I am soon to purchase some 7 core trailer wire but wanted to over engineer the job so I have been looking at different amp ratings.My conundrum is why copper wires with the same cross section,strand number and size have different ratings.I will include a couple of links for examples both made by tycab ...could it be the heat generated in a 7 core cable that marks down its amp rating v's a single core cable ?

• Conductor: Tinned copper wire to AS/NZS1125
• Nominal Area (mm²): 7 X 1.84
• Strand No. / Size (mm): 23/0.32
• Nominal OD (mm): 9

• Core Colours: 1.White 2.Yellow 3.Brown 4.Red 5.Green 6. Black 7.Blue

https://www.ebay.com.au/itm/MARINE-...e=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649


https://www.ebay.com.au/itm/11-roll...767022?hash=item261fc5156e:g:0iAAAOSwqH9etQR~

Many thanks for reading

 

DC wiring is a bit tricky due to length. DC wire over a few feet derates fast. 3 basic kinds, uninsulated, PVC insulated, Silicone Rubber insulated. I don't think I have ever seen solid core Silicone. Uninsulated typical for grounding or with a shellac coating for magnet/coil winding. PVC for most uses. Silicone Rubber for heat resistance, both external and internal protection. I like the flexibility and heat resistance of silicone but it has no shape-holding ability. Amps/cmil is pretty standard with the AWG here in the US but there is a lot of metric around the world. Looking at your link, the specs are a bit short on data. 10 meters is a long way for DC amps. I would contact the manufacturer to find out just what the distance derating is for that particular cable. My rule of thumb from experience is anything over ~6' in 12V DC automotive/boat wiring, I check the derating.

 

DC wiring is a bit tricky due to length. DC wire over a few feet derates fast. 3 basic kinds, uninsulated, PVC insulated, Silicone Rubber insulated. I don't think I have ever seen solid core Silicone. Uninsulated typical for grounding or with a shellac coating for magnet/coil winding. PVC for most uses. Silicone Rubber for heat resistance, both external and internal protection. I like the flexibility and heat resistance of silicone but it has no shape-holding ability. Amps/cmil is pretty standard with the AWG here in the US but there is a lot of metric around the world. Looking at your link, the specs are a bit short on data. 10 meters is a long way for DC amps. I would contact the manufacturer to find out just what the distance derating is for that particular cable. My rule of thumb from experience is anything over ~6' in 12V DC automotive/boat wiring, I check the derating.

Multicore

Single core

 

Normal wiring guide is 9Amps per 1mm2 @ 20C,,

Then it reduces for multicore due to temperature and space cooling..

 

Here is a calculator that uses the Vs, A for ckt., and distance that will use 12VDC. Somewhere there is a good table for it but I can't find it.
https://www.powerstream.com/Wire_Size.htm

This will be for a single conductor so it will have to be further derated for cable.
Edit: Hmmm... doesn't show much V drop. I'll try and find the table.

 

Found it, or at least a similar one.
https://www.bluesea.com/resources/1437