INTEGRATING THE RACK
©2009 Middle Atlantic Products
STRUCTURAL,
SEISMIC & CABLE
MANAGEMENT
CONSIDERATIONS
EXCEPTIONAL SUPPORT
& PROTECTION™
THE POWER OF INTEGRATED THINKING: HOW THE SYSTEMS APPROACH GUARANTEES SYSTEMS INTEGRATION SUCCESS
A little bit of planning goes a long way. When consideration is given to certain factors during the
system planning stages, the result will be the most complete, professional system that is outfitted
to live a long life yet is easy to service when the time comes.
When proper care is given to Cable, Structural (Space) and Thermal Management, the system
will make excellent use of the space given for the installation, will be optimized for simple future
upgrade and will be able to properly function with the heat its components produce.
Key Benefits of the Systems Approach
• Ease and speed of integration and installation
• System reliability
• Ease of servicing and upgrading
SPACE MANAGEMENT (STRUCTURAL CONSIDERATIONS)
RACK BUILDING TRICKS OF THE TRADE
1. Keep a low center of gravity. Heavier components should be placed at the bottom.
2.In-Shop Integration, On-Site Installation. The benefits of integrating equipment in the shop are numerous: it allows
the installer to program and test equipment and troubleshoot problems easily, out of the watchful eye of the customer.
Tools will always be at the installer’s disposal and there will be more room to work. Wiring up equipment before on-site
installation will make cable management in the field fast and simple.
3.Plan for future expansion. Use blank or vent panels in unused rackspaces depending on the appropriate method of
thermal management. This will facilitate the future upgrade of equipment.
4.Begin at the bottom. When loading equipment in a vertical rack, always begin at the bottom (the lowest rackspace
is No. 1) and distribute the weight as evenly as possible (or as low as possible with heavy items such as power amplifiers).
When ergonomic considerations require loading equipment from the top down (i.e. placing source equipment and
monitors between waist-high and eye level), care must be given to “accumulated tolerances.” Because the mounting
holes on equipment are larger than the rack screw, by the time a few pieces are mounted, they may begin to impede the
next rackspace. This can be solved by using shoulder washers to center the equipment within the rackspace.
ORIGINS OF RACKMOUNTING
George Westinghouse developed the Rack System in the late 1800’s. His early work involved railroads
and he developed the Rack System as a means of keeping interchangeable pieces of railroad
communications switches, devices of different sizes, available in one common box.
THE CANTILEVER EFFECT
In a vertical rack, always support equipment from the bottom and
fasten the two lower rack screws first. The cantilevered weight of
the component will pull the face snug against the rackrail, allowing
the installation of the top screws.
(The top screws don’t bear any weight and are only for stability).
Mounting with screws in only the upper holes, or with one
in each upper and lower corner, risks torquing the faceplate and
damaging the component.
2
INTEGRATING THE RACK
©2009 Middle Atlantic Products
the cantilever effect
EXCEPTIONAL SUPPORT & PROTECTION™
SEISMIC
CONSIDERATIONS
Earthquakes are not limited to the state of California, nor are
they infrequent. Seismic events take place every day
throughout much of the continental western United States.
It’s only the big ones that make news. In many instances,
millions of dollars worth of technology depends on the
quality of the racks it is stored in for its continued
performance after an earthquake
All facilities classified as essential (i.e., fire and medical
structures, police facilities, critical government agencies)
have to be seismically rated. Systems designers are
increasingly interfacing with the architects and engineers
who create and renovate such facilities.
In addition, even facilities that are not rated essential are
implementing more highly sophisticated and expensive
electronics, which benefit from an overall higher level of
physical protection offered by seismically rated enclosures.
It takes very little time and expense to obtain seismic levels
of structural integrity.
SEISMIC RATINGS
The guidelines for seismic ratings are derived
from two sets of specifications established by
independent organizations.
The 1997 Uniform Building Code (UBC) is a definement
of the UBC specification created in 1994. The earlier
version was relatively general in scope and broadly
divided the United States into four zones. One such
zone is Zone 4, comprising most of central and
coastal California, and was rated the most prone to
earthquake activity.
EXCEPTIONAL SUPPORT & PROTECTION™
©2009 Middle Atlantic Products
INTEGRATING THE RACK
3
The other standard, the 2000 International Building Code (IBC), is considerably more precise: In addition to viewing
the entire continent as a series of potential seismic locations, the specification has resulted in maps that measure a
given location’s potential for experiencing seismic activity relative to an identified fault, along with probability maps
for every 100-foot section relative to the fault’s location. This information, along with historical information about the
severity and duration of previous seismic events, enables physical engineers and architects to determine the level
of seismic resistance that equipment racks will require.
