Inverter installation

to all you techno heads out there, I wish for some wisdom,and maybe a lot of knowledge. I am installing an inverter pure sine wave into the van primarily to run the lap top and the digital t.v. on the instructions for installation it says that it has to be earthed, now I am putting in the boot of the caravan,I know it has to be mounted on a flat surface, hence putting in a shelf to mount it on the question is if it is mounted on a wooden surface would I have to run the earth wire down onto the chassis of the van or can I just attach it to the metal[tin] inside casing of the boot which is surrounded by ply wood, would that prohibit the earthing of the inverter any help would be greatly appreciated
Broodie H3
Broodie H3
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Reply By: Ross M - Tuesday, May 08, 2012 at 21:44

Tuesday, May 08, 2012 at 21:44
G'day Broodie

There are lots of people with different views on inverter use and connections.

Are you going to use the output direct to the laptop or tv?
To run the laptop, the most efficient use of the 12v is to run the laptop from a DC to DC converter, around $60-$70 from Jaycar.
Doing this will use less AH out of your battery than the double loss conversion of the inverter to laptop switchmode supply and back to 19vdc.

Inverters are electrically isolated and in normal use the is little danger.
If you are earthing the case to the van, then the isolation of the inverter is still ok but if dust ingested into the inverter and moisture is also present the electrical isolation may not be so isolated.

If this situation occurs then any abnormal contact with the 240v from the inverter, normally isolated from you, can pass current through anyone in the least path of electrical resistance.
If your van has a safety switch you can pass the current from the inverter through this to the devices you power up and it will provide an extra level of safety.
Generally no problem with using an inverter but if you have it earthed to the van then make it as safe as you can.
You will have to test if the inverter mounting area is or isn't earthed to the van earth pin with a multimeter.

Ross M
AnswerID: 485311

Follow Up By: Dennis Ellery - Tuesday, May 08, 2012 at 22:07

Tuesday, May 08, 2012 at 22:07
Ross M - you stated;
"If your van has a safety switch you can pass the current from the inverter through this to the devices you power up and it will provide an extra level of safety"

This sort of advice shouldn't be followed - the ELB won't function correctly in this situation.
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Follow Up By: Ross M - Wednesday, May 09, 2012 at 18:29

Wednesday, May 09, 2012 at 18:29
An inverter is usually used in less than ideal conditions.
Condensation can/will form in an inverter, the fan pulls in dust and this can become conductive at 240v level.
If the case is earthed to the van chassis the unit can kill you when a fault is present and the conduction to the vans chassis is through a human.
If the power is fed through an RCD/ safety switch it can't be less safe and in less than ideal conditions as above it will detect the leakage and switch off as it does in a home situation.
Having had a shock from a "totally isolated inverter supplying a faulty/dusty TV in a coach/bus, a safety switch would have activated.
Obviously people don't think this can occur and totally trust a fully isolated inverter.
I don't totally trust them and yes I do use them, with respect and use an RCD where needed for safety. An RCD won't decrease the safety so I think the advice is valid.
If your not sure, try it out on yourself and see.

Ross M
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Follow Up By: Dennis Ellery - Wednesday, May 09, 2012 at 20:38

Wednesday, May 09, 2012 at 20:38
Ross your electrical knowlege leaves something to be desired - unless you are a qualified and licensed electrician you shouldn’t be giving this advice.
In the unlikely event that you are an electrician - you need to update your knowledge by taking a unit in the appropriate course at a government authorised technical college or maybe locate an engineer with qualifications in this area and seek his advice.
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Follow Up By: skeeterau - Wednesday, May 09, 2012 at 21:04

Wednesday, May 09, 2012 at 21:04
I am no expert on this but I don't think the RCD/ safety switch will work properly unless the van is properly earthed and that means it plugged into an earth power stand like at a caravan park. You will notice when you don't have power and run a generator- the generator should be only used with its earth in place. (stake into the ground)
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Follow Up By: Dennis Ellery - Wednesday, May 09, 2012 at 21:49

Wednesday, May 09, 2012 at 21:49
Skeeterau - don't worry about the earth stake on your genset - it still won't make the RCD operate.
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Follow Up By: The Bantam - Wednesday, May 09, 2012 at 23:13

Wednesday, May 09, 2012 at 23:13
Again further to the issue.

The australian standard specificaly forbids the earthing of all protable 240v supply devices, that includes inverers and generators.

