Earth bonding - confused

[Spriddler]

Ah, not this sort of Earth bonding then?

 

[tonyidle]

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..

If it suggests a ground spike you'd have to assume the correct internal connections already exist otherwise there's no point in the spike connection. If it has the correct internal connects there's still no point in an earth spike if you are connecting it to your motorhome via the EHU lead - the EHU lead earthwire is a far better conductor than the ground.

Edit: Useful if using outdoor tools or heaters though - unless they're double-insulated (which most, tools at least, are).

 

[andy63]

If it suggests a ground spike you'd have to assume the correct internal connections already exist otherwise there's no point in the spike connection. If it has the correct internal connects there's still no point in an earth spike if you are connecting it to your motorhome via the EHU lead - the EHU lead earthwire is a far better conductor than the ground.

It definitely has a facility to connect a ground spike and I'm also sure the earth or generator frame is isolated from the windings.. im sure I've checked that in the past..
Ill check the book that came with it ..its a common enough unit.. the Honda 2kw inverter generator.
Andy

 

[tonyidle]

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..

It isn't true that E/N are bonded in the Consumer Unit in 'most' domestic installations - in fact I've never seen one but I know they exist. If you think about van EHU it would be pointless (if not dangerous under certain fault conditions) to have E/N bonding in the van. A minor inconvenience would be to trip every RCD in every hook-up that you connected to Including the one in your house .

 

[andy63]

It isn't true that E/N are bonded in the Consumer Unit in 'most' domestic installations - in fact I've never seen one but I know they exist.

I thought that was pretty standard practice in most domestic installations ..
Ie bonding the earth and neutral in the consumer unit..
Andy.

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[tonyidle]

I thought that was pretty standard practice in most domestic installations ..
Ie bonding the earth and neutral in the consumer unit..
Andy.

I've just done (very little) research and it is never done. There's a video here showing a Consumer Unit connections - which is like all the ones I've seen.

 

[andy63]

I've just done (very little) research and it is never done. There's a video here showing a Consumer Unit connections - which is like all the ones I've seen.

Ill have a look myself

 

[63720]

Watching this with interest.
If someone were to stand in complete isolation then touch a live conductor they would be ok until the circuit was completed back to source, then possibly huge amounts of current would flow until a safety device cuts out. The problem is identifying what safety device to fit and where in the circuit. So I'm coming back to thinking it's either an MCB in the live pole only or the correct size fuse in the appliance plugtop on the assumption - dangerous I know - that fault current much larger than the steady load would then blow the fuse in the live conductor.

 

[andy63]

I've just done (very little) research and it is never done. There's a video here showing a Consumer Unit connections - which is like all the ones I've seen.

Here's my research
It says its the most common form of connection for domestic installations in the UK.. ..
It does say itsnot suitable for certain installations..caravan parks been one..

 

[andy63]

Watching this with interest.
If someone were to stand in complete isolation then touch a live conductor they would be ok until the circuit was completed back to source, then possibly huge amounts of current would flow until a safety device cuts out. The problem is identifying what safety device to fit and where in the circuit. So I'm coming back to thinking it's either an MCB in the live pole only or the correct size fuse in the appliance plugtop on the assumption - dangerous I know - that fault current much larger than the steady load would then blow the fuse in the live conductor.

Line workers for electric companies I believe work on live circuts using various forms of insulation to prevent contact with surroundings...so do birds on high voltage overhead lines
But its not the MCB that is going to give the protection to you in a circut..the current flow would have been far to high to prevent death before it operated..
It's the RCD that should save your life..
Andy

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[tonyidle]

Watching this with interest.
If someone were to stand in complete isolation then touch a live conductor they would be ok until the circuit was completed back to source, then possibly huge amounts of current would flow until a safety device cuts out. The problem is identifying what safety device to fit and where in the circuit. So I'm coming back to thinking it's either an MCB in the live pole only or the correct size fuse in the appliance plugtop on the assumption - dangerous I know - that fault current much larger than the steady load would then blow the fuse in the live conductor.

Neither a fuse nor an MCB would offer any protection at all from electrocution. Both exist to prevent fire, wiring damage, and/or overload damage.

Edit: as andy63 said .