Some other standards are often used in seismic installations, and these requirements are in addition
to the IBC and UBC. These relate specifically to the components themselves, such as the racks and
electronics housed within. NEBS (Network Equipment Building Standards) are derived from the old
“Bellcore” standards, which were exclusively Telco (telephone Central Offices). When the older relays
changed to analog electronics, then to high-speed digital switching, it was realized CO’s were more
like giant digital networks. Therefore, network standards were adopted. Telcordia now provides all the
NEBS standards. There is also the ETS (European Telecom Standard), and local exchange carriers like
AT&T, Verizon, and SBC have their own standards that must be met in addition to the NEBS standard.
The project engineer involved
in the design and construction
of a facility is responsible for
determining the rating of the
facility, because the rating is
applied to the structure itself
(which is viewed as a system
with numerous components).
One component is the electronics
enclosure, which must comply
with the seismic specifications
that are set forth. Certifications
of the enclosure in the form of
test results comply with the
associated standards.
4
INTEGRATING THE RACK
©2009 Middle Atlantic Products
EXCEPTIONAL SUPPORT & PROTECTION™
INTEGRATING THE RACK IN A SEISMIC INSTALLATION
Critical aspects of racks in a seismic installation:
• Installation of the racks – interaction of the rack
and the physical building
• How the equipment is distributed within
those racks
NOTE: Both of these considerations will have
significant effects on the performance of the
racks under stress.
FLEX YOUR ANCHORING MUSCLE
To achieve maximum protection for the equipment in the rack, and to comply with the code specifications outlined by
the IBC and UBC, the rack itself needs to be properly and firmly anchored to the facility floor. All other physical and
structural pragmatics considered, if you don’t anchor the rack to the floor properly, all other preparations would not
matter. The PE responsible for the job usually specifies the fasteners, as that firm knows the floor construction details.
Seismic-rated floor anchor clamp kits MUST be
installed in the rack’s corners prior to fastening
the rack to the floor.
Used in conjunction with the floor anchors, these
flanged channels are made from structural steel
and are designed to resist the twisting and
wrenching they would receive in an earthquake,
while transferring all the heaving motion of a
trembler directly to the rack’s vertical surfaces
via the corners where it is the strongest.
HOT TIP!
Though not as critical as the floor anchors, anchoring the top of the rack is
also important. If you anchor the top of the rack with a cable ladder, it also
offers a convenient method for cable entry. Most people living in active seismic areas
prepare their houses for a trembler by anchoring the top of dressers and tall objects. Many fires start when a gas water heater topples, breaking a gas connection. A simple
bracket prevents that from happening.
EXCEPTIONAL SUPPORT & PROTECTION™
©2009 Middle Atlantic Products
INTEGRATING THE RACK
5
REAR SUPPORT THE RACK MOUNTED EQUIPMENT IF
• The unit exceeds 10 lbs. per rackspace and the center of gravity is toward the rear and the overall depth of the unit
is greater than 2.5 times the racking height
• The rackmount ears of a piece of equipment cannot support the weight of the unit
• The unit flexes when it is pushed down or when the rear of the unit is lifted. Rear support will prevent the equipment
from “whipping” during a seismic event
REAR SUPPORT SOLUTIONS
• Brace between components
with solid lacer bars
• Block with wood (temporary)
• Use rear hanging brackets
Rear support mechanisms can take many shapes and forms. There are rear-hanging brackets available that attach to
equipment outfitted with rear-hanging ears secured to a rear mounted set of rackrails. For transporting a loaded rack
to a jobsite, many contractors have relied upon the rear-supporting technique of cutting wood chocks and inserting
them between pieces of equipment. While effective, this method requires the removal of the chocks once the rack is
installed, because the presence of wood inside a rack violates fire codes. Given the amount of time it takes to measure,
cut, and install these chocks and then remove them once the rack is secured in place, it makes more sense to choose
something more permanent and secure that meets the seismic Uniform Building Code (UBC). This becomes a simple
and inexpensive task with the addition of a pair of mid-mounted rails and a horizontal lacing bar, which is employed as
a support directly beneath and above the piece of equipment to be supported. This is ideal for equipment that is not
equipped with rear-hanging mounting ears.
FOR THE BEST EQUIPMENT CONFIGURATION, ASK THESE QUESTIONS:
1. How much weight is going in the rack? Heavy equipment like amplifiers and UPS’s must be placed at or near the
bottom of the rack. The rule of thumb is: the heavier the individual piece of gear relative to all the other equipment,
the lower the placement.
