Download Plug and Receptacle Basics for Eaton ePDUs

Plug and Receptacle Basics for Eaton ePDUs
One of the biggest challenges in selling and configuring power quality products is providing the correct plug and
receptacle combinations for the protected IT equipment. Eaton’s ePDU® products, also known in the industry as
power distribution units, provide numerous output combinations to match a large variety of requirements. This
application note clarifies the difference between receptacle types and offer a recommendation for receptacle
solutions.
Plug and receptacle types
Connectors in both Europe and the U.S. are standardized by overseeing organizations. In the U.S. and Canada, the
American National Standards Institute (ANSI) and the National Electrical Manufacturers Association (NEMA) develop
common standards, while most areas of Europe, Asia and the Middle East follow standards setout by the
International Electrical Commission (IEC). There are a wide variety of differences between the two standards
including operating voltages and regulatory requirements.
NEMA nomenclature
Standard NEMA connectors use four basic character designators to create a part number. Figure 1 shows a basic
breakdown of an L14-30R receptacle.
Figure 1. NEMA Nomenclature Breakdown
Locking designation
The prefix “L” designates that the receptacle is locking. Plugs or receptacles without the “L” designation, such as a 515R, are not locking but are direct connections.
Voltage designation
The second term in the connector ID signifies the wires involved. For instance, a 5-type connector is a 120V rated
receptacle, containing one hot, neutral and ground wire. More powerful connectors provide a mixture of wires such as
the 14-type, which yields two 120V hot wires as well as a neutral and ground wire. The 14- and 21-type plugs on
ePDUs usually provide the most flexibility due to their ability to power both 120V and 208V single-phase
loads.
Application Note
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January 2011
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Amperage designation
Each plug and receptacle has a maximum amperage rating. In the NEMA nomenclature, this is listed after the dash.
In the L14-30R example, the receptacle is rated at 30A. It is important to keep in mind that plugs, receptacles and
breakers are 80% rated and should not be 100% loaded per National Electric Code (NEC). Though this is a main
concern of NEC and safe electrical practices, it is also a smart idea to abide by this rule to in order to limit the chance
of tripping a breaker and dropping the critical loads.
Connector designation
The final suffix “P” or “R” refers to the connector being a plug or receptacle respectively. As you go from the utility to
the load, the utility is always the receptacle while the load is always the plug. Because the receptacle may be carrying
live voltage, it would be dangerous to leave the terminal exposed to contact.
IEC 60309 nomenclature
The most obvious difference between IEC and NEMA standards is the lack of locking plugs in international solutions.
IEC code mandates that line cords be detachable, where NEMA cords are often fixed or locking.
Figure 2. IEC 60309 Nomenclature breakdown
Industrial designation
IEC connectors vary widely. For the purpose of this
application note, IEC 60309 and IEC 60320 connectors
are the focus. The IEC 60309 and IEC 60320, commonly
referred to as IEC 309 and IEC 320, designations call out
the type of electrical environment for which the connector
is suited. IEC 309 connectors, like the one in Figure 3, are
variable in design but are generally larger, pin and sleeve
connectors.
Figure 3. IEC-60309-560P9W corded plug on
an Eaton BladeUPS® connecting to a
matching corded connector providing 4wire plus ground at 208Y/120 Vac.
Pin designation
This designation signifies the number of pins within the
connector. A three-phase wye, 4-wire plus ground
connector would be a 5-pin type connector, while a singlephase 2-wire plus ground single-phase connector would
be a 3-pin type. It is important to match the pin type along
with the voltage designation to make sure the receptacle
being chosen matches the requirements.
Application Note
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January 2011
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Amperage designation
Like the NEMA nomenclature, the amperage designation is given to signify the current rating on the connector. The
80% NEC rule still applies to the IEC connectors.
Connector designation
IEC 309 connectors vary slightly from their NEMA counterparts. There are specific designations for plugs and
receptacles on cords (this includes whips). Below are common connector types and their form factor:
Receptacle — May also be referred to as a port connector. This is a fixed-type receptacle that
would be mounted on a wall or a conduit box. It is generally not on a cord.
Connector — Commonly referred to as a whip in raised floor applications when fed directly
from a breaker in a PDU. This is a receptacle that is on a flexible cord, not fixed on a wall.
Plug — Like the connector, the plug is a male connector on a flexible cord. This would
commonly be pre-installed on the ePDU, input to UPS or IT equipment.
Inlet — This is a fixed plug that would be pre-installed on manufactured equipment. It would be
fed from a connector or whip.