DO NOT drive an earth stake for your generator.....it is safer as a floating supply.

If your generator is connected to and "electrical installation" it will be earthed as well as the installation permits via the earth pin on the 3 pin plug

Even if you can drive and connect a functional earth stake, you can not ensure that everything else, including every metal tent pole, table, chair and even the damp canvas of the tent is properly bonded.

In our homes and businesses the electrical system and in particular the earth is very stiffly specified and regulated, that includes every conductive surface in the building....once we are away from the grid or outdoors all bets are off.

AND you can not depend on your earth leakage circuit breaker.

cheers

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Follow Up By: Ross M - Thursday, May 10, 2012 at 12:17

Thursday, May 10, 2012 at 12:17
Be careful with the advice from an electrician as many only comment on the inverter use from the totally clean/uncontaminated ideal.

Point out to your advising electrician that the inverter may ingest dust and also have moisture present which will possibly conduct via a fault back to the generating source.
Quiz him/her to see what there opinion is. Some will have no idea and others might be insightful to the situation and advice differently to other electricians.

The whole idea of my comment is because an inverter does get dirty inside it IS NOT therefore isolated anymore. A point totally missed by some.
The dirty inverter will kill you as one of the posters mentioned.

The advice of using a RCD in no way decreases your level of safety, another point missed by some.
Ross M
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Follow Up By: Dennis Ellery - Thursday, May 10, 2012 at 12:39

Thursday, May 10, 2012 at 12:39
Ross I think my reply is going to be a waste of time, but here goes again.
Your following comments are misleading and are technically incorrect.
“will detect the leakage and switch off as it does in a home situation”.
“Having had a shock from a totally isolated inverter supplying a faulty/dusty TV in a coach/bus, a safety switch would have activated”
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Follow Up By: The Bantam - Thursday, May 10, 2012 at 12:42

Thursday, May 10, 2012 at 12:42
Dirt and moisture are two issues that are very commonly ignored in camping and caravanning associated with 240v supply.

The boot of a van may seem to be a clean dry place.....but as soon as the door or lid is open it is not it becomes a wet area just like your bathroom.

That is even if the lid or door seals......who has a caravan that does not leak......um any body.

cheers
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Follow Up By: oldtrack123 - Saturday, May 12, 2012 at 11:38

Saturday, May 12, 2012 at 11:38
Hi

In a strange way all three of the above are correct
[1] A RCD is useless with a Fully isolated inverter[D.E]
[2] If an inverter develops an internal fault [leakage] it may no longer be fully isolated & a RCD could offer some protection[R]
[3]Bantam has summed it up pretty well

No one should take it for granted that a fully isolated inverter is safe.

To minimize risk the SAFETY "RECOMMENDATION "is :
DO NOT CONNECT MORE THAN ONE CLASS 1 device AT ANY TIME
You may connect multiple class 2 devise with a reasonable high level of safety

NOTE
Class 1 devices have 3pin plugs
Class 2 normally have 2 pin plugs but may have 3 pin plugs

Peter
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Reply By: ABR - SIDEWINDER - Tuesday, May 08, 2012 at 21:46

Tuesday, May 08, 2012 at 21:46
There should be a small earth screw on the inverter, this should be earthed to the chassis.

Regards

Derek from ABR
AnswerID: 485312

Follow Up By: Member - Broodie H3 - Wednesday, May 09, 2012 at 01:32

Wednesday, May 09, 2012 at 01:32
yes there is a small wing nut on the inverter, for the earth wire, and the recommendation is to keep the earth wire as short as possible, and if I run it to the chassis. I will need at least a meter of 8 wire minimum, would that cause a problem with earthing?
Broodie H3
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Follow Up By: ABR - SIDEWINDER - Wednesday, May 09, 2012 at 07:47

Wednesday, May 09, 2012 at 07:47
1m is fine and as stated the inverter should not be in the same location as explosive gasses.

Regards

Derek
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Follow Up By: oldtrack123 - Saturday, May 12, 2012 at 11:48

Saturday, May 12, 2012 at 11:48
Hi

There is no requirement to earth the inverter to the chassis, & as pointed out by Bantam ,they should NEVER be deliberately connected to the general mass of earth by earth stake or other means

BUT they can emit high frequency interference , this can be minimized by using the SHORTEST possible heavy earth strap between case & chassis.

