Legalities of electrical work on recreational vessels in QLD

[PinHead]

this is getting good now finga...I do have a question..what velocity will that water be travelling at as it exits the hose? Will it damage the leaves on the plant i am watering..I can see this thread heading towards correct watering of rose bushes soon.

[finga]

Always aim to please Pinhead.
As for the rose bush. Dig the b@stard of a rose bush up.
The prickles will get you when you least expect it.
I hate spikes of any sort on plants especially Bougainvillea's.

As for velocity....how much have you got the nozzle turned down and what's the care factor??

[Fed]

How does if feel Finga, you've just been sucked into his jibberjabber vortex.
Gotta be very scary in there.

[Fed]

If a cable section is shorter than the critical length it will tend to fuse or melt it's insulation at a lower current.

So long cables can carry more current than short cables.
I think you're making this up as you go Oldboot.

[finga]

How does if feel Finga, you've just been sucked into his jibberjabber vortex.
Gotta be very scary in there.

Good matey.
Nothing like a bit of jibberjabber to amuse oneself.
And you know what??
With this form of amusement you don't go blind like you can with another popular form of amusement.

[PADDLES]

phwoaaar, talk about clash of the electrical titans. the thread's initial question was answered on page 1. elv = anyone (unfortunately includes fitters and operators) and lv and over = licensed electrician.

compliance with australian standards is not mandatory, but if you've not complied and something's gone pear shaped, you'd better have some good science to explain to the judge. recent examples of this in the electrical world are arc flash energy standards/calculations and the current theory being refuted by some very clever dudes. apparently the theory's been incorrect since day dot.

i've never heard of 'critical length' myself but what the old boot is saying is sort of correct, current carrying capacity of cables is not necessarily an electrical issue but more a thermodynamics issue (how much heat it can handle without the insulation breaking down) the main influence being method of installation. likewise, a cable's performance under a fault condition is also a thermodynamics issue related to temperature rise due to the energy let through by the protective device (fuse or CB) before it interrupts the circuit.

lv cables sold for use in australia must comply with as3008 so the length issue is irrelevant for the current carrying capacity consideration of most of us punters as the cable must be able to handle the specified currents regardless of it's length. i'm not familiar with elv cable standards if they do in fact exist.

about that garden hose pinhead, i can personally recommend a 18mm NB type connected to a 1hp spear pump, doesn't seem to harm the palms but boy it gives the grasshoppers a headache.

[oldboot]

I only came acroos the concept of "critical length", when I was doing some research into fusable links made of insulated cable........and in the documents explaining it, it was not given a name it was just discussed as a fact that had to be considered.

Fed, mate ya simply don't get it do ya.

Finga If you cant grasp the concept of current rating of a cable or wire as a factor in isolation, independent of voltage drop.....I am sorry I cant help you

This Critical length only applies to wire under test or used as fuses and the length is as I indicated quite short like as little as a couple of inches.....longer than that cables behave consistently

I am sorry I ever mentioned it

In future I will refrain from mentioning issues obviusly too complex for an internet forum on fishing.

Hell even the concept of "not mandatory" seems to be a but hard.

cheers

[PinHead]

I only came acroos the concept of "critical length", when I was doing some research into fusable links made of insulated cable........and in the documents explaining it, it was not given a name it was just discussed as a fact that had to be considered.

Fed, mate ya simply don't get it do ya.

Finga If you cant grasp the concept of current rating of a cable or wire as a factor in isolation, independent of voltage drop.....I am sorry I cant help you

This Critical length only applies to wire under test or used as fuses and the length is as I indicated quite short like as little as a couple of inches.....longer than that cables behave consistently

I am sorry I ever mentioned it

In future I will refrain from mentioning issues obviusly too complex for an internet forum on fishing.

Hell even the concept of "not mandatory" seems to be a but hard.

cheers

fantastic idea..here here..and why is it a fantastic idea? cos no one really cares about so called critical length..load of nonsensical crap.

Let's go back to the start..no legalities required on wiring a boat on low voltage..simple.
as a matter of fact wiring one is very simple..nothing hard about it at all..the hardest part is deciding where you are going to mount the items.

Next..can we have a thread on the current torque required to tighten a scre in a BP connector? That would make interesting reading for many days.

