Earth bonding - confused (1 Viewer)

[BigDean]

I know this is really elementary, but I don't want to electrocute myself or the family.....

I understand that when I am on EHU, then there is earth via the mains cable.

Question 1. If I am not plugged into EHU, where does the earth come from/go to. I understand the physical wiring intimately, so the chassis is earth, but where would that "dissipate" to? Being on 4 round rubber things surely is a insulator to the physical/real earth? I understand it is all safe, but just a layman's query really. I have never seen an earthing rod on a campsite.....

Question 2. If I install an inverter, and are off-grid, presume the inverter will be earthed to the chassis? So the answer to Q1 above will probably provide the answer to this one.

Question 3. If I were to purchase a "solar generator", which is a battery, charger and inverter in 1 box, there is no earth at all. It works without being connected to anything. So is it safe? If so, how?

I have watched so many videos and read so many articles, but have found it very difficult to find a straight answer in a format I can digest.

Thanks in advance.
BigDean.

 

[EuroTrotters]

Ignore that

 

[TinaLes]

Thats why we have RCD's fitted on the 240V side of the incoming EHU, they are fitted before the consumer unit fuses or are integral part of it, so as to detect any leakage or fault between Live & Earth/Neutral or the chassis in a MH.

This should always be the case when an inverter is fitted if it does not have built in protection. So take the 240V output from the inverter, put an RCD device in series before feeding any sockets/extension leads etc in the van.
They are normally quite sensitive for vans or outside items, no more than a 30MA trip. They even have a test button for peace of mind.

The solar power packs that emit both 12V & 240V and are stand alone, should offer RCD protection on the 240V output side so as to get the appropriate CE rating, I haven't checked this, but would before buying.
Having these RCD's protects the end user from short circuits in any device that is plugged in, think of all the double insulated devices we use these days which only have two wires, live/neutral no earth wire.
LES

^{_{Subscribers  do not see these advertisements}}

 

[SandraL]

Rcd, residual current device.
There will be one on your ehu incoming to the van, mounted in the van.
It will disconnect power if you are about to get a shock.
Unless you have some clever wiring you will need a second rcd to protect yourself on the output of an inverter.
In a general sense a good earth is required to allow a path back to supply authority so under fault condition a fuse will blow quickly.
As for latest regulations I cannot help, am well out of date.

Edit, I am a really slow typist, see above.

 

[BigDean]

Thats why we have RCD's fitted on the 240V side of the incoming EHU, they are fitted before the consumer unit fuses or are integral part of it, so as to detect any leakage or fault between Live & Earth/Neutral or the chassis in a MH.

This should always be the case when an inverter is fitted if it does not have built in protection. So take the 240V output from the inverter, put an RCD device in series before feeding any sockets/extension leads etc in the van.
They are normally quite sensitive for vans or outside items, no more than a 30MA trip. They even have a test button for peace of mind.

The solar power packs that emit both 12V & 240V and are stand alone, should offer RCD protection on the 240V output side so as to get the appropriate CE rating, I haven't checked this, but would before buying.
Having these RCD's protects the end user from short circuits in any device that is plugged in, think of all the double insulated devices we use these days which only have two wires, live/neutral no earth wire.
LES

Thanks Les, that’s makes absolute sense.
Worrying that I have seen many videos online with “cheap” inverters just wired straight off the battery and no RCD protection.

Will investigate the standalone boxes like Poweroak, but suspect they do not have an RCD.

Thanks again

 

[BigDean]

Rcd, residual current device.
There will be one on your ehu incoming to the van, mounted in the van.
It will disconnect power if you are about to get a shock.
Unless you have some clever wiring you will need a second rcd to protect yourself on the output of an inverter.
In a general sense a good earth is required to allow a path back to supply authority so under fault condition a fuse will blow quickly.
As for latest regulations I cannot help, am well out of date.

Edit, I am a really slow typist, see above.

Thanks for that. I am getting the picture now.

