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PDU Cables FAQ's

Frequently Asked Questions

 

What is a PDU Cable?

Where are PDU Cables used? 

Is Flexible Metal Conduit OK in a raised floor plenum environment?

How is a PDU Cable made?

Why is UL Listing important?

What types of cable options does PDU Cables provide?

Can PDU Cables provide Multiple Circuit Cables or Daisy Chains?

If wiring to a tall RPP unit, can PDU Cables provide tails to fit?

What are the benefits of using the different colors of liquid tight conduit?

What different mounting options does PDU Cables offer with its cables?

How are PDU Cables tested?

What is the benefit in labeling the cables?

How are PDU Cables packaged?

Why does PDU Cables offer circuit breakers?

What if I need cables right away?

Can PDU Cables help configure my cables?

Does PDU Cables offer a warranty?

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What is a PDU Cable?

A PDU Cable, branch circuit power distribution cable or “power whip” is a cable that carries power from a Power Distribution Unit (PDU) or Remote Power Panel (RPP) underneath a raised floor, or overhead to power up equipment, typically computer equipment like servers. 

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Where are PDU Cables used? 

A PDU Cable can be found in almost any environment that has a raised floor.  Data centers, telecom offices, hospitals, laboratories.  Thousands of data centers, including many Fortune 500 Companies, financial institutions, schools and universities, manufacturing and industrial facilities, and government organizations have made PDU Cables their first choice for power whips. 

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Is Flexible Metal Conduit OK in a raised floor plenum environment?

NEC article 645.5 modifies article 300, permitting branch circuit conductors to be installed under a raised floor using Liquid Tight, Flexible Metal Conduit or MC Cable if the computer room meets the qualification as an Information Technology Equipment (ITE) room. 

 

For more on NEC article 645.5, click here

For more information on the different types of conduit most suitable for supplying power to mission critical facilities, click here

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How is a PDU Cable made?

A PDU Cable is made out of a liquid tight conduit intended for underneath raised floor environments.  On one end of the cable a tail, or exposed wire, (standard tail is 8’ but can be made to any customer specified length) will be used to go up and connect into the PDU.  On the other end of the cable is the receptacle, this is the end of the cable that supplies the power to the different types of machines.  Each piece of equipment will have different power needs and require a special receptacle type to accommodate its outlet; these factors determine the number and size of wires used to build the actual PDU Cable. 

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Why is UL Listing Important?

Underwriters Laboratory (UL) is the standard for safety and compliance.

PDU Cables meet all requirements of Underwriters Laboratory to assure the electrical inspector that the cables will meet the stringent UL Standards and not cause electrical hazards in your mission critical facility. All cables are manufactured with UL Listed components and are then certified as a complete UL Listed Assembly.

 

An important labor savings benefit that the UL Listing provides, under the National Electrical Code (NEC) Article 645.5 (C) and NFPA 75 10.4.1 and 10.4.2 state that UL Listed interconnecting (branch circuit) cables do NOT have to be securely fastened in place every 4.5 feet - expediting cable installation and integration.

 

Using UL Listed cable assemblies assure the data center manager and electrical inspector of code compliance and provide certainty of data center up-time.

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What types of cable options does PDU Cables provide?

PDU Cables offers power cable assemblies for both under-floor and drop-down power solutions, including: 

  • · Liquid-Tight Flexible Metal Conduit (LFMC)
  • · SO Cord Assemblies
  • · Metal Clad (MC) Cables
  • · Molded Cord Assemblies

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Can PDU Cables provide Multiple Circuit Cables or Daisy Chains?

Yes, space under the data center floor is always difficult to allocate and manage.  When you consider the number of “line-powered” devices to be provisioned, you should also consider installing multiple circuit cables (MCC’s).  Multiple circuits can be run through the same cable conduit allowing for 2, 3 or more pieces of equipment to be powered off the same power whip, saving you time and money.  Our cable technicians can help you decide when and where daisy chains or multiple circuit cables make sense.  

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If wiring to a tall RPP unit, can PDU Cables provide tails to fit?

Yes, our standard cable tails are cut to an 8’ length, but longer tails are available when wiring to tall RPP units or connecting to a cable trough. 

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What are the benefits of using the different colors of liquid tight conduit?

