Power inverters?

Cricket · Member

Power inverters?

Peter_n_Margaret · Guru

solaraustralia.com.au/tempo.html
I have had a 1300W PSW inverter from these guys for 8 years.
It has been impeccable.

Cheers,
Peter

brian · Guru

Be aware that hard wiring an inverter to more than one outlet introduces dangers that are not present when the inverter is supplying only one outlet/appliance. If you have an RCD installed in your van, then it will be inoperative as a safety device unless the inverter is either specifically made for the purpose or is legally altered to permit the RCD to perform its safety functions as intended. An inverter is an isolated supply device with the inherent earth fault safety that goes with such equipment, however, that safety feature is compromised once you connect more than one appliance to the inverter. This can apply even if only one appliance is in operation at the time. When the inverter is hard wired to the van wiring then the van itself effectively becomes the first appliance and so has the ability to introduce a first earth fault that will go undetected by either the RCD, the inverter overloads or the van circuit breakers. Any further earth fault in an appliance etc could cause death. If you do it, make sure it is done correctly and legally by someone who really understands the situation. Be aware also the the test button on an RCD is a mechanical test only, it does not ensure that the device will trigger on an earth fault.

oldtrack123 · Guru

brian wrote:
Be aware that hard wiring an inverter to more than one outlet introduces dangers that are not present when the inverter is supplying only one outlet/appliance. If you have an RCD installed in your van, then it will be inoperative as a safety device unless the inverter is either specifically made for the purpose or is legally altered to permit the RCD to perform its safety functions as intended. An inverter is an isolated supply device with the inherent earth fault safety that goes with such equipment, however, that safety feature is compromised once you connect more than one appliance to the inverter. This can apply even if only one appliance is in operation at the time. When the inverter is hard wired to the van wiring then the van itself effectively becomes the first appliance and so has the ability to introduce a first earth fault that will go undetected by either the RCD, the inverter overloads or the van circuit breakers. Any further earth fault in an appliance etc could cause death. If you do it, make sure it is done correctly and legally by someone who really understands the situation. Be aware also the the test button on an RCD is a mechanical test only, it does not ensure that the device will trigger on an earth fault.

HI

A BIG DITTO to that

PeterQ

oldbobsbus · Guru

Can I add my to Brians advice as well..

dorian · Guru

battery -> inverter -> RCD -> GPOs -> appliances

I can't see where the problem is with the above setup. Have I misunderstood the van wiring?

The inverter is isolated, so it is inherently safe, as has been stated.

The RCD triggers when there is an excessive difference between the currents flowing in the active and neutral circuits. As long as there is no earth leakage, then the RCD won't trigger. If the earth leakage exceeds 20mA or 30mA (?), then the RCD does its job.

If the RCD feeds all the appliances, then what difference does it make how many there are?

As for the RCD test button, why is it a "mechanical test only"? AIUI, the button connects a test component (capacitor?) between the line side of the active conductor to the load side of the neutral, thereby simulating an earth leakage. How is that any different to a real earth fault?

Here is a diagram and explanation:

http://www.crossy.co.uk/wiring/elcb.html

-- Edited by dorian on Thursday 2nd of January 2014 08:28:50 AM

brian · Guru

An attempt to answer your questions in sequence dorian. 1. An inverter is inherently safe because it is an isolated supply in that both live conductors are above earth potential, and therefore there is no reference to earth for either of those conductors. If you were to touch only one of those live conductors plus anything connected to the general mass of earth, you would receive no shock. If you were to come between both live conductors you would receive a possibly fatal shock. The problem arises where the appliance (which may be the hard wiring in the van ) has one live conductor short circuited to earth which is not necessarily the general mass of earth but can be any exposed conducting material that you may come into contact with, let's assume it's the frame of the van in this case. Because the inverter has no reference to earth, no fault will be detected. This is known in the industry as "first fault detection" Now you somehow come between the other live conductor and the frame of the van ( maybe another faulty appliance or sticking the knife in the toaster etc.), the current will now flow between the 2 conductors via your body and you will receive a shock. 2. The RCD will only trigger when it detects an imbalance between the current flow in both live conductors, this occurs when there is some leakage current to earth and this is not what is happening here. Both currents are equal as there is no leakage outside of the circuit, and the RCD will not trigger. 3. The reason that the test button is not a true indicator is exactly as you have said, it artificially tests the mechanicals of the device by creating an internal circuit imbalance between the input and output of the device, this does not test the integrity of the connected circuit. Hope this helps.

dorian · Guru

Thanks.

