# Making MoHo sockets work form the inverter



## Pudsey_Bear (Sep 25, 2008)

Before going further, I did ask a well known sparky ex member (on fun now) about doing this as it seemed to be the perfect solution for wild camping only vans, I'd not do it on EHU, as it'd not be required, you also need to have your brain in gear too.

Basically you need to put a 13a plug onto both ends of a 2.5mm2 flexible cable, and *with the inverter turned off* plug one end into a handy 230v socket near the inverter, then into the inverters socket, do it this way round for safety, reversal to remove of course, you then have all your sockets live so you can plug in your TV etc where it's convenient and not have leads trailing everywhere to trip over.

I've done this on my last 3 vans with no problems, you just need to *remember to plug and unplug with the inverter off, and maintain the order above*, the only issue I have in the Tiki, is the Sargents box of trick has a red light on it saying incorrect polarity, it works as normal once the link to the sockets has been removed.

*Remember this, if you remove the plug from the vans sockets while the other end is plugged into the inverter whether it is on or off, you risk an electric shock from the pins on the free plug, ALWAYS unplug from the inverter end first and connect last.*

.


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## Harrers (Dec 21, 2011)

Isn't it simpler and safer to mount two sockets next to each other. One comes from the inverter and the other from your mains feed. Then you have a single plug which feeds the rest of the outlets (sockets). If the inverter is on you plug into that socket and if you are on hook-up you plug into the other. You may find that you can break into the existing feed from the ehu to your first socket and mount your additional sockets there. If you are wilding most of the time just leave the plug in the inverter socket.

I attach a picture of my set-up. The upper double socket is fed from the inverter. I actually broke into the mains feed within that cupboard to attach the other double socket to the main-fed end and put a plug on the cable which continues to feed the sockets on that side of the mh. This was sufficient for me as I only needed the microwave and another couple of sockets. You are unlikely to be wanting to run much else off the inverter or be able to do so.

This seems much safer than having a possible live plug lying around. I think you were referring to Techno100's thread and his solution was to fit relays that switched the power automatically - probably too difficult for me!


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## Pudsey_Bear (Sep 25, 2008)

Harrers said:


> Isn't it simpler and safer to mount two sockets next to each other. One comes from the inverter and the other from your mains feed. Then you have a single plug which feeds the rest of the outlets (sockets). If the inverter is on you plug into that socket and if you are on hook-up you plug into the other. You may find that you can break into the existing feed from the ehu to your first socket and mount your additional sockets there. If you are wilding most of the time just leave the plug in the inverter socket.
> 
> I attach a picture of my set-up. The upper double socket is fed from the inverter. I actually broke into the mains feed within that cupboard to attach the other double socket to the main-fed end and put a plug on the cable which continues to feed the sockets on that side of the mh. This was sufficient for me as I only needed the microwave and another couple of sockets. You are unlikely to be wanting to run much else off the inverter or be able to do so.
> 
> This seems much safer than having a possible live plug lying around. I think you were referring to Techno100's thread and his solution was to fit relays that switched the power automatically - probably too difficult for me!


Yes you could do it that way, and a good solution, mine was more of a quick way to do it with no technical skills needed, and it's obvious that there is a link in place, not hidden away.

Post has nothing to do with any post/thread from Techno100, although as you say he did make up a box of tricks to do the same job.


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## powerplus (Oct 6, 2014)

hi kev

i would be worried that i would do some damage to the Sargent box

you could possibly pull the fuse in the sargent box that supplies the 240v to the sockets

i just wired in a couple of extra sockets powered by the inverter

i have a ring 2000w inverter and i do run the tv from it and the draw of current is so low that the cooling fan never comes on and after a coiuple of hours the inverter is only slightly worm


barry


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## Drew (May 30, 2005)

This is a NO NO NO.

You have highlighted this in red as being dangerous. It is dangerous.

It is against IEE regulations.

I believe this thread should be removed immediately.


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## raynipper (Aug 4, 2008)

Yep, very dangerous Kev.
Saying that I have used a similar set up to power the house from our RV generator in a power cut. Even worse I put a 30 amp fuse in both plugs.!!!
But it was vital to disconnect mains supply from the grid. My problem then was not knowing when the power had been restored.??

