240V earthing (1 Viewer)

[sinbad1]

The 240V system on the van is is basic consisting of a simple consumer unit and CB's & RCD's for the basic lighting and plug circuits +ve -ve and earth.

With the EHU this provides continuity ie the earth is grounded at the source of supply and thats ok.

My question is how is the system earthed? when using an onboard generator.

regards

 

[Linda and Steph]

When I use a genny for outside performances I use an earth spike - basically a large rod with an earth cable running to an earth stud on the genny.

 

[pappajohn]

dont forget....if you use an unearthed genny the RCD's will NOT work.

they rely on a balance between LIVE and NEUTRAL which can only alter if theres an EARTH fault meaning something that is not normally live has become live and current will go to earth causing the imbalance amd trip the RCD.........no earth......no protection.

as steelysteph says.....a copper earth spike and 10sqmm cable will help but it has to be driven well into the ground.
for domestic earthing we drive a 4ft spike in with just 4" sticking out.

 

[sinbad1]

When I use a genny for outside performances I use an earth spike - basically a large rod with an earth cable running to an earth stud on the genny.

thanks
I guess the spike is really the only answer, from what i've seen i don't think many people do this or are perhaps aware.

dont forget....if you use an unearthed genny the RCD's will NOT work.

they rely on a balance between LIVE and NEUTRAL which can only alter if theres an EARTH fault meaning something that is not normally live has become live and current will go to earth causing the imbalance amd trip the RCD.........no earth......no protection.

as steelysteph says.....a copper earth spike and 10sqmm cable will help but it has to be driven well into the ground.
for domestic earthing we drive a 4ft spike in with just 4" sticking out.

thanks
You are correct the rcd's would not work quite dangerous when you think about it
gonna need a bigger hammer

 

[hilldweller]

dont forget....if you use an unearthed genny the RCD's will NOT work.they rely on a balance between LIVE and NEUTRAL

Just a thought......

If the generator is on board and the there is no earth at all ( see later ) then you can't get an electric shock from live to earth.

( later ) But of course the earth will be connected via the plug on the genny so live to earth/chassis short inside will trip the RCD.

Maybe it's late but I can't think of a way not having an earth spike could cause a problem with the genny on board.

Genny outside on the ground..... With no earth you can't get a current flow from 240V to earth.

Where does the earth go on a genny anyway ? Just to the chassis or to the neutral as in normal mains ?

Of course the easy answer is stick an earth spike in wet ground which means you can electrocute yourself with a Live to ground short.

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[shifter]

earth spike

In some plaises you might not get an earth withe a spike even at 4foot or more.we had to reearth our house when they replased the old mains water pipeline with plastic.could not get an earth anywhere around house with a 4 foot spike.the nie came to test the spike and could,nt believe their was no reading of it.endid up the nie got us a earth of the main over head cable.
Had to apply for planning permision first before they did it.

 

[scotjimland]

I think there is much misunderstanding of what earth is.. it is the center tap of the supply transformer which gives the consumer an 'earth' The Earth is not a big sponge soaking up all the stay currents going around..

Consider an aircraft, boat oil platform or even a space craft .. they all have an 'earth' return system without having a four foot spike in the ground..

Back to the genny, it has it's own earth return provided by the socket outlet, so the RCD WILL trip if there is a leakage back to the genny via the 'earth' connection.. nothing what so ever to do with the muddy ground outside the van..

If you want to be absolutely safe you should bond the genny case or frame with the van, on board gennys already have this.. smaller portable ones depend on the cable.. as most suitcase models have plastic cases it would be impractical to do that.

 

[pappajohn]

Just a thought......

If the generator is on board and the there is no earth at all ( see later ) then you can't get an electric shock from live to earth.

( later ) But of course the earth will be connected via the plug on the genny so live to earth/chassis short inside will trip the RCD.

Maybe it's late but I can't think of a way not having an earth spike could cause a problem with the genny on board.

Genny outside on the ground..... With no earth you can't get a current flow from 240V to earth.

Where does the earth go on a genny anyway ? Just to the chassis or to the neutral as in normal mains ?