So what is the correct wiring setup? Would it be OK to wire one side of the inverter's output to vehicle "earth", like a MEN system?

-- Edited by dorian on Thursday 2nd of January 2014 09:52:43 AM

dorian · Guru

AISI, if the inverter is isolated, then no fault or combination of faults will ever trip the RCD. That said, if you were to touch any single part of the circuit, then you should be safe. It is only if you touch two points in the circuit that you may be hurt, but only if these two points are at sufficiently different potentials. All of the current would flow through you -- none would be diverted to earth. Therefore, AISI, the only way for a fault to generate a current imbalance would be for the inverter to be referenced to earth. So ISTM that you would have to make the inverter unsafe by defeating its inherent isolation, and then protect the circuit with an RCD. Have I got it right now?

KFT · Guru

yes dorian it appears you now understand how it works(or not) depending on the installation.

If your inverter or isolated genny(eg Honda Eu20i) is connected by means of an extension lead to the mains inlet on the van/mh then the RCD will be ineffective.

The legal solution to this issue is to have an EN junction installed in the inverter/genny WITH a built in RCD on the device (inverter/genny), you can not just instal an EN junction in the device without also installing an RCD.

hope that helps

frank

-- Edited by KFT on Thursday 2nd of January 2014 11:31:15 AM

Cricket · Member

Thanks for the advice. To put your minds at ease, I am only planning on having one PowerPoint connected to the inverter and the wiring is going to be done by a qualified electrician before I take delivery of the van.

rockylizard · Guru

KFT wrote:
yes dorian it appears you now understand how it works(or not) depending on the installation.

If your inverter or isolated genny(eg Honda Eu20i) is connected by means of an extension lead to the mains inlet on the van/mh then the RCD will be ineffective.

The legal solution to this issue is to have an EN junction installed in the inverter/genny WITH a built in RCD on the device (inverter/genny), you can not just instal an EN junction in the device without also installing an RCD.

hope that helps

frank

Gday...

I really get so lost with all the advice provided for electrical 'issues' etc on the forum. I read them slowly and sometimes more than once but still get very confused by the advice - much of which seems to be spoken in very technical, rather than lay-person, language. Trust me - it is my problem not that of the posters I would think. confuse

However, am I correct in reading the comment above (in blue) that when a generator (Honda Eu20i) is connected to the van to charge batteries as well allowing we ordinary folk to use our appliances, the RCD in the van is ineffective, therefore the van is 'unprotected/dangerous/potentially fatal' ? This is for those of us without an inverter in the van.

So this EN junction (a lay-person explanation would help as I have no knowledge of what this is confuse ) must be installed into the Honda genny along with an RCD into the genny. Does this mean Honda (and other gennys) do not have such devices as their standard configuration? and if so, why isn't it mandated to provide the "legal solution".

I again apologise for my complete lack of understanding of any of this. All I want to do is be able start the genny, plug it in to the van, charge the batteries, run the appliances,and be both legal and safe. I am sure every camper on this forum, and generally, would also like to be able to do that as well.