Voltage designation
This digit is filled based upon the voltage and number of poles in the connector. In IT applications, commonly used
connectors use are single-phase 208V (6), three-phase delta (9) and three-phase wye (9). To determine whether the
connector is a delta or wye, it is necessary to cross reference the voltage designation with the pin designation. For
example a 60A, 208Y/120V, plug would be IEC 60309 560P9W.
Watertight designation
In raised floor applications, it is required to use watertight power cables. This is meant to prevent short circuits and
dangerous situations caused by water leaks or condensation from computer room air conditioning.
IEC 60320 C13/C14 and C19/C20
The IEC 60320 designs are non-industrial and are
common on servers, monitors, switches and other IT
devices. IEC 320 line cords are not fixed, but are
detachable cables. The most commonly used IEC 320
connectors are the C13/C14 and C19/C20.
Rather than calling out each connector with the “P” or
“R” designation, the IEC 60320 part number signifies
whether it is male or female. The C13 is the female
receptacle which is compatible with the C14 plug.
Likewise, the C20 plug corresponds to the female
C19 receptacle.
Figure 4. Recessed IEC C14 inlet on a PC monitor
Application Note
www.eaton.com/powerquality
January 2011
Page 4 of 7
Under NEC, the C13 and C14 are capable of being fed from 15A breakers1, allowing for a maximum current capacity
of 12A. The C20/C19 connectors are able to provide up to 16A with a 20A maximum breaker for line protection. IEC
320 connectors are also unique because they have the ability to operate at 120V, 208V, 230 or 240V single
phase. This makes them extremely popular in IT equipment such as servers, monitors and switches.
2
IT manufacturers energize their equipment with power supplies converting the AC utility power to useable DC
capable of using either 120V or 200-240V3. Some power supplies auto-sense incoming voltage, while others contain
toggle switches allowing the user to change the switch to match the incoming voltage rating. IT equipment capable of
accepting voltages between 100-250 Vac most likely has a detachable cord with a fixed, recessed C14 or C20 plug
on the UPS as shown in Figure 4.
The true advantage of 100-250 Vac power supplies is that equipment does not need to have multiple designs for
specific markets. Instead, models shipped to locations following IEC, like Europe, will ship with IEC C13 to C14 line
cords, so the server can plug in to 230 Vac. Customers within NEC locations such as North America are shipped with
IEC C13 to 5-15P cords for operation at 120V. As a result, manufacturers save the time and effort of customizing
their product to certain markets by providing one single solution throughout the world.
Figure 5. Server cords: C13 to C14 jumper cord (Left) and C13 to 5-15P adapter cord
The 5-15P or C14 choice
In data centers and high density applications where efficiency and power delivery is critical, IT managers often take
advantage of the power supply capabilities and operate their servers at 208V. This has two main advantages. First,
208V circuits experience less voltage drop across circuits than 120V. Voltage falls to lower levels as it passes
through wire. A longer wire results in a higher voltage drop. Operating at lower voltages requires higher current to
meet the same power demands. Operating at higher voltages require less of a rise in current to counteract the
voltage losses. This is important because electrical efficiency in a wire is related to the amount of amperage passing
through the wire. Typically, installations using less operating amperage are more efficient.
The second advantage of the higher voltage is that circuits drawing less amperage allow for wire and breaker sizes to
be significantly smaller. Where a normal 5-15R can supply a maximum of 1440W at 12A, a C14 can supply up to
2600 VA at the same amperage. This makes the 208V operating voltage the primary voltage choice for users trying to
maximize power density. For customers trying to switch between 120V and 208V power, jumper cords are provided
both from the IT manufacturers and Eaton®.
Plug and receptacle selection in ePDU applications
As IT manufacturers produce equipment with faster speeds and more processing power, ePDUs must be able to
provide more receptacles and watts per an enclosure. Standard ePDU offerings which might be bundled with
enclosure solutions are no longer adequate.
Figure 6. Basic ePDU with (24) 5-20R and L6-20P
1
C13 and C14 connectors in high-powered ePDUs may also be protected by 20A circuits in certain circumstances.
Power supplies are rectifiers converting voltage from utility ranges down to 12-25 Vdc.
3
IT power supplies running off of two hot wires largely accept all 200V, 208V, 220V, 230V and 240V forms of incoming voltage.
Hence, power supplies will give a range of accepted voltages such as 200-240V.
2
Application Note
www.eaton.com/powerquality
January 2011
Page 5 of 7
120V load applications
The key to delivering more power through an ePDU is to select the correct input plugs. A common ePDU with a 120V,
L5-20P input can only deliver 1.92 kW (16A at 120V) falling well short of the modern enclosure power requirements of
5 kW or greater. While a larger 120V plug like the L5-30P can deliver more amperage, it is still limited to 2.88 kW
(24A at 120V).
