12v/240v Electrics and RCD & Inverter

[ChrisPy]

I worked with a 'highly qualified' British electrical technician in a foreign country where the power supply suffered constant 'brown-outs'. He would rush around turning off all the tungsten lights.

 

Why?

 

Because if a lamp is rated 60Watts, and the voltage drops from 240V to 60V, the current in the lamp will increase from 0.25A to 1.00A to maintain the power rating which is fixed and set by the manufacturer, and that could cause a fire. He justified this by Ohm's Law.

 

Learning by rote and unable to apply the simple laws of physics!

[jollyroger]

Sorry but that doesn't make sense.

 

Cables are current rated.

 

You would hardly put starter motor current at 12v through a 2.5 mil mains twin and earth.

 

And you don't want to run 10 mil cables to your mains just because you have 10 mil cables on your starter.

<{POST_SNAPBACK}>

 

The size of the conductor determines the current rating, the size of the insulation determines the voltage rating, if you don't believe me look at some 240v cable and compare it to 12v. On one of the other points, yes I do agree that there are a lot of cowboys out there but please don't tar us all with the same brush. I am looking on the safe side, how many fires are caused by faulty wiring?

[John Orentas]

J R

 

I would like to know that, how many fires are started by faulty wiring ?

 

I'm also a bit intrigued as to what 12 volt cable is.

 

John Squeers

[Richard Bustens]

Hi all how do i add a pic to this page it is in .jpg?

[maffi mushkila]

yes I do agree that there are a lot of cowboys out there but please don't tar us all with the same brush. I am looking on the safe side, how many fires are caused by faulty wiring?

 

I am not tarring you all with the same brush but you were tarring the amateurs.

[Richard Bustens]

Well iv'e got a pic i took this afternoon i need to share with you all partiqualy Stewart, but i can not seem to get it to attach

[Paul Evans]

Richard - I don't think you can just copy and paste a picture into your post. You need to have the picture on a website and then use the IMG tag to add it like this:

 

[.img]http://mysite.wanadoo-members.co.uk/windfield/images/1-picture3.jpg[./img]

 

Miss out the full stops before img and /img and you get:

 

 

Unless somebody knows otherwise - Maffi seems to be up on all this techie stuff.

Edited December 1, 2004 by Paul Evans

[Richard Bustens]

hi do you mean like i put the signature and avitar on?

[Paul Evans]

That's the way Richard. Have a go - I'm just waiting to see your pic.

[maffi mushkila]

Richard: Still think you should (probably have to) run the 230V AC in separate conduits to 12/24V.

 

From a regulations point of view you may have to but earthing through the hull is doable if the hull resistance is low.

[maffi mushkila]

Unless somebody knows otherwise - Maffi seems to be up on all this techie stuff.

 

 

Bu993r3d if I know. I have been trying to get a pic here from my computer for the last 3 days. I even tried uploading it to my webpage and using the image codes but that didn't work. If I find out I will let you know.

[Richard Bustens]

well why ?if i now have got to bond the neg to the hull have i bothered to run seporate returnes everyware, why not just use the hull as a return as in a car etc.

It says in all the books you must not do that as a wire (pos) with a damp connection will cause problems well so will bonding the return.

[Guest]

My biggest fear about using the hull for a return would be corrosin around the connection (you have to bare the steel to get a connection and then vaseline/whatever over it to stop rust), and the actual practicalities of connecting to the hull. What does one do? drill and tap it?, weld a lug on? Unless I am missing something here (and I usually am) I believe it is easier and more reliable to use a piece of cable for neutral. I know that commercial vehicles long since abandoned using the chassis for "earth" for these very reasons (starting circuit excepted).

[Guest Sweeney]

Richard,

 

Have a look at this. I'm inclined to trust this source, unless anybody has other experience.

 

http://www.reading-college.ac.uk/marine/Ma...S%20ELECTRICITY

 

It's quite long and the meat is towards the end.

 

Regards,

Sweeney.

[stuart]

Well iv'e got a pic i took this afternoon i need to share with you all partiqualy Stuart, but i can not seem to get it to attach

<{POST_SNAPBACK}>

 

Hi all how do i add a pic to this page it is in .jpg?

<{POST_SNAPBACK}>

 

 

As already mentioned you need to send the picture/image to another website to "host" the picture for you. I dont use them but been told they offer a good free service at http://www.villagephotos.com/.

 

Once you have a picture hosted with them simply view it through your webbrowser, right click on it and select "Copy Image Location" (if your a non Internet Explorer user) or select "properties" and cut and paste the text in the "Address (URL)" area (for internet explorer people). I think there is also an option to "Copy URL" within the VillagePhotos website - this does the same.

 

You should end up with an address like this

http://img.villagephotos.com/p/2004-12/900453/semitrad.jpg

which points to the picture

 

Once you have the address, in your forum post, click "IMG" and then cut&paste the address - thats it!

 

The only limit is that your JPEG pictures must be under 120Kbytes in length - but thats fairly easy to achieve.

