What Exactly is Primary Wire?

Primary wire is primary wire, right? Not exactly true. There are different “grades” of primary wire, based on temperature ratings (voltage ratings are typically the same at 50V DC). Buy the wrong type, you could wind up melting the jacket and causing a short or electrical fire. Not good at all. So let’s go over some basics.



Generally, standard primary wire is the most popular, widely used and economical type of wire. The insulation jacket is normally smooth and brightly colored and is manufactured from PVC (polyvinyl chloride).

HDT – Heavy-Duty Thermoplastic and TWP – Thin wall Thermoplastic primary are also available, but I will be focused on the standard wire.

The internal copper strands of standard primary wire are bare copper (BC) and gauge size of the wire is measured to SAE standards. Stranding is often represented by 7/.0126. The first number is


the number of strand and the second is the outer diameter (OD) of each of those of strands.



When shopping for primary wire, be sure to look at temperature ratings. The two temp ratings that I have seen are the 80°C (176°F) and 105°C (221°F). Keeping the wire temp ratings in mind, you have to understand your unique application. Where is the wire going? Will it be exposed to high temps or simply run down railing of a trailer. You can save a little money by buying the lower temp rated wire, but is it really worth it? The higher temp wire gives you greater flexibility as to where you can use it, but is a tad bit more. Maybe stock both types, but then run the risk of dual and mixed inventory. It really comes back to your application and what you feel comfortable with.        

1118503_primary.jpgAt Del City, we carry 20 gauge wire through 8 gauge wire. Once you get to 6 gauge, it is no longer wire, but rather cable. But that is another topic for another time. Spool sizes range from 100’ to 4,000 or 5,000 foot spools, depending on gauge of wire. There are also Thrifty Spools of wire, which are merely spools of wire with less than 100 feet. We carry the most popular colors and have the ability to do custom ordering if need be.      

As I said earlier, primary wire is extremely popular. It can be used across industries and applications. You can use it for wire harness components, connect lighting and I even talked with a customer who used it for a clothes line. I wouldn’t recommend that though – there are cheaper alternatives! If you are running multiple wires, I would recommend using some kind of loom and cable ties to keep the wires properly bundled.    


You can also check out our primary wire chart on our blog! For more information on primary wire or detailed spec sheets, please contact one of our very helpful Customer Satisfaction Representatives at 1.800.654.4757 or via email at info@delcity.net.

Posted in Wire & Cable.