^{_{Subscribers  do not see these advertisements}}

 

[andy63]

I know this is really elementary, but I don't want to electrocute myself or the family.....

I understand that when I am on EHU, then there is earth via the mains cable.

Question 1. If I am not plugged into EHU, where does the earth come from/go to. I understand the physical wiring intimately, so the chassis is earth, but where would that "dissipate" to? Being on 4 round rubber things surely is a insulator to the physical/real earth? I understand it is all safe, but just a layman's query really. I have never seen an earthing rod on a campsite.....

Question 2. If I install an inverter, and are off-grid, presume the inverter will be earthed to the chassis? So the answer to Q1 above will probably provide the answer to this one.

Question 3. If I were to purchase a "solar generator", which is a battery, charger and inverter in 1 box, there is no earth at all. It works without being connected to anything. So is it safe? If so, how?

I have watched so many videos and read so many articles, but have found it very difficult to find a straight answer in a format I can digest.

Thanks in advance.
BigDean.

A not necessarily an elementary subject..
I've tried on many occasions to get my head round earthing and the need for it and its relevance to safety..certainly where it concerns mobile supplies ..
It's far from straight fwd..just look at the subject been discussed on an electricians forum ..
If you are not connected to a supply which provides an earth and connects your system to it ..I think what you have is a floating earth..in a similar way to that of many portable generators.. there is an earth electrode but it just runs to the generator frame.... in a similar fashion to you having mains via an inverter in your motor home... its considered safe to use if say you are only using one device from the supply and there is no danger of contacting another circut from the power supply... failing that then the class of equipment becomes a safety factor..ie it should be double insulated..
An rcd isn't reliant on an earth been provided as far as I know..it only monitors the current flow in the live and return lines.. so if there is any leakage of current say through your body it will operate..
Andy

 

[TinaLes]

BigDean The small power packs that only deliver 12 vdc to charge devices wont have an RCD, however all the mains power ones, especially The Poweroak that give 1/2 KW outputs should have, as they are made in the UK.
They could be very dangerous if they dont have RCD protection, bearing in mind they are portable devices to be used outside when mains power is needed.
PS: although not cheap, I think these solar powered power packs are the future, saves spending a load of money on additional van batteries inverters, or simply as additional power to back up whats already in the van.
They are portable, although heavy in some cases, can be charged up from any 240V outlet ,so I can see the Vanlifers spending more on coffees for longer periods at MacDonald's now.
LES

 

[BigDean]

BigDean The small power packs that only deliver 12 vdc to charge devices wont have an RCD, however all the mains power ones, especially The Poweroak that give 1/2 KW outputs should have, as they are made in the UK.
They could be very dangerous if they dont have RCD protection, bearing in mind they are portable devices to be used outside when mains power is needed.
PS: although not cheap, I think these solar powered power packs are the future, saves spending a load of money on additional van batteries inverters, or simply as additional power to back up whats already in the van.
They are portable, although heavy in some cases, can be charged up from any 240V outlet ,so I can see the Vanlifers spending more on coffees for longer periods at MacDonald's now.
LES

Thanks again Les

Are Poweroak made in the U.K.? They don’t have U.K. sockets although Maxoak and Bluetti do; and all seem to be the same make. Confused, I am.

As we have the MoHo and a day van, this would be my preferred option so I can take it in whichever vehicle we use.

Will check out further.

^{_{Subscribers  do not see these advertisements}}

 

[BigDean]

A not necessarily an elementary subject..
I've tried on many occasions to get my head round earthing and the need for it and its relevance to safety..certainly where it concerns mobile supplies ..
It's far from straight fwd..just look at the subject been discussed on an electricians forum ..
If you are not connected to a supply which provides an earth and connects your system to it ..I think what you have is a floating earth..in a similar way to that of many portable generators.. there is an earth electrode but it just runs to the generator frame.... in a similar fashion to you having mains via an inverter in your motor home... its considered safe to use if say you are only using one device from the supply and there is no danger of contacting another circut from the power supply... failing that then the class of equipment becomes a safety factor..ie it should be double insulated..
An rcd isn't reliant on an earth been provided as far as I know..it only monitors the current flow in the live and return lines.. so if there is any leakage of current say through your body it will operate..
Andy