[Lovey80]

I cant believe I read all of that. You blokes need to take up another hobby or something, this is taking up far too much of your time. Funny read in parts and certainly a whole lot of jibber jabber coming from all sides here. Keep up the good work lads

[PinHead]

I cant believe I read all of that. You blokes need to take up another hobby or something, this is taking up far too much of your time. Funny read in parts and certainly a whole lot of jibber jabber coming from all sides here. Keep up the good work lads

Chris..I bet that not once in your life would you ever think you would get a chuckle over a piece of electircal wire?

[finga]

And one thing that quite a few don't seem to grasp is that the "current carrying capacity of a cable" stands alone as a specification for the cable and the cable alone.
No one is arguing that. We are trying to stress that.

It is most usually specified at a specific tempeature and with the cable in open air laid straight.

It specifies what maximim current the specific cable is capable of safely carrying (with or without a safety margin) before some sort of "material failure". In insulated cables that is usualy the insulation melting.
OK....that's about right by my reckoning.

This remains the same once critical length is achieved, critical length is where the the cable is long enough to be consistently measured.
This is where it gets interesting

This is the figure specified by manufacturers and in many tables that can not account for the use or method of installation.
So where are the manufacturer tables and data on this??
It is the starting point.
Your not wrong there. It's the starting point of the yellow brick road that's leading to fantasy land

Those of us that have not had our heads burried in electrical industry standards and blinkered by the methods specific to those standards will recognise this valid and real specification for what it is.

I know there are tables upon tables and a couple of formulars for current carrying capacities for cables of specific lengths and in specified situation or methods of installation. Most of them totaly irrelivent outside of the building industry.
That's bull dung but I'll let that slip

BUT
I am only too well aquainted with methods and means specifying cable IN SITUATION both those methods contained in standards and other valid methods used in engineering.
Well where else do you cable if it's not in situ??

Voltage drop is completely irrelivent in calculating current carrying capacity of cable in isolation.
Any cable has voltage drop not matter how short or long it is due to resistance of the copper. It is an inherent property of all metals.
You sure your not thinking about fibre-optics...but even they have a loss?

Regardless of length once critical length is achieved, the same or similar amount of current in cable or wire will result in failure........the same amount of energy is disipated per unit length......voltage drop is irrelivent untill there is insufficient voltage remaining to make sufficient current flow.
So what happens when voltage drop is sufficient to stop the flow of current ?? What does it matter??

That is not regardless of length. That is length dependent.
Now explain this to me please.
A cable has, say, a 20A load on it. That's 20A at the end of the cable.
So if you put a DC tong-tester on the wire next to the load it'll say 20A.
Goodo then. Now when you put the tong-tester on the supply end of the wire what does it say??
Answer would be that depends on how long the wire is and the supply voltage and whether it's AC or DC.
Why??
Internal resistance of any length, or type, of wire creates it's own load and as the length increases so does the load.
How do you get a consistent 20A in a wire 20km's long??

Sure you coud use volatge drop in one method to calculate this failure..... but no one has even touched on such a method.
You sure??

Failure to grasp the concept of current carrying capacity of a cable in isolation is to fail to understand one of the simplest facts about cable and how it is specified.
What facts and how is it specified?? I reckon most of us has a very good grasp on current carrying capacities of cable

Believe it or not, there is an electrical world that exists out side of the building industry standards, and believe it or not outside of the " electrical industry" voltage drop is not the all consuming matter.
Ya reckon??

now back to the link to a table from the ABYC standards.

No australian manufacturer I know would speciffy 1mm2 cable at 25 amps, Like it or not in this country we work off arround 10 amps per mm2 for light cables under 2.5mm2 above that there is a correction for conductor bulk
That's because they are talking about a foot of cable in a single circuit configuration and Australian's don't.
Work out the current capacity of that 1mm cable by the ABYC methodology for a length of 1m or 30m. What figure do you get??

25 amps in 1mm2 cable of any length in any insulation....... not comming out of my workshop unless it was a fusable link.
Goodo. Your choice
I have even mentioned 1mm cable will carry much larger currents but the current carrying capacity is very much length dependent. That was brought up by me in post #87
cheers

I only came acroos the concept of "critical length", when I was doing some research into fusable links made of insulated cable........and in the documents explaining it, it was not given a name it was just discussed as a fact that had to be considered.
I thought fuses were not allowed to have normal plastic or other types of insulation you normally find on cables because of heat dissipation and the risk of fire. If fuses are encased it's normally porcelain or similar type materials not plastic or the like.