2.Where is the center of gravity? Keeping the center of gravity in the lower third of the rack puts less strain on the
footing and wall anchors.
3.How is the load dispersed? If there is more heavy equipment than you have space for in the bottom third of a single
rack, spread the load out over other racks
4.Will the rack be standing alone or ganged together? Racks that are ganged are inherently more stable.
OTHER CONSIDERATIONS FOR COMPLETING THE RACK IN A SEISMIC-READY FASHION:
• Clamping kits for all shelf-mounted components
• Rack screws should be tighter than normal, to enhance lateral strength
• All spaces must be filled with blank or vent panels. This provides the required
strength for the rack face, which is the weakest part of the enclosure
• Rack must be installed plumb
• One of the collateral benefits of a seismic design is that it travels well to the jobsite
6
INTEGRATING THE RACK
©2009 Middle Atlantic Products
EXCEPTIONAL SUPPORT & PROTECTION™
using
clamping kits
for shelf-mounted
components
RACK CONSTRUCTION
Rack construction is important; some racks are built using
corner butt joints that are welded and ground smooth for
aesthetic reasons. Ground down welds reduce corner
strength by approximately 80%. Racks ideal for seismic
applications are seamless in that the sides are created by
taking a full sheet of metal and cutting the center out,
thereby eliminating the need to employ stress fracture-prone
welds at the corner.
Seismic installations require more fasteners between the
rackrail and rackrail bracket, and many seismic kits include
these simple-to-install bolts and oval nuts.
Seismic Compliance
Rackrail Mounting
A unique solution that complies with seismic codes is a rack on wheels that can be rolled out of a hospital operating
room for sanitizing the room, and rolled back in and anchored. This design incorporates a pair of thick tapered-front
ramp rails that are permanently installed in the operating room, and has threaded holes for securing the rack once
rolled onto the ramp. At that point, the wheels are floating and the base of the rack can be securely fastened using
the pre-threaded holes in the ramp to meet code.
HOT TIP!
The most important thing to keep in mind is that any system will perform as well as the weakest link.
Racking may not be as glamorous or as technically exciting as the equipment it holds, but it is the first
line of defense that will keep that equipment – and the client’s business – working without interruption in the event
of a 7.0 earthquake. Dollar for dollar, proper rackmounting is the best insurance a facility can buy.
EXCEPTIONAL SUPPORT & PROTECTION™
©2009 Middle Atlantic Products
INTEGRATING THE RACK
7
CABLE
MANAGEMENT
Every installer wants to save time and make the installation of electronics systems as easy as possible. Having a
system that is simple and quick to service and upgrade will additionally benefit both the installer and the customer.
When care is given to planning the management of cable entering the rack or enclosure system and maintaining it
neatly throughout that system, the goals of providing your customers with a neat, organized and effective system
are easily attained.
Today’s electronic systems wiring includes voice, data, video, audio, security, and control. The facilities and wiring
systems must be planned in an integrated manner; all these different wires make their way into racks of equipment.
Managing these cables creates some interesting challenges, as wire bend radius and fastening must meet the
standards set forth, even inside the rack. With video going over twisted pair, and digital audio transmitted through
CAT-5 / CAT-6, it is important that audio/video systems integrators be familiar with the associated standards.
Additionally, more devices are being controlled and monitored via Ethernet nodes.
The TIA/EIA (Telecommunications Industries Association & Electronic Industries Association) building
telecommunication wiring standards are used to ensure the desired performance. These standards provide
guidelines that reduce long-term building operation costs, lead to a better infrastructure, and are adaptable to
changes. TIA/EIA-568A is for commercial buildings cabling, and specifies a generic cabling system that will
support a multi-product, multi-vendor environment. Anybody working with these wiring systems in commercial
installations should obtain and adhere to the procedures set forth. TIA/EIA-569 relates to commercial building
standards for telecommunication pathways & spaces. TIA/EIA-570 covers residential and light commercial wiring standards. These important documents can be ordered at http://global.ihs.com.
HOT TIP!
The installation of cabling systems during building construction or renovation is significantly less
expensive and less disruptive than after the building is occupied. Convincing your client that the
small cost associated with running extra wires for future expansion will save them money down the road is important.
As a matter of code according to the NEC (National Electrical Code), abandoned cables must be removed, or tagged
“For Future Use”.
FIVE DISTINCT AREAS OF
CABLE MANAGEMENT
•
•
•
Horizontal cabling
Backbone cabling
Telecommunications
closets
• Equipment rooms
• Equipment racks
Note: The types of cables used can be unshielded
twisted-pair (UTP), shielded twisted pair (STP or
“screened” cable) or coax to name a few.