Of course the easy answer is stick an earth spike in wet ground which means you can electrocute yourself with a Live to ground short.

i see where you're coming from Brian,

the genny will have an earth tag/bolt somewhere on it.

yes....in household mains the earth does go to the neutral BUT at the local substation...not in the house.

the ONBOARD genny should be earthed to the chassis so yes it will be earthed at the sockets/switches. i didnt read the bit about 'onboard'

as for a stand-alone un-earthed genny on the ground......when i pitch the first thing to be done is the corner steadies......instant earth maybe a poor one but an earth non the less.

then if it rains the tyres become an earth conductor as well, also every time you step from the van you become an earth conductor.

then we come to the real problem. what if you use an invertor.....they have no earth at all.

once saw a bloke on a JCB accidently lift a live an 11,000v mains cable.....he was told to sit still until the power was cut. if he'd stepped off he'd be dead in an instant. human earth conductor.

 

[pappajohn]

I think there is much misunderstanding of what earth is.. it is the center tap of the supply transformer which gives the consumer an 'earth' The Earth is not a big sponge soaking up all the stay currents going around..

Consider an aircraft, boat oil platform or even a space craft .. they all have an 'earth' return system without having a four foot spike in the ground..

Back to the genny, it has it's own earth return provided by the socket outlet, so the RCD WILL trip if there is a leakage back to the genny via the 'earth' connection.. nothing what so ever to do with the muddy ground outside the van..

If you want to be absolutely safe you should bond the genny case or frame with the van, on board gennys already have this.. smaller portable ones depend on the cable.. as most suitcase models have plastic cases it would be impractical to do that.

so why do gennies have an earth tag on them and instructions to earth the genny to ground.....my kipor does!

 

[sinbad1]

So am i right in thinking that the onboard genny earthed to the chassis would be safe provided there is some metal connection between chassis and ground only if i remained inside the faraday's cage (the van) ;but if i use 240v outside of the van it could be dangerous if or not?:Sad:

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[Linda and Steph]

I think there is much misunderstanding of what earth is.. it is the center tap of the supply transformer which gives the consumer an 'earth' The Earth is not a big sponge soaking up all the stay currents going around..

Consider an aircraft, boat oil platform or even a space craft .. they all have an 'earth' return system without having a four foot spike in the ground..

Back to the genny, it has it's own earth return provided by the socket outlet, so the RCD WILL trip if there is a leakage back to the genny via the 'earth' connection.. nothing what so ever to do with the muddy ground outside the van..

If you want to be absolutely safe you should bond the genny case or frame with the van, on board gennys already have this.. smaller portable ones depend on the cable.. as most suitcase models have plastic cases it would be impractical to do that.

My licensing authority would be rather annoyed, actually they'd shut us down, if they spotted us using a genny that didn't have an earth spike.

 

[scotjimland]

My licensing authority would be rather annoyed, actually they'd shut us down, if they spotted us using a genny that didn't have an earth spike.

so why do gennies have an earth tag on them and instructions to earth the genny to ground.....my kipor does!

The original question was about an on board genny ,.. it is bonded to the vehicle so it does not require a ground spike.. if a genny is used away from the vehicle as a stand alone unit and it has exposed metal parts it should be grounded with a spike to prevent any possibility of the user getting a shock from the frame.

there is a thread here that deals with the question ..
IET Forums - Horsebox to be wired for 230v

 

[sinbad1]

Your right Jim my original question was regarding onboard gennies ;but i guess if its onboard or standalone outside does bring up some confusing issues.

if as you say stand alone metal gennies should be grounded by a spike, then surely earthing the onboard metal genny to the chassis would only be an extension of its metal case so could be more dangerous if outside using 240V?

I still believe some kind of grounding between onboard genny, beit to chassis then a spike is the safest option, unless your in a thunderstorm

RCD's Not sure how or if they are effective in a groudless situation, just don't want to be a human conductor

 

[hilldweller]

RCD's Not sure how or if they are effective in a groudless situation, just don't want to be a human conductor

Easy enough to find out - press the test button.

Being fearless I would get a small lamp, stick one wire in the Live somewhere and jab the other to chassis or earth. The breaker should trip.

