wiring in inverter

chatteris

chatteris

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I am adding an extra battery and a invertor, do i put in extra 240v sockets for the invertor or wire in to my existing 240v system, do i need to put in an isolator for invertor when using hook up and where should i join wiring to original as if I add before my 240v fuse box that would make hook up point on side of van live when I switched invertor on ?. should I put in another rcd fuse box for invertor and join into original system after the original fuse box,
sorry for the long post and hope I have explained it properly
Thanks
 
My stuttering attempt to install an inverter is described in the thread below. However, your post lights up a few warning lights for me. If you are confident working with 240 volts and understand the risks involved then a DIY Inverter fit is perfectly feasible. Only you can answer that. :)

Mine has automatic change over but this isn't essential. You could just use the sockets on the inverter.

https://tinyurl.com/y5gjksrm
 
The simplest thing is to have separate inverter-powered and hookup-powered sockets. Then you just need an RCD or RCBO on the inverter output to protect from electric shock.

The alternative is to have a switch to change the 240V supply source from hookup to inverter. This avoids the hookup inlet pins going live when the inverter is on, and avoids the two unsynchronised mains waveforms from fighting each other. The switch can be manual or an automatic changeover relay.

If you choose the second method, you should arrange it so the mains battery charger is not powered by the inverter (trying to charge the batteries with power from the batteries).
 
thanks had not thought about battery charger, probably best to add a couple of sockets just for inverter will be easier to install but not quite so good for different appliances around the van but an extension lead will suffice
 
I have separate wiring and sockets for the inverter. A double pole RCD is important because many inverters do not have neutral and live but use both wires to deliver out of phase power. The all too common single pole RCDs may only be switching off half the supply. I use one of these connected to the inverter outlet.
www.screwfix.com

PowerBreaker 13A 2-Gang Unswitched Metal Clad Passive RCD Socket with Neon with White Inserts - Screwfix

Order online at Screwfix.com. Robust, easy to install RCD with neon indicator and power cut-out for added protection. 13A max load, trips under 20ms at 30mA. Double pole. Passive operation. FREE next day delivery available, free collection in 1 minute.
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Not to be confused with this one which is about half the price but only single pole.
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British General 13A 2-Gang SP Switched Metal Clad Passive RCD Socket with White Inserts - Screwfix

Order online at Screwfix.com. 13A max. load. Trips at 30mA. Passive operation. Heavy duty, metal-clad moulded safety RCD switched socket that protects against the risk of a fatal shock. Latched with no need to reset after a loss of power. FREE next day delivery available, free collection in 1...
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Thanks, will get the double pole, there is more to fitting an inverter than i realised
 
My inverter is only a simple 300W version wired out to one socket however to make it totally automatic I have a micro switch inserted in the CBE type socket which operates a relay to switch on the inverter when a plug is inserted into the socket. The micro switch is operated by the movement of the shield inside the socket. This provides 240v for small gadgets, laptop etc. when not on a hook-up which for us is most of the time. The size of the inverter could of course be larger but 300W serves our purpose.
 
chatteris said:
Thanks, will get the double pole, there is more to fitting an inverter than i realised
Click to expand...
Ideally you want a latching RCD, which will stay on when the inverter is turned off. Conventional non-latching ones will need to be reset every time you turn on the inverter although this isn't a hardship if it is easy to get at.

I haven't done this on my installation but I'm considering connecting one side of the output to the vehicle chassis. This makes it the same as the neutral wire in the normal mains, which is also connected to earth. This should make the system safer, assuming the inverter is also earthed to the chassis.
 
DBK said:
I haven't done this on my installation but I'm considering connecting one side of the output to the vehicle chassis. This makes it the same as the neutral wire in the normal mains, which is also connected to earth. This should make the system safer, assuming the inverter is also earthed to the chassis.
Click to expand...

Oh no it doesn't make it the same as the neutral wire!!!

What you are suggesting is dangerous.
 
thebriars said:
Oh no it doesn't make it the same as the neutral wire!!!

What you are suggesting is dangerous.
Click to expand...
The neutral wire in conventional household electrical installations is connected to the earth, usually at the local sub-station. If you measure the voltage between neutral and earth it should in theory be zero but in practice, because of imbalance between the phases, there might be a voltage in the low tens of volts.

Doing the same for the output of an inverter isn't dangerous although I can see why in might seem so. :) However, I'm not suggesting anyone does this. Partly because inverter designs may be different but mostly I'm not insured to give electrical advice! I might do this on my installation but don't suggest other copy me.

Have a read up here if you like but you will note in the last comment someone suggests this shouldn't be necessary but it is widely done. The argument seems to be it is safer as it is more likely the RCD will trip if a fault develops in whatever the inverter is running, if it is earthed which some devices aren't.

electronics.stackexchange.com

AC line from inverter grounded to vehicle chassis

What happens if a hot line from an inverter powered by a vehicle battery contacts the vehicle chassis? This will form a circuit connecting the hot line from the inverter to the negative terminal o...
electronics.stackexchange.com electronics.stackexchange.com

Just found this page from a UK company and it specifically says the "neutral" on the output of an inverter must be grounded.


The relevant paragraph states:

The neutral (common) conductor of the 2500W INVERTER AC output circuit is connected to chassis ground. Therefore, when the chassis is connected to ground, the neutral conductor will be grounded. This conforms to National Electrical Code requirements that separately derived AC sources (such as inverters and generators)
have their neutral conductors tied to ground in the same way that the neutral conductor from the utility line is tied to ground at the AC breaker panel.

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Last edited:
A little knowledge is a dangerous thing, and picking stuff up at random from the web is certainly NOT the way to do it.

I could certainly argue with some of the comments on your links.

