A purely academic response as PeterQ made a reference earlier that there can be no 'neutral' without an earth connection. I understand the concept of calling a connection at earth potential neutral (with respect to earth) which is logical. However, I also accept the concept where we adopt nomenclature to indicate that one source is at a potential difference from another. The idea of naming any two sources with a potential difference between them and where they are totally isolated from any other source as 'active' is illogical. In my opinion, it would be the same as marking both battery terminals 'positive'. But once again, I accept that things change and my ideas are probably very outdated - like me.
HI Chris
You will not find a "neutral" in any reputable articles on "Isolated supplies"
They are simply referred to as L1 & L2 & both are consider as being ACTIVES,LIVE, even the Standards use that terminolgy!! see Switching required AS/NZS 3000 cl 7 Electrical isolation .
In fact Cl 7 should be read by ALL who believe it is simple to have an "isolated supply " mixed in a van etc which has mains power wiring
Cl 7, 4.4 states "switching SHALL operate in all LIVE conductors it then in fig77.7 shows DOUBLE POLE switching
Earth and neutral are two different circuits .. Earth is mainly for safety.. Don't rely on safety devices alone..
If you get between an open point neutral and earth .. With appliances on .. It's potential is active..
It WILL kill you no problem? There's. No MEN on RCD protected circuites..
Take this as a comment from me having no formal qualifications electrically but some experience in associated areas. Note referring to off grid use.
I thought the reason for not having more than one class 1 appliance plugged in was this. If there was a fault to earth in the appliance switched on, then the voltage on the earth would be transferred to all the other appliances that are plugged in and the chassies would be live on all of them. Having no external earth it would not trip a breaker. That is a very dangerous situation.
So my understanding is that all other appliances should be unplugged not just switched off to comply.
If you ever plug your van into a generator (or inverter) your RCD will not work and risks of electrocution are possible.
An RVD will provide additional protection.
Available at www.safelec.com.au
If you have specific questions about the product, email Ian (the developer) at info@powersafe.com.au He provides exceptional product support.
It is almost pointless talking to most electricians about this as their knowledge or floating systems is usually negligible, unfortunately.
Take this as a comment from me having no formal qualifications electrically but some experience in associated areas. Note referring to off grid use.
I thought the reason for not having more than one class 1 appliance plugged in was this. If there was a fault to earth in the appliance switched on, then the voltage on the earth would be transferred to all the other appliances that are plugged in and the chassies would be live on all of them. Having no external earth it would not trip a breaker. That is a very dangerous situation.
So my understanding is that all other appliances should be unplugged not just switched off to comply.
Jaahn
Hi Jaahn
The fault to earth in Appiance #1 only creates an EN system
With the other appliances it would be no different to what you have at home except it is only an EN system not a M.E.N system
The Frame of all plugged in Will still be at earth potential
Remember double pole switching SHALL be used with isolated supplies & In Aus ALL "Transportable structures SHALL have DP switching
Its interesting to read some of the posts on this subject.
[1]From memory, there will be a slight shock for up to 30mS (at full current) before the RCD trips. IF and only IF the person receiving the shock is in a bad state of health (eg. bad heart) and the path the current takes through the body will determine the outcome of that event.
[2]1]In conclusion, RCDs and RVDs will protect life in the majority of cases, however there will be individuals in bad health who MAY suffer badly or become deceased. In the most cases these devices have saved lives and will continue to do so thank goodness.
[3]Im not sure I agree with the definition of class one and class two appliances, I have seen many class two appliances with 3 pins (earth not connected) the correct definition is the square within square located on the appliance body (AS/NZS 3760:200?)) I believe they stopped producing 2 pins for double insulated devices as manufacturers had returns with the complaint that there were only 2 pins on the plug (conjecture).
Again this is an interesting thread, I wish you all the compliments of the season.
