Inverters Feedback

HI Old patrol

Thanks for that support
I find it a bit frightening the amount of false , incorrect or misleading information posted on many forums
Often posted by some who one would expect to know better
The problem is that many of them seem unwilling or unable to explain their reasoning & raise red herrings not relevant to the facts

Peter

Hello oldtrack123,

you've probably got it all sorted meanwhile. Personally I believe RCDs do offer protection from some failure modes, but not all.
First scenario: floating inverter output feeding into metal skinned appliance: if fault develops inside appliance, there is a 50/50 chance to get zapped if you touch both the appliance and one wire which is now life.
RCD obviously won't protect.
Second scenario: floating inverter output feeding into hard wired 240V caravan circuit: if fault develops in the caravan wiring, and you've got the RCD plugged into the 240V wall outlet, a faulty appliance won't hurt you much if you touched either wire. In this case the RCD would offer protection.
The trick is to have the RCD as close to your appliance as possible because now faults will tend to develop 'upstream' from the RCD.

Either way, RCDs will always protect you from faults developing inside the inverter itself so I'd say there are more pros than cons for using an RCD.

For better illustration, I've included a little picture:

Image Could Not Be Found

The yellow bar is the floating inverter output, blue the RCD, dotted line is the fault current path to some metal object you grab, or stand on, the red and green spots are the wires inside your 240V socket. Red means danger, green means life goes on.

Best regards, Peter

a correction is in order:

...if fault develops in the caravan wiring, and you've got the RCD plugged into the 240V wall outlet, a faulty appliance won't hurt you much if you touched either wire. In this case the RCD would offer protection....

It should read: the RCD would offer protection against a fault in the caravan wiring, in case you touched either wire at the 240V socket (socket on the RCD that is).
There is still a 50/50 percent chance of course if you touch either wire in the socket while a fault has developed inside the appliance (which you'd have to touch also to get zapped). But if the appliance is also in touch with the caravan chassis (the return path, dotted line), the RCD will trip.

It's a game of probabilities really.
But proper use of a plug in type RCD will certainly help preventing nasty shocks by removing some of the most likely fault scenarios from the list of possibilities.

Best, Peter

Hi Peter

Re:Battery Value Pty Ltd posted:
Hello oldtrack123,

#1 Personally I believe RCDs do offer protection from some failure modes, but not all.
#2 First scenario: floating inverter output feeding into metal skinned appliance: if fault develops inside appliance, there is a 50/50 chance to get zapped if you touch both the appliance and one wire which is now life.
RCD obviously won't protect.
#3 Second scenario: floating inverter output feeding into hard wired 240V caravan circuit: if fault develops in the caravan wiring, and you've got the RCD plugged into the 240V wall outlet, a faulty appliance won't hurt you much if you touched either wire. In this case the RCD would offer protection.
#4 The trick is to have the RCD as close to your appliance as possible because now faults will tend to develop 'upstream' from the RCD.

# 5Either way, RCDs will always protect you from faults developing inside the inverter itself so I'd say there are more pros than cons for using an RCD.

#6For better illustration, I've included a little picture:


Here is my position on your post:
#1 Totally agree No devise is 100% safe,but an functioning RCd gives a high level of protection.
#2 Exactly,
Why ,because it has no earth to source link [frame, metal skin,floating Earthed metal etc.
You can obviously see the point I have been trying to make
#3
Yes you are again correct & why ?? because you now have an EARTH to LINE bond ie an EN system
That fault is between the source & the power outlet which is the same as having a permanently fitted & wired RCD on the Source [genny /inverter]

#4 No, the best location ,if permanently fitted & wired is @ the genny or inverter [if portable] This gives protection against active to earth faults from the genny socket to extension lead ,van wiring & all appliances
It ensures the genny has RCD protection in all cases
If an isolated genny /inverter is permanent & hard wired then a 3 pole double throw changeover switch is required , one pole switching the van frame earth
to one line of the genny forming an EN again when in geeny position

Both #3 & #4 systems also allow the van RCD if fitted to function

#5 Yes if a fault developed to frame in the genny , the fault may be sufficient for the required leakage current to flow back to the genny & the RCD MAY be functional
I agree I believe all gennys /inverters should have a fully functional RCD[ i f portable.This would allow them to be simply plugged into the van power inlet socket & both the van & genny RCD would be functional
If permanently fitted & hard wired the van RCD will serve it's purpose
#6
Yes shows YOU understand where the the earth neutral requirement lies
& that there MUST be a leakage current return path to the source for a RCD to function
Peter

Hi Peter (Battery Value Pty Ltd)

quote :-
Second scenario: floating inverter output feeding into hard wired 240V caravan circuit: if fault develops in the caravan wiring, and you've got the RCD plugged into the 240V wall outlet, a faulty appliance won't hurt you much if you touched either wire. In this case the RCD would offer protection.

A (common) RCD is rated to trip at 30mA. That is still a considerable amount of energy depending on the exact circumstances of the shock ( resistance of the current path). To say that it wont hurt you much could be slightly misleading in my opinion.

Great discussion by the way folks.

Thanks Old Patrol,

for mentioning this trip current level.

When I was at school, I remember the teacher talking about human equivalent resistance in terms of electrical protection.
I think this resistance was 1000 Ohms. So 30mA would mean a voltage of 30V, quite low really.

Nevertheless, 30mA are 30mA and it obviously depends on many physiological factors what damage this can do to a living organism (heart). I think a few microamps across a certain area (pacemaker?) of the heart muscle can be lethal to a perfectly healthy individual.

