Correct wiring for an Inverter in a 110 Land Rover

[wuntenn]

I'm fitting a small inverter but a good quality pure sine one. Instructions says that to install safely I need to 'Neutral Earth Bond' it and run an RCD inline to ensure I don't get fried.

Here's the instructions: link.

SO, having looked at the drawings and text I'm contemplating doing the following:

Connect the battery Positive to the Live on Inverter through isolator and fuse.

Connect the battery Negative to Neutral on Inverter

Connect an Earth from the vehicle chassis to Inverter.

Insert small fuse at rear of inverter (which I presume makes a connection between Earth and Negative to give the Neutral-Earth bond)

Purchase a Safetysure (or similar) internal RCD 13 amp socket (so the RCD is built-in and neat as I have inverter in a separate location from the socket outlet).

From the Inverter's 3-pin plug outlet run a suitable plug fitted with 3-core wire to the built-in RCD socket that I'll fasten in the desired location.

Is that me safe?

I've already installed a mains hookup on an isolated circuit, with an RCD Consumer Unit, feeding a single 13 amp socket. Is it wise to utilize the substantial earth to chassis I've fitted for this mains hookup, and loop the earth from the RCD 13 amp socket on the inverter into the Consumer Unit to connect it (I used a chunk of 4mm /2 cable) or should I keep the inverter circuit totally separate?

I AM NOT AN EXPERT!

 

[dwh]

I'm fitting a small inverter but a good quality pure sine one. Instructions says that to install safely I need to 'Neutral Earth Bond' it and run an RCD inline to ensure I don't get fried.

Here's the instructions: link.

SO, having looked at the drawings and text I'm contemplating doing the following:

Connect the battery Positive to the Live on Inverter through isolator and fuse.

Fine so far.

Connect the battery Negative to Neutral on Inverter

NO!

The neutral->earth bond is already being done internally in the unit (or will be after you install the optional fuse), and is protected by that fuse inside the unit. If you tie neutral to earth at any other point, you will be bypassing that internal fuse. Note in the manual, in the diagram for wiring Option 2, that it is the inverter output EARTH which is tied to the chassis - NOT the NEUTRAL!


But actually, I believe you simply mis-spoke there. I'm verbally "viewing with alarm" so that no one else ends up getting confused. Judging by the context, what I'm sure you actually meant is: "Connect the battery Negative to Negative on Inverter". That would be proper.

(When dealing with inverters, I find it less confusing to speak in terms of "input" and "output" and to keep the DC side verbally separate from the AC side, so I would have said "connect battery positive to inverter 12v positive input through fuse and switch, connect battery negative to inverter 12v negative input".

Pedantic yes, but old electricians tend to be pedantic (that's how they live to be old), and I'm an old electrician. )

Connect an Earth from the vehicle chassis to Inverter.

I think what you actually meant to say was: "Connect an Earth from the vehicle chassis to Inverter chassis" (there's that pesky pedantry again) . If so, then sure, go ahead; though it would probably be a lot easier to simply earth the inverter chassis to the battery negative at the back of the inverter, since the vehicle chassis is already connected to the battery negative.

Insert small fuse at rear of inverter (which I presume makes a connection between Earth and Negative to give the Neutral-Earth bond)

Purchase a Safetysure (or similar) internal RCD 13 amp socket (so the RCD is built-in and neat as I have inverter in a separate location from the socket outlet).

From the Inverter's 3-pin plug outlet run a suitable plug fitted with 3-core wire to the built-in RCD socket that I'll fasten in the desired location.

All good.

Is that me safe?

Yes.

The only possibly dangerous failure mode would be if the "live" wire between the inverter output and the remote RCD were to short to the chassis. That would be "ahead of" the RCD and so would not be protected by the RCD.

But the inverter would read that as an overload on the 230v output side and shut down - so no worries.

I've already installed a mains hookup on an isolated circuit, with an RCD Consumer Unit, feeding a single 13 amp socket. Is it wise to utilize the substantial earth to chassis I've fitted for this mains hookup, and loop the earth from the RCD 13 amp socket on the inverter into the Consumer Unit to connect it (I used a chunk of 4mm /2 cable) or should I keep the inverter circuit totally separate?

A bit confusing, as you seem to be saying that the inverter has an RCD, but you've already stated that yours has a 3-pin plug outlet.

So, assuming that your inverter has a receptacle (3-pin plug outlet) and the only RCD on the 230v output side of the inverter is the remote RCD receptacle you intend to install: No, you do not need to loop the remote RCD's output side earth back around to the chassis.

