Power FAQs

Power FAQs

Use our Power frequently asked questions to help find the answer to your question. Select a topic below to get started.

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Current Monitoring (EM)
Current Monitoring (EM)

Are power sensors external on Geist units?

No, the power sensors are internal.

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.


All of my external sensor graphs have disappeared and the sensors are showing up as "Unplugged" in the Display page. What's wrong?

The problem is most likely that one of your external sensors has a crossed wire. Follow this procedure to test the sensors: 1. Unplug all of the sensors and check the "Remove all unplugged devices" check box on the Display page. 2. Plug in one sensor and wait for it to be detected. 3. If the sensor works, leave it plugged in and plug in another sensor. 4. If the sensors stop responding, the last sensor to be plugged in is faulty. If your unit is under warranty, call support for a replacement.

Can R-Series units present data as an Excel spreadsheet?

Information collected by R-Series units can be exported to Excel or another spreadsheet software by downloading the CSV log file from the unit's Logs page.

Can the buzzer on my Remote Display (RSD) or Environmental Monitor (RSE) unit be turned off remotely?

The test alarms function can be used to turn the buzzer off remotely. The following steps will lead you through this process: 1. Go to the Alarms page. 2. Scroll down to the Test Alarms section. 3. Pick one of the internal sensors from the Sensors drop-down box. 4. From the Alarm State drop-down, choose Buzzer. 5. Select Clear from the Trap Type drop-down. 6. Click on the Test button. 7. The buzzer should turn off in a few seconds.

Do all R-Series units monitor power?

The RCX, RCM, RCO and RCU monitor power and provide RMS volts, amps, watts, volt-amps, kilowatt-hours and power factor for each circuit monitored.  RCO and RCU also feature outlet level power monitoring.

How can MIBs be obtained for R-Series units?

For R-Series units the MIB can be found in two places. In the header of the units web page, under Alternate Formats, is a link to the MIB. A copy of the MIB is also included in the firmware zip file of version 2.53 and higher.

I am continually receiving alarms that say one (or more) of my sensors are "unplugged" and then a few minutes later I get a "clear" alarm for that sensor. How can this be corrected?

Some customers with DC-powered units (Watchdog 1200, Watchdog 1000) have found that grounding the chassis of the unit to an isolated ground point in their rack helps in this situation. The Watchdog 1200 and Watchdog 1000 contain a 10-32 threaded hole on the back of the unit which is used for grounding purposes.

I can access the D-link camera with Internet Explorer, but the R-Series unit doesn’t display an image from the camera. How can this be corrected?

Check the camera IP address and camera model on the R-Series unit's Configuration page. If the camera model number and IP address are correct, you may need to update your camera to the latest firmware.

I can no longer access the Web interface on my R-Series unit. What can I do to fix this?

It may be that someone has turned off the HTTP access and is only allowing HTTPS (secure) access. Try typing https:// into your browser to see if you can access the unit. If this works you can go into the configuration page and change from HTTPS only to HTTP and HTTPS access. Some users in enterprise environments have proxies enabled that can block access to R-Series devices. In Internet Explorer: 1. Go to Tools->Internet Options and click the Connections tab. 2. Click ""LAN Settings"" at the bottom of the tab. 3. If you have a proxy enabled, make sure that "bypass proxy server for local addresses" is selected. You may need to uncheck this to access other sites on your network once you are done using the R-Series. You may need to undo these steps to access other sites on your network once you are done using the R-Series unit. If you are still experiencing difficulties, please contact Geist at 800-432-3219.

Are R-Series units field-upgradeable?

Most R-Series units have field-upgradeable firmware. The Satellite Power Monitoring Plus (RSS) units function as external sensors and do not contain their own firmware, therefore they are not field upgradeable.

Can R-Series units present data via SNMP?

Yes, R-Series units can report data via SNMP.


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

Geist has the largest in-house engineering department in the industry. Geist’s in-house engineering department includes mechanical, electrical, conformance, board layout and software specialists. The testing lab at Geist is authorized to conduct UL® testing on Geist 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. Geist also has an in-house team responsible for embedded circuit design, which allows for faster turnaround on custom applications requiring circuit boards. Geist’s engineering team is dedicated to providing the highest quality products and service available in the industry. Geist invests in continuous improvement. The Geist Metalworks division allows us to punch, bend and paint our own metal products. This allows Geist to reduce already short lead times by eliminating scheduling conflicts with suppliers. The Geist 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 a PDU for my installation?