Cheers - John

-- Edited by rockylizard on Thursday 2nd of January 2014 12:32:25 PM

brian · Guru

At the risk of further complicating this issue, it is important to understand that a single phase isolated supply has 2 actives and no neutral. The act of connecting one of those actives to earth is what makes it a neutral. What this achieves is to make that wire the same electrical potential as the earth, and therefore the remaining active will be at the supply potential above both the neutral and the earth. "Earth" in this context does not necessarily mean the general mass of earth unless there is also an electrical connection to same by means of an earth stake or similar. Generally, in the case of an rv, the act of connecting the frame of the rv to the earth terminal of the inlet socket and to all of the other 240v outlets in the rv constitutes an earthed situation whereby a fault to earth in any appliance or even the wiring in the rv itself will cause either or both of the RCD and the overload circuit breaker to trip when on mains power provided that there is continuity of the earthing conductor from the rv to the main earthed neutral point at the supply. This is first fault detection, and is one reason for the MEN supply system that is universally used throughout the world for general power distribution. An isolated supply such as is the case with those generators and inverters that do not include a bond between one of the actives and earth, is much safer than the MEN system only so long as one only device is connected to each isolated supply. Because an isolated supply does not provide any alternative path for leakage currents to produce an out of balance situation between the 2 active conductors, a simple RCD will not trigger on either first or subsequent faults and, whilst a first fault will not be dangerous, subsequent faults may well prove fatal. Please note that multiple faults between the same active conductor and earth still do not present a shock hazard and that a shock hazard only exists when earth faults exist in both active conductors, an overload device will normally trigger when both faults are in different active conductors and there is electrical continuity between the exposed metal of both appliances, ie. a class one appliance with an earth wire in the lead. Normally, smaller generators and inverters are maintained as isolated supplies due to their greater safety, but this safety is lost once multiple appliances are in use. When they are required to supply multiple appliances, then the bond and RCD are required for continued safety. Current wiring rules require that this bond and the RCD be an integral part of the generator or inverter to prevent inadvertent use of the device without such protection.

dorian · Guru

Thanks for the additional clarification, KFT.

When you refer to installing an EN junction and RCD in the device, are you permitted to add these components externally in such a way that they can be detached, or must they be hardwired internally?

As for the second RCD, is this just a legal requirement rather than a practical one? I mean, if there is an RCD in the van, do you really need a second one on/in the inverter for safety reasons, or is this legal requirement just there to ensure that there is at least one RCD downstream from the inverter?

BTW, the term "mechanical test" is ambiguous, IMO. AFAICS, the test button is a complete mechanical and electrical test of the RCD. If the RCD trips when the button is pushed, then it is fully functional. The original implication, as I interpreted it, was that there was some distinction between the way that the RCD responded to an internally generated current imbalance as opposed to an external one. That's why I took issue with that statement.

That said, ISTR that my electrician friend tested each GPO with some kind of home-made tester after installing our RCD/breaker. My memory is hazy, and I never asked him what was inside (or perhaps I did, but he didn't know), so I'm wondering how other electricians test their work. Could it be as simple as connecting a string of resistors, or a capacitor, between active and earth? If so, what test current would they normally use? Would it be 30mA, 20mA?

oldtrack123 · Guru

dorian wrote:
Thanks.
So what is the correct wiring setup? Would it be OK to wire one side of the inverter's output to vehicle "earth", like a MEN system?

HI Dorian
A responsable Electrician will not give you the Answers to that question on an open forum
Amatuers playing with 240 v can be deadly

It is not as simple as some may believe
The Standards SPECIFY HOW IT SHALL BE DONE

Brian's posts are spot on, but a sound knowledge of electrics may be required for some to understand the possible problems

AND required wiring methods & CONSEQUENCES OF DOING IT WRONG

Re the risks of multiple Clas 1 devices being connected[[Remembering that if connected via the van inlet socket ,the van itself is a Class1 device]

If permantly wired into the vans existing wiring ,Special requirements are needed to ensure :

no risk of back feeds or possible exposed live parts [inlet socket]

A fully operational RCD,

Correct earhing methods

COMPLETE isolation of the inverter output lines]from the VAN'S mains wiring when the inverter is not in use mains

PeterQ

brian · Guru

1. You are not permitted to add the bond or the RCD external to the generator or the inverter in such a manner as to allow it to be removed ad hoc, ie. it must be permanently installer either in or on the device. 2. The RCD is intended to protect everything downstream from the inverter, there is no legal requirement for a second one, however, it is a practical matter to leave the main ones in place and simply feed the inverter supply through them. 3. The test button is recognised as a mechanical only test, if you wish to call it something else, then that is your choice. It is not the same as ensuring that the device is fully functional on the connected circuits as it only tests the operation between both active conductors by creating an imbalance situation between the input and output. If you require further evidence, try connecting an isolated inverter to an RCD and then connect a 240v light globe between active and earth at one of the power points. The RCD will not trip. Now press the test button and the device will trip. This proves the point.