Peter
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Reply By: Ozhumvee - Tuesday, May 08, 2012 at 21:57

Tuesday, May 08, 2012 at 21:57
If you are intending to hardwire it so that the power points etc in the van will work off the inverter then it has to be done by a licensed electrician.
If you are going to plug the appliances directly into the inverter then you should earth it as Derek advised.
I hope that the gas bottles and/or batteries are not in the boot as well? If they are then there is a large risk of explosion if either the batteries gas when on charge or there is an LPG leak.
There should never be a possible ignition source in the same compartment as batteries, gas or fuel.
Peter
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Follow Up By: Member - Broodie H3 - Wednesday, May 09, 2012 at 01:25

Wednesday, May 09, 2012 at 01:25
thanks for the info fellas I think I shall call the sparkies to come and do the job . Then if it fials I can blame some one else, and O.S.W.M.B.O. can NOT blame me. Both the gas bottles and the batteries are in the boot and I have no where to move them too. So now to call the sparkies in for another grand appearance. once agian to you all for the advice
Broodie H3
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Reply By: The Bantam - Wednesday, May 09, 2012 at 13:19

Wednesday, May 09, 2012 at 13:19
Sorry chaps but unless you are a licenced electrician, you should make no attempt to earth your inverter.

The current version of AS3000 "Australian elecrical wiring rules" specificaly forbids earting of portable sources of supply unless they are part of a permanent installation....the reasoning is complex but sound.

If you are hard wiring and it is a permanent installation it should be done by an electrician.

If you are connecting via a 3 pin plug and cord, the earth connection to an existing installation will be provided by the earth pin in the 3 pin plug.

I will argue that unless hard wired and installed by an electrician the inverter should be mounted on an insulating block.

The existing 240V electrical system in the van should have a compliant earth bond done the correct way.

Please do a search on inverters, there has been a lot said and recently

Theseinverters are little portable boxes of death, they and the 240V supply that comes from them requires far more care than that supplied by the grid conneted stuff at home.
AND
Depending on the situation the earth leakage breaker my provide little or no protection.

cheers
AnswerID: 485350

Follow Up By: Dennis Ellery - Wednesday, May 09, 2012 at 20:44

Wednesday, May 09, 2012 at 20:44
Bantam you suprise me.
I agree with you on most of what you've said.
Not all - but hey! nobody's perfect
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Follow Up By: The Bantam - Wednesday, May 09, 2012 at 23:03

Wednesday, May 09, 2012 at 23:03
Brother thats probaly because we are singin' from the same hymnal.

Even in the best chiors there are disagreements on harmony even though the song remains the same.

cheers
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Follow Up By: Member - bungarra (WA) - Thursday, May 10, 2012 at 10:19

Thursday, May 10, 2012 at 10:19
Hi Bantam / Dennis

"If you are connecting via a 3 pin plug and cord, the earth connection to an existing installation will be provided by the earth pin in the 3 pin plug."

re your quote above..........by "an existing installation" does this mean an appliance?

I would appreciate comments on the safety aspect of my setup

My Scenerio

1... Inverter mounted in the caravan boot, the inverter mounting holes are in the chassis of the inverter and have been utilised to screw the inverter onto the internal head wall of the boot (metal construction)....no dedicated earthing of the inverter onto the caravan....no isolation between the inverter body and the metal head wall.............the inverter is only activated when needed via its own circuit switch

2) All simply used as an extension lead principle (the "extension lead" actually is a 3 core cable extension lead (placed inside the 'van wall during construction)...... a 3 pin plug at the inverter end from the GPO of the inverter feeding a dedicated wall mounted hard wired GPO within the van)...simply for neatness and keeping all cables out from under feet etc........I saw no difference between this principle and a 3 plin plug/socket on an extension lead
3) By existing installation does this mean / include portable appliances such as microwave, printer, kettle, computer etc......be they 2 or three pin?

Thanks

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Follow Up By: The Bantam - Thursday, May 10, 2012 at 12:32

Thursday, May 10, 2012 at 12:32
Firstly and bluntly, this is a typical, noncompliant permanent installation....frankly illegal....definitely presents unnecessary dangers.

I am not up with the specific current provisions of the caravan wiring standard Its been a while since I read it BUT.

It is generally not considered compliant to simply have a piece of flex with a plug on it disappering into a wall cavity in any installation.....noncompliance 1.