What's more, the set of contacts in the RCD take some milliseconds to open. So chances are that the initial current spike through your body will be much higher than that, but it won't hurt you much because of the spike's short duration.
Of course, 'won't hurt you much' is relative too. For the majority of people that is.
If I had a heart condition, I'd certainly look into other shock protection options.

Best regards, Peter

Hi Peter & Old Patrol

Both very true.
RE:" Of course, 'won't hurt you much' is relative too. For the majority of people that is.
If I had a heart condition, I'd certainly look into other shock protection options.: ""

Ambulances , hospitals , nursing homes etc are now fitted with 20mA RCD, I believe
A little safer !!!
Peter

Hi
Correction to above
!0 mA are used in high care areas
Peter

sorry above comments assume 2 pole RCD

Hi Barry
What I am saying is that the current through the body to earth must have a return path back to the power source lines before the RCD & preferably@ the power source
That requres a suitable connection between one of the lines & the earthing system
The standard fully isolated genny or inverter do not have such a connection,so the RCD cannot function
Now this is OK provided a certain combination of faults [only needs two] do not occur
The problem is one of those faults could be present & you would not know .The 2nd fault could be through you & the Rcd may not operate

WARNING
UNDER NO CIRCUMSTANCES ATTEMPT TO MAKE SUCH A CONNECTION UNLESS YOU ARE QUALIFIED & KNOW WHAT IS REQUIRED.

From http://en.wikipedia.org/wiki/Residual-current_device

"An RCD will help to protect against electric shock where current flows through a person from a phase (live / line / hot) to earth. It cannot protect against electric shock where current flows through a person from phase to neutral or phase to phase, for example where a finger touches both live and neutral contacts in a light fitting; a device can not differentiate between current flow through an intended load from flow through a person."

Theoretically because the inverter is "floating & isolated from ground", you can touch the active because the current cannot flow through you to the neutral connection. The Earth path through your feet, to the battery side of the inverter is isolated at this point.

However if you where to touch the active & the neutral, the RCD would not know if the power is going through the load or thru you & you get a shock!

Thanks Barry, its always good to understand how things actually work & not assume that a 240V inverter will behave the same as a GPO.

Cheers

Thanks Allan an excellent post.

I always take inverter or genny 240V power lead into the 15A van receptacle as it then goes straight to the RCD. I then use power from van power points as required.

My risk is therefore reduced to insulation breakdown etc as you mentioned above and the extension cord, so to my mind I've reduced my risk and if I don't touch a conductor or metal component that is a conductor with a short etc and just plug in extension cord (both inverters have isolation switch to turn on/off) i'm pretty safe.

Hi Allan
Again I ask the question how can the RCD operate if there is no EN bond?
A standard genny or inverter has no such bond
Now A fault may develope @ the source that MAY form a suitable bond but the most likely areas of such faults are in the van wiring ,appliances etc[After the RCD]& the RCD will not function
Peter

Hi Allan

A PS Re
"RCD's do not rely upon an "earth" connection for their operation, merely a connection to the live conductors to detect an imbalance in the current in those conductors"

This is an oft quoted statement & is correct

PeterThe double pole RCD only has 4terminals ,two lines in & two lines out & NO DIRECT CONNECTION TO EARTH
However, with out a earth system connected back to one line of the source, it cannot operate
An earth system is an essential part of it's operation!!

Hi Barry
Sorry You have the same mistaken belief as many!!
Your van RCD is inoperative & will give you no protection if supplied from a standard isolated genny or inverter via the power inlet plug.
Faults within the van will not be detected

Peter

Hi Peter,

My expression "RCD's do not rely upon an "earth" connection for their operation" meant that the RCD itself does not require a deliberate connection to earth, not that the system does not require an earth, e.g. MEN bond.

Agreed that without MEN and a double fault (one line to earth and the other through a person to earth) downstream of the RCD then the RCD will not trip and protect. Similarly, a double fault as above will cause electric shock even with a fully isolated source such as inverter or alternator.

For full protection with an RCD then the supply should incorporate a MEN bond which would mean to the vehicle body and perhaps even an earth stake.

HI Allan
Re :For full protection with an RCD then the supply should incorporate a MEN bond which would mean to the vehicle body and perhaps even an earth stake"

No need for MEN just one single frame [earth] to one line connection to form a neutral @ the genny

NO Earth stake required or recommended

Peter

Peter, I have no education on the official considerations re earth stakes in non-grid installations but my suggestion came from fundamental reasoning with particular attention to the desirability for equi-potential bonding.

Take a look at the sketch below where an alternator (or inverter)is supplying a load via an RCD and the system incorporates an EN bond before the RCD. Consider now if a fault were to occur between the Active and Ground (terra firma) as shown by the dotted line, say a short to a building frame etc. If the alternator chassis and the load chassis are not making good connection to ground then the whole installation, neutral and earth wire and chassis are now elevated to 230 volts ABOVE ground, and a person standing on the ground and touching the alternator or load frame could receive a shock. I would believe that an earth stake should be connected to the EN point. (not shown)

Am I missing a point in the considerations of earth stakes? After all, the reason for a local earth stake in a permanent MEN installation is to ensure that the neutral/earth in that installation is maintained at local ground potential.

Image Could Not Be Found

Hi Allan

Geeez , you are putting my poor old brain to the test.
I agree the situation would be as you describe.
A good reason to have the RCD mounted on the genny to minimize such risks
However this would not cover an internal fault from active to genny frame .


The full reasons for the rules saying an earth stake[in portable situations] is
not required or recommended have as far as I am aware never been spelt out.