KFT · Guru

Hi Dorian,

sorry I could have explained that a little clearer than I did,

If an EN junction is installed in a device it MUST have an RCD installed to the device, removable is not an option. This is to ensure that if the unit with the EN junction is used to power something other than the van/mh it is providing RCD protection. Normally the EN junction would be connected at the RCD when it is installed.

The test button only tests the RCD function at the device to ensure it will trip. It does this by adding a predetermined earth leakage value across the RCD. A sparky should trip test each and every outlet connected on the circuit to ensure they are all protected. A tester usually can perform several tests eg, non trip test at half rated leakage current, fast trip at double rated trip current and a normal test at rated trip current and all at either 0 or 180 degrees of the sine waveform.

There is a "second" RCD in modern vans/mh as a legal requirement for those times when you may be connected to non RCD protected mains power.

hope that helps

frank

rockylizard · Guru

Gday...

Firstly, thanks Brian, KFT, Dorian (I think), oldtrack123 for all the words of description - but I guess I didn't ask my question very well.

I do try to understand the jargon and technical 'explanations' provided so far but they may as well be written in Greek cry . Sorry.

My question evolved from this statement - when an "isolated genny (eg Honda Eu20i) is connected by means of an extension lead to the mains inlet on the van/mh then the RCD will be ineffective".

And my question is - "when a generator (eg Honda Eu20i) is connected to the van to charge batteries and to use our appliances, does this make the RCD in the van ineffective, therefore making the van 'unprotected/dangerous/potentially fatal' ? I don't have an inverter in the van."

If that is so, then is the "legal solution" - "an EN junction must be installed into the Honda genny along with an RCD into the genny." ??

I also have no idea what an EN Junction is. hmm

What I am trying to determine is whether attaching a generator (such as the Honda Eu20i) to the van with an extension cord is illegal/unsafe/potentially dangerous without the addition of an EN junction and an RCD dedicated and installed on the generator. Is this so? If so, does that mean I need to get my generator to a qualified, authorised sparkie to have this rectified and have an EN junction and RCD installed?

Again, sorry to be ask what are dumb questions, but I am really trying to understand advice that is confusing.

Cheers - John

brian · Guru

When a generator that does not have a fitted RCD is connected to the power inlet on your van, the internal van RCD will be inoperative. If you are going to connect the generator in this manner and want maximum available protection from electric shock, then you should have an RCD fitted to the generator. As I said earlier, an isolated supply has 2 active conductors, no neutral. The neutral is created by connecting one active to the earth. This connection is known as the earth neutral (EN) bridge or en bond. It is different from another bond known as an equipotential bond which is generally used to connect the exposed metal of different pieces of equipment together in order to prevent a potential difference from existing between them and so presenting a shock danger. It is potentially dangerous to connect the generator in this fashion, I am unsure as to the legality of doing so and oldtrack should be able to give you this information. The level of danger is relatively low as 2 very specific types of fault need to be in place simultaneously to present a danger, but it does exist. If you can connect your generator to just one appliance at a time, the danger is removed

