What you will learn Key element for building a reliable DC electrical system Design strategies for inroom and standby electrical infrastructure Best practice for labeling and system monitoring ID: 917362
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Slide1
Chapter 6:
Creating Robust Electrical System
Slide2What you will learn:
Key element for building a reliable DC electrical system
Design strategies for in-room and standby electrical infrastructure
Best practice for labeling and system monitoring
End-to-end testing procedures
Slide3Recommended Electrical system Features
The system should be dependable and ensure the continuous running for DC components (servers, networking devices,…etc)
Electrical system should be studied and planed carefully
System features that need to be included in the design:
Slide4System
features to avert unnecessary downtime.Isolated PowerAvoiding Single Points of FailureMaintenance Bypass Options
Remote Infrastructure
Management
Slide5Recommended Electrical system Features (Cont.)
Isolated Power
D
ifferent
power source for DC
equipments
than
other
electrical devices in the
building
Avoiding single point of failure
provide
standby power system
redundancy for critical devices and functions
physical separation for key systems
don’t share circuit breakers
plan for additional electrical power in the
future
Slide6Recommended Electrical system Features (Cont.)
Maintenance Bypass Options
Design
the system so that regular maintenance can be
performed
without the taking major
components
offline
Remote Infrastructure
Management
Consider computer based building management system for mid and large size DC
benefits of such systems would include
Early warning of problems
Savings in terms of staff and running costs
Chosen system should provide high interoperability, easy to program, graphic interface and produce useful data metrics
Slide7In-Room Power
Electrical infrastructure elements include:
Power distribution units
Circuit breaker panels
Electrical conduits
Wiring configurations
Choose how to terminate, route and label the components
Pre power cabinet locations with power receptacles
Slide8In-Room Power (Cont.)
Determining Power Requirements:
Electrical infrastructure should support the room with its full capacity (completely full with servers
)
The more information about incoming DC equipments the more accurate calculations for electrical
needs
Provide abundant number of
circuits
Basic formula for the maximum power needed:
max
kva
=(volts * amps)/
1000
example: for a DC with 50 cabinet locations each with two power strip (120 volts & 20 amps)
In-Room Power (Cont.)
Power Distribution:
Run flexible electrical conduits(whips) from large power distribution units(PDU) directly to each cabinets for small DC
Use segmented power for large server environment (running electrical conduits from PDUs to circuit panels at the end of each row and then a subset of connections to server cabinet locations).
This
option would be easier to manage, less expensive more resistant to physical accidents
Power Redundancy:
Require for redundant power supply for each server and network equipment and plug each one into different receptacle
Slide10In-Room Power (Cont.)
Figure 6-3. Direct-Connect Power
Figure 6-4.
Distributed (segmented)Power
Slide11In-Room Power (Cont.)
Wiring, components &termination options:
Be familiar with local power requirements (220/240 volts vs. 100/127 volts) and predominant power requirements for incoming equipments
Good design practice:
Use flexible whips (easier to install, less expensive, rearranged quickly)
Use heavy gauge of wire (the lower the gauge the thicker the wire)
Don’t terminate more than one receptacle on a conduit
Avoid dirty power
Slide12In-Room Power (Cont.)
Labeling & Documentation:
Use thorough and unambiguous signage, labeling and documentations that is understandable by everyone
Label power receptacles with the circuits they possess and the location in the circuit breaker panel where they originate.
At that breaker panel, list all of the circuits it contains and which cabinet locations they are located at
Use color-code to indicate parallel infrastructure
Create a blue print of the room during construction (as-built) and keep it updated
Mark electrical equipments that users need to stay away from it with hazard tapes
Slide13In-Room Power (Cont.)
Convenience Outlets:
Install convenience electrical outlets in multiple locations to be used instead of cabinet power outlets for rechargeable batteries, power drill, vacuum cleaner, …etc.
Don’t connect these outlets to the standby power system
Emergency Power Off (EPO)
Required by fire codes in many countries
Intended to prevent fire suppression materials from coming into contact with live electrical current
EPO types:
Push-up button (easy to use, most common EPO controls)
Pop-up button (second frequently used, require a new piece of glass to restore power, accidental activation is less likely)
Control Knob (require the knob to be rotated 90 degrees to activate, better design, simple to use, accidental activation is less likely)
It is highly recommended to cover EPO controls with a
transparent plastic shell, wired to an audio
alarm
.