One, has been the concern that random driving of earth stakes could damage other underground services
They may also be trying to maintain a floating system ,relative to ground
Another more relevant to van frame earthing by earth stake while connected to mains MEN supply which I see is the potential for stray earth currents to actually overload the extension lead earthing conductor'. I have experienced just such problems on several occasions in industrial locations
A van park , covering a wide area, could have a similar potential
Peter

Good one Allan.

I now understand OldTrack's problem - he does not understand why introducing and "earth stake" is a hazard.

Put simply, a floating system is floating. If you touch one side - say L1 aka "Active", you become its reference and hence no harm.
If you are earthed, the same thing happens - you become its earth reference and the L1 is at earth potential. (L2 then goes to 240V and hence becomes "Active" in reality - and I think by definition...?)

There may be "static" shock as you or the L1 "equalise", but that is RARELY fatal.
An extreme case of the latter is transmission line de-icers.... A helicopter comes long, connects itself to an HV line (one phase of a 100kV to 2MV transmission line etc) to equalise, then the linesman jumps on the lines and starts chipping away.
The same is done in reverse when the chopper returns to collect the chippy.
The static "equalising" spark can be quite big - especially because such cold conditions have very dry air (no coronas or other leakages), and we are talking about several hundred kV - even with static charges that tends to be fatal. (Yes - the chopper is a bigger conductor & capacitance than a human, but still... they play it safe.)

However, a 240V AC static equalisation isn't anywhere near that same order of magnitude. Actually it is only half that since the floating voltage is "balanced" ie both L1 & L2 are 120VAC (out of phase).
Even less now that we are 230VAC!


Now I realise that readers have not understood my previous writings about floating and "earth referenced".

The problem with a floating system is if it is NOT floating.... but I do not wish to repeat that again.
It's like seatbelts - sometimes they will kill you, but usually not.
Hence why the recommendation NOT to earth reference a small-capacity and simple floating system.
However, if RCDs were to ALWAYS prevent electrocution (in leakage situations - NOT between the lines as an A-N only fault!), then the authorities would IMO mandate earth stakes and RCDs.
I can only assume the authorities still feel "isolated" is safer than earth referencing and RCDs.

Ah - the dilemna.... introduce a hazard so that a safety feature might operate...? (Like when the banned laminated windscreens, and air bags.)


BTW - your hashed Active fault will not trip the RCD, but if heavy enough should trip any alternator protection (fuses, breakers etc).

But excluding your hashed fault, you diagram is effectively what I tested with an earth leak in the load from Active to its earthed chassis.
The RCD was not earthed (as per your diagram) but it still tripped as expected.
To put it another way, how does the RCD detect the current in the LOAD that faults from A to Earth?
For the done-to-resurrection'th time, by its core IMBALANCE.

Thank you.

Hi ChipPunk
I am beginning to think YOU have A major Problem reading anything but your own B#&*it
Why don't you just go back & read it ALL very, very slowly.Maybe even make some notes so you do not forget what you just read.

I have consistently said ,in what I believe are simple terms, "DO NOT USE AN EARTH STAKE"

RE :Put simply, a floating system is floating. If you touch one side - say L1 aka "Active", you become its reference and hence no harm.
If you are earthed, the same thing happens - you become its earth reference and the L1 is at earth potential. (L2 then goes to 240V and hence becomes "Active" in reality - and I think by definition...?) "


Again you seem to have a serious misunderstanding of terms .
I believe what is generally being referred to in this & most similar threads here & on other forums , is Earthing the genny or inverter FRAME.
Not connecting one line to a earth stake.
To create a ground earthed neutral[MEN]
I think you will find that if you read similar threads & can forget about MEM systems
That is the question generally asked: "should I connect the van frame or the genny /inverter frame to an earth stake"

My answer has always been "NO"
I doubt if any are referring to earthing via an earth stake one line of the genny/ inverter

RE :"then the authorities would IMO mandate earth stakes and RCDs.
I can only assume the authorities still feel "isolated" is safer than earth referencing and RCDs. "
Why would they mandate earth stakes when they have specifically said" an earth stake is neither required or recommended"??
Even when using now mandatory RCD protected gennys or inverters on building & construction sites where the risk is even higher??
Perhaps John does not know what he did either but I will spell it out for you ,You may then be able to understand,
He connected a RCD input terminals to a source [active & neutral ],He had NO connection to the load terminals or earth , he pressed the "test " button ,the RCD tripped, The core balance was upset INTERNALLY by by the test button

That is in line with what anyone who KNOWS about RCDs operation would expect

RE :"or the done-to-resurrection'th time, by its core IMBALANCE. "

Who is saying otherwise , again you may be having a comprehension problem


But MANY electricians do not know these simple facts .It is becoming more & more obvious that you are in that category

Get A copy of AS 3001 :2008.
Sit back & clarify your terminology.
Understand the many ways in which the term "earth" is used in the electrical sense
Get out of your mind that every thing is MENed
Understand that fixed installations are not in the same category as vehicles .
Understand that portable gennys & inverters are just that,not attached by fixed wiring to permanent or semi permanent buildings vans etc but connected by extension lead
That is what this forum & similar are about,vans motor homes & similar using PORTABLE gennys & inverters.

If you wish to discuss hard wired installation of gennys & inverters You may find the below links of interest IT is an electrical FORUM
http://www.phased.com.au/index.php

I have endeavoured not to give detailed info for the simple reason that unqualified people may attempt to modify equipment &/or wiring
THAT HAS BE KEPT IN MIND ON THIS TYPE OF FORUM
I think you mentioned DUTY OF CARE very applicable to this type of forum
However I would EXPECT a qualified person aware of the appropriate rules
to understand without such details
Peter


stakin

Sorry OldTrack,
I have only read the first lines of your last.