This is where plugs such as the L14-30P have distinct advantages. The L14-30P contains two hot wires (each at
120V), a neutral and ground. The presence of the neutral wire allows 5-15 or 5-20 receptacles to be powered. Figure
6 shows a one-line diagram of the L14-30 ePDU with four circuits of 5-20 receptacles. Each one of the four
receptacle circuits is protected by a 15A circuit breaker, which allows each 120V segment to provide 12A or 1440W.
Combining all four segments, the entire ePDU is capable of giving 5.76 kW — almost twice the amount of power
provided in the L5-30 ePDU.
Figure 7. L14-30P ePDU with (24) 5-20R
Similarly, an L21-20P displayed in Figure 8 can provide a three-phase solution allowing for 5.76 kW. The three-phase
ePDU may be more advantageous in applications involving a three-phase source where IT and facility managers are
concerned with balancing phases. Because the L21-20 is fed from a 20A breaker, the ePDU does not contain internal
breakers and is limited to 16A per phase.
Figure 8. L21-20P ePDU with (42) 5-20R
208V load applications
Customers looking to power 208V loads with L6-20P, IEC C14, or IEC C20 plugs often default to ePDUs with L6-30P
inputs. This is a good solution providing 4.99 kW with two segments of IEC C13s (15A breakers protecting two 12A
circuits at 208V).
Application Note
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January 2011
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Figure 9. L6-30P ePDU with (24) C13 and (4) C19
Larger IEC connectors can provide more single-phase power than conventional NEMA connectors. The 60A single
phase connector, IEC 60309 360P6W, can carry up to 48 amps at 208V providing 9.98 kW. An ePDU with this
connector might have three segments of (14) C13 receptacles providing a grand total of (42) C13 outputs. Each
segment is protected by a 20A breaker, making it possible for up to 3.33 kW at 208V.
Figure 10. IEC 60309 360P6W ePDU with (42) C13
As with the 120V applications, three-phase ePDUs can provide more power than traditional L6-30 inputs while phase
balancing. An ePDU with an L21-30P can provide up to 8.65 kW through three segments of IEC C13 and C19
receptacles. With these high powered receptacles, UL permits a segment to contain multiple C13 and C19 protected
by a single 20A breaker. In this case, the limiting factor on the ePDU is actually the 30A input plug, which limits the
system to 24A per phase.
Again when higher power is needed, IEC solutions can deliver. The three-phase IEC 60A connector, IEC 60309
460P9W, operates at 208V 3ph and 48A maximum. This allows the ePDU to power up to 17.29 kW worth of power
via (12) C19 receptacles in (6) 3.33 kW maximum segments of (2) C19 receptacles. This type of ePDU is specifically
tailored toward high density blade server applications.
Figure 11. IEC 60309 460P6W ePDU with (42) C13
120V and 208V load applications
Sometimes, having equipment that all operates at the same voltage can seem to be an impossible task. Input plugs
containing both 120V and 208V capabilities make it easier to provide a consolidated power solution within the
enclosure.
Application Note
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January 2011
Page 7 of 7
The L14-30P can be used to provide a 4.99 kW solution configured with (4) 5-20R, (24) C13 and (2) C19. This can be
a very productive mix for customers trying to operate their equipment at 208V, but have a few small products only
capable of 120V input.
Figure 12. L14-30P ePDU with (4) 5-20R, (24) C13 and (2) C19
Three-phase L21-20P or L21-30P inputs can provide 5.76 kW and 8.65 kW, respectively. The receptacle outputs are
another mix of 5-20R, C13, and C19. In larger solutions, with three-phase PDUs and raised floors using whips, these
can be the most cost-effective ePDU choice — providing a good variety of receptacles and limiting the number of
cable drops to a single cabinet.
Figure 13. L21-30P ePDU with (4) 5-20R, (24) C13 and (2) C19
General comments
With any ePDU, it is very important to evaluate the breakers protecting each receptacle and ensure that the breaker
is adequate for specific load requirements. In order to reduce overall cost for the customer, there is a wide variety of
ways breakers can be configured to protect receptacle banks. Configurations on an ePDU might not be completely
intuitive or match every application. Evaluating line drawings can help ensure that every ePDU selection is the correct
one.
For more information on Eaton ePDUs, please visit www.epdu.com.
Eaton, ePDU and BladeUPS are registered trademarks of Eaton Corporation.
Application Note
www.eaton.com/powerquality
January 2011