You also need to consider where the mains side of the inverter wiring will be placed in relation to the RCD.
 
thebriars said:
A little knowledge is a dangerous thing, and picking stuff up at random from the web is certainly NOT the way to do it.

I could certainly argue with some of the comments on your links.

You also need to consider where the mains side of the inverter wiring will be placed in relation to the RCD.
Click to expand...
I have a very short length of cable going directly from the inverter to the RCD. Is this what you mean by the placement of the RCD in relation to the inverter?
 
thebriars said:
A little knowledge is a dangerous thing, and picking stuff up at random from the web is certainly NOT the way to do it.

I could certainly argue with some of the comments on your links.

You also need to consider where the mains side of the inverter wiring will be placed in relation to the RCD.
Click to expand...
As a former member of the IEE (when it was called that!) you are quite right. I have a little knowledge. :)
 
DBK said:
The relevant paragraph states:

The neutral (common) conductor of the 2500W INVERTER AC output circuit is connected to chassis ground. Therefore, when the chassis is connected to ground, the neutral conductor will be grounded. This conforms to National Electrical Code requirements that separately derived AC sources (such as inverters and generators)
have their neutral conductors tied to ground in the same way that the neutral conductor from the utility line is tied to ground at the AC breaker panel.
Click to expand...
And to do that you will need a proper earth spike & 10mm/16mm earth cable fixed to the chassis and use it every time you stop and use the inverter
The motorhome is stood on four rubber tyres so the chassis is insulated from earth.
Even in a house the neutral isn't connected to earth except at the substation which could be tens of miles away.
 
Pausim said:
I have a very short length of cable going directly from the inverter to the RCD. Is this what you mean by the placement of the RCD in relation to the inverter?
Click to expand...
Which side of the RCD are you going to wire the inverter output.

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thebriars said:
Which side of the RCD are you going to wire the inverter output.
Click to expand...
The inverter outlet feeds a plug that leads directly to the inlet side of the double pole RCD, which has 2 socket outlets.
 
Don't forget the inverter is powered form your battery bank. Trying to run too much will kill them very quickly.

Why not see what can be powered by 12v? You'll be surprised how little you NEED 240v.
 
TerryL said:
Don't forget the inverter is powered form your battery bank. Trying to run too much will kill them very quickly.

Why not see what can be powered by 12v? You'll be surprised how little you NEED 240v.
Click to expand...

I don't see the need for an inverter for our setup. I use adaptors so that low powered devices like notebook computers and phones run or charge off 12 volts. For high powered devices like the portable oven and hairdryer these could never be powered off the battery using an inverter and so they are only ever used when we have hook up.

Mark
 
There's a link to a top-end DIY installation with automatic switching in my inverter guide on Fun resources.

For me, the convenience of an integrated inverter-charger is worth the extra.

Dave
 
Mark and Mindy said:
I don't see the need for an inverter for our setup. I use adaptors so that low powered devices like notebook computers and phones run or charge off 12 volts. For high powered devices like the portable oven and hairdryer these could never be powered off the battery using an inverter and so they are only ever used when we have hook up.

Mark
Click to expand...
I generally agree with that. If you are not on EHU always use gas to heat anything up. And nearly everything that uses low power electricity can be worked on 12v.

But in our motorhome the one exception is SWMBO's hairdryer. That is the only thing I use our inverter for.

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DBK said:
My stuttering attempt to install an inverter is described in the thread below. However, your post lights up a few warning lights for me. If you are confident working with 240 volts and understand the risks involved then a DIY Inverter fit is perfectly feasible. Only you can answer that. :)

Mine has automatic change over but this isn't essential. You could just use the sockets on the inverter.

https://tinyurl.com/y5gjksrm
Click to expand...

The only thing with relays is they need to have a delay!
 
TeeMyob said:
The only thing with relays is they need to have a delay!
Click to expand...
Mine passes through a moment when all contacts are open as it changes over so it should never be connected to the mains and inverter output at the same time. I guess if you had large inductive loads this might not be enough but for what we run off the inverter it has proven fine so far.
 
DBK said:
Mine passes through a moment when all contacts are open as it changes over so it should never be connected to the mains and inverter output at the same time. I guess if you had large inductive loads this might not be enough but for what we run off the inverter it has proven fine so far.
Click to expand...

Do you mid sending a link to the relay you used please?
 
TeeMyob said:
Do you mid sending a link to the relay you used please?
Click to expand...
I bought it from Maplins, sadly now defunct. :(

They can be a minefield with significantly different current ratings for whether they are opening or closing. The first one I bought I had to bin when this was pointed out by a sharp-eyed LennyHB. :)

RS might have something suitable.
 
I fitted a double pole changeover switch with a centre 'off' position. It suits us to have the EHU connected but the choice whether to use it (hair dryer??)

IMAG1027.jpg

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I can't see the point of connecting 2 neutrals from different sources.
 
TeeMyob said:
Do you mid sending a link to the relay you used please?
Click to expand...
My clunky solution to avoiding auto relay separation problems. Blue from Inverter, Grey from EHU. Turn off charger and swap blue plugs over between EHU and 12v off grid.


hookinv.png
 
TeeMyob said:
Do you mid sending a link to the relay you used please?
Click to expand...
This sort of thing might be what you want. It is 'DIN rail mounted', which means it clicks onto the metal rail in the mains consumer unit just like standard RCDs and MCBs. There might be blank space in your consumer unit box. If not, maybe you could swap it for the next size up, or add a small 'garage CU' type of box.
leisurelines.net

RELAY CHANGEOVER MAINS INPUT SOURCE

This DIN module is added to the DS-120S mains consumer unit to automatically switch from mains hook up plug to generator or vice versa to prevent
leisurelines.net leisurelines.net
 
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