The Crocks
-- Edited by Crockie on Monday 22nd of December 2014 06:31:49 PM
Hi
[1]
30ms is the max time the RCD should take to trip @ its rated trip current
Anyone doing a proper test has to esure they perform to That requirement
[2]
THe actual curent that can be wihtstood with out serious harm does depend on age & health
OLD persons,the unhealthy & yes, those with heart problems, &very young children are at higher risk
For healthy persons,RCDs that trip @ no more than 40ms at rated current are used
RCDs rate @30mA are the normal one used in domestic situations
But in high risk areas , hospitals, old age homes ,ambulances & similar Lower current rated RCDs are used down as low as 10mA trip current & still within 40ms,
In some situation 100mA or even higher may be required to avoid nuisance tripping
due to known high leakage standing currents
Problems that I encountered way back when ELCbs first came onto the market [ late 50s early 60s]
[3]I think you will find that factory fitted plugs to class 2 products will generally be 2 pin.
I see good reasons to remove 2pins from the open market
One being a DIYer buys one then fits it to a class1 device & just leave the earth disconnected
they are still listed in the AUS standards, As is required even when FACTORY fitted
PeterQ
-- Edited by oldtrack123 on Tuesday 23rd of December 2014 03:11:43 PM
-- Edited by oldtrack123 on Wednesday 24th of December 2014 12:31:35 AM
I did a stint at camalec (pirelli erricson) years ago as the quality manager in the cable factory. We kept getting a number of returns from retailers withe the complaint that customers thought there was a pin missing, so we stopped making the two pin plugs for class 2 products.
Thanks you for correcting my mistake I thought the authorities had withdrawn 2 pin plugs. I agree it will confuse the novices who go to Bunnings and get the goodies to construct their own (now that does boil my blood, very dangerous practice).
I think the worst case of DIY I had ever come across was an "extension lead" that was made from figure 8 lamp wire (about 7.5 amp) with a 3 pin plug on one end and a 3 pin socket on the other. Of course fig 8 is only 2 core and has no sheath.
from memory this lead was about 15m long and used to run power to the shed for power tools which back then were all metal cased.
The bloke near had apoplexy when I cut it up. I did offer to make him a proper one and that calmed him down.
You see some real shockers from DIY. And I mean that literally.
frank
-- Edited by KFT on Tuesday 23rd of December 2014 04:40:33 PM
__________________
Avagreatday.
Kathy and Frank currently at Home near Quirindi NSW
I was in Bunnings buying some stuff one day and saw this guy rolling out a lot of 2.5mm sq tps. He had a handful of switch mechs and plates and baton holders.
He saw I had some electrical stuff in my trolley and asked me how he needs to wire up some lamps for his spare room. When I suggested he looks in the yellow pages under electrical contractors he got rather stoppy and said to me I only asked you a simple question. I looked him in the eyes and told him his look in the yellow pages may save him from goal or the cemetery.
It's very handy to have Bunnings if you need something in a hurry or L and H are too far away, just an aside in my whole electrical career I have only been asked ONCE for my licence when I purchased a switch box for my caravan recently, back on track, I spoke to the manager of the Bunnings store I was in (I had a full head of steam) and told him how dangerous it was selling this stuff to novices anyway he didn't give a hang and gave me the company line, they are just products we sell, what people do with them is not our concern. The fellow who asked me the question kept up his tirade and became aggressive telling me it was only electricity and what was I so afraid of. Yikes!
Caravans don't have the earth neutral link. Houses have all their neutrals hard on earth called the MEN link, it's in the switch box, houses also have an earth stake driven into Mother Earth. There are different standards for transportable structures and domestic houses.
You will only be susceptible in a caravan with a generator or inverter going unless they are equiped with a RCD or RVD.
PeterQ knows a whole lot more about caravans electrics etc. than I do.
I have to ask ? Why not power point RCDs like domestic homes can have? The circuit won't be protected .. But from RCDGPOs it would be !
-- Edited by Aus-Kiwi on Tuesday 23rd of December 2014 09:34:14 PM
AK an RCD will not work without the earth and Neutral bonded upstream of the RCD unless you are connected to mains supply which does have earth and Neutral bonded at the switchboard.
This is the beauty of the RVD it does not require that bond for it to work.
frank
__________________
Avagreatday.
Kathy and Frank currently at Home near Quirindi NSW
Qld is often referred to as the king of the nanny states
'Quite strict with who shall do what on low voltage work
Virtually anything that requires a tool to connect or dosconnectis considered electrical work
Limited licenses are possible for non electrical peiersons to a limited range of "ELECTRICAL work ,such as a plumber disconnecting & reconnecting a HWS on an existing circuit same for air con installers etc
But allshops selling electrical accessories that require tool to connect SHALL have highly visable sgns advising that such work shall only be carried out by licensed persons & the sales staff are suppose to also make that same point.
