Power Distribution

Frequently Asked Questions on Rack PDUs

Navigate to the section to view frequently asked questions about the following products:
Rack PDU
Surge rPDU
Auto Transfer Switches
Power Definitions and Terms

Rack PDU

How can Vertiv Geist deliver customized products in 1 week when others take months?

Vertiv Geist has the largest in-house engineering department in the industry. The in-house engineering department includes mechanical, electrical, conformance, board layout and software specialists. The testing lab at is authorized to conduct UL® testing on Rack PDU products to 60950 IT equipment standards as part of the UL® Data Acceptance Program. Our software specialists can create software for new or custom products and deploy directly to production to reduce lead times. There is also an in-house team responsible for embedded circuit design, which allows for faster turnaround on custom applications requiring circuit boards. The engineering team is dedicated to providing the highest quality products and service available in the industry and invests in continuous improvement. The Metalworks division allows us to punch, bend and paint our own metal products. This allows Vertiv to reduce already short lead times by eliminating scheduling conflicts with suppliers. The Metalworks team also helps reduce the lead time on custom units, making products available to the customer faster than anyone else in the industry.


What rating should I use to correctly select an rPDU for my installation?

There are several factors to consider when selecting a Vertiv Geist rPDU to ensure that the rPDU has sufficient capacity for the intended application. The three main factors to consider are (1) nameplate rating, (2) receptacle ratings, and (3) internal breaker configuration. NAMEPLATE: The nameplate rating marked on the rPDU is the intended operating voltage range and maximum operating input current. Nameplate ratings are based on both regulatory requirements and design factors and represent the continuous total current that the rPDU will be able to deliver to a load. The rPDU should not be installed in an application where the nameplate ratings are exceeded. RECEPTACLE: The rPDU’s output power is connected to information technology equipment through either NEMA or IEC receptacles. The rPDU should not be installed in a manner that will exceed the maximum current rating of any individual receptacle. For example, a NEMA 5-15R receptacle should not be loaded to over 15A regardless of the nameplate rating of the rPDU it is installed in. INTERNAL BREAKERS: The rPDUs can be equipped with internal circuit breakers that are used to protect the circuit in case of overload or earth fault conditions. For rPDUs rated 12A or 16A, the circuit breakers are optional components that act as supplementary protectors. For rPDUs rated higher than 16A, the circuit breakers are required components that provide primary overcurrent and earth fault protection for the rPDU’s internal circuits. The rPDU should not be connected to a load that will exceed the current rating of an internal breaker. For maximum protection against nuisance tripping, it is recommended that internal breakers are only loaded to 80% of the breaker current rating.


Can I purchase an rPDU without a circuit breaker?

Yes, some configurations can be purchased without an internal circuit breaker. All Vertiv Geist’s rPDUs require an appropriately sized branch circuit breaker in the building installation. Branch circuit breakers should be sized according to the rPDUs namplate rating, and electrical code requirements. To comply with the NEC the circuit breaker in the building installation should have a trip current rating that is 25% higher than the rPDU’s nameplate. For example, a 16A rated rPDU requires a 20A circuit breaker.


How do I determine how much power is needed in a cabinet?

Perform the following for a quick estimate of the power needed in a cabinet: Add the power ratings in Watts from the nameplate labels of the equipment you want to put in the cabinet. [Sometimes, the labels indicate Amps instead of Watts. In this case, multiply Voltage and Current values to get an approximate value for power.] Example: 30 servers each using 300 Watts= 30 x 300 = 9,000 Watts or 9kW.

Why are Vertiv Geist cord-connected units listed with a de-rated Amperage?

Cord-connected rPDUs carry a nameplate current rating that is 80 percent of the branch circuit rating listed in the catalog specification. The nameplate current rating has been lowered in order to comply with UL®/NEC requirements. Vertiv Geist rPDUs are UL® Listed as Information Technology Equipment to the UL® 60950 Standard. UL® 60950 requires that the attachment plug of Listed Information Technology Equipment shall be rated not less than 125 percent of the Rated Current of the equipment at the nominal system voltage range as defined by the configuration of the plug. This clause in UL® 60950-1 is based on the requirements of the National Electrical Code (NFPA-70), which state that branch circuit conductors and overcurrent protection devices shall be sized to carry 125 percent of the continuous load and 100 percent of the non-continuous load on the circuit breaker. Due to this UL®/NEC requirement, the nameplate current rating of an rPDU is 80 percent of the maximum current rating of the branch circuit used to power the rPDU. Most of our customers base their rPDU input current specifications on the branch circuit ratings; consequently, the catalog lists the ratings of the branch circuit that the rPDU is intended to be connected to. In addition to the branch circuit rating, it is important to consider the nameplate rPDU rating which includes the 80 percent de-rating factor required by UL®/NEC when calculating rPDU requirements.