There are several factors to consider when selecting a Geist PDU to ensure that the PDU 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 a Geist PDU 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 PDU will be able to deliver to a load. The PDU should not be installed in an application where the nameplate ratings are exceeded. RECEPTACLE: The PDU’s output power is connected to information technology equipment through either NEMA or IEC receptacles. The PDU 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 PDU it is installed in. INTERNAL BREAKERS: Geist’s PDUs can be equipped with internal circuit breakers that are used to protect the circuit in case of overload or earth fault conditions. For PDUs rated 12A or 16A, the circuit breakers are optional components that act as supplementary protectors. For PDUs rated higher than 16A, the circuit breakers are required components that provide primary overcurrent and earth fault protection for the PDU’s internal circuits. The PDU 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 a PDU without a circuit breaker?

Yes, some configurations can be purchased without an internal circuit breaker. All Geist’s PDUs require an appropriately sized branch circuit breaker in the building installation. Branch circuit breakers should be sized according to the PDUs 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 PDU’s nameplate. For example, a 16A rated PDU 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 Geist cord-connected units listed with a de-rated Amperage?

Geist’s cord-connected PDUs 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. Geist PDUs 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 a Geist PDU is 80 percent of the maximum current rating of the branch circuit used to power the PDU. Most of Geist’s customers base their PDU input current specifications on the branch circuit ratings; consequently, the catalog lists the ratings of the branch circuit that the PDU is intended to be connected to. In addition to the branch circuit rating, it is important to consider the nameplate PDU rating which includes the 80 percent de-rating factor required by UL®/NEC when calculating PDU requirements.

Why should I consider designing my data center with 208V instead of 120V?

The electrical power consumption of electrical appliances is measured in Watts. Wattage (Watts value) is a product of the rated Voltage and Current. The higher the Voltage the lower the current required to supply the same Watts. The same size wire can carry nearly 2x as much power (Watts) @ 208V versus 120V. A Voltage of 208V yields 1.73 times more power than 120V.

What are the benefits of utilizing two 20A breakers versus two 15A breakers on a 30A PDU?

20A breakers in a 30A unit allow maximum flexibility of load connection without nuisance tripping. The receptacles in a 30A PDU are divided into two independent groups. A 30A PDU distributing to 15A or 20A receptacles must be broken down into either 15A or 20A circuits internally. By opting for 20A internal circuits, PDU circuit balance is less critical. One circuit may be loaded to greater than 15A. This would not be possible if each breaker were rated at 15A.

Is it possible to distribute both 120V and 208V from a PDU with a single input cord?

PDUs with 3-phase WYE input allow for the option of distributing 120V and 208V in a single power strip. 3-phase WYE consists of three phases, one neutral and one ground conductor. 208V output is achieved across two phase conductors and 120V output is achieved across one phase conductor and the neutral conductor.

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. A computer 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 computer. As the computer 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?

Geist PDUs are high quality power strips intended to be used to distribute power to information technology equipment within a data center. These PDUs, 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 PDUs 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 PDU; 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?

1) 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.

Definitions & Terms
Definitions & Terms

Are power sensors external on Geist units?

No, the power sensors are internal.

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 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.

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). 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 PDUs, each of which is capable of handling the power requirements of the entire cabinet. Plug one PDU 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 Geist use an L22 plug that is rated at 277/480V on a PDU that is rated at 230/400V?

The L22 plug has been approved for use @ 230/400V by UL. The nameplate rating of the PDU 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. Geist offers this on North American 230/400V 3~ PDUs as an alternative to the IEC 309 4P/5W Pin and Sleeve connector. Note that the intended operation of this unit is for 230/400V 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 PDU on the products spec sheet?

On a 3 phase PDU 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 PDU is outputting 208V, the calculation would be Volts x Amps (80%) x SQRT(3). The SQRT(3) is used as line voltage for 208V output is derived from using two hot conductors. For example, a 30A 3 phase unit outputting 208V would be 208 x 24 x SQRT(3)=8.6kW.