I have to ask ? Why not power point RCDs like domestic homes can have? The circuit won't be protected .. But from RCDGPOs it would be !
-- Edited by Aus-Kiwi on Tuesday 23rd of December 2014 09:34:14 PM
AK an RCD will not work without the earth and Neutral bonded upstream of the RCD unless you are connected to mains supply which does have earth and Neutral bonded at the switchboard.
This is the beauty of the RVD it does not require that bond for it to work.
frank
If MEN is up stream it picks up out of balanice load and trips in domestic houses ...Why they have seperate N link ..
Qld is often referred to as the king of the nanny states
'Quite strict with who shall do what on low voltage work
Virtually anything that requires a tool to connect or dosconnectis considered electrical work
Limited licenses are possible for non electrical peiersons to a limited range of "ELECTRICAL work ,such as a plumber disconnecting & reconnecting a HWS on an existing circuit same for air con installers etc
But allshops selling electrical accessories that require tool to connect SHALL have highly visable sgns advising that such work shall only be carried out by licensed persons & the sales staff are suppose to also make that same point.
There is no requirement to see a licence
PeterQ
Yeah, so I have heard. This is another thing that has me baffled. Each state has different rules and structure regarding electrical and electricians. For instance in Victoria there are a number of different licences a person can have A can connect to mains B can not then there are fitters etc. In SA (which I believe is well behind the times, and I live here) only an A grade, in training licence and a special class to connect and disconnect.
I wonder when this country will get its act together and have ONE common way to categorize electrical workers.
Common,.standardized, State rules/regulations, licensing[electrical] was to be agreed to this year but it needed all the states to be in agreement
[A move by the last Commonwealth gov]
Qld& NSW were in agreement, a couple of others were sitting on the fence, but one state could not agree on major points,at all, so the whole idea has been shelved
The Next stage was with GAS , I think that has also now been shelved,
Most states do have classes of electricians
Qld, electrical mechanic [wiring] electrical fitter [working on electrical equipment], ELECRICIAN which covers both, [ but some endorsement are often required] .linesman
then a mass of restricted licenses for non electricians doing minor electrical work[ Each only licensed to do specific work]
PeterQ
PeterQ
-- Edited by oldtrack123 on Wednesday 24th of December 2014 12:58:02 PM
-- Edited by oldtrack123 on Wednesday 24th of December 2014 03:05:39 PM
10 years ago, the 240V system on the OKA was given a full certificate of approval by a qualified electrician who specialised in RVs. It comprised some power points fed by a PSW inverter and protected by a dedicated RCD.
This would be similar to virtually all RVs whenever the input is plugged into a generator or inverter. It is an "isolated" system.
Well, after 10 years of constant use, I recently discovered that the RCD was in fact totally useless, despite tripping when pressing the test button.
I now have an RVD-EI (Residual Voltage Detection Unit) installed and am now getting the protection I always thought we had. Thanks to Ian (Powerstream) for his service and advise. http://www.safelec.com.au
Cheers, Peter
there is an added thing you need to be careful of.
1 - RVD are sensitive to polarity of how they are connected up..
you need to make sure that what ever the source of power that goes thru the RVD, you need to make sure that the Active is active and neutral is neutral.. If they are reversed for any reason they will cause the RVD to fail...
So if you happen to be pluging into an alternative source of power other than what is in the vehicle you need to double check the polarity of the connection..
A simple device from jaycar.. QP-2000 Will allow you to test the rvd/rcd's and also indicate to you that the polarity of the device is correct..[ Please Note that it is only an indication and make sure you test the tester on a regular basis on a known power system]
juergen
__________________
IF I say something Dumb.. Just Smack me..
I'm full of Knowledge.. I don't profess to know EVERYTHING, but I'm constantly Learning new thing's..
10 years ago, the 240V system on the OKA was given a full certificate of approval by a qualified electrician who specialised in RVs. It comprised some power points fed by a PSW inverter and protected by a dedicated RCD.