Are you now saying that an RCD does NOT ITSELF have to be earthed?

HI ChipPunk

Perhap you should do as I have said repeatedly go back & very very slowly read ALL the posts.
Maybe even take some notes so you can remember what you have read
Take particular note of my reply 3of 11
BUT just to make sure you understand IT here it is again IN BIG PRINT SO YOU CAN SEE IT

oldtrack123 posted:
Hi Allan

A PS Re
"RCD's do not rely upon an "earth" connection for their operation, merely a connection to the live conductors to detect an imbalance in the current in those conductors"

THIS IS AN OFT QUOATED STATEMENT & IS CORRECT

THE DOUBLE POLE RCD ONLY HAS 4 TERMINALS, TWO LINES & TWO LINES OUT & NO DIRECT CONNECTION TO EARTH.
HOWEVER WITHOUT AN EARTH SYSTEM CONNECTED BACK TO ONE LINE OF THE SOURCE IT {RCD}CANNOT OPERATE
AN EARTH SYSTEM IS AN ESSENTIAL PART OF IT'S [RCD'S ] OPERATION!!!!!!!
Hopefully YOU can understand that!!!!
Peter

Good - so we both agree that an RCD does NOT ITSELF have to be earthed.

EXCELLENT!


As to the rest, I suggest that RCDs are included an any power systems whether floating or not. (For reasons I discussed, and unless too much false triggering occurs.)

Except where regulations etc state or recommend otherwise, I recommend that floating systems NOT be earth referenced except where complex load interconnections exists (eg, whitegoods and other metal-chassied 230VAC loads).

I apologies if the above has not been clear or if it has been misunderstood.

Thank you.


I'll leave the local EN bond as this will further confuse - eg - the distinction between "isolated" as in "AC output galvanically isolated from internal DC" and "AC output (....) isolated from frames, earths, PE, SE", and "terminals normal designated and N & E in Aussie GPO outlets" and "actual Neutral & Earth" etc.
Maybe then we can discuss the linked inverter wiring diagram(s) and their approvals.


And thanks to Allan B (ava good trip!) and Barry, Daryl, Stormy, OldPatrol & Peter for your qualifying information. The issues seem reasonably understood.

HI ChipPunk

I agree with you on the above
In fact that was the problem I was having , we seemed to be saying the same thing yet you where disagreeing.
Re the EN subjects etc I do not think a detailed discussion is really suitable for this forum.
Just might make too many would be sparks!!!
Also I seems you agree that the terms, earth , ground , frame etc, isolated, EN,MEN,non isolated, etc can be quite confusing even among lecys

You may note, I try to avoid tech words as much as possible,on the basis that they are meaningless to many other forumites
Regards
Peter

Yeah - I wrote a few times that I did not see your problem - we were saying the same thing.

AFAIAC, I originally stated that and RCD does not have to be earthed. That does NOT mean the system (either side) doesn't require any reference (I wrote "whether earth & heaven" AIR), but means merekly what I said - the RCD itself required no earth - it is merely an imbalance between its two "Lines".

Re you OP above - I agree it may be misleading in that people may think an RCD will protect them, but the statement to include an RCD is not incorrect - it will certainly NOT do any harm (except electrocute people that don't know better, and may be subject to many false trips for various reasons).


To not have an the inverter output's E & N bonded as per the linked inverter diagrams I think is wrong and dangerous - what choice is there? But that relates to the clearance of load faults.
FYI - former inverters and UPS were often single-pole switched - ie, only the Active pole. This lead to DANGEROUS situations - eg, firefighters would disconnect the MSB (main power) hence believing the site to be powered down and safe. Imaging their shock (pun intended) when they found the downstream MSB-isolated Active to be live (typically around 120VAC).
Whilst not fatal for small UPS & inverters (except for the same reasons people get killed by 9V batteries), on large inverter or UPS installations it could be.
The single-pole switching inductive-feedback problem was solved with dual-pole switching of UPS & inverter outputs to & from the mains Active and Neutral.
In fact the spec that those diagrams were taken from was probably the first (at least in Australia, but probably the world) that dual-pole switching was specified (and approved and endorsed by an electricity authority). The same spec was probably the first that had a REPO (Remote Emergency Power Off) - a normally-closed circuit that when broken would force the inverter or UPS to the mains supply AND disconnect its battery.

BTW - those inverter "EN" bonds are what I call an EN bond - it is relative to "GPO outlet pins" etc and has nothing to do with "mains" E & N, but merely becomes an E & N relative to the downsteam AC system. It can still be floating (unless a downstream E-frame connects to earth etc) wrt to "Earth" as well as its DC input polarities. The clearing of faults under AS3000 (Australian wiring) is only dependent on a (local) EN bond - eg - at the switchboard else powerstation - the EN bond itsled does NOT have to be earthed (but is is supposed to be if domestic mains etc etc)


I thought my RCD test was quite clear. An unearthed RCD connected to mains and the RCD's load/output subjected to an earth leakage.

"Nor does an RCD require an EN bond" depends on definitions. As long as the generator is EN bonded and the fault has sufficient earth leakage, that's it. The MSN etc needs to EN bond (that is done for "tightness"). (Dare I mention certain power stations that have over 20V difference between their N and Earth!? But they were NOT subject to AS3000 LOL!)

I described the two RCD test-button scenarios and predicted(?) that IMO it should not work if the RCD itself was not earthed.



As to other issues - I generally do not bother too much with pointing blame.

False accusations like "some cannot or will not support their case with details & just disappear" I find reprehensible (that's my #2 for this site). Even to stoop to such flaming is undesirable. But (if) as a statement of fact, I love it.