The earth of the RCD receptacle will be connected back to the inverter's receptacle earth via the wire you run between the inverter and the RCD, and you will be essentially wiring the 230v output side of the inverter as per the manual wiring diagram Option 1.


There is another reason to keep the inverter's output separate - RCD's tend to "not play well with others". If for instance, you have your mains feed hooked up to the truck through an RCD, and you are doing something like charging the battery from that, and then you also happen to be using the inverter and have something else running from the inverter's RCD - the two RCDs could end up causing each other to nuisance trip.

It's rare, but I have seen it happen and it's a real bugger to diagnose, so my default policy is "don't stack up RCDs".

I AM NOT AN EXPERT!

Aside from a few quirks in the nomenclature, I think you're doing quite well, so:

'Lay on, Macduff, and damned be him who first cries "Hold! enough!"'

 

[wuntenn]

Oh bugger bugger!

Well spotted!

But actually, I believe you simply mis-spoke there. I'm verbally "viewing with alarm" so that no one else ends up getting confused. Judging by the context, what I'm sure you actually meant is: "Connect the battery Negative to Negative on Inverter". That would be proper.

You're right - I wrote neutral meaning negative! But thanks for pointing out in writing in case anyone else misinterprets!

Ok to clarify:

I have a compact consumer unit with RCD installed in the van. It is on a mains hook up circuit. It is wired 'normally' Pos, Neg and earth. The earth rail in the consumer unit is connected directly to the vehicle chassis with a substantial piece of cable (4mm /2 and I'm ensuring ALL wiring is multi-strand rather than solid core).

From the consumer unit I wired in a 13 Amp socket outlet, with the socket high up in the vehicle out of the way of damp and accidental impacts. SO this outlet has proper Pos and Neg and earth to chassis.

Inverter:
For practical reasons of space and access the inverter is mounted on the van ceiling on passenger side (UK) directly above the battery box which is under the passenger seat. That means I need about 4 feet of cable from the battery to the inverter - the closest I can get it without it being exposed to fiddling small child fingers and wet. As you can see from the instructions the inverter has a 3 pin outlet on the front. I intend to run a plug/cable from that outlet to a 3 pin socket/outlet that I will fit on the opposite side of the van from the inverter, and this socket will have an internal RCD. (as link I provided earlier). This I intend to be the inline RCD specified in the inverter fitting instructions.

As the Consumer Unit (with its own internal RCD) is mounted close to the intended inverter power output socket, can I utilize the earthing inside the Consumer Unit to put a wire from the Inverter rear earth post to the substantial earthing setup I've attached inside the Consumer Unit? Or should I run a separate circuit for the Inverter earth directly to chassis and thus bypassing any connection to the circuit for the mains hookup?

Thanks for the MacBeth encouragement! Not often we get Shakespeare on vehicle forums!

See attachment for a schematic of my wiring.

 

[redneck44]

Either/either personally I would keep them separate and as short as possible.
Read the earth link instructions very carefully though
Use an RCD plug straight from the inverter http://www.screwfix.com/p/masterplug-rcd-plug/44855 rather than a flying lead.

 

[wuntenn]

SO is it best practice to keep the RCD as near as poss to the inverter? Which makes some sense when I think about it; is this the same principle as keeping the fuse as near the battery as possible?

Is a 4 foot run to the inverter from the battery pushing it?

 

[redneck44]

It should be best practice, take a look at your house wiring the main breaker/RCD is as close to the point of entry as possible.
For the cost of an rcd plug, why not do it? How much do you trust that piece of wire not to chafe through?

 

[wuntenn]

I see what you mean. Yes that makes sense. Thanks.

 

[dwh]

I have a compact consumer unit with RCD installed in the van. It is on a mains hook up circuit. It is wired 'normally' Pos, Neg and earth.

Actually, that would be live (or hot), neutral and earth. Pos and Neg are for DC. (Yet MORE pedantry! )

The earth rail in the consumer unit is connected directly to the vehicle chassis with a substantial piece of cable (4mm /2 and I'm ensuring ALL wiring is multi-strand rather than solid core).

Okay.

From the consumer unit I wired in a 13 Amp socket outlet, with the socket high up in the vehicle out of the way of damp and accidental impacts. SO this outlet has proper Pos and Neg and earth to chassis.

Live and neutral, not Pos and Neg.