Thanks Andy. Motorhoming is one long lesson

 

[autorouter]

The whole subject of earthing and electric shock protection is not simple. There are cut-and-dried methods involving RCDs and linking the earth ground to the neutral conductor for fixed installations such as houses and garages. For mobile systems like motorhomes and boats, it's more complex. Especially if they can sometimes be connected to mains power and sometimes running an inverter, and sometimes both at the same time. There are several possible solutions, including no earth at all. Or a relay that connects neutral to ground if hookup is not connected, and disconnects automatically when hookup is connected because the hookup post will have its own ground.

If you really want more information, Victron have a free book on wiring, and Chapter 7 Ground, Earth and Electrical Safety discusses the detail, with applications to systems like motorhomes.

https://www.victronenergy.com/upload/documents/Wiring-Unlimited-EN.pdf

 

[Sandancers]

A not necessarily an elementary subject..
I've tried on many occasions to get my head round earthing and the need for it and its relevance to safety..certainly where it concerns mobile supplies ..
It's far from straight fwd..just look at the subject been discussed on an electricians forum ..
If you are not connected to a supply which provides an earth and connects your system to it ..I think what you have is a floating earth..in a similar way to that of many portable generators.. there is an earth electrode but it just runs to the generator frame.... in a similar fashion to you having mains via an inverter in your motor home... its considered safe to use if say you are only using one device from the supply and there is no danger of contacting another circut from the power supply... failing that then the class of equipment becomes a safety factor..ie it should be double insulated..
An rcd isn't reliant on an earth been provided as far as I know..it only monitors the current flow in the live and return lines.. so if there is any leakage of current say through your body it will operate..
Andy

Not sure if I am mis-reading what you are trying to say.

But the for an RCD to work the current flow in the live and the return must be different. If you put a person across them, with no leakage of current to a different potential, then the RCD would not trip as the current going thro the person is just an additional load.

For an RCD to trip it needs a person to take hold of a conductor and then touch something which will provide a path for the current so it does not return to the RCD, which is an earth, normally. It becomes a safety device due to the fact that it cuts the current to the circuit before the current can rise to a lethal level over a short period of time.

It is a difficult issue to solve on some pieces of equipment. Imagine the problems of having a generator with an earth rod into the ground powering your MH. The generator might have an RCD on its output, but does that RCD see any leakage to earth inside the MH ?

^{_{Subscribers  do not see these advertisements}}

 

[68c]

Autorouter post #11. That is a really good link, I am sure 50% of electrical threads would be answered by this ebook.

 

[BigDean]

Morning all,

Attached is the Bluetti manual for one of the UK versions. I can see no CE approval (is this important any more?), and no mention of earth or RCDs of any sort.

If you are charging from the plug/power supply, then you have to presume you are plugged into a 13A socket which will be safe.

If you are charging from solar, then the unit has no earth.

If you are off grid, then the unit has no earth.

So, where does that leave us with regards the safety of using such a unit?

Thanks
BigDean.

 

[eddie]

Morning all,


So, where does that leave us with regards the safety of using such a unit?

Thanks
BigDean.

Suspicious

^{_{Subscribers  do not see these advertisements}}

 

[BigDean]

Suspicious

Agreed, I am, very.....

 

[tonyidle]

For a portable supply to be 'dangerous' one of the supply lines has itself to be in contact with earth so that the other can complete the circuit through the person in contact with it. A 'mains in a box' unit that has no contact with anything poses no danger to a person touching either one of its output connections. As stated by Sandancers an RCD is of no value unless it is 'earthed' which means it having internal connections that would support such an arrangement. I doubt that there is any internal connection to the earth pin of the output socket. Or that either of the supply lines has any connection to the earth pin.

