off one connection, leaving the other live at 115V. One canal boater found this out the hard way when stripping down an appliance that he thought was switched off. Fortunately he lived to tell the tale and warn others. Single pole switched sockets are a liability on a motorhome where inverted power and reverse polarity are not uncommon. Better to have no switch and just pull the plug out.

 

[Itsmcb]

I was aware of this so have fitted a double pole RCD socket feeding two further sockets which are also double pole switched.

 

[autorouter]

I switched on the inverter and tried the test button on the RCD and it tripped. Excellent I thought, all is well. I then tried a little heat gun in The socket and that worked so I tried the microwave and that also worked . HOWEVER, this morning I found my socket tester and tried it only to find that it's reading as in the photo and the RCD test button on the tester does not trip the RCD socket.

The test button on the RCD device doesn't check the earthing. Note that it has access to the input live/neutral feed and the output live/neutral feed. It sends a tiny current, about 30mA, from the live output to the neutral input. The RCD detects that there is 30mA less current returning at the neutral than is going out through the live, so it trips. The test button only checks that the 30mA trip mechanism is working, not that the earthing is correct.

The socket tester doesn't have access to the input side of the RCD. It can only test by trying to send 30mA to the earth. If the earth wire is not connected to the neutral, it won't work.

 

[Itsmcb]

The test button on the RCD device doesn't check the earthing. Note that it has access to the input live/neutral feed and the output live/neutral feed. It sends a tiny current, about 30mA, from the live output to the neutral input. The RCD detects that there is 30mA less current returning at the neutral than is going out through the live, so it trips. The test button only checks that the 30mA trip mechanism is working, not that the earthing is correct.

The socket tester doesn't have access to the input side of the RCD. It can only test by trying to send 30mA to the earth. If the earth wire is not connected to the neutral, it won't work.

I'm not sure where that leaves me now. I had assumed that the pre-wired earth was connected to the neutral. So as things stand, if I accidentally short the 230v live and neutral wires the rcd wont trip as it wont detect a current drop? but the 5 amp fuse should blow? If the microwave develops a fault and the metal case was 'live' I would not get a shock as there is no leakage to earth, is that correct?

 

[Richard n Ann]

Yes you have to touch both lives (or live and neutral if you want to call one neutral) at the same time to get a shock from most unmodified small inverters.

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[Itsmcb]

So basically I should stop worrying