Inverter:
For practical reasons of space and access the inverter is mounted on the van ceiling on passenger side (UK) directly above the battery box which is under the passenger seat. That means I need about 4 feet of cable from the battery to the inverter - the closest I can get it without it being exposed to fiddling small child fingers and wet. As you can see from the instructions the inverter has a 3 pin outlet on the front. I intend to run a plug/cable from that outlet to a 3 pin socket/outlet that I will fit on the opposite side of the van from the inverter, and this socket will have an internal RCD. (as link I provided earlier). This I intend to be the inline RCD specified in the inverter fitting instructions.

Fine, no worries. As redneck44 noted, it would be best - in that situation - to have the RCD at the inverter end of the wire run.* The reason is, that even though the inverter will detect a shorted wire as an overload and shutdown, that won't protect a human from a shock in the event of an exposed wire that is not shorted and causing an inverter shutdown.

But, not strictly required. If you ran the cable inside of some sort of protective shell (like a length of PVC pipe), then that would protect a human from an exposed wire and you would be fine putting the RCD at the receptacle end of the wire.

As the Consumer Unit (with its own internal RCD) is mounted close to the intended inverter power output socket, can I utilize the earthing inside the Consumer Unit to put a wire from the Inverter rear earth post to the substantial earthing setup I've attached inside the Consumer Unit? Or should I run a separate circuit for the Inverter earth directly to chassis and thus bypassing any connection to the circuit for the mains hookup?

Well...it really doesn't matter. You've already earthed the mains to the vehicle via the consumer unit. So any which way you earth the inverter to the vehicle, the inverter earth and the consumer unit earth will be making contact with each other. Go with the easiest method.

Thanks for the MacBeth encouragement! Not often we get Shakespeare on vehicle forums!

AND with proper Queen's English quoting style I hope you'll note!





*Our rednecked friend is slightly off in another way though...in house wiring, the RCD is to protect a human from a shock, not to protect the wiring system from a short - that's what the earth wire back to the mains panel is for. So there is no need in house wiring to have the RCD as close as possible to the mains panel.

This is why they make RCD receptacles. RCD breakers in the mains panel are just for convenience - for example you can feed all the receptacles in a kitchen from a single RCD breaker, and won't need to install a whole bunch of RCD receptacles.

Whichever way you go - RCD at inverter end of wire or RCD at the user end of the wire - DO NOT DO BOTH. That would be the stacking I referred to before and would almost certainly result in the two RCDs nuisance tripping each other.

 

[wuntenn]

Great detailed post and very much appreciated. Thank you.

REALLY useful that you use the proper nomenclature too, I was not aware that 'Pos' should be termed 'live' in an AC circuit but thinking about it, it makes perfect sense.

My 'problem' with the RCD at the inverter end is that the inverter unit is built with the intention that it is surface mounted on its base so the digital display on it is the right way up and legible. I'm mounting it on the ceiling, but the right way up, in a small wooden receptacle. However to enable the UK 3-pin plugs to be fitted the plug socket on the front of the inverter is inverted (ie single pin at bottom) so the wire exits upwards (which makes sense as otherwise it would be really difficult to fit a plug when it is used on a wall or floor). So in my use the plug wire will foul the ceiling and therefore the plug types with built-in RCD will not fit at all as there is not enough space.

However what I can do is use a small inline RCD something like this which can be tucked into a gap I've got, but kept close to the inverter end of the wire run.

Anyway the whole setup is a lot clearer thanks to all your help ( and red too!). So thanks for that.


PS - aye, your Queens english is mightily impressive, there are people 'over here' who could learn a lesson from you!

 

[redneck44]

Wuntenn can't you exchange the inverter for the one fitted with an RCD?

Yes DWH you are correct, however in my defence, I was using the house wiring as an example. Placing the RCD as close to the incoming supply protects the whole system rather than individual sockets.

 

[wuntenn]

Wuntenn can't you exchange the inverter for the one fitted with an RCD?

Yes DWH you are correct, however in my defence, I was using the house wiring as an example. Placing the RCD as close to the incoming supply protects the whole system rather than individual sockets.

Bought it ages ago and have fitted it, so its got screw marks and obvious signs of having been installed so doubt I'd get an exchange. Didn't actually realize until going to wire it up that the RCD aspect was so crucial. Live and learn!

 

[dwh]

However what I can do is use a small inline RCD something like this which can be tucked into a gap I've got, but kept close to the inverter end of the wire run.

I like it. You have my blessing my son. <waves around the thurible and mimes the benediction>

PS - aye, your Queens english is mightily impressive, there are people 'over here' who could learn a lesson from you!