Slide14In-Room Power (Cont.)
Figure 6-6. Sample Emergency Power Off Controls
Slide15Standby Power
Aimed to keep servers & network devices running when main powers fails
3 factors for designing standby system
Redundancy (the more level of redundancy the more complex and expensive the system would be)
Simplicity
Cost
Load requirements (start with max.
kva
load the room can produce and then adjust in 2 ways:
Size the standby infrastructure to handle 110 to 120 percent of the projected maximum power needs
Build out your standby infrastructure based upon what level of redundancy you want for your server environment
Design the standby system to handle both network & server rooms if they are close to each other, otherwise, have separate standby infrastructure if the network room is far from the servers room
Slide16Standby Power (Cont.)
Batteries:
UPS is considered
t
he most common source of standby power
Use one UPS for each cabinet for small server environment or temporary DC as they are portable and inexpensive
large floor-standing UPS model installed in the electrical room are used for all other size of DC as they are more robust, have greater capacity
Run time
term is used to identify how long standby infrastructure can support DC electrical load
Required run time should be built on the assumption that the room is fully loaded
Slide17Standby Power (Cont.)
Generators:
Size the generator to support at least 10 percent more than DC maximum power capacity
Skip installing generators in small server environment with reliable utility power and invest more in installing UPS that has 2 hrs of run time
It is recommended to have generators that can run for 8 hrs before refueling
Use enclosed protected area to install generators with short distance from DC
Protect against unauthorized employees
Protect against noise and vibration
A good ventilation and enough space around the unite is required
Slide18Standby Power (Cont.)
Monitoring Lights:
Install monitoring lights high up on the both side of the wall inside (DC entrance, end of DC major aisles), outside and other strategic locations in the DC to indicate standby system activation
Use different color demes for UPS and generators (avoid amber or white as they are used for fire alarms)
Using large rotating beacon-style lights are recommended
Installing monitoring lights outside the DC with an explanation signage with emergency phone number would help non DC users to report such incident
Slide19Standby Power (Cont.)
Figure 6-7 Monitoring Lights for the Standby Power System
Slide20Labeling and Documenting
Make the labeling consistent with the servers room as possible (using the same terms and labeling schemes)
Maintain a wiring diagram and keep it current
No common standards for orienting electrical switches, on common and simple practice is to mark on position for all circuits and switches
Slide21Installation and Grounding
Installing of grounding system help protecting electrical infrastructure and people from excess electrical charges (generated by faulty circuits, static dischargers, or lightening strike)
Grounding system usually involves copper wires connected to the building steel and linked to copper rod deep in the ground (moist soil)
Install a second grounding system
“Single Reference Grid”
to provide more protection to servers and network devices from interference, it should be connected to each power distribution unite and air handler
Slide22Testing and Verification
The contractor must perform a series of tests before any servers/devices are installed in the DC to make sure that the infrastructure work as it should be
Area of testing
Load bank test (make sure that both UPS and generator can support the level of power as designed, the goal is to check the max. capacity and runtime of the UPS)
Injection test (injecting electrical current through circuit breakers to ensure that they perform correctly during a real life power spike)
Circuit & labeling verification (
at
least
for the main breakers and recommended for all circuits)
Full power test (cutting DC utility power to verify transferring of electrical load to standby infrastructure and back again)
EPO system test (activating EPO controls to ensure that all power sources and outlets shutdown properly)
Slide23Testing and Verification (Cont.)
Table 6-1. Typical Load Bank Test
Slide24Testing and Verification (Cont.)
Table 6-2. Typical Full Power Test and EPO Check
Slide25Common Problems
Power receptacles or circuit breakers are mislabeled (obtain a power tester and have two people verify all receptacles in the room)
Monitoring lights for standby power are wired incorrectly (having monitoring lights configured to engage after 30-second which may result in no one will see UPS monitoring lights activation)
Circuit breakers are left off (this may confuse people, they may think serious problem exists)