How does Wattage relate to heat in a cabinet?

Heat is measured in BTUs and power is measured in Watts. Almost all electrical energy used in computing is converted to heat. An IT equipment power supply can be as low as 80 percent efficient. This means that for every 100 Watts it draws, 20 Watts may be converted directly into heat without ever being used by the device. As the IT equipment processes information, the rest of the power is dissipated throughout the system as heat. Since all power can be counted as heat, adding the Watt ratings of all equipment in a cabinet will give a relatively 1:1 relationship to heat generated. Example: 40 servers x 300 Watts each = 12,000 Watts (12kW) heat. Also, Watts can be converted to BTUs by multiplying Watts by 3.412.


Why can’t I output 120V from a 208V single-phase input?

Vertiv Geist rPDUs are high quality power strips intended to be used to distribute power to information technology equipment within a data center. These rPDUs, which are available in single or three phase configurations, are not designed to increase or reduce the input circuit’s voltage level. Single-phase 120V rated power distribution units installed in North America will typically be powered by a 120V line-to-neutral circuit. The outlets on these rPDUs will all be wired line-to-neutral and will output 120V. Single-phase 208V rated power distribution units installed in North America will typically be powered by a 208V line-to-line circuit. The neutral conductor is not connected to a standard 208V single-phase rPDU; consequently, all outlets will be wired line-to-line and will output 208V.


What are the advantages of bringing 3-phase power to my cabinet?

Less wire under the floor improves airflow and reduces wiring confusion. A 20A 3-phase installation contains five wires where the equivalent single phase system would require nine wires (3x3). 2) Fewer whips to pull saves you time and money. A 3-phase system has one whip for the electrician to bring to the cabinet where the equivalent single phase system would have three whips. This saves both material and labor cost. 3) Simplified load balancing reduces technician installation and troubleshooting time. With all 3 phases available in a single cabinet, load balancing can be achieved at the cabinet level where similar type equipment is often found. In a single-phase system, a minimum of three cabinets may need to be examined to balance the same load.

Surge rPDU

What is surge suppression?

Surge suppression technology helps to limit voltage spikes from potentially damaging the sensitive electronics in IT equipment, televisions, audio components and other devices.


Do Vertiv Geist surge suppression units have RFI/RMI filtering?

No, the Vertiv Geist line of surge suppressed power strips do not contain any RFI/EMI filtering.


What are the protection modes of Vertiv Geist surge suppressed power strips?

Vertiv Geist surge suppressed power strips provide 3-levels of protection: line to neutral, line to ground and neutral to ground.


What is the Joule rating of Vertiv Geist rPDUs with surge suppression?

Vertiv Geist unit have a rating of 720 Joules.

Can I order a surge unit without a circuit breaker?

No, Vertiv Geist surge products require over current protection to meet regulatory requirements. This is accomplished with the use of a resettable circuit breaker.


Does Vertiv Geist offer 208V units with surge suppression?

Vertiv Geist does not offer standard surge units in 208V. Please contact Inside Sales at 800-432-3219 to discuss what custom options may be available.


Are Vertiv Geist 3-phase units available with surge suppression?

Vertiv Geist does not currently offer any 3-phase product with surge suppression.

Auto Transfer Switch

Can I select the input from the front of the Auto Transfer Switch?

No, the Vertiv Geist Auto Transfer Switch input sources are not selectable.  The ‘A’ input should be connected to the primary power source, with the ‘B’ input being connected to the secondary source.


What is the expected operational life expectancy of the Auto Transfer Switch?

The Auto Transfer Switch has been designed with a life expectancy of 100,000 operations. Within a Data Center environment this would be considered a life time warranty for the switching system.


What is the warranty of the Auto Transfer Switch?

Units without a local display have a lifetime warranty. Units with the local display have a 3 year warranty.

What indications do I have on the Auto Transfer Switch?

The Auto Transfer Switch unit has LEDs on the front of the unit to show which source (A or B) is being used at the moment and what sources are available (A/B). With the local display option you get the ability to see either Volts/Amps/Watts or Power Factor when using the Power Meter, or Amps only when using the Current Meter option.


What is Phase Synchronization?

Phase synchronization is the process by which two or more cyclic signals tend to oscillate with a repeating sequence of relative phase angles.


What happens if my inputs are not synchronized?