Probably comes from my mother's swelled pride of being a member of The Clan Lamont Society of North America.

Here's yours truly with my lowlander sword, "The Lamont Pikebreaker" (click to enlarge, then click the enlargement for full size):






Hand forged by the English Master Blacksmith Tony Swatton at his shop in Burbank, The Sword and The Stone, using authentic methods. Well, he did ship the forged metal blank to a specialist for tempering, but otherwise did it all himself.

It is a REAL sword, and not a movie prop and is razor (literally) sharp.

Mother secretly had it made for me. Talk about giving someone a gift that they never would have thought to buy for themselves...she won the Grand Prize with that one.


I drew the line though at the Scottish Games. After being swindled into the Caber Toss (Mom signed me up and the first I heard about it was when they were calling my name to take my turn) and making a total hash of it, I resigned to the sidelines in ignominy where I gladly remain.

 

[dwh]

Whoa! Didn't know that Tony had is own TV Show, "Man at Arms"!

https://www.youtube.com/results?search_query=man+at+arms




Good to see him so successful. My sword was made...I dunno...almost 20 years ago I suppose. He threw in the Stag Horn and Redwood display hanging as a surprise, which tells you the kind of guy he is.

 

[wuntenn]

Whoa! That's some bit of kit.

NB those of you unfamiliar with the highland method of warfare - note there is no single-handed sword handling nonsense involved. It's two-hand whole-body-behind-it whacking and hacking! DO NOT BURGLE THIS MAN'S HOUSE AND BEWARE THE SECOND BLOW! (Why? Because his first whack will destroy his ceiling, but after that your arms are coming off if you're lucky, or your head if you're less fortunate!).

Looks like a great bit of craftsmanship. Nice to see.

Wee Mel Giblet was in my home town for the making of Braveheart (and we had Christopher Lambert doing 'Highlander' and Liam Neeson doing Rob Roy as well, at different times). The Highlander filming was fun - several of my mates were involved, recruited down the pub, and suddenly taking to wearing baseball caps and bumbags as befitted their elevation from unemployed drinker to 'film extra'. Things were er...lets say....slightly more epic than the director wanted in the fight scenes in Glencoe. Asked to "make it look realistic" the 'troops' who had the previous night been in the pub doing the usual thing, but now cast as film extras had a bit more money to spend, were next morning rather 'jaded' and the fight scenes quickly deteriorated. I believe at least three people needed hospital treatment, and when the shooting resumed the day after, the director made a desperate plea to the 'soldiers' to "make the fight scenes look less realistic" - ie "please don't actually try to cut anyone's arm off for real, this is only make-believe".

Silly man, I mean - give Scots jaggy weapons and ask them to pretend to be fighting! Ha!

But Mel Gibbon's arrival was fun. The crew had cleared an area of forest in the glen behind my house, and put their trailers and kit there. Mel's personal trailer was all ready for him and the director thought it would be a good touch for the cast, all done up in kilts and woad, to stand outside Mel's trailer so that when he emerged all done up as you see him the picture above, with the hair extensions all the rest, the cast would cheer.

Two problems. Mel took ages to get ready. The midges (no-see-ums) were hellish. Within 5 minutes the cast, with bare legs, were in agony. Mel dithered. The midges ate. The cast complained. Mel dithered. The midges feasted, and more arrived to join them. The cast grew mutinous. Eventually after 40 minutes of agony for the extras, Mel emerged, blissfully unaware of the frustration his delay had caused. Smiling broadly, arms outstretched, he welcomed the cast.

"Ye look grrrreat! Tell me whit arrr yoo troo Scotsmen wearing underrr yer kilts today then!"

And from the back came a loud, but disgruntled voice "Yer wife's lipstick Mel, yer wife's lipstick!".

Mel laughed heartily and proved he had a sense of humour and fun, and got a great welcome.

Another story for another time is the day my mate Tom and I attempted to smuggle a dinosaur onto the Braveheart film set in the back of a Series 3 Land Rover. Ah life in the Highlands!

 

[dwh]

Hahaha!


"Beware the second blow!" I'd say that was the best quote about that hunk of iron yet. Previous best was, "Hell of a last line of defense..."

Ceiling hell...the bloody thing is almost 6 feet end to end and I'm 6'4" to start with...it'd go right through the ceiling and poke a hole in the roof and maybe scrape the belly of a low-flying jumbo-jet.

And yea, two hands for sure. Big as I am, I can actually swing it one-handed. Problem is, I can't CONTROL it one-handed.