Question about electricity

[savageseadog]

What is not often mentioned in discussion of wire diameters is that insulation matters as well. Current carrying capacity is dependent on temperature rating of the plastic or whatever that insulates the wire. PTFE will for example degrade at much higher temperatures so thinner wire can be used.

 

[aluijten]

Thanks guys for all the interesting views! I just spend so many days routing new cables in the boat that I'm having bad dreams about it

A.

 

[ap073]

Current carrying capacity

The current carrying capacity of a cable (mm2) is dependent on many factors, so there is no easy sum (ie, halving the current or whatever) that can be done.
Some of the factors are;
Type of conductor; ie, copper, steel, etc.
Type of insulation; PVC usually
Fixing method; A cable running in a void can carry more current than a cable running between two pieces of insulation foam.
Whether the cable is running alone or alongside others.
The length of the overall cable run.
The type of circuit protection.
There are more.......
Many sparkies will use a rule of thumb, and add a bit more to be safe, but if cost and weight are issues, then all of these issues must be calculated.

 

[elton]

Many sparkies will use a rule of thumb, and add a bit more to be safe, but if cost and weight are issues, then all of these issues must be calculated.

The electrician's "17th Edition" contains a comprehensive set of tables for calculating conductor specifications under a multitude of installation parameters.