# AC cable for DC applications

I've searched a lot and found differing opinions so I'll ask here.

Can I use 1.5 mm2, 1 core, 7/0.5 mm strand building wire rated for 0.6/1 kV AC in small < 24V DC applications.

I know AC and DC utilise the cable differently, but is there any difference in using this over the 'automotive' wire sold at electronics shops? This stuffs a hell of a lot cheaper so it'd be great if its the same.

• I don't see why not. There's no problem with using cable better than necessary. – user253751 Aug 19 '19 at 4:42

You can definitely use it. Please consider the resistance of the cable. The ohmic losses will reduce the 24 V supply voltage to a lower level at the remote end. If the resistance is 5 ohms for example, in total ohmic losses will be twice the 5 ohms multiplied by the DC current. If that is accounted, then your application should run fine.

Shielded cables have good benefits of being immune to noise as well as not being a good noise transmitter. If the cables are shielded, well and good. If not, you should be ready to investigate(and adapt design) in detail for noise immunity and noise emission topics.

• I'm only using short (5-20cm) lengths here and there, so it should be suitable being the cables for switchboards etc. Thank you. – mrkd1991 Aug 19 '19 at 6:14

Can I use 1.5mm2 1 core 7/0.5mm2 strand building wire rated for .6/1kV AC in small <24V DC applications.

TL;DR While you should be able to use it based on voltage alone, there may be reasons why you shouldn't.

Cable has several specifications to meet, voltage related (insulation), current related (area and copper purity), mechanical (insulation thickness, robustness, flexibility, and copper strand size and number). There are others, for instance insulation softening temperature, flammability and whether it releases toxic gases when it burns.

It's fine to use a cable at a lower voltage than rated. For small diameter cables, there's no real difference between DC and low frequency AC.

BTW, your cable area and build has an inconsistent specification, if it's 7/0.5mm, then the total copper area is 1.37mm2. If it's 7/0.5mm2, then the total is 3.5mm2. So it's probably the former, and they've helpfully 'rounded up'.

7/0.5mm is a curious configuration. The strands seem to be too thick for a true 'flexible' power cord, but thinner than they need to be for stapled-down power cable. It's probably intended as equipment wire for the internal cabling of cabinets, and not for continuous flexing.

With high voltage systems, cables tend to be rated thermally for current only as the voltage drop is usually an insignificant fraction of the total voltage available. With low voltage systems like 24V, you usually need to take account of the voltage drop as well as the thermal limit for the cable, often ending up with a thicker cable than you expected.

small <24VDC application is not a complete specification. If it's automotive, then using wire not rated for automotive use may be a non-approved 'modification' and invalidate your insurance, depending on your location. If it releases toxic gases on burning, or doesn't remain flexible down to -20 degrees, then it could cause dangers not forseen by just staying within the voltage and current rating.

• 7 strands could be intended for use in a conduit. possiblty $7/0.21mm^2$ – Jasen Aug 19 '19 at 5:22
• Apologies, it is 7 strand at 0.5mm per strand, I've corrected the original post. Additionally, it is for wiring up switchboards etc, where flats etc. aren't suitable. So from this I'm guessing it'll be fine for most all of the concerns you've raised. Lastly, 24vdc is much higher than I'm playing around with at present, more like 3-6vdc mainly so I'm going to say it's alright in that respect also. Thank you. – mrkd1991 Aug 19 '19 at 6:09