Chapter 5: Overhead or Under-Floor Installation?

Chapter 5:Overhead or Under-Floor Installation?

What You Will Learn?

• Benefits and drawbacks between ceiling and raised floor to run power, data connection and cooling system

• Detailed overview of components involved in both options

• Common problems associated with both options

Options• Overhead installation

- Use of false ceiling in which cabling, electrical conduits are routed

- Termination are done above the servers rows • Under-Floor installation

- Flat panels are placed in an elevated grid of horizontal and vertical bars, electrical conduits, cabling and cooling system are routed under this raised floor.

- Termination are done in a subfloor or into patch panel and power receptacles within the DC cabinets

Overhead Installation

• Advantages– Less expensive (Cable try ladder racks and raceways are less

expensive than a complete raised floor system)– More suitable for limited spaces – Requires less floor spaces (no entrance ramp) – Reduce chances to snagging or damaging data cables

• Disadvantages – Challenges for air circulation within the DC and servers cooling

system– Unplugged power cable or patch cord due to gravity and cord weight

Under-Floor Installation

• Advantages– Better cooling capabilities– Protecting infrastructure (patch cords, power cables) against

accidental damage or unplugs– Easier to support and access infrastructure

• Disadvantages – More expensive

• Most Data Centers are built with a raised floor system.

Deciding on whether to go with overhead Or Under Floor installation depends on:The needs for the data centerThe size of the data center

• If the Data Center is small— In round numbers, generally less than 1000 square feet (100 square meters)—or is being constructed in a building that has limited space from floor to ceiling, I design it with overhead infrastructure. The ramp needed for a raised floor and the height it occupies simply take up too much space in such a small room.

• If the Data Center is larger— I design it with a raised floor and place its various infrastructure down below. I find the raised floor system essential for controlling airflow and neatly routing infrastructure. I've also learned that it is much simpler to lift a floor tile and plug in to or disconnect from infrastructure components than to climb a stepladder and stretch above a server cabinet to make connections.

Separation of power & Data• Separation is a must, EMI may distort information on data cable• No standards available for the separation distance

Separation of power & Data (Cont.)• It is not recommended to use overhead & under-floor for

separation (exposed to disadvantages from both scenarios)

• Precautions with using fluorescents lights specially with copper cables (at least 5 inches distance is recommended)

Plenum and Non-Plenum Spaces• Plenum