BEWARE OF THE BENDS
AND OTHER THINGS TO AVOID
• Cable Twists
• Staples
• Tight wire-ties
• Bends greater than 90º
• More than 25 lbs. of
pull force
Note: All twisted pair cable is manufactured as
“loose-fill”, meaning there has to be a slight air space
inside the sheathing. This reduces mutual capacitance,
which reduces data packet error rates. Things like a tight
wire-tie will increase data errors.
NEXT loss (near-end crosstalk) is also a problem, and is eliminated with proper terminating
procedures. The twist in a pair must remain right up to the connector; too often people un-twist
the cable for an inch to aid in termination, and that violates the standards. NEXT is tested with a
swept-frequency through a “disturbing pair” and measured. Optical fiber cabling standards are
increasingly becoming a factor, as more data is passed through fiber in buildings and racks.
8
INTEGRATING THE RACK
©2009 Middle Atlantic Products
EXCEPTIONAL SUPPORT & PROTECTION™
METHODS OF BRINGING CABLE
INTO YOUR ENCLOSURE OR RACK SYSTEM
CABLE ENTRY: FROM ABOVE THROUGH TOP OF RACK
Standard enclosure with wide-open top – cable is
dropped in from above.
Standard enclosure with top option shown – aluminum
panel is removed to drop cable bundle into enclosure
Some rack top options can accept a 12” wide cable tray or
cable ladder. These tops allow for a 12” wide cable tray to
attach coming in from front or rear and left or right. The
opening in the top also allows for the use of a cable drop on
the ladder to maintain proper bend radius of the cable.
The easy to machine aluminum panel
in some rack tops can also be easily
field punched to accept multiple sizes of conduit.
HOT TIP!
CABLE ENTRY: FROM BELOW THROUGH BOTTOM OF RACK
The bottoms of many enclosures are designed just as the tops with a
wide-open set-up to accept large cable bundles. There is about 3” of space
in the bottom of the enclosure before reaching the rackspace area to allow
for cable entry up into the enclosure. Each enclosure’s unique “upformed base” provides interior room for cable management and coiling unused wire. In the rear of the bottom base of many enclosures are multiple sizes of
EKO’s to allow for conduit to be piped in directly.
Riser Bases give enclosures an
additional 2-1/2” clearance off the floor
and can be used for cabling below each
enclosure or cabling from one to another
when ganged. Laser knockouts on the
ends allow ganging of riser bases to
pass cables through.
When riser bases are used with
feet and angles it allows the
installer to firmly attach enclosures
to the sub floor in Raised Floor/
Access Floor applications.
EXCEPTIONAL SUPPORT & PROTECTION™
©2009 Middle Atlantic Products
Some wall racks feature a
bottom cable entry platform.
Laser knockouts on both sides
of the base allow cable pass
through in multi-bay installations.
INTEGRATING THE RACK
9
DRESSING YOUR CABLE INTERNALLY
Segregation of cables inside the rack is important – NEVER run AC cables parallel within close proximity to signal wires.
Speaker wires can act as AC cables in high-power situations, so the same care should be taken in keeping signal wires
away from close parallel runs. Speaker and AC wires can be run in closer proximity, however.
Bend radius for twisted-pair cables is set by the standards at 1.5” radius (3” diameter). This needs to be taken into
consideration during the internal wiring layout of a rack. Coax cables should not be kinked, although they are more
tolerant to tighter bends than high-speed data.
HOT TIP!
It is a little known fact that bundling AC cables is a violation of the NEC. This is rarely if ever caught
by an inspector.
VERTICAL LACER STRIPS
Vertical lacer strips are designed to mount to the rail brackets in many enclosures. Add as many lacer strips as
necessary in order to bring the maximum amount of cable into the enclosure, as well as keeping power and signal
separate. The vertical strips allow the installer to lace cable from the top to the bottom of the rack or vice-versa. They
are available in different widths such as 1”, 2” & 3-1/2”. Some lacer strips employ bridge lances so that cable ties or
hook and loop fasteners can be used.
HOT TIP!
WHEN TO USE HOOK AND LOOP STYLE TIES
Hook and loop style cable fasteners should be used
when installing cable that is sensitive to strain or when the wrap is so
tight that it affects the performance of the cable. This problem is
common when installing Cat 5e or Cat 6 cables.
The hook and loop style is also recommended when cable will be
added to or removed from the bundle on a regular basis. Hook and
loops can be opened and reused unlike wire ties, which must be cut
off and replaced when cable is being switched out.