Ray.


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## listerdiesel (Aug 3, 2012)

Just power a 2-pole change-over relay from the inverter output, which then switches the feed to the sockets from EHU to the inverter whenever the inverter is powered up.

Foolproof and safe.

Putting a plug on each end of a cable is not safe and really shouldn't be promoted as a way of doing this.

Black mark for Kev 

Peter


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## peribro (Sep 6, 2009)

I think this set up is worth a read

http://www.motts.org/INVERTER.htm


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## Pudsey_Bear (Sep 25, 2008)

Well I did say required the head to be in gear, and the precautions to take, I've not had any problems, only control the lectrics in the van, Liz has no need to touch them, and I'd not do it in a van where there were kids, or in fact anyone else, because it would be dangerous to anyone unaware, I only use this method as it's a temp measure for watching TV, otherwise it's all disconnected and put away out of site.

It's not for everyone, and if it bothers anyone don't do it.


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## Pudsey_Bear (Sep 25, 2008)

listerdiesel said:


> Just power a 2-pole change-over relay from the inverter output, which then switches the feed to the sockets from EHU to the inverter whenever the inverter is powered up.
> 
> Foolproof and safe.
> 
> Peter


Could you elaborate on that Peter please.


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## Pudsey_Bear (Sep 25, 2008)

peribro said:


> I think this set up is worth a read
> 
> http://www.motts.org/INVERTER.htm


Not for me Peter, totally meaningless.


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## listerdiesel (Aug 3, 2012)

Kev_n_Liz said:


> Could you elaborate on that Peter please.


A 2-pole change-over relay, with 240V coil, will do the required changeover automatically if the relay coil is wired to the inverter output, so that the relay only works if the inverter is running.

The COMMON pair of relay contacts go to the sockets, one to L and one to N.

The NORMALLY OPEN pair of relay contacts go to the inverter output terminals.

The NORMALLY CLOSED pair of relay contacts go to the incoming EHU feed.

If the inverter is not powered up, the relay will feed the EHU to the sockets as a default, if the relay fails it will always feed the EHU to the sockets.

If the inverter IS powered up, the relay will operate and the contacts change over so that the inverter feeds the sockets.

You can get either a flat mount 2-pole 16A 240V coil relay or a plug-in type which needs a base.

RS Stock No.245-2396









You may well find that a 3-pole relay is cheaper as it is more widely used.

Peter


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## Sprinta (Sep 15, 2010)

I'd not thought of that way of doing it as I simply run an extension from the inverter to the appliance on the odd occasion I want to power up off-site

I was thinking of perhaps making up a lead to go from the Inverter out to the EHU input socket, but I've not got around to bothering yet.


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## raynipper (Aug 4, 2008)

I think Peter, although correct as soon as you introduce safety but complications, the need to comply goes out the window.
I would assume that anyone now seeing all these other options will revert to plan 'A'.

Ray.


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## philoaks (Sep 2, 2008)

The other problem with connecting directly into the existing mains wiring of the van (whether it's done by the method suggested by Kev or using a link to the EHU point) is that as far as the van is concerned it now has a 230v supply available so the battery charger will attempt to charge the batteries that are running the inverter and (if it's AES) the fridge will try to run from mains. So as well as remembering any safety procedure that must be followed you would also need to remember to switch off the onboard charger and force the fridge to stay on gas.

As others have said, dedicated inverter supplied sockets are IMO the best way to go both from safety and ease of use.


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## Pudsey_Bear (Sep 25, 2008)

philoaks said:


> The other problem with connecting directly into the existing mains wiring of the van (whether it's done by the method suggested by Kev or using a link to the EHU point) is that as far as the van is concerned it now has a 230v supply available so the battery charger will attempt to charge the batteries that are running the inverter and (if it's AES) the fridge will try to run from mains. So as well as remembering any safety procedure that must be followed you would also need to remember to switch off the onboard charger and force the fridge to stay on gas.
> 
> As others have said, dedicated inverter supplied sockets are IMO the best way to go both from safety and ease of use.