 

[Linda and Steph]

The original question was about an on board genny ,.. it is bonded to the vehicle so it does not require a ground spike.. if a genny is used away from the vehicle as a stand alone unit and it has exposed metal parts it should be grounded with a spike to prevent any possibility of the user getting a shock from the frame.

there is a thread here that deals with the question ..
IET Forums - Horsebox to be wired for 230v

Oops :Blush: another case of me not reading the question properly :Blush:

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[sinbad1]

Easy enough to find out - press the test button.

Being fearless I would get a small lamp, stick one wire in the Live somewhere and jab the other to chassis or earth. The breaker should trip.

Hey never thought about that can i borrow your wellies

 

[hilldweller]

Hey never thought about that can i borrow your wellies

Wellies ?

I wear a Faraday cage, except when in the bath.

 

[Linda and Steph]

Wellies ?

I wear a Faraday cage, except when in the bath.

That's a bit personal

 

[olley]

Hi I think you are worrying un-necessarily, here is my understanding of the situation.
With household electrics sockets you are looking at an almost unlimited momentary amperage before a fuse blows, that's why RCD's are so essential, and its the amps that kill you, with a 1000watt genny only about 4amps, so it will make you jump but its unlikely to kill you.

That's why you can have a shaver socket in the bathroom, your protected from the household mains by a mains isolating transformer, its still 230v but at a much lower amperage so is considered safe.

Olley

 

[smifee]

my head hurts

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[Tony Lee]

Live dangerously - come to Morocco where most outlets don't have eart pins and don't have individual protection either. ELCBs here? Ha.

Took a photo of the pedestal we are hooked up to and there are 7 cords plugged in with the eighth outlet not working. Two of those feed two vans each so that is 9 MHs and all the outlets are paralleled off one circuit which may even loop into other outlets. Goodness knows what size circuit breaker is on the other end. All 8 outlets are two pin - no earth.

Just had two French MHs squeeze into the one site next to me. Ended up less than 3' from my van so there were 4 vans each 3' apart. Told the closest one it was very dangerous if there was a fire and in my broken Australian told him if they wanted to be that close together then he should get over touching his mate and leave me some safety space.. Guess there will be 11 MHs fed from that same pedestal now.

What is it with the French. They travel in 6 vehicle convoys up each other's behinds at high speed and then sardine themselves into tight spaces. Here there are heaps of spaces free and they want to get into my space as well.!!!!!

 

[Tony Lee]

Hi I think you are worrying un-necessarily, here is my understanding of the situation.
With household electrics sockets you are looking at an almost unlimited momentary amperage before a fuse blows, that's why RCD's are so essential, and its the amps that kill you, with a 1000watt genny only about 4amps, so it will make you jump but its unlikely to kill you.

That's why you can have a shaver socket in the bathroom, your protected from the household mains by a mains isolating transformer, its still 230v but at a much lower amperage so is considered safe.

Olley

Sorry if I upset you Olley, but if you do claim an area of special knowledge, it is surely not associated with the electrical field. Might be best not to give advice on electrical matters in case someone takes your advice.

 

[sinbad1]

Sorry if I upset you Olley, but if you do claim an area of special knowledge, it is surely not associated with the electrical field. Might be best not to give advice on electrical matters in case someone takes your advice.

I second your post was just about to reply ;but you beat me to it

here is a quote from the proffessional

Danger of electrical shock


The severity of injury from electrical shock depends on the amount of electrical current and the length of time the current passes through the body. For example, 1/10 of an ampere (amp) of electricity going through the body for just 2 seconds is enough to cause death. The amount of internal current a person can withstand and still be able to control the muscles of the arm and hand can be less than 10 milliamperes (milliamps or mA). Currents above 10 mA can paralyze or "freeze" muscles. When this "freezing" happens, a person is no longer able to release a tool, wire, or other object. In fact, the electrified object may be held even more tightly, resulting in longer exposure to the shocking current. For this reason, hand-held tools that give a shock can be very dangerous. If you can't let go of the tool, current continues through your body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). You stop breathing for a period of time. People have stopped breathing when shocked with currents from voltages as low as 49 volts. Usually, it takes about 30 mA of current to cause respiratory paralysis.

Underestimate electricity at your own peril

 

[Tony Lee]

Easy enough to find out - press the test button.

Being fearless I would get a small lamp, stick one wire in the Live somewhere and jab the other to chassis or earth. The breaker should trip.