 

[BigDean]

For a portable supply to be 'dangerous' one of the supply lines has itself to be in contact with earth so that the other can complete the circuit through the person in contact with it. A 'mains in a box' unit that has no contact with anything poses no danger to a person touching either one of its output connections. As stated by Sandancers an RCD is of no value unless it is 'earthed' which means it having internal connections that would support such an arrangement. I doubt that there is any internal connection to the earth pin of the output socket.

Excellent, thanks Tony.

^{_{Subscribers  do not see these advertisements}}

 

[andy63]

an RCD is of no value unless it is 'earthed'

Thats the bit I think I'm struggling to understand tony...I thought an rcd had no connection to earth..but simply monitored the current flow in two wires and as soon as there was an out of balance it would isolate the supply..
I appreciate that the earth can provide a path for the current to escape and cause that imbalance ..but would it not also be possible for a person at a high potential relative to earth and in contact with it to pass a current large enough to cause an rcd to trip..we are talking a very small current ..
One day I'll get there
Andy

 

[Richard n Ann]

Thats the bit I think I'm struggling to understand tony...I thought an rcd had no connection to earth..but simply monitored the current flow in two wires and as soon as there was an out of balance it would isolate the supply..
I appreciate that the earth can provide a path for the current to escape and cause that imbalance ..but would it not also be possible for a person at a high potential relative to earth and in contact with it to pass a current large enough to cause an rcd to trip..we are talking a very small current ..
One day I'll get there
Andy

No, the only reason electricity wants to flow to earth is because one of the outputs is earthed, we rename that output 'neutral' and the other wire becomes 'live'.

Before the outputs are messed about with they are both 'lives' or 'line outs' and have no interest in flowing to earth so an rcd won't ever trip.

 

[andy63]

No, the only reason electricity wants to flow to earth is because one of the outputs is earthed, we rename that output 'neutral' and the other wire becomes 'live'.

Before the outputs are messed about with they are both 'lives' or 'line outs' and have no interest in flowing to earth so an rcd won't ever trip.

Cheers Richard..I think you have been here before with me ..
And I sort of get what I'm been told but still in my head imagine any charge on a body wanting to dissipate to an area of lower potential regardless of connections..
I suppose like a static build up ..
Cheers
Andy

^{_{Subscribers  do not see these advertisements}}

 

[autorouter]

As I mentioned in post#11, one possible solution is no earth at all. This is used for example in domestic bathrooms for shaver sockets. There is an isolating transformer, and the output has two conductors with 240V between them. Neither of the conductors is connected to an earth point.

The theory is that if you touch either conductor at any single point, there is no voltage between the conductor and earth. So no current will try to flow, and no electric shock.

Isolating transformers are also used in very hazardous wet conditions in industrial settings like building sites. For high power, transformers are expensive, so RCDs can be used to prevent electric shock in these conditions. They were originally developed in the South African gold mines, and spread to the engineers' houses, and then throughout the world.

But about this Portable Power Station: it is self-contained and isolated, and I presume even the mains charger has isolated DC output, so the safety works in a similar way to an isolation transformer.

I kinda have a feeling that it's OK to plug it into a motorhome designed for an earthed system, but I haven't really thought it through so could easily be wrong.

 

[Catpirate]

Hi, Most portable generator manufacturers recommend using a ground spike connected to the generator chassis, or MOHO chassis if that is connected to the gen chassis. Beware if you use a ground spike when on EHU you may be the earthing point for the entire site if the site earth is faulty................

This could apply to Inverters too, as long as the inverter is connected to the chassis.

 

[andy63]

Hi, Most portable generator manufacturers recommend using a ground spike connected to the generator chassis,

But on most portable generators the earth is simply connected to the framework and has no connection to the power source.. so what is the point in providing an earth spike..unless you make a connection to it from one side of the alternator windings..ie alter the wiring..
It is an option on some portable units I understand..
Andy

^{_{Subscribers  do not see these advertisements}}

 

[Catpirate]

Hi Andy you are correct.