There are many effective methods of vertical cable management,
although different regions of our country have adopted some
unique styles. East coast integrators in a high-density environment
sometimes use the “tie & slide” technique, which allows smaller
cable bundles to be dressed and slide into “no-man’s land”,
greatly increasing the utilization of enclosure depth. This requires
an enclosure with welded horizontal tubes. Many west coast
integrators prefer using individual thin vertical lacers with tie-saddles.
Both work, so choose whatever method best fits your particular layout.
Where large (4” diameter) bundles are required, a rack with large
flanged rackrail should be chosen. This provides the space required,
without having to “fish” the wires behind rail brackets.
10
INTEGRATING THE RACK
©2009 Middle Atlantic Products
EXCEPTIONAL SUPPORT & PROTECTION™
HORIZONTAL LACER STRIPS
Many enclosures are furnished with a set
of rear rackrail that can be used to mount
the lacer bars at any height position.
These lacer bars will address two common
problems that occur: cable strain relief and
running cables from one side of the rack to
the other.
Use lacer bars when running
cables horizontally
Use lacer bars as strain relief
for connectors
Lacer bars help facilitate cable management in a variety of applications:
USE FLAT LACER BARS WHEN
•
•
•
•
Running large cable bundles vertically
Running bundles horizontally then sliding
into position
Rear support for equipment is required
Field drilling is desired (3/16” aluminum
facilitates field drilling)
Vertical Lacing
Horizontal Lacing
Vertical Lacing
Horizontal Lacing
USE “L” SHAPE LACER BARS WHEN
•
•
•
•
Running large cable bundles vertically
Running fixed cables horizontally
Using hook & loop fasteners
Rear support for equipment is required
USE “L” SHAPE OFFSET LACER BARS WHEN
USE ROUND SHAPE LACER BARS WHEN
•
•
•
•
•
•
Positioning lacer bar close
to the rear of the unit for
cable strain relief
Managing multiple horizontal
cable bundles at different
depth positions
Running cable bundles vertically
Running cable bundles horizontally
that can be dressed then slid into
position
Using hook & loop fasteners
Rear support for equipment is required
USE ROUND SHAPE OFFSET LACER BARS WHEN
•
•
•
•
Cable labels need to be seen (offset away from patch field or unit)
Rear rail is set in one position and there are various equipment depths; the lacer bar should be
placed close to the rear of the unit for cable strain relief
Managing multiple cable bundles horizontally at different depth positions
Bend radius must be taken into consideration
EXCEPTIONAL SUPPORT & PROTECTION™
©2009 Middle Atlantic Products
INTEGRATING THE RACK
11
DRESSING CABLE INTERNALLY
In racks where there is a high
density of cables anticipated, it
is often helpful to cut cable and
bundle for testing what bend
radius is possible.
Power strips that incorporate
tie lances along the length
provide “free” tie points, and
are ideal for AC cables. The back flange of rackrail
is also a “free” vertical tie point
for managing cables.
Many times integrators find out
too late that the cables simply
cannot be effectively run. Prior
testing on a bench allows better
planning.
HORIZONTAL CABLING TIPS ‘N TRICKS
WHERE CAN EXCESS CABLE GO?
•
•
•
•
•
•
Feed from both sides when
cable radius is large
Offset bars get in close,
to the rear of equipment
without adding rackrail
Leave room for cable labels
Coil in base
Looped in bottom
Along sides in
“No Man’s Land”
NOTE: Neat & tidy is always best
Different cables and signals have different needs. The data market has high densities, and is bend-radius
sensitive. Video broadcast has a large quantity of coax cables. Security installations have DVR’s whose
camera cables don’t run to a switcher; rather the DVR provides that function. This means many cables
need to be dressed directly to the equipment. Audio with its sensitive gain structure needs special care
for hum and buzz propagates. By following standards and common-sense rules, today’s complicated
rack integration can look and work well thanks to proper cable management.
CORPORATE HEADQUARTERS
Corporate Voice 973-839-1011
Fax 973-839-1976
International Voice +1 973 839 1011
Fax +1 973 831 4982
middleatlantic.com
export@middleatlantic.com
ISO 9001 REGISTERED
ISO 9001 registration ensures a world-class
quality management system that provides the
assurance that our customers will receive the
same consistently high quality products and
service they have come to rely on and expect
from Middle Atlantic Products, Inc.
©2009 MIDDLE ATLANTIC PRODUCTS, INC.
ALL RIGHTS RESERVED
NOT RESPONSIBLE FOR TYPOGRAPHICAL ERRORS
100M8/09
PRINTED IN U.S.A.