Hang on fellas - this thread is getting quite dangerous. Pushing the test button on an RCD does not always exactly simulate an earth fault from either active conductor to ground. Unless there is an actual earth conductor connected to the breaker and it is used as part of the test circuit, the usual way the test functions is to connect a resistor connected so as to bypass the test current around the breaker. This bears no relationship to an earth fault external to the breaker and tells you nothing about how good the protection is for the actual load circuit.

-------------------------------------------------------

I'm interested in the theory behind earth stakes for generators though. Perhaps it is a specific UK or European requirement. I can see certain situations where it is commonly required - ie it is permanently connected to a factory or house normally supplied from the mains supply system (via a transfer switch) , but why is it required for a stand-alone generator supplying a separate load?

 

[scotjimland]

Just to clarify

A shaver socket is safe because it has an isolating transformer, the secondary side isn't earthed so it's impossible to get a shock from a faulty razor as there is no earth return to the transformer via a metal surface, tap, or wet bathroom floor.

This is one example where it not having an earth return is used as a safety feature.

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[Tony Lee]

Just to clarify

A shaver socket is safe because it has an isolating transformer, the secondary side isn't earthed so it's impossible to get a shock from a faulty razor as there is no earth return to the transformer via a metal surface, tap, or wet bathroom floor.

This is one example where it not having an earth return is used as a safety feature.

Pretty much similar to most stand-alone generators isn't it?

It may be safer under normal circumstances but it is not absolutely safe in all circumstances - in the same way that ELCBs provide some good protection in the case of the usual electrocution path from a live conductor through the body to an earth of some sort, but does nothing at all to protect in the case of getting hooked between the two active conductors. Isolation does make it safer in the case where there is one fault, but if there are two faults all bets are off.

"Safe" is an impossible situation to achieve in an electrical situation -maybe in baseball or cricket and even then it lasts only until the ball comes into play again.

 

[scotjimland]

Pretty much similar to most stand-alone generators isn't it?

It may be safer under normal circumstances but it is not absolutely safe in all circumstances - in the same way that ELCBs provide some good protection in the case of the usual electrocution path from a live conductor through the body to an earth of some sort, but does nothing at all to protect in the case of getting hooked between the two active conductors. Isolation does make it safer in the case where there is one fault, but if there are two faults all bets are off.

"Safe" is an impossible situation to achieve in an electrical situation -maybe in baseball or cricket and even then it lasts only until the ball comes into play again.

Hi Tony

Thanks for the correction, I should have said 'safer' ..

There was a debate some years ago about non earthed systems .. the idea was that the grid transformer would not have an center tap to earth .. therefore you couldn't get a shock to earth .. removing the need for bonding .. or grounding .. but was never adopted .. possibly because faults to the cases of appliances could have gone unnoticed.. giving rise to more danger if the second conductor was exposed .. as you have illustrated with the shaver socket scenario.

Jim

 

[Geo]

Sorry if I upset you Olley, but if you do claim an area of special knowledge, it is surely not associated with the electrical field. Might be best not to give advice on electrical matters in case someone takes your advice.

Sorry followed by those comments
Its a pity you don't take the time to get to know Olley before making such a derogatory statement
I take it your an expert and we all know that definition don't weoh:
for those that don't,
An Ex is something that was, and a spurt is a drip under pressure
for what its worth I value his opinion on most things:thumb:
Geo

 

[sinbad1]

Thought this was a fun forum? keep it cool

Anyway i'm still not sure wether a genny needs grounding I am by no means an expert ;but do know 240v is dangerous . Reading on genny manuals they say to ground them, googling also shows many instances of electricution . so without a definative answer i'm going to err on the side of safety .

Thanks for your feed back

Roy

 

[pappajohn]

Thought this was a fun forum? keep it cool

Anyway i'm still not sure wether a genny needs grounding I am by no means an expert ;but do know 240v is dangerous . Reading on genny manuals they say to ground them, googling also shows many instances of electricution . so without a definative answer i'm going to err on the side of safety .

Thanks for your feed back

Roy

the best option and nowt to loose.....
i only work on the 'bulk' stuff, not what you buy in little plastic box's but the principals are the same.....treat it right and its your friend....treat it wrong and it bites you.:thumb:

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