This would be similar to virtually all RVs whenever the input is plugged into a generator or inverter. It is an "isolated" system.
Well, after 10 years of constant use, I recently discovered that the RCD was in fact totally useless, despite tripping when pressing the test button.
I now have an RVD-EI (Residual Voltage Detection Unit) installed and am now getting the protection I always thought we had. Thanks to Ian (Powerstream) for his service and advise. http://www.safelec.com.au
Cheers, Peter
there is an added thing you need to be careful of.
1 - RVD are sensitive to polarity of how they are connected up..
you need to make sure that what ever the source of power that goes thru the RVD, you need to make sure that the Active is active and neutral is neutral.. If they are reversed for any reason they will cause the RVD to fail...
So if you happen to be pluging into an alternative source of power other than what is in the vehicle you need to double check the polarity of the connection..
A simple device from jaycar.. QP-2000 Will allow you to test the rvd/rcd's and also indicate to you that the polarity of the device is correct..[ Please Note that it is only an indication and make sure you test the tester on a regular basis on a known power system]
Now I am completely bamboozled. I have aquired an old caravan and Coaster bus. The caravan wiring was just nasty. I ripped out everything 240v. The bus I thought was OK - it had RCDs that had been signed off but they were pretty old. When I pulled down the ceiling I found 240 volt wiring that had been disconnected and folded over and covered in Electrical tape. I wasn't happy with that. If the tape went all gooey and fell off / had water seep in it could short to chassis. I just didn't like that either. I ripped out everything 240 volt in the bus as well - paranoia.
So now I have no appliances that aren't double insulated. i.e. TV laptop chargers etc. I am pretty sure the Lemair washing machine is? It has no metal chassis and I cant see how a fault could lead to electrocution. The rice cooker could be dangerous. Everything is connected to the 600 watt inverter by extension leads and power boards. There is no way to hook up either "dwelling" to mains power. I don't own a genset and everything is solar and batteries. All lighting is LED.
I am not kidding myself that this is safe either. The 12 volt in the bus is just as dodgy and my jury rigged 12 v charger / inverter / fridge wiring went up in smoke yesterday where it hooked into the already "birdsnesty" wiring done by the previous owner. I haven't had the heart to find out what went wrong yet.
I am not that concerned to nitpick over legalities. I live alone and no kids are ever in either dwelling. That said I was under the , perhaps mistaken, impression that extension leads and power boards could just as well be set up outside and dont constitute part of the "dwelling" Just the inverter is hard wired to the 12 volts which will be safe once I have gutted out the dodgy wiring and replaced it with appropriately fuse protected adequate gauge fair-leaded low voltage wiring.
-- Edited by Mark Bolton on Friday 27th of February 2015 09:10:43 PM
-- Edited by Mark Bolton on Friday 27th of February 2015 09:17:44 PM
Even though you MAY have all double insulated appliances, wiring faults could still occur that could create dangerous situations.
Such accidents have occurred
I am not sure but are you saying that ALL your 240V wiring now only consists of power boards & extension leads?
* I plug a powerboard into the Inverter and run laptop charger etc from the powerboard / extension leads.
How do you connect to MAINs supply ??
* I dont. I have removed the external 240 volt connector. It is all batteries and solar.
How do you use the inverter?
* I will have it and the lighting / Engels fridge / 240 volt 7 amp battery charger/ 12 volt acessory plug hard wired into the back of the 2 way dual battery isolator with an appropriate fuse as close to the isolator switch as pratciacal. The charger will be used with it's powercord via an extesion lead for emergency flat batteries.
I am sure that the van will have exposed "earthed" metal.
*It will but the chassis of the vehicle is not connected to the wiring in any way.
But it is your decision as to if you wish to comply with the rules & regs, including ALL those that apply to low voltage work .
*As to the regs pertaining to low voltage work I spent ages following discussion on Whirlpool? if memory serves. I was thoroughly confused by a discussion as to supposed regs on limits to installed Ah and solar wattage. I asked a friend who is an electrical engineer who works on mining solar off grid installs and he told me the discussion was utter tripe. I was at a loss and needed a roof over my head so I just lased together a system to get me by and plan on doing it properly once I have a clear idea what best practice / regs require.