If the input sources are not synchronized it could lead to damaging the relay causing the unit to fail. It could also lead to an upstream breaker sensing a fault condition and opening the circuit.

Power Definition and Terms

What is an Amp?

An Amp (or Ampere) is the standard measure of electrical current.  Much like water flowing through a pipe, the Amp is a measure of how much electricity is moving through a wire at a given time.  The Amp draw of a circuit is dependent on the needs of the devices plugged into it, and is limited by the branch circuit protection.


What is a Volt?

A Volt is the standard measure of electrical potential and a fixed value for every circuit. Voltage is measured with respect to a reference point (usually between the two respective conductors of the circuit). Voltage is analogous to pressure in a water pipe. Higher pressures, or higher voltages, allow more energy to flow within a given amount of time for a given wire size. Standard voltages present in most data centers are 120V and 208V in the U.S., and 230V in continental Europe. Some newer U.S. data centers are being designed to utilize 230V.


What is a Watt?

A Watt is the measure of total work performed by the energy consumed in a system. The calculation is: Watts = Volts x Amps x Power Factor.


What does RMS mean?

RMS stands for Root-Mean-Squared. It is used in conjunction with AC Volts and AC Amps to express an average value. A true RMS calculation takes into account the shape and phases of the wave forms being delivered to a circuit. AC voltage and current are ever-changing values. Using RMS measurements provides useful values.


What is Apparent Power?

Apparent Power is the instantaneous calculation of Volts x Amps.


What is PUE?

PUE stands for Power Use Effectiveness. PUE is a measure of how efficiently power is being used in a data center, and is becoming the standard benchmarking metric in most data centers. PUE is determined by dividing the total facility power use (Building Watts) by the IT equipment load (IT Watts).


What is DCiE?

DCIE stands for Data Center Infrastructure Efficiency. DCIE is IT Power divided by Total Facility Power, expressed as a percent (%). DCIE is the inverse of PUE.


What is Power Factor?

Power Factor is used to define the ratio of Real Power to Apparent Power, or how much of the power is being used to do work. Power Factor is therefore a number zero to one but may also be displayed as a percentage. Lower power factors have the additional cost of energy loss in the distribution system and require a larger infrastructure.

The power distribution within the building has several points where losses occur (UPS, transformers, wire runs), so the ideal place to measure the IT power load is at the cabinet level within the power strip. These readings can be collected and aggregated to determine the IT power load. Once an initial assessment of PUE has been made, efforts can be made to improve PUE by applying various methods to improve operational efficiencies in the data center.


What is Real Power? How is this useful?

Real Power is sometimes referred to as ‘True’ power. Real Power is the actual power being used by the load and is measured in Watts (W). Real Power takes into account the phase angle of the current and this is typically the nameplate rating on IT equipment.


What is Redundant Power?

An absolute must in mission-critical applications, the general concept behind power redundancy is to connect critical equipment to two independent power sources. If one line of power is interrupted, the second is able to power the critical equipment. This is accomplished in the following. First, equip the cabinet with two rPDUs, each of which is capable of handling the power requirements of the entire cabinet. Plug one rPDU into the first power source and the other into the alternate. Plug each piece of equipment into both (most data center equipment today has multiple power supplies as a fail-safe).


What is the difference between Apparent Power and Real Power?

Apparent power is the calculation of volts times amps. Real power is RMS power (real-time) plus the power factor calculation.


How can Vertiv Geist use an L22 plug that is rated at 277/480V on a rPDU that is rated at 230/400V?

The L22 plug has been approved for use at 200-240/346-415V by UL. The nameplate rating of the rPDU identifies the 230/400V rating in addition to labeling by the plug.


What is an L22 plug?

An L22 is a NEMA 4P/5W 277/480V 3~ WYE Twist-lock plug. Vertiv Geist offers this on North American 200-240/346-415V 3~ rPDUs as an alternative to the IEC 309 4P/5W Pin and Sleeve connector. Note that the intended operation of this unit is for 200-240/346-415V only.


What is an IEC 309 4P/5W Pin in Sleeve connector?

The IEC 309 Pin and Sleeve connector is more commonly used in European applications, however it is common in North America as well on devices rated at 60A and higher.


Why use an L22 plug?

An L22 plug may be desired over the equivalent IEC 309 plug as it is often more commonly found in North America in addition to being a smaller connector.


How is the kW rating calculated for a 3 phase rPDU on the products spec sheet?

On a 3 phase rPDU outputting 120V the calculation would be Volts x Amps (80%) x 3 (# of independent conductors). For example, a 30A 3 phase unit outputting 120V would be 120 x 24 x 3=8.6kW. If the rPDU

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