But I am unsure who ridiculed or disagreed with my statement that and RCD need not be earthed. I never wrote - or never meant to write - that the "system" need not be earthed - I do know I wrote that referencing was required (heaven or earth LOL), but not the RCD itself.
And I am unsure who first recommended contrary to the statute authorities (as I understand them) the an earth stake "not" be fitted. (Suffice to say it seems explorox.com have changed THAT wording.)
I may well get to that, but first I'm off to meet a friend of old. Then maybe a few battery issues. And maybe see what significant changes have occurred in related Aussie Standards over the years (though my local master hasn't mentioned any - other than their recent errors, and their usual "too late" status).
Time to go!!!!

HI Terra firma
In the article shown in top right corner or via this link
http://www.exploroz.com/Vehicle/Electrics/Inverters.aspx
Peter

That's the page that apparently had the incorrect statement about RCDs needing to be earthed, but all I see is the inverter needing to be earthed for the RCD to work. That is not incorrect, just as long as that is not deemed to be suggesting (or recommending?) earthing.

But I reckon the stuff under "Isolated Output" is incorrect.....

And I think my elsewhere mentioned "should earth-stake" has been changed.
Good - no obvious liability....

What is stated is merely "fact".
My litigious comrade reckons that is fine - there is no stopping people silly enough to misapply a statement of fact (that's paraphrasing a late emotive session last night....).

Yes I was telling my son this just this morning....

A normal multimeter set to measure resistance with the probes under your skin would be enough!

Hi ChipPunk

I afraid I cannot make any sense out of your above post

Does not answer direct questions & seems to be a bit rambling.
Perhaps you need to start from scratch
What is the relevance of 3pole RCDS to what is being discussed?
Peter

Some one made mention of a 2-pole or 2-line RCD. Is there any other type for single-phase installations?

I thought too that someone suggested fitting an earth-stake and hence "earth reference" for otherwise isolated systems (like mobile inverters).
I was wondering why that recommendation despite authorities' recommendations? (I basing that "recommendation" info on the posting in that "caravanning site" thread you referenced as well as my experience several years ago.)

Is that clearer?

HI Allan

Allan you are totally correct & understand.
A RCD CANNOT function without a return path for the leakage current
That leakage path has to be via the earthing system [wiring] ,in the case of vans, vehicles etc, back to the source with a link forming an EARTH /NEUTRAL ]
Which I believe you well understand
That is the reason an external RCd plugged into the fully isolated portable genny/inverter socket cannot function
It has to be by rules apart of the of the portable genny & correctly & permanently wired
I wish SOME others could understand that simple fact!!

Yes the last part you posted from that article :safety switches etc"is totally incorrect
I refrained from pointing it out as I was /am having enough trouble to get SOME to understand the RCD operation

Again you are completely correct with:

"With a fully isolated inverter (as they all should now be) the "Earth" connection on the inverter is merely the metal casing (with possibly some suppression components connected to it internally) and earthing it is only of value to suppress radio interference from the inverter electronics. This earth connection has no bearing on the 230v wiring and will not provide protection against electric shock, RCD or not.""

Yes & that's why I say :The portable RCDs [Clipsal etc] plugged into the genny socket do not function
Peter

It's done to death in exploroz-78780-Solar Panel/BatteryInvertor query.

The RCD itself does not have to be earthed (I proved that this morning) but the source & load do if it is to act as an "earth leak detector". (But bonding to Earth is not recommended in typical portable situations.)

Nor does an RCD require an EN bond - that is only required to clear faults - ie, blow fuses.

An EN bond does not necessarily mean an real "earth" - merely that the Earth and Neutral conductors be joined - eg at the sources and switchboard - ie, the inverters "Earth" pin output is bonded to its "Neutral" output. (Again, to clear downstream faults.)

Earthing itself to the ground is another topic. It may be done for shielding reasons, or - as with an increasing number of locations around (planet) Earth (pun!) - for domestic and industrial safety reasons etc.

It seems that local authrorities are still advising AGAINST an Earth Stake (to planet Earth ground) for typical mobile inverter and generator situations (as would apply to most 4WD & recreational campers etc.

Other than the possibility of false tripping, there should be no reason NOT to fit an RCD to any inverter or generator. It may not operate if the system is Earth isolated, but should some Earth reference occur or be fitted, then it may operate.
But RCD (aka Safety Switches etc) should NEVER be relied upon for safety. They are merely another tool to save lives & injury.


But there are enough others on this site that have paraphrased and agreed with what I have written. I have spoken. I have tested. I have not found anything to contradict what I have said - except for opinions.
I have finished.
Over & Out.

Hi ChipPunk
You seem to be unable to give a direct answer to my questions
So perhaps you could explain to all of us the test you did this morning??

RE" Nor does an RCD require an EN bond - that is only required to clear faults - ie, blow fuses. "
Again I cannot believe what you are saying " rcd Does not require a EN to operate i"COME OFF IT
Perhaps you could post a SIMPLE current flow path description explaining how it will operate under such circumstances
I'll even start it for you! [note I Use term L1 & L2 because there is no neutral unless anEN bondis made @ the source

A simple explanation of the current flow path for a RCD to operate ith a fully isolated genny
The current leaves the source @ L1 flows thru one side of the RCD thru the load & back thru the other side back to L2
WHEN a fault occurs between L1, your body & earth the current flows again from L! thru one side of the RCd to the load &YOU,the leakage current flows thru the earth wiring to ??????
Or explain how else it can get back to L2& trip the RCD