Good point Phil


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## listerdiesel (Aug 3, 2012)

There are ways around that problem as well, but every motorhome is different so impossible to cover all installations.

In the trailer we have a Waeco in the back that has its own 13A socket outlet, we just plug our phone chargers into that, we don't use it at all in the living section.

The Mercedes has a 1500W sine wave inverter with its own dedicated sockets.

Peter


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## Pudsey_Bear (Sep 25, 2008)

I did put dedicated socket in the build, but it's not so easy in some Mohos, this one is terrible because of the LB location, without having to move the inverter & quite thick leads to supply it, no sockets on the same side of the van until you get to the kitchen.


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## listerdiesel (Aug 3, 2012)

You can afford to lose a few volts out of 240, put the inverter by the LB and run the 240V in 2.5mm three-core.

Peter


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## Geriatricbackpacker (Aug 21, 2012)

Another vote for a dedicated inverter socket from me for no other reason that it was the simplest solution for my limited skills. I was able to take the wires to the on/off switch and connect them to a dedicated switch within the van next to the plug socket. That socket is wired to a three pin plug which is inserted into the 3k inverter which is next to the LBs in an outside locker. It's the third van we have had this setup in and it seems to fit our needs (Mrs GB apparently needs a hair dryer).


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## Jean-Luc (Jul 21, 2005)

This is how mine is done, and it's perfectly safe.

Disconnect cable serving socket ring circuit from its MCB (make sure the ring only serves sockets and not the battery charger, fridge or heating etc.)
Mount single socket next to inverter
Connect the single socket to the MCB, in place of the cable serving the socket ring
Connect a plug to the cable serving the socket ring which has been disconnected from the MCB

Insert the plug in the socket connected to the MCB = socket ring live from mains
Insert the plug into inverter = socket ring live from inverter 

Simple, safe and cheap.


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## Pudsey_Bear (Sep 25, 2008)

Sounds fine to me.


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## mike800966 (May 1, 2005)

I tried the auto change over method some time ago, the buzzing from the relay made it unacceptable. 
What I did in the end was cut into the output cable from the 240 distribution and terminate it in an ordinary unswitched socket. This was mounted adjacent to the inverter, I then put a standard 13amp plug on the cable feeding the van 240 circuits. 
When I want to power from the inverter, I simply remove the plug from the hookup supplied socket and put it into the inverter output socket.
Simple and safe
Mike

Thsi is almost the same as the method suggested by Jean Luc, apologies!


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## leseduts (Jun 3, 2008)

We have a socket in the garage that is connected to the inverter. The only thing we use off it is the microwave, we also have a remote switch for the inverter. Porridge in the microwave saves time and washing a sticky pan. We can reach the switch through the small door between the habitation area and the garage.


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## Harrers (Dec 21, 2011)

mike800966 said:


> I tried the auto change over method some time ago, the buzzing from the relay made it unacceptable.
> What I did in the end was cut into the output cable from the 240 distribution and terminate it in an ordinary unswitched socket. This was mounted adjacent to the inverter, I then put a standard 13amp plug on the cable feeding the van 240 circuits.
> When I want to power from the inverter, I simply remove the plug from the hookup supplied socket and put it into the inverter output socket.
> Simple and safe
> ...


It is also the same solution that I posted in reply to the OP on 25/9. I even posted a picture of my setup although for some reason it is sideways on.


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## chasper (Apr 20, 2008)

What sort of battery capacity are we using, just interested. Chas.


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## rayrecrok (Nov 21, 2008)

I have a three way switch mounted that I can turn to, 240 hook up, inverter, or generator.

The inverter is wired into the fuse box on the van as is the generator, any 240 power is run down the existing 240 volt on the van as on hook up, with the 3 way switch the power source has to be switched manually to what ever source of power I am using making it so no two things can operate at the same time...

The Honda Generator is converted to run on gas and lives in the old outside gas bottle storage, no longer needed now we have an underslung gas tank.