Edited December 1, 2004 by stuart

[Richard Bustens]

lets give it a go

Yesterday i went to the place that is building my electric board and was telling him about the method Stewart was planing." you mean like this " he replied and took me into the workshop to see the itim below

This is what can happen when you start putting bits and bobs together with a B&Q fuse box. this is the same as your planing except it is 3 way one for generator as well

Edited December 1, 2004 by Richard Bustens

[rustyduck]

There's a moral to that story methinks.

[John Orentas]

Hi Richard.

 

That's not quite fair, what the picy shows is a catastrophic fault (can't see much detail) caused by:

 

Component fault

Wiring error

Design error

 

It must be diagnosed properly to see what went wrong, preferably not by the person who built or designed it.

 

I used to design and build control panels and I have to say that a lot of if does amount to "putting bit's and bobs together", paying for the most expensive equipment you can find is not the answer, B&Q items are quite ok as long as everything is correctly rated.

 

You can't spend your way into reliability. The Titanic wasn't cheap and nobody skimped when the Comet was designed.

 

It will be interesting to read the result of an independant apraisal of what went wrong. An imotive photo of a few burned out components with fire extinguisher dust all over them does not add much to anything.

 

 

John Squeers

[Richard Bustens]

Well i know what went wrong John IT SET ON FIRE.

Something was obviousley wrong for it to happen.

There are 3 female sockets one to the landline one to the inverter and one to the gen set with a mail plug to the fuse box to swap between the three. to all intence and purposes this should be ok ish. but it is apparent it was not.

I do not think that making up patch panels like this is good pratice and 3/4 position switches that insure that you can only have one thing conected at any time is esential for safety, with properley worked out fuses, it was noted that the ones in the fuse box were 1 x 10a and 2 x 32a now i suspect this was not the reason for the burn out.

Edited December 1, 2004 by Richard Bustens

[John Orentas]

Hi Richard.

 

Things dont set on fire because you didn't spend enough money. Something in that lot got very hot. It could have been the wrong size of wire, an underated component or a termination that was not tightened properly, or the circuit design was wrong or it wasn't fused correctley, or it was put to a use it wasn't designed for, or someone decided it was a handy place to keep his spanners.

 

You can go on forever

 

John Squeers

[rustyduck]

Apart from giving us an idea of what it looks like when you get it wrong.

[stuart]

I agree that the photo obviously shows that care must be taken to select the correct compontents.

 

This could quite easily have been an expensive purpose made board - again if used or installed incorrectly (by using over rated fuses/breakers etc.) then the melting mess of plastic and cable will result.

 

I'm confident that as long as the correct rating of cable, connectors, fuses and type of load is taken into consideration then the installation will be perfectly safe.

 

I actually think that most "amateurs" over estimate the capacity required for electrical installs and usually buy higher rated cable and connectors than actually required. Rather than a "just use whats on the van" type of installer!

[stuart]

Well i know what went wrong John IT SET ON FIRE.

Something was obviousley wrong for it to happen.

There are 3 female sockets one to the landline one to the inverter and one to the gen set with a mail plug to the fuse box to swap between the three. to all intence and purposes this should be ok ish. but it is apparent it was not.

I do not think that making up patch panels like this is good pratice and 3/4 position switches that insure that you can only have one thing conected at any time is esential for safety, with properley worked out fuses, it was noted that the ones in the fuse box were 1 x 10a and 2 x 32a now i suspect this was not the reason for the burn out.

<{POST_SNAPBACK}>

 

In effect three female sockets and a male plug are just a simple switch - its impossible to select more than 1 because theres only 1 plug!

 

With regard to the fuses, if the cables were not rated above 32A - then they could have quite easily melted/burnt through and caused the fire. Especially if there were any flamable substances near eg. storing cans of stuff in the fuse cupboard!

 

This photo does not show how the internal wiring inside the plugs was done either - it may have been very messy - even conductors shorting out/reversed - this could have caused the fire because it would have been before the fuses and nothing to stop the current heating the wire.

 

But I agree the photo does make you stop and think a lot harder! As a side, I cannot seem to find any suitable 2 or 3 way DPDT switches for a high current capacity - where did you get yours?

Edited December 1, 2004 by stuart

[John Orentas]

I still maintain that the one bulkhead plug and two or three free socket method is as foolproof and failsafe as it is possible to be. A three position switch, though more convenient is not as failsafe.

 

John Squeers

Edited December 1, 2004 by John Orentas

[Paul Evans]

John - I'm sure you meant 1 plug, 2 socket method - socket supplied by land line, socket supplied by inverter, plug in your appliances (through a RCD and fuse box of course) to one or the other socket. The other way round would be very dangerous indeed. I speak from knowing somebody (who is fortunate to still be here) who put a socket on the end of his lawn mower lead and then created an extension lead with plugs on both ends. The result was inevitable!

 

Perhaps we should be advocating the 3-way switch (Land line On, Inverter On, Both Off) to avod the very real possibilty of live plugs being left lying around.