Doubling a cable

[Flo-w]

G'day.

I recently had the situation where I ran out of the correct cable (min 50 amp) but I had enough 30 amp cable to double it up (2x 30 amp). Is that a really bad idea or not a problem?

Cheers

[Bloodyaussie]

?? not sure but that is still a 30 amp cable caring a 50 amp load x2 is it not!!!!

Wait for Yendor or the like to answer???

[Ben-e-boy]

I have paralleled cables a number of times, as long as the current carrying capacity from the 2 cables is greater than or equal to your current requirements of the single cable

[Flo-w]

That's what I meant. 2 cables with 30amp capacity each, running in parallel and being attached to the same connectors. So that makes a 60 amp connection then?

[macca]

From an electrical point of view it is done often with large installations. With more than 2 as well.
All cables must be the same size, type and length etc and the connections must be good.
Under the same terminal if possible and properly crimped lugs is best.
I have seen it posted about crushing lugs in a vice and hammering flat, well you can do that in an emergency.
I can assure you an electrician of the 240volt or 12 volt types would shudder to see that done.
Cut a lug open and see what a proper sized crimper does, all the cores are compressed equally and captured inside the tunnel, no chance of any coming loose with vibration as in a vehicle.
So it is safe to use more than one cable to get your current carrying capacity for your install.

[Ben-e-boy]

I have seen it posted about crushing lugs in a vice and hammering flat, well you can do that in an emergency.
I can assure you an electrician of the 240volt or 12 volt types would shudder to see that done.

too right there macca

Flo-w if you have a sparkie mate get him to crimp it, if not get one out of the phone book. if they are decent and you have everything ready they'll help you out for a tiny fee

[Irvs]

Just for the record 2 x 30amp cables do not equal 60 amps. It depends on the cable but as a rule (in low voltage electrical) you would generally derate the cables by 0.8, that is to say you multiply the current carrying capacity by the amount of conductors to be run in parallel and then multiply by 0.8, you will find that in your scenario your only capable of pulling 48amps with those particular cables. I would get a new cable or run three in parallel if it was 240/400v wiring, because your using automotive wiring (I hope)there may be different derating factors. Also consider voltage drop when you're only just going to be within the current capacity of your given cables as when you drop voltage your current increases to make up the required wattage. Hope this helps.

Irvs

[Flo-w]

I've two crimping tools myself. One for smaller connections and a hydraulic hand crimper with max 8 ton pressure. Connections are rock solid I reckon.

[Yendor]

I have no concerns with doubling up cable, in theory each cable should be carrying 25 amps (this may not be the case in the real world).

Depending on the length of the cable you may find voltage drop to be an issue, as Irvs pointed out.

If it's just in the engine bay it should be fine, if it's down the rear of the vehicle and it's a minimum of 50 amp then I would replace it.

[Irvs]

I should mention that the reason we derate cables is because of the heat they generate when under load so as you can imagine when you run conductors in parallel they retain more heat thus the derating factor comes into play. What is the load and how long is the cable run and does it run across/near any hot surfaces?