 

[tonyidle]

using various forms of insulation

Helicopters for example. They're pretty well disconnected from ground. However there's another hazard at play: they're big enough to hold a pretty substantial static charge. Watch the engineer equalising potentials in the video:

 

[tonyidle]

Here's my research
It says its the most common form of connection for domestic installations in the UK.. ..
It does say itsnot suitable for certain installations..caravan parks been one..
View attachment 460724

I'm aware of that system but bonding is not done in the consumer unit.

 

[63720]

Line workers for electric companies I believe work on live circuts using various forms of insulation to prevent contact with surroundings...so do birds on high voltage overhead lines
But its not the MCB that is going to give the protection to you in a circut..the current flow would have been far to high to prevent death before it operated..
It's the RCD that should save your life..
Andy

Yes I understand and in domestic installation I agree. However in local power situation, as stated earlier, a balanced fault current load through an RCD may not trip it out.

 

[68c]

I wonder if Jim should moderate this thread. I am not an expert but worry, having seen the thread wander around, that potentially lethal advice may have been posted.

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[gpat]

There is a lot of information here

Just a few conclusions for me based on my rudimentary understanding

1. Portable devices do not need an earth. To require an earth would render it not portable device any more. A generator or invertor may have an earth circuit built in but it will obviously only run if there is a fault or short circuit.
A generator frame is sufficient as an earth so long as it is metal and not sitting on a rubber mat!
2. RCDs do not need an earth. They trip before current can run to earth. They sense current running form live to neutral. They are extremely sensitive.

 

[andy63]

I'm aware of that system but bonding is not done in the consumer unit.

My apologies..I thought it was..
In fact I'm beginning to wonder if me brain is working at all now..
Thanks for the patience..
Andy

 

[Raul]

Andy as tonyidle says, you miss understanding the PE bonding. It’s not done in the consumer unit, because it’s already done at the transformer, supplying the dwelling with 3 conductors. If you bond in the consumer again, you create a multiple path which is bad. The bonding is done only once and closer to source.
If your supply is only two wires, common in EU states, then the bonding is done before your meter and the consumer enters 3 conductors. One resulting from the bond. You can not do another bond, PE to work needs to have a single path directing the fault away to a rod or source.

 

[andy63]

I wonder if Jim should moderate this thread. I am not an expert but worry, having seen the thread wander around, that potentially lethal advice may have been posted.

Just a discussion..

Andy as tonyidle says, you miss understanding the PE bonding. It’s not done in the consumer unit, because it’s already done at the transformer, supplying the dwelling with 3 conductors. If you bond in the consumer again, you create a multiple path which is bad. The bonding is done only once and closer to source.
If your supply is only two wires, common in EU states, then the bonding is done before your meter and the consumer enters 3 conductors. One resulting from the bond. You can not do another bond, PE to work needs to have a single path directing the fault away to a rod or source.

Cheers.. as I said I think I've spent to much time thinking about this sort of stuff today ..

 

[eddie]

I wonder if Jim should moderate this thread. I am not an expert but worry, having seen the thread wander around, that potentially lethal advice may have been posted.

What could possibly go wrong!

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[63720]

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.

My final thoughts on this are that you are dealing with an item that you may choose to resell or exchange at some time in the future. Bearing this mind perhaps you should seek professional advise from someone with current and valid qualifications who will install the equipment and issue a completion certificate. If I were to buy a van with similar I would be asking for this for my safety.

 

[Sandancers]

Line workers for electric companies I believe work on live circuts using various forms of insulation to prevent contact with surroundings...so do birds on high voltage overhead lines
But its not the MCB that is going to give the protection to you in a circut..the current flow would have been far to high to prevent death before it operated..
It's the RCD that should save your life..
Andy

The live line workers don't use insulation when suspended from live cables, the insulation would have to be immensely thick. Instead they use a faraday suit;

In electrical engineering, live-line working is the maintenance of electrical equipment, often operating at high voltage, while the equipment is energised. A lineman wearing a Faraday suit can work on live, high-power lines by being transported to the lines in a helicopter. Wearing the suit, they can crawl down the wires.