rockylizard · Guru

brian wrote:
When a generator that does not have a fitted RCD is connected to the power inlet on your van, the internal van RCD will be inoperative.
So, does the Honda Eu20i generator have a fitted RCD? I am unable to confirm if this is so. If not then the RCD in the van, as you say, is inoperative.
If you are going to connect the generator in this manner and want maximum available protection from electric shock, then you should have an RCD fitted to the generator.
I therefore assume that connecting "in this manner" is using an extension lead, and does not provide sufficient protection?
As I said earlier, an isolated supply has 2 active conductors, no neutral. The neutral is created by connecting one active to the earth. This connection is known as the earth neutral (EN) bridge or en bond. It is different from another bond known as an equipotential bond which is generally used to connect the exposed metal of different pieces of equipment together in order to prevent a potential difference from existing between them and so presenting a shock danger.
I am sure there are many who understand what you have said in the para above, but it means nothing to me - neither should it, I guess, as I am not an electrician.
It is potentially dangerous to connect the generator in this fashion,
So, unless the Honda Eu20i generator has an RCD (and the earth neutral bridge) already installed, then many (most? all?) caravaners are in potential danger?
I am unsure as to the legality of doing so and oldtrack should be able to give you this information.
Hopefully oldtrack will come on and provide advice on whether a standard Honda Eu20i generator is therefore able to be legally connected to a caravan by an extension cord.
The level of danger is relatively low as 2 very specific types of fault need to be in place simultaneously to present a danger, but it does exist. If you can connect your generator to just one appliance at a time, the danger is removed
However, from advice provided previously, the CARAVAN is "an appliance" in this instance and therefore no other 'appliances' should be connected - eg the kettle, microwave etc.
I am beginning to get very apprehensive about using the generator now as, unless it has its own dedicated Earth Neutral Bridge AND its own RCD, all users of generators are placing themselves in dangerous situations.
Cheers - John

dorian · Guru

Thanks again, KFT. That answers all my questions ... I think.

To Brian, take an RCD, switch off the AC power, and then press the test button. What happens? The answer is, absolutely nothing. That's because the RCD's mechanical bits are dependent on the RCD's electrical bits. In other words, the RCD is an electromechanical device, so IMO it makes absolutely no sense to refer to a self-test as a "mechanical test only".

BTW, I do know how an RCD or ELCB works. That's quite straighforward. I'm just not familiar with the wiring rules (for this reason they should be made publicly available, to everyone, and for free), and it didn't occur to me to consider a situation with two faulty appliances, but all those questions have now been answered.

KFT · Guru

rockylizard wrote:
Gday...
Firstly, thanks Brian, KFT, Dorian (I think), oldtrack123 for all the words of description - but I guess I didn't ask my question very well.
I do try to understand the jargon and technical 'explanations' provided so far but they may as well be written in Greek . Sorry.
My question evolved from this statement - when an "isolated genny (eg Honda Eu20i) is connected by means of an extension lead to the mains inlet on the van/mh then the RCD will be ineffective".
And my question is - "when a generator (eg Honda Eu20i) is connected to the van to charge batteries and to use our appliances, does this make the RCD in the van ineffective, therefore making the van 'unprotected/dangerous/potentially fatal' ? I don't have an inverter in the van."
If that is so, then is the "legal solution" - "an EN junction must be installed into the Honda genny along with an RCD into the genny." ??
I also have no idea what an EN Junction is.
What I am trying to determine is whether attaching a generator (such as the Honda Eu20i) to the van with an extension cord is illegal/unsafe/potentially dangerous without the addition of an EN junction and an RCD dedicated and installed on the generator. Is this so? If so, does that mean I need to get my generator to a qualified, authorised sparkie to have this rectified and have an EN junction and RCD installed?
Again, sorry to be ask what are dumb questions, but I am really trying to understand advice that is confusing.
Cheers - John

No worries, a Honda Eu20i genny is the same as an inverter(except it is petrol motor driven rather than battery supplied)

YES get an EN junction installed with an RCD on the genny and you will be covered.

as it is attaching your genny to the van/mh inlet could become dangerous so better to get it modified.

hope that helps John if not get back to me, happy to keep changing the way I explain it until it becomes clear to you for safety's sake.

frank

-- Edited by KFT on Thursday 2nd of January 2014 05:48:33 PM

brian · Guru

Taking you points in order. 1. The Honda in question did not have an RCD fitted as standard, but I have heard that they are now available in that format, you would have to check that. 2. Connecting to the van inlet essentially makes the van an appliance and therefore any further connection to an internal device becomes a second appliance. 3. You asked what an EN connection was, and I have told you here. 4. The potential danger only exists if you connect your charger etc. via the van inlet, if you connect directly to the charger then the danger is minimised. 5. I expect that oldtrack will have that knowledge as he follows the regulations pretty closely. 6. The van does become the first appliance, and as I said, whilst the danger is fairly remote, it does exist, and it would be remiss of me to ignore this fact, or to advise you differently. You make your own choices, hopefully based on a clear understanding of the risks involved. 7. Provided you connect the generator sans RCD directly to the one appliance, it is safer to use than having the en link and an RCD fitted to said generator. I will be unable to add further to this thread for a while as I am about to board my flight home from Canada.