This power point, is it double pole switched..bet it isn't..noncompliance 2

Is there any circuit proterction fuses, breakers fitted to the installation..bet there isn't...noncompliance 3

This extension cord and powerpoint, is the earth circuit in this arrangement bonded to a central earth and to the metal chasis of the van....bet it isn't...noncompliance 4

If you pass an extension cord thu a hole in a wall, that hole must be big enough to allow the plugs to pass thu, or it ceases to be an extension cord in the eyes on the standards and the law, as it is no longer portable and would have required "electrical work" to be put there.

As soon as there is a power point screwed to a wall, there is an implied expectation of permanence and compliance with safety needs.
Most people will look at it and say.."its a power point" and think no more of it and treat it just like at home.

The inverter may be screwed to a metal bulkhead, but we can not be sure that the metal bulkhead and all other metal in the caravan is bonded to a central earth and also to the chasis of the van.
Neither can we be sure that the connection between the metal body of the inverter and the metal pannel is adequate or reliable.

Appliances.....that is any portable item that is conected by a 3 pin plug and cord are not part of an installation.

The above is just a quick assessment of the situation.....let me look directly at the installation and put a few standards in my hand and I could get a hell of a lot more picky.

One other issue that may or may not be mentioned in the standards BUT is a safety issue is having a source of electrical supply switched from a location not accessable from its place of use...IE the inverter in the boot.

Frankly there are two options.
1 is to use the inverter as a portable device ( my preference) or to mount it on an insulating block inside the van close to the item being supplied...this requires no licence.

2 is to have the system installed properly by someone who knows the specific regs and issues involved.......your best option.....this requires a licenced electrician.

cheers

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Follow Up By: Member - bungarra (WA) - Thursday, May 10, 2012 at 14:48

Thursday, May 10, 2012 at 14:48
Hi Bantam

Thanks for that info......unfortunately I have described my installation is exactly as it was supplied in a NEW caravan..........

It is not my work but as supplied at delivery......I would assume that the electrical contractor woould have done it all correctly....

but then on the other hand the 240v sparky may have done his side of things....and the 12v installer...done his (including the inverter)...they were different contractors and I believe the 12v man was responsible for the inverter side of things

The inverter is swithced on /off from inside the caravan.

Things I can and will do ASAAP

1) install GPO Double pole switched
2) Mount the inverter on an insulated board

Thanks for your input




looks like a conversation coming up with the manufacturer for some clarification.
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Follow Up By: The Bantam - Thursday, May 10, 2012 at 16:12

Thursday, May 10, 2012 at 16:12
As many of us will be well aware, there are many things done on caravans that are not compliant..........yes and straight from the factory.

OH yes and indeed some of them will have been done by licenced full ticket electricians......hmmm but why would a properly trained person do such things......HMMM one may well ask

Perhaps, because, in my belief a very large portion of electrical installation work in caravans is carried out by the unlicenced.....

OH BTW........how many people got a "certificate of test" with their new van.......signed by a licenced electrician with his or her full name, address and licence number on it, certifying that the electrical work was done by a licenced person, it complied with austalian standards and was in fact tested according to the requirements of the standards.

Hmmm....I don't see many hands.

I cant comment about other states, but in QLD all eletrical workers are required to issue a certificate of test in relation to any and all electrical work they do....even if it is just putting a plug on a cord or changing a jug element.

Actually if you realy want to get narky over the whole thing and push the letter of the law....screwing an inverter to the wall is electricians work.

Because it is installing a 240v electrical item and should involve work on the "earthing system"...either ensuring that it is corretly earthed or is corretly insulated.

Sorry but there is a great deal more to this whole inverter thing that most people want to know.

cheers

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Follow Up By: oldtrack123 - Saturday, May 12, 2012 at 11:56

Saturday, May 12, 2012 at 11:56
Hi Bantam

Double ,double ditto to all your above posts
The message may get through in time

Peter
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Follow Up By: oldtrack123 - Saturday, May 12, 2012 at 12:06

Saturday, May 12, 2012 at 12:06
Hi
While the "related article "inverters ' top right corner has @ last been updated a some seriously incorrect advise has been corrected it still has one serious error

"Safety Switches will only protect against electrocution to earth if you connect the Earth Terminal on the Inverter to an earthing rod that has a good earth connection - a rod into dry sand is useless.
"
AS pointed out

the Standards for the use of portable inverters AND generators specifically says" AN EARTH STAKE IS NEITHER REQUIRED OR RECOMMENDED

Peter
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