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FAQs for Data Center Power Cords

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Posted on May 20, 2020
September 18, 2020
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Data center power cords are important for improvements in energy consumption, data center uptime and service response times. Improper cabling or choice of data center power cables may wreak havoc on the whole network infrastructure. Therefore, it is important to figure out the confusing questions concerned with data center power cords for better network status. Listed below are the frequently asked questions (FAQs).

FAQs on Data Center Power Cord Definition, Types and Jackets

Q1: What is a data center power cord?

A1: A data center power cord represents any power cables installed in a data center.

Q2: What types of power cords are used in a data center?

A2: There are many types of international data center power cords of different standards such as IEC power cords, NEMA power cords, Schuko/CEE7 power cords, BS1363 UK power cords, etc. Among them, the IEC power cords and the NEMA power cords are suitable and commonly used for connecting computer and network equipment (servers, network switches) in a data rack to a power distribution unit (PDU). The most common IEC outlet types in data centers are C13 and C19 connectors as defined by IEC 60320. And the most common NEMA power connectors or plugs are NEMA 5-15P.

Q3: What’s the difference between C13 and C15 power cords?

A3: Both C13 and C15 power cords are 3-hole with earth touch, and defined with the same rated current and voltage. However, they have distinct features in shape characteristic, appliance inlet type, temperature rating and applications as follows:

Connector Type C13 C15
Ground Post Yes Yes
Rated Current/Voltage 10 A/250 V 10 A/250 V
Shape Characteristic No notch

A notch opposite the earth

Appliance Inlet Type C14 C16
Temperature Rating 70 ℃ 120 ℃
Applications PCs, printers, monitors, instrument amplifiers to fixed-configuration switches Electric kettles, computing networking closets, server rooms, PoE switches with high wattage power equipment

Q4: What voltage should I use? 120V, 208V, 240V, AC or DC?

A4: Since the availability of DC power delivery systems outside of telecom equipment racks is not widely supported, AC power cords are still the mainstream in data centers. Most modern information technology equipment are designed to operate at AC 100 V to 250 V to accommodate North American 120/208 V, Japanese 100/200 V, and 230 V used in the rest of the world to allow for worldwide power compatibility. Normally, AC 240V power is recommended because of many reasons. For example, 277/480V to 240/415V step down autotransformer is 90% smaller and less expensive than 120/208V PDU isolation transformer and 240V distribution yields the same power capacity with nearly half the current as 120 V.

Q5: What does the data center power cord jacket abbreviations mean?

A5: Here is the most common nomenclature used for power cable jackets:

S—Service Grade (Extra-Hard Service Grade if not followed by J, V or P); normally rated to 600 V

J—Junior Grade; a “J” cord is rated for hard service up to 250-300 V

V—Vacuum Cleaner Cord; light-duty cable

P—Parallel Cord; light-duty zip cord

T—Thermoplastic; most often polyvinyl chloride (PVC)

E—Elastomer; a copolymer that adds flexibility, especially in sub-freezing conditions

O—Oil-Resistant outer jacket

W—Outdoor; stands up to moisture and sunlight

Normally, the power cable jacket consists of a combination of these letters to define various cable jacket types. Here is an overview of the most common jacket types in North America.

Type Description Jacket Material Application
SJT Junior Hard Service Thermoplastic Thermoplastic (PVC) insulated conductors and jacket Indoor use; tools and equipment, lights, power extensions
SJTW Junior Hard Service Thermoplastic, Outdoor Rated Moisture- and sunlight-resistant thermoplastic (PVC) insulated conductors and jacket Indoor/outdoor use; tools and equipment, lights, power extensions
SJOW Junior Hard Service Oil-Resistant Outdoor Rated Oil-, moisture- and sunlight-resistant thermoset insulated conductors and jacket Indoor/outdoor use; small motors and machinery
SVT Service Vacuum Thermoplastic Light-duty thermoplastic (PVC) insulated conductors and jacket Indoor use; small appliances such as vacuums, fans and lamps
SEOW Extra-Hard Service Thermoplastic Elastomer Oil-Resistant Outdoor Rated Oil-, moisture- and sunlight-resistant heavy-duty thermoplastic elastomer (TPE) insulated conductors and jacket Outdoor use in extreme weather conditions

FAQs on Using Power Extension Cords in the Data Center

Q1: Can extension cords be used in ITE rooms?

A1: According to section 400.8(1) in NEC (National Electrical Code), flexible cords and cables including power extension cords are not permitted to be used as a substitute for permanent wiring of a data center structure.

Q2: Are cord sets and interconnect cables considered "fixed wiring"?

A2: According to NEC 645.9(F), power cables, communications cables, connecting cables, interconnecting cables and associated boxes, connectors, plugs, and receptacles that are listed as part of, or for, information technology equipment shall not be required to be secured in place. That is, cord sets and interconnect cables are not considered as "fixed wiring".

Q3: Can cord sets be replaced in the field with cords of different lengths?

A3: Some cord sets designed and listed as replaceable can be replaced with cords of different lengths, while others can not.

Q4: Why is it dangerous to use extension cords?

A4: An extension cord is a bundle of insulated electrical wires with a plug on each end in essence. When much electrical current flows through wires, the heat the current generates can overheat and melt the plastic insulation of the wires, causing short circuits and fires. This issue is not likely to happen when one plugs an appliance directly into an outlet using its factory cord designed with appropriate size for that appliance.

Q5: Are there any extension cord rules to improve worksite safety?

A5: There are five rules listed below to improve worksite safety.


  • Meet OSHA (Occupational Safety And Health Administration) requirements: Using an AEGCP (Assured Equipment Grounding Conductor Program) and using a GFCI (Ground Fault Circuit Interrupter) are two ways to meet the OSHA requirements. The AEGCP method requires multi-point cord inspection every work day, which is time-consuming and is often ignored by users. And there is no protection if some dangerous situation happens when in use. The GFCI will disconnect power right away if a potentially dangerous situation occurs. Normally, every extension cord on a job site has to have a GFCI to protect users.

  • Keep the extension cord length within safety requirements: The extension cords should not exceed 100 feet in length. If the job requires more than a 100-foot distance, a temporary power distribution box is required.

  • Discard damaged extension cords: Although the power cord can still work, the damaged power cord is a violation of the OSHA regulations. Discard the damaged power extension cables to prevent potential electrical hazards.

  • Avoid initial installation mistakes: Do not fix extension cords to walls or ceilings using metal nails or staples because there may be possible damage to the power extension cable jacket.

  • Do not run extension cords through doorways: One should avoid laying extension cords across the room to minimize trip hazards.

Q6: Power strip vs. extension cord: which one should you use?

A6: The main difference between power strip and extension cord lies in the purpose. If you want to multiply the number of electrical outlets from a single source, use a power strip. If you want to stretch out a power source towards a distant appliance, use an extension cord.

Q7: Surge protector vs extension cord, what’s the difference?

A7: Surge protectors are totally different from extension cords. A surge protector diverts any extra power surges that might come through the electrical outlets to keep equipment safe. While, extension cords are crucial when you need to stretch an appliance from one location to a distant electrical outlet.