Re "i may not operate if the system is Earth isolated, but should some Earth reference occur or be fitted, then it may operate"
It is not a question of it may operate ,IT CANNOT OPERATE< THAT IS THE WHOLE POINT OF WHAT IAM SAYING
YES IT NEEDS AN EARTH NEUTRAL connection TO operate
ARE you now agreeing with what I have been saying.
Therehas to be a return path for the leakage current back to the source

By the way I have been involved with RCDs since their introduction in mid 50s as service section head tecnician,until I retired by the company that first introduced them to QLD
They were referred to then as "core balance earth leakage circuit breakers".The name says it all
Peter

HI Chip Punk
Further to your above posts:
," the inverters "Earth" pin output is bonded to its "Neutral" output. (Again, to clear downstream faults"
Are you saying that all portable inverters & gennys have the earth pin of the outlet connected to one line , forming a neutral
I hope NOT because if you are, you have little knowledge of the fully isolated portable gennys & inverter on the market
The earth pin is only connected to the genny frame as posted by John

This Is the reason a plugged in RCD CANNOT FUNCTION.
Time you sat down & drew up the circuit
Peter

Hi ChipPunk

Re :The RCD itself does not have to be earthed (I proved that this morning) but the source & load do if it is to act as an "earth leak detector". (But bonding to Earth is not recommended in typical portable situations


You seem to not understand that a RCD is an earth leakage cb[old name in the older rules ELCB, earth leakage circuit breaker, before that ,core balance elcb. Now the worst possible name used by many SAFETY SWITCH
Perhaps you could explain what other function it has , surely NOT an overload CB?

Peter

Followup...

The RCD test will work, but it will not protect you from a shock if you touch both the active & neutral. This is the same as in a normal GPO to BTW.

The RCD only trips if the current from the active is different from the neutral, which would happen if some current is flowing thru you instead of thru the load & back via the Neutral.

This current has to be able to complete a circuit for it to flow. It flows all the way back to the source....how that exactly happens has been difficult to research. The issue I have is that transformers effectively isolate the supply & each house has a transformer somewhere to step down the voltage.

Perhaps someone can explain the earth return current path for GPO's?

Cheers

HI StormyKnight
I am afraid you do not understand the function of the test button ,'as with some others on this thread
The test button only test the RCD mechanism[again some do not seem to understand that either]
It does this by shunting a small part of the current around the balance section upsetting the balance & tripping the RCD

IT DOES NOT CHECK THE TOTAL CIRCUIT {wiring] FOR RCD functionality.
IT does not know if there is a return path for the leakage current back to the source
It cannot verify that.as it has no DIRECT connection with the earthing system
A point that SOME seem to be labouring & saying the SYSTEM does not need an earth for the RCD to operate

Re :"This current has to be able to complete a circuit for it to flow. It flows all the way back to the source....how that exactly happens has been difficult to research. The issue I have is that transformers effectively isolate the supply & each house has a transformer somewhere to step down the voltage. "

There IS NO MYSTERY .
It has to flow back via the earthing system to an EARTH TO LINE bond which then becomes a NEUTRAL in the case of portable gennys & inverters,
THEY are then not FULLY isolated & MUST HAVE A RCD PERMANENTLY FITTED
The house has an EARTH NEUTRAL bond & the appropriate place in the switch board.
The Domestic gpos work along this line
The current comes from the active thru the one side of the RCd out the other & thru the load back thru the other side of the RCD to the neutral . the currents are in balance the RCD does not trip
With a FAULT : the current flows as above until it reaches the fault, your body in contact with some part of the active line [this may be a knife poked into a toaster for example] & earthed metal or ground
AT this point the current splits some goes back as before thru the RCD to the neutral
The part thru you goes back via the earth system to the switchboard neutral link BYPASSING the RCD

Upsetting the balance & the RCD trips .
IT IS AS SIMPLE AS THAT BUT it does require an EARTH /NEUTRAL BOND /LINK
Something that does not seem to be getting across TO SOME

Hope this helps you to understand
If not I WILL GLADLY GIVE A MORE DETAILED ANSWER ,unlike some
Peter
PS
I will not give a detailed description off HOW to do it .
That work should only be carried out by a qualified & COMPETENT electrician

Hi StormyKnight, Yes every house is suplied by a transformer, But the Neutral is conected to Earth. Commonly called MEN, multiple earthed neutral & every street pole in SA there is an earth bond to the mains neutral. I know this as i was an ETSA linesman. Daryl

OldSpark - He won't like my attitude!! (?)

StormyKnight - I did! Both RCDs did NOT trip if NOT earthed. I know this contradicts what OldTrack wrote, but I am merely reporting what I observed.
If OldTrack had test-buttoned an unearthed RCD and it tripped, then we can address that later....
But as others and OldTrack said, RCDs respond to a core imbalance.

Let OldTrack explain what path the "test-buttoned" core imbalance takes if it in NOT to earth. (Maybe it's back out L1 & L2 after transformation?? Or it arcs to heaven?)


There must be a return path, but the RCD per se has no connection to that.
IE - if the supply is earth referenced, and the fault is earth referenced (with sufficient leakage - eg 30mA for domestic RCDs), then the RCD "should" trip.

Repeating: The RCD test function did not trip wiithout the RCD earth.
I would hope this is consistent with the RCD Standards, but I can see the argument for the test merely testing the mechanics which is what OldTrack was suggesting - albeit NOT involving an "imbalance". (However I would argue against an artificial injection (unless OldTrack can explain the "imbalance" opath?) - to me the test should include the (eg) 30mA leakage/imbalance. But that is in IMHO.)


Otherwise I can't understand what OldTrack is on about. He is saying the same things as I wrt RCD operation EXCEPT the insistence that the RCD ITSELF must be earthed. WHY? - it is a CORE IMBALANCE.