Most data centers have adopted the use of redundant power sources and a good way to organize those dual power feeds is to match liquid tight conduit by color for each power source.  For added convenience and improved cable management, PDU Cables offers eleven colors of conduit allowing data centers to have unique colors for each primary and redundant PDU/RPP unit. 

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What different mounting options does PDU Cables offer with its cables?

PDU Cables offers a variety of options to facilitate elevated mounting positions including pedestal clamps attached to the back of the box, mounting bolts through the back of the box for the receptacle to be attached to the uni-strut, and mounting ears. 

 

Mount power receptacles closer to the plug and off the floor to help protect against possible pooling water and address cable air dams under the raised floor.  Elevated mounting positions allow for better airflow and improved CRAC unit (computer room air conditioning) efficiency.   

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How are PDU Cables tested?

ALL (100%) of PDU Cables power distribution cable assemblies are thoroughly factory-inspected and tested to ensure unsurpassed performance and reliability. 

Insulation Leakage Test

PDU Cables performs insulation testing on all of its power cable assemblies.  The test ensures minimal leakage through wire sheathing and verifies that the conductors were not damaged during assembly which can create arching between conductors or to ground, causing a circuit to trip.  This also tests for proper phase rotation to ensure all conductors are connected to the proper terminations. 

 

Phase Rotation Test

In addition to the tests required by Underwriters Laboratory, PDU Cables performs an additional continuity test on each conductor to ensure each device is wired properly.  This tests continuity between each blade or socket of the supplied plug or receptacle and the correct color conductor at the opposing end of the cable, ensuring the device is wired according to the correct color code. 

 

Ground Continuity Test

This test ensures that there is grounding continuity between the grounding blade or socket of the supplied plug or receptacle and the supplied grounding conductor on the opposing end of the cable.  The continuity testing ensures that there are no breaks in the conductors used. 

 

Dielectric Withstand Voltage Test (Hi-Pot)

The Hi-Pot test is performed on each conductor at 60hertz, 1200 volts (AC) + 2.4 times the marked voltage for one second.  For instance, if the cable is for a 120 volt application, the voltage amount applied to the cable would be 1200 + 288 (2.4 x 120 volts) or 1488 volts applied at 60 hertz for one second.  There can be no breakdown (shorting or arcing) of any conductor during the test.

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What is the benefit in labeling the cables?

Each PDU cable includes a cable identification label which references the circuit number, equipment, PDU panel, receptacle and length, as well as the UL certification.  This allows for easier installation when on site and for quicker isolation of cables if you need to shut equipment down. 

 

Individual labels are protected with clear heat shrink wrap tubing to prevent alteration or accidental removal, and are located at both ends of the cable (or located per customer specification for convenient identification). 

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How are PDU Cables packaged?

PDU Cables power cable assemblies are coiled into sturdy fiber drums, from shortest to longest cable length and barreled by PDU designation, panel and row (or any other customer provided specification) for ease of in-row installation.  Cables are wiped clean prior to barreling to ensure cleanliness and minimize the introduction of contaminants into the data center.  Each drum is labeled with a sheet that identifies exact contents and showing Hi-Pot test results, and loaded onto a standard shipping pallet.  The fiber drums provide cable protection during shipment and make it easy to unload and move cables around the job site.

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Why does PDU Cables offer circuit breakers?

With each cable purchase PDU Cables can provide a circuit breaker matched to the cable and your main breaker, giving you one less thing to worry about.  PDU Cables stocks a full line of both plug-in and bolt-in style circuit breakers, including Square D, GE and Cutler-Hammer. 

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What if I need cables right away?

PDU Cables is known for its quick turnaround and prompt delivery; most orders can be built and shipped within 24 hours.  Expedited orders and shipping are available as well. Our quick turn philosophy, with attention to detail, has helped many data center professionals meet tight deadlines.

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Can PDU Cables help configure my cables?

Our cable technicians provide project take-off, panel schedules, schematics and labeling services.  If you have engineering or architectural drawings, we can create a list of cable requirements for a quote as part of a take-off process. 

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Does PDU Cables offer a warranty?

PDU Cables ensures that all power cable assemblies are free from defects in quality and workmanship from the date of original purchase.  PDU Cables warranty excludes connectors, circuit breakers, and devices and does not cover damages due to accidents, abuse or improper installation.  Contact your regional sales manager for more information about registering for the limited lifetime warranty. 

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