Picture this, you are in a data center, stacked with C13 PDUs, but you’ve got a low amperage piece of equipment with a C8 inlet such as a KVM console or LCD monitor. A C14 to C7 power cord is the obvious bridge — and it works. We sell plenty of them right here at StayOnline. But there is a hidden gotcha of which you may be unaware. There is no UL mark on the C14/C7 cord — and that’s by design. Per UL rules, if the plug has a ground so too must the connector. A C14 to C7 simply cannot be UL listed. C18 to the rescue.

What is a C14 to C7 cord?

If you’ve been following along, you know that C14 is the most common inlet found on servers and other commercial devices such as printers, monitors and TVs. A cord with a C14 connector is designed to interface with a PDU equipped with a C13 outlet. You are probably also familiar with the C7 connector (aka figure-8 or infinity connector) as it is very commonly found on the cord that attaches to your laptop’s power brick. A device with a C8 inlet is inherently low draw (2.5 amps) so there is no danger pulling from a C13 PDU rated for up to 15 amps. So the C14 to C7 seems like the obvious choice.

The UL Problem

Per UL, if the plug end carries a ground, the connector end has to carry it too. The C14 is a 3-wire plug and the C7 is a 2-wire connector. The ground pin on the C14 has nowhere to go on the C7 connector. While safe to use, the C14 to C7 cannot be UL listed – the rationale being that the ground pin on the C14 end implies protection that is not actually delivered. If UL listed products are a part or your procurement requirements, this cord will not do.

Many facilities, integrators, and OEMs require UL listed cords. If the power cord doesn’t have the mark, it can delay an install or cause an audit to fail. A C14 to C7 power cord could be convenient today, but a compliance headache tomorrow.

C18 to the Rescue

C7 to C18 Power Cord

The C18 is the ungrounded cousin to the C14 plug. The same external form factor, but with only two pins instead of three. It’s internally consistent with the C7 so it can be UL listed with two pins on the plug, two conductors in the cable, two pins on the connector. Because it has the same external form factor as the C14 it can plug into the ubiquitous PDU with C13 outlets. Meanwhile, the C17 (the C18’s female counterpart) cannot accept a C14 plug. So if you happened to have a power source with a C17 outlet (uncommon), it would not allow a grounded C14 connection.

Shop C18 to C7 Power Cords

Summary

While C14 to C7 cords are on the market, and are safe to use, they cannot be UL listed because the plug end carries a ground whereas the connector end does not. That’s where C18 to C7 cords come into the fold. The C18 has the same shape as the C14, just without the ground pin making it able to be UL listed.

For more information, you can reach us at 888-346-4688 or by email at sales@stayonline.com.