My generator manual quotes "Grounding The generator system ground connects the frame to the ground terminals on the power panel.–The generator (stator winding) is isolated from the frame and from the AC receptacle ground pin.–Electrical devices that require a grounded receptacle pin connection will not function if the receptacle ground pin is not functional, unless the neutral wire is bonded to the frame."

So i have connected the neutral to the generator frame

 

[eddie]

Well Sterling fit an RCD in some of their larger inverters, MasterVolt and Victron instruct us to install one on the load side of the inverter, so we do.

We test the operation of the RCD by pressing the "T" test button.

I admit that we have never put anyone's hand into a sink full of water, a dropped a hairdryer in the sink, working on the inverter !

Probably won't and will rely on the test button lol

 

[Sandancers]

Hi Andy you are correct.

My generator manual quotes "Grounding The generator system ground connects the frame to the ground terminals on the power panel.–The generator (stator winding) is isolated from the frame and from the AC receptacle ground pin.–Electrical devices that require a grounded receptacle pin connection will not function if the receptacle ground pin is not functional, unless the neutral wire is bonded to the frame."

So i have connected the neutral to the generator frame

In simple terms I always understood that you used an earth spike on a generator in case the frame somehow became live. ie by earthing the frame, then if you touched it you would not be earthing the now live frame via your own body to earth.

^{_{Subscribers  do not see these advertisements}}

 

[tonyidle]

Thats the bit I think I'm struggling to understand tony...I thought an rcd had no connection to earth..but simply monitored the current flow in two wires and as soon as there was an out of balance it would isolate the supply..
I appreciate that the earth can provide a path for the current to escape and cause that imbalance ..but would it not also be possible for a person at a high potential relative to earth and in contact with it to pass a current large enough to cause an rcd to trip..we are talking a very small current ..
One day I'll get there
Andy

That's all correct. It does require a path though whatever potential a person is relative to earth - so the person has to be connected to either line of the RCD and to earth. (normally via the ground the person is standing on). To cause an imbalance the person must cause more current to flow in one line of the RCD than the other. For current to flow there must be a circuit with the person as part of the conductor. In the case of mains (real mains, from the grid) one of the lines is earthed (to the planet ) and called Neutral. So a person standing on the ground (or touching any major metallic part of a domestic installation) and then touching the Live wire will cause current to flow from Live, through the person, and to Earth. The RCD spots this extra current flow affecting only the Live and trips. A motorhome on EHU mimics the effect because it, and all its metalwork, is connected to Earth via the earth wire in the EHU cable. Any metal-cased appliance in the motorhome or in the home has the casing connected to earth via the third wire in the plug - so an RCD provides protection in each location. Where it gets complicated is when 230v isn't derived from the mains but from a portable appliance such as a generator or inverter/battery. Sorry for my earlier poor description.

Earthing a generator casing or that of an inverter will not be effective unless, internal to the device, there is a connection between one output line and either the casing or the 'earth' pin of the output socket. On the other hand, if there is no such connection, it should not be possible to receive a 'shock' from contact with either of the line terminals anyway.

 

[andy63]

So i have connected the neutral to the generator frame

And the Honda i have has a facility to connect a ground spike...and I assume I would have to make a connection to the windings for that to be an option..
What are the downsides or dangers of using a generator supplied to be used as an isolated supply that you then alter to bond the winding and earth....
I just struggle to see all the dangers..but im sure they exist given the right circumstances..
Andy
Andy..

 

[andy63]

Another point I sometimes ponder..which some may be able to keep me right on..
Most domestic institutions have the earth and neutral bonded in the consumer unit..so when you connect a hook up cable from your domestic supply to the motorhome you are in fact providing the same bond to the system in the van ..
it's not practice to wire the consumer unit in a van with the earth and neutral bonded...is it?..or am I missing something here...
Andy..

^{_{Subscribers  do not see these advertisements}}