As I used to get it across to my subjects "How does an RCD measure the leakage current to Earth?"
Usually after pondering that, even the most challenged got it.

AFAIAC, this whole mess started with an objection to my comment that an RCD need not itself be earthed. All I have spoken with agree. Just to confirm, I tested it.

Other things I have written have been focused primarily on that and the issue of "isolated" generator/inverter "safety", but let's try to solve one issue at a time.
It sounds like OldTrack isn't game to test the un-earthed RCD. Geez - what is so dangerous about that - assuming have the experience and know what you are doing? (Others - do not try this test. It is not one for flying leads etc!)

I also asked (elsewhere) why people thought an inverter in a car was dangerous - specifically "more dangerous" than AC in a house. Has anyone responded?


As for RCDs on floating systems, all I meant was that they should be included (unless they false trigger excessively). They will not work in a true floating system, but I too know of fatalities in "floating" systems (as was described in OldTrack's link to an caravaning site). (No - it wasn't across "both" lines.)


As to EN as in MEN - yes, I should have used the term PE, but I though it obvious I was discussing the "output earth and neutral" pins in a prescribed Australian GPO socket.
(Does this mean inverters are sold WITHOUT an output EN bond????)


If OldTrack wishes to draw a line diagram, I will gladly annotate (provided I can understand it). (EG - unearthed RCD in a normal domestic earthed MEN supply with a victim downstream of said RCD.)


Meanwhile, I have found diagrams of inverters with both EN connections AND mains-earth connections when connected to a mains supply.
The EN connection is to provide the PE.
The mains-earth connection is to conform to AS3000 (which is also the inverter's PE if the mains is connected (as a bypass)).
The problem is, I cant host it - but I'm working on that.

And finally - some diagrams from old specs.





(I hope that worked!)

Rats, try....

http://img84.imageshack.us/img84/458/inverterwiringtype0noma.gif

http://img19.imageshack.us/img19/5883/inverterwiringtype12mai.gif

Hi ChipPunk


You seem to be coming very confused & confusing .Suggest you start from scratch & read it all again totally differant thing I have not said @ the RCD
For a start i believe we both agree that a RCD has no direct connection to earth???
If it has no connection to earth, how does pressing the test button get a leakage current to earth???
YOUR line diagram should explain & then all will be clear???

My explanation of the test button operation is simple & as I posted earlier :
The test button ,in series with a resistor [appro 8k] ,internally by passes the small test current [30mA] around the balance system [ could be done externally by a switch & series resistor [8k]from inlet to outlet side of either line] , Current in core out of balance unit trips, no requirement for connection to earth. does not prove earth integrity.


I have consistently said there is no direct connection from the RCD to earth But that an EN link is required for operation . I have not said @ the RCD!! perhaps you have difficulty in understanding that.?

RE :Meanwhile, I have found diagrams of inverters with both EN connections AND mains-earth connections when connected to a mains supply."

Again ,as I have said BEFORE THAT is not the topic of this thread & why all you say is just not on subject.
Often a problem with those with a narrow field of experience.
The subject is PORTABLE GENNYS & INVERTERS as used by RVers as per AS 3001 :2008.& construction industies , Builders ETC
Not standby or or similar hard wired systems!!

Re :(Does this mean inverters are sold WITHOUT an output EN bond????)"" :

In Australia for PORTABLE use,YES , Unless fitted with a RCD!!!!!!
In fact now illegal to sell PORTABLE non isolated due to deaths

You also seem to believe I am against fitting RCDs to PORTABLE gennys & inverter ,again if you read all my posts you will see I believe it should be mandatory.
What I have said, on this thread & others is that the use of an external plug in type rcd is not functional .SIMPLY because there is NO EN LINK BEFORE IT.


RE :If OldTrack wishes to draw a line diagram, I will gladly annotate (provided I can understand it). (EG - unearthed RCD in a normal domestic earthed MEN supply with a victim downstream of said RCD.) "
Again you are the one using confusing terms ""Unearthed RCD"" when RCDs are never DIRECTLY earthed

I explained earlier in answer to another poster how the RCD operated in a domestic situation perhaps you should read THAT

Again I would point out this thread/ Is not about domestic MEN systems .!
It is about "Transportable structures & vehicles AS 3001 :2008 "
I hope your ""students "" went away understanding what you where saying!!

Perhaps I have become a little slow in my old age but I certainly have problems following your inconsistencies & also for your failure to answer direct questions.
You seem reluctant to do that!!

Having said all that I agree with most of your posts re MEN systems & after some problems understanding just what you were saying I believe we are saying the same thing regarding the need for an EN link before the RCD for a RCD to operate

We do not agree on the function of the "test button".
I have detailed how I understand it operates.
I am waiting for you to explain how you believes it operates
A line diagram or point to point explanation from you should quickly clear that up

Peter

Hi ChipPunk

The links to inverters again are not for a floating EN system ,but for a MEN
{grounded} earth system. & do not include a RCD
Are not relevant to the subject of PORTABLE inverters or gennys & Aus regs

Peter

Hi Allan
Yes it did become quite long.
Not sure who was converted but as usually happens some cannot or will not support their case with details & just disappear.
It is also surprising just how many, apparently or claiming to be qualified do not seem to really know their subject
Peter

Hi ChipPunk
"Now OldTrack, do you have problems with that arrangement? "

No
But it just prooves what I had started to suspect ,YOU are talking about a totally differant situation & not relavent to THIS thread / forum, ieTo those covered by As 3001: 2008
Perhaps you are /were not aware of the differance

All your comments are relavent to hard wired gennys or inverters in standby or stand alone power to systems that incorporate a MEN sysyem as covered be AS 3000

TOTALLY OFF TOPIC
Peter

PS - to answer the OP - The use of a Safety-Switch(sic) isn't wrong.