Where is a few references on fuseable links made of insulated wire?? I wouldn't mind read up a bit.

Fed, mate ya simply don't get it do ya.
I reckon he does.

Finga If you cant grasp the concept of current rating of a cable or wire as a factor in isolation, independent of voltage drop.....I am sorry I cant help you
Fair enough. Lots of other people can't help me either.

This Critical length only applies to wire under test or used as fuses and the length is as I indicated quite short like as little as a couple of inches.....longer than that cables behave consistently
Well bugger me. I thought critical length and the ability to carry a set current was independent of length and you actually said words to that effect above. I'll put them in red for you and you have continually re-enforced that belief.
Am I wrong in this belief??

I am sorry I ever mentioned it
We're not...well maybe we are.

In future I will refrain from mentioning issues obviusly too complex for an internet forum on fishing.
Only thing complex is your mind.
Everyone else is pretty much in agreeance.
Hell. Even the wider world known as WWW. I can't find anything to do with critical lengths of cable.com cannot help me understand this concept.

Hell even the concept of "not mandatory" seems to be a but hard.
Having an anchor, oar and drinking is not mandatory either. It is only recommended, but you have them and if you don't and the poo hits the fan your gunna have to do a lot of explaining Lucci.
So yes (back to the story) following AS 3004.2:2008 IS NOT MANDATORY. But (from the mouth of a senior advisor (maritime) of the Safety Standards Branch within Maritime Services Queensland) it is highly recommended.
I have never said it's mandatory and if you find a reference where I did then I owe everyone an appologee.

cheers

Still waiting for the reference for where you said it's mandated that you have to have drinking water, oars and an anchor. That was back in post #43

Lots of people have asked for other references too so they may learn something but no references submitted. Why??

[finga]

Chris..I bet that not once in your life would you ever think you would get a chuckle over a piece of electircal wire?

Been a chuckle alright.
Believe it or not I've actually broken a chair through this.
I was reading and started laughing and leaned back and the chair broke.
The cook nearly p!ssed herself laughing at me laughing on the floor with Pongo licking my face.
Now I'm handicapped. I welded the base back onto the chair but she's got a permanent list to the right now.
I might have to fix that soon.

[oldboot]

I was going to leave this alone....... but I simply can not believe what I am reading.

That is not regardless of length. That is length dependent.
Now explain this to me please.
A cable has, say, a 20A load on it. That's 20A at the end of the cable.
So if you put a DC tong-tester on the wire next to the load it'll say 20A.
Goodo then. Now when you put the tong-tester on the supply end of the wire what does it say??
Answer would be that depends on how long the wire is and the supply voltage and whether it's AC or DC.
Why??
Internal resistance of any length, or type, of wire creates it's own load and as the length increases so does the load.
How do you get a consistent 20A in a wire 20km's long??


If current is flowing in a wire, the same amount of current flows at all points in a wire.

if you take you current clamp meter to any point on the same wire......the current measured will be the same


Same as the same amount of water is flowing at all points in a pipe and the same amount of tension is at all points in a rope


Hell mate this is first year college...... a couple of days after ohms law..

Look at any electrical text book under "Direct current analisis" or "Series circuit analisis" ( or somes such) it will be right at the front.


I quote "Electrical Principles for the Electrical Trades" by JR Jenneson.....when I baught my copy this was the text used by TAFE QLD for all electrical apprentices.

In my second edition on page 45


3.3.2
If there is only one path for current flow, there can only be one value for current. It is said that the current flow in a series circuit is constant; that is, the current is the same value at any point in the series circuit. .......


None of our electrical maths would work if this was not so.
All our electrical theory depends on this simple fact.

and it remains true for AC current as well

It is expressed further in "Kirchoff's current law"



Serioulsy you can try this at home........

sorry


cheers

[Fed]

Give him a break oldboot he's been reading all your other posts, he fell of his chair & now it's broken, the dog licked him and his missus is laughing at him.

[finga]

Oops. I made a boo boo.
A bad boo boo.
It happens and I accept that.
It must have been the concussion.

I meant... get a load on a short bit of cable so the tong reads 20A.
Place the same load on the end of a 2000 metre bit of cable at the same supply voltage and read the tong. What's it say?

Now where are all the references you've been talking about Oldboot??

All I can say is my Kingswood's battery leads are not crimped and there's no way in hell can I get the same amount of water out of 30m of 12mm garden hose as I can get out of just the tap.