 

[Sandancers]

Andy as tonyidle says, you miss understanding the PE bonding. It’s not done in the consumer unit, because it’s already done at the transformer, supplying the dwelling with 3 conductors. If you bond in the consumer again, you create a multiple path which is bad. The bonding is done only once and closer to source.
If your supply is only two wires, common in EU states, then the bonding is done before your meter and the consumer enters 3 conductors. One resulting from the bond. You can not do another bond, PE to work needs to have a single path directing the fault away to a rod or source.

Certainly in older UK houses, you only get a live conductor which is within insulation and that is surrounded by a metallic sheath. The sheath gives mechanical protection, but also carries the combined neutral and earth. If you look closely at the incoming wire to your house, just before it goes into the main fuse you might see the earth connection from your house strapped to the sheath of the cable.

 

[Sandancers]

View attachment 460754
What could possibly go wrong!

He is a posh Indian worker, the ones we saw up the poles, didn't even have flip flops on!

 

[Sandancers]

Andy as tonyidle says, you miss understanding the PE bonding. It’s not done in the consumer unit, because it’s already done at the transformer, supplying the dwelling with 3 conductors. If you bond in the consumer again, you create a multiple path which is bad. The bonding is done only once and closer to source.
If your supply is only two wires, common in EU states, then the bonding is done before your meter and the consumer enters 3 conductors. One resulting from the bond. You can not do another bond, PE to work needs to have a single path directing the fault away to a rod or source.

Don't think it's prohibited to have an earth spike and the incoming cable sheath both connected to your main earth block in a UK house ? What you do need is a measurement of the earth loop impedance from your main earth block to a good earth.

If the impedance to earth is too large then RCDs might not work.

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[andy63]

Don't think it's prohibited to have an earth spike and the incoming cable sheath both connected to your main earth block in a UK house ? What you do need is a measurement of the earth loop impedance from your main earth block to a good earth.

If the impedance to earth is too large then RCDs might not work.

I rely on an earth rod for my house (TT).. im fairly sure the earth loop impedance permissable on my installation is higher than one making use of the boards own connection.. but can't remember what that figure is...
My trip does work so I'm assuming my earth rod is doing its job and my system is ok..
Andy..

 

[Sandancers]

I rely on an earth rod for my house (TT).. im fairly sure the earth loop impedance permissable on my installation is higher than one making use of the boards own connection.. but can't remember what that figure is...
My trip does work so I'm assuming my earth rod is doing its job and my system is ok..
Andy..

If you think the RCD is working because it trips when you press the test button, then your not doing a full test. What you want is the combined test machine that you push the probes or sometimes a three pin plug into your house sockets. Press the button and that machine causes an earth fault of known size. The machine will then measure how long in milliseconds it takes for the RCD to trip.

 

[andy63]

If you think the RCD is working because it trips when you press the test button, then your not doing a full test. What you want is the combined test machine that you push the probes or sometimes a three pin plug into your house sockets. Press the button and that machine causes an earth fault of known size. The machine will then measure how long in milliseconds it takes for the RCD to trip.

The system has never been tested with the tester you described or certainly not for more years than I care to remember..
Apart from the test button I've had the trip come out while working on an isolated ring main circut..even though its isolated at the consumer unit ..if the wires on the circut are shorted or touch the earth on that circut the trip will still operate..ive often wondered how that can happen and just put it down to possibly a small induced voltage in the isolated conductor..
Anyhow thanks for the input and apologies to the op ..but I hope you got something out of your thread as well as me..
Andy

 

[Raul]

Certainly in older UK houses, you only get a live conductor which is within insulation and that is surrounded by a metallic sheath. The sheath gives mechanical protection, but also carries the combined neutral and earth. If you look closely at the incoming wire to your house, just before it goes into the main fuse you might see the earth connection from your house strapped to the sheath of the cable.

The sheathing bonded to PE is common practice, but I have never came across a cable with a single conductor only, this is a new to me.

 

[autorouter]

Don't think it's prohibited to have an earth spike and the incoming cable sheath both connected to your main earth block in a UK house ? What you do need is a measurement of the earth loop impedance from your main earth block to a good earth.

I think if you want to fit an electric vehicle charging point some way from your house, you need an additional earth spike in the ground for most of the charging points.

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