wire amp ratings

Thread Starter

jonnydolt

Joined Oct 23, 2015
124
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-TINNED-7-CORE-MULTI-CORE-10M-WIRE-CABLE-1-84mm-14-AMP-TRAILER-BOAT-TYCAB/233338158661?ssPageName=STRK:MEBIDX:IT&_trksid=p2060353.m1438.l2649

1589018517613.png
https://www.ebay.com.au/itm/11-rolls-30m-x-28-Amp-Auto-cable-4-mm-General-pupose-electrical-wire-TYCAB/163741767022?hash=item261fc5156e:g:0iAAAOSwqH9etQR~

Many thanks for reading
 

SamR

Joined Mar 19, 2019
2,096
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.
 

Thread Starter

jonnydolt

Joined Oct 23, 2015
124
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
1589022930244.png
Single core 1589023006948.png
 

SamR

Joined Mar 19, 2019
2,096
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.
 
Last edited:
Top