Do I need to re-wire my toilet...?

[VicS]

To correct the first line of my hastily made post at 10:14 it should of couse have read: watts = volts x amps.

Re the discussions about cable sizes They are always quoted as crossectional area. I would assume that if you measured the diameter of a solid conductor and calculated the area from that you would get the figure quoted but I don't know about multistranded (flex). I assume its the total of the cross sectional areas of all the strands so that would be difficult to measure and calculate accurately.

 

[2Tizwoz]

Cable Current Ratings

A cable's current carrying capacity is limited by its cross-sectional area and its ability to disperse the heat generated by the current passing along it. If its in a warm spot or bunched with other cables or enclosed in trunking it will reach its safe working temperature when carrying less current (which is measured in amps). Table of cable capacity

This is not a complete guide to cable capacity as cable sheaths are made from different materials. Think of it as a rough guide.

This Electricians Guide gives all you may need.

 

[VicS]

Re: Cable Current Ratings

Thanks for those links. Saving them both to favorites. Some of the others on the Standards and formulae website look useful as well.

As every one must realise by now collecting useful (and useless) info is a "hobby" of mine.

 

[Karel]

Re: Cable Current Ratings

So - at the end of the day - the ability of a conductor to carry a particular current is down to how warm it gets, and how much of a voltage drop it adds to the circuit?

So a thin wire that's kept in a bath of liquid nitrogen (not very practical on my boat as it happens) provided it didn't drop the voltage too much could support a high current load efficiently because it didn't get warm... /forums/images/graemlins/smirk.gif

 

[2Tizwoz]

Re: Cable Current Ratings

Well you now get into the area of superconductivity. /forums/images/graemlins/laugh.gif

 

[Karel]

Re: Cable Current Ratings

You're right: at -196C most of the planet would become a superconductor! (But wouldn't it look amazing...)

I guess I meant something like dry ice at -79C. But that's still not very practical on my boat...

What I really meant was that I'd always seen the warming up of wires as a 'symptom' of the wiring being inadequate, whereas (now I stop to think about it) it is the very problem itself.

 

[Phoenix of Hamble]

OK... thinking it through, I was wrong!

Mea Culpa....

Although to be really really pedantic I would have thought that (and correct me if i'm wrong!) there will be a (very) slight difference in blowing point, as the voltage drop across the fuse will be different between the two voltages (although in ratio will be identical) whereas resistance will remain constant, and surely its really power that blows fuse, not current... however the voltage difference will be so small as to be negligible... hope that i've got it sussed/forums/images/graemlins/grin.gif

 

[William_H]

Hi Karel Electricity runs through all the copper not just the surface. Except in the case of high frequency AC as in SSB earthing straps. It is in this and higher frequency range where surface area does improve conduction. Not DC.

Don't fit an extra battery for your loo. You don't wan the extra cost of battery and charger and later more battery replacement. The main domestic battery will do fine. Just use heavier wire and correct current fuse. (as dictated by the wire size) I don't think you have a case for real fear with the wire running in the enguine compartment. olewill