D and D · Guru

I have given up trying to understand how electricity works. I've had numerous sparkies and engineers try to explain it to me but my eyes glaze over, my head spins and I fall off the chair and make a total fool of myself. I don't trust electricity, you can't see it, you can't smell it, you can't hear it (usually) then it kills you. There is a reason God invented electricians - just find one you trust and leave it to them.

oldbobsbus · Guru

OK I will try to put it a little more plain....

WTF is an EN....

and a RCD...

rockylizard · Guru

Gday...

Thanks again to all you patient sparkies who have tried to enlighten me on whether it is safe/legal to use a Honda Eu20i generator to charge/power my caravan through an extension lead connecting the generator to the power inlet on the caravan and to then use the appliances within the caravan.

I no longer know whether I can or not. I seem to need to have an authorised, qualified electrician modify the generator or I am at risk of either creating a potential dangerous electrical situation or in being illegal electrically.

I guess the only real solution is to approach a qualified, authorisied electrician for the final answer.

I do understand that it is not possible for a responsible electrician to give detailed answers on an open forum.

Again, thanks for trying. I will cease using the generator until I have sought personal electrician advice to ensure both my, and the van's, safety.

Cheers - John

-- Edited by rockylizard on Thursday 2nd of January 2014 07:17:35 PM

native pepper · Senior Member

oldbobsbus wrote:
OK I will try to put it a little more plain....

WTF is an EN....

and a RCD...

An RCD is a residual current devise, in other words it disconnects when there is an unbalanced current in the system, or an energy leak. In plain English, they stop you from being electrocuted.

Don't know what an EN is, maybe a neutral conductor to assist the RCD. Not that tech savvy, but try to get my head around it enough to understand what it means in real terms, which to my mind, is the most important thing.

KFT · Guru

Ok, if you can accept that an isolated supply consists of two live wires that have no reference to "earth" and all Eu20i gennies are like this as are most inverters.

A domestic M.E.N. supply has the Neutral-(one of the live wires) bonded to "earth" at each residence/installation.

An RCD works if there is an imbalance in the two live wires caused by a leakage to "earth" this leakage could be you touching a faulty "earthed" appliance and the RCD detects this and trips before you even feel the "shock"

An EN junction is similar to the M.E.N. system in that we bond the "neutral"(one of the live wires) to "earth"(frame of genset/inverter) so the RCD can see any leakages and trip before you feel the shock. Doing this does NOT cause the genny or inverter to become "live"

the EN junction must be done at the source of the power(genset/inverter) and in case your van/mh does not have an RCD the EN bonding MUST be done in conjunction with the installation of an RCD on the power source(genset/inverter) in order to be an effective protective device.

I hope this helps people with no understanding of electricity see how it works.

if not please say so and I will try to phrase it in simpler terms that may help you understand.

remember that any of this type of modification MUST only be carried out by a licenced electrician and the genny/inverter marked to indicate an EN junction is installed.

frank

-- Edited by KFT on Thursday 2nd of January 2014 08:12:22 PM

oldtrack123 · Guru

A
Hi
All of what Brian & Frank have said
And in answer to the question regarding the RCD location

Rules are CLEAR
A non isolated inverter or generator SHALL have A RCD PERMANENTLY FIXED & PERMANENTLY wired in .
It cannot be remote
It cannot be a plug in type / RCD protectd power box

PeterQ

-- Edited by oldtrack123 on Thursday 2nd of January 2014 09:13:13 PM

Peter_n_Margaret · Guru

The next problem, of course, is that many licensed electricians are not familiar with either the regulations, as they apply to transportable structures, or the work that needs to be carried out.

The field is huge, and like most medical people, sparkies tend to specialise and stay up to date in particular areas where they do most of their work.
You need to find the right sparky.
No point going to a brain surgeon for a broken leg.

Cheers,
Peter