But "it’s very cheap protection against a fatality" is misleading.

Chip, No, I am not "supporting" OldTrack. I agree with some of what he has said, disagree with some other of what he has said and have no view on some more of what he has said.
What are "Non-specific ambiguities"? Are you using a buzz-phrase generator?

Seems to me that this whole thread has become a dog's breakfast and apart from point-making it is serving no useful purpose. I do have some difficulty in following some of your statements, not technically, just the expression and semantics, and I am sure those with an interest but not well versed technically would have no idea of what this is now all about. Incidentally what do you mean by "PE".

Knowing how the Test Button function is arranged within a RCD I was surprised that you could not get one to trip when simply connected to the mains with flying leads. I wondered if maybe I was missing a point so went out to the workshop and hooked an RCD up with no more than two flying leads with 230v input and YES, it trips repeatedly with the Test button. (The button connects a resistor between the input side L1 and the output side L2 thus passing current through only one winding of the core balance transformer.) Either yours was not correctly connected or the Test trip is malfunctioning. (Yes, I know you got it to trip by other means.)

Sorry Allan - I was being objective (or insecure?), hence thinking you may have been subtly answering my earlier question (wherever...?!) regarding agreement with OldTrack.
Hence the "unspecific ambiguities" - ie, it could be taken by either of us (OldTrack & ChipPunk) to refer to "us".

I see lots of misunderstandings in this and the other related thread(s).
One seems to take other contributor's replies as endorsements.

I'm not aware of anyone disagreeing with what I have written.
Confused maybe, and maybe unsure, unknowing and uncommital - but not in disagreement.
I reckon many are agreeing with what I have written - at least several aspects.

At least I have tested one aspect. Either I am lying, or I have RCDs that are different to those described by OldTrack.

If OldTrack's opionions and statements are NOT supported by others, I'd rather drop this.
IMO it seems obvious to those in the know... And that includes the other site's thread that OldTrack linked to (as if that somehow refuted what I had written).
Anyone else should speak up - I'm happy to "try" to clarify...
I try to avoid too much technospeak, but I can't seem to win either way....

And normally I wouldn't carry on to this extent, but this may have had safety issues (I may even have to clarify my own statements...).
And I am already wary - I've already been subject to what I consider unsubstantiated bullsh, probably to push someone's product. This is #2 (though not for any material gain AFAI can see). I'm not one to waste my time on such sites.

Maybe I have been away too long, and am too out of touch.
I only viewed this site in preparation for a homecoming celebration...


Again Allan - sorry. I hope you understand my tact & POV.
And thank you for your clarification.
(No need to empathise... But if I misunderstand, feel free...)

Cheers.

S'orright Chip, I understood and appreciated every word of that.

Now I must drop this and get ready to leave for The Cape in two days. Wheeee!

Allan, you won't get far at the moment, the unseasonable rains have some roads waterlogged and 8 of the graders are still waiting just south of Cairns to be given main roads permission to leave to go up to do their job up there.

We are waiting till late june early July.

Maîneÿ . . .

Hi Allan
Off topic, I know ,
But have a great trip unfortunetly if you take the high road instead of the old OTL track you will miss the best parts.
Also a few KS north of the ferry is a track leading out to the east coast ,comes out south of Ushers Point ,some nice scenary & good camping by a little fresh water stream right on the coast. [as soon as you get to the coast]
Last trip was about 20yrs ago
1st was in 1968, no ferry thiose days or the high road,
Peter

Hi All
I fully endorse Allan's above comments.

Do not attempt any changes or mods to any 240v gear or wiring because you believe you understand , someone could end up dead.

No Doubt the layman is by now very confused as to just what protection RCDs give.
The below may help to clarify:
[1]A correctly installed RCD offers a very high level of protection against shock but NOT 100%
[2] The test button on a RCD does not indicate that the RCD is correctly installed or operational .
IT only tests the RCD unit itself
[3]The above [2] should not be a problem with a permanently installed RCD such as in your home
[4] IF your HOME does not have a RCD fitted @ the switch board . the use of portable RCds will give a high level of protection against faults in gear plugged into them
The portable RCD will not give protection to other outlets in the home .


With a van, motor home etc:
[5] The extension lead is a critical part of the system .IT MUST be kept in good order & SHOULD be in only ONE LENGTH'
[6]The van RCD if fitted gives s an additional line of protection to faults within the van WHEN plugged into mains power, this will apply even if the supply does not have a RCD
[7]If the van is not fitted with a RCD but the mains supply is you have a good level of protection,this relies on a good extension lead.
[8]If the van is not fitted with a RCD, the use of portable RCD as in in [4] above will give a high level of protection from faults with devises plugged into it, but not other power points in the van, when connected to mains supply.

When using fully isolated portable gennys or inverters:
[9]Normally ,The van RCD is not functional
[10]Normally Portable RCDs are not functional
[11]If a certain type of fault occurs in the genny or inverter then the van & or the portable RCD MAY be functional
[12]If a certain type of fault occurs external to the genny/inverter , a plug in RCD @ the genny /inverter will not be functional
[13 ] If a certain type of fault occurs before the van RCD[ if fitted] the van RCD MAY be functional
[14]If the van or the genny/inverter do not have a permanently fitted RCD, the use of portable RCD offer some protection from faults in gear plugged into it.

[15] Permanently installed genny /inverter should be correctly wired for the van RCD to give a very high level of protection'
Peter