All this set up works well apart from one thing which can be resolved on the inverter side, when the 240 volts goes through the system it is effectively charging up the batteries on the van so not very efficient, but we usually have the inverter on when traveling to fire up the slow cooker placed in the sink, using the handy socket near by so we can have a meal when we stop.... With the engine running no problems with the inefficiency of the inverter set up, works for us.. to watch the telly I just plug it straight into the inverter with the three way switch set to the 240 volt setting, isolating the inverter side..

ray.


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## Pat-H (Oct 30, 2009)

Ray what you want for slow cooker when traveling is a pot on the manifold 

Or a 12V slow cooker http://www.ebay.co.uk/itm/12V-Slow-Cooker-/321991912324


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## LT Man (Nov 11, 2016)

Just to add apart from the Fridge , heating and battery charger getting 240v the outside hook up socket is also live . very dangerous for 
anybody was fiddling around the van , kids etc.

If this was a temp measure how come it has been done on last 3 vans ? Just thought I would ask.

I have two circuits running side by side in van . one set off inverter and the other off EHU 
One socket in the kitchen area is on a hidden flex and the plug in where two sockets are in cupboard so can swop that one if 
I want to use it on either supply.

The other dangerous thing that ids done a lot is run the van aboard on EHU without checking if the polarity is reversed.
Worse still know it is reversed without correcting it.
They think they are protected by the RCD. 
If a fault occurs the rcd trips on the neutral side and the van is still live ..


Stay safe 

LT man


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## philoaks (Sep 2, 2008)

LT Man said:


> Just to add apart from the Fridge , heating and battery charger getting 240v the outside hook up socket is also live . very dangerous for
> anybody was fiddling around the van , kids etc.
> 
> If this was a temp measure how come it has been done on last 3 vans ? Just thought I would ask.
> ...


Good point regards the EHU point being live but as far as the reverse polarity is concerned, I thought an RCD was a double pole device so if it is tripped then both the neutral and live will be disconnected.


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## mike800966 (May 1, 2005)

*Inverter power setup*

This backfeeding is a good point to be aware of . 
At least, with Jean Luc's and my setup, the inverter cannot power the external socket as the whole charger and distribution unit ( Calira) is disconnected.
Hence the inverter , which is run from the battery is not also trying to charge the battery!

Another point. My mains input plug is a type that has a two pin socket under a flap on the back of it. It was pointed out to me, very correctly that this external socket had no RCCB protection but we have found it very useful for cooking outside when its hot (like in Spain).

To protect that lead and any user I have an inline rccb in that loose cable which ends in a screwfix external plastic socket box under the table.

The other point mentioned, and I dont wish to aggravate that can of worms, is that line reversal may not matter if all the switches are double pole as the continentals use.
However in UK we only just seem to be offering Double pole switches. 
So its best to know whats happening with one of those 3 pin testers every time you connect , especially in Europe. I was horrified the first time the site man just pulled the 2 pin plug out and put it in upside down!

Mike


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## LT Man (Nov 11, 2016)

philoaks said:


> Good point regards the EHU point being live but as far as the reverse polarity is concerned, I thought an RCD was a double pole device so if it is tripped then both the neutral and live will be disconnected.


Yes Phil you are correct I meant to say if the MCB tripped not the RCD,


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## philoaks (Sep 2, 2008)

LT Man said:


> Yes Phil you are correct I meant to say if the MCB tripped not the RCD,


That is a good point! Reverse polarity + tripped MCB + single pole switch on 13A sockets = potential for accident!


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## LT Man (Nov 11, 2016)

Had to go and look today.
MCBs on my 2010 van are in fact double pole as is the RCD .
I know on my last van which was a 2002 the MCBs were single pole .

This all does not effect me as I said my inverter is on a separate circuit to my
hook up sockets and I always correct the polarity if I hook up. 
But if it helps somebody stay safe worth mentioning 

Dangers you can not see or hear are the worst ones.

LT Man


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## Pat-H (Oct 30, 2009)

Polarity of supply has no relevance if the supply isn't related to ground earth. So unless one side of a mains supply is grounded (neutral) then its an alternating supply and L & N are effectively the same.
The RCD looks for a difference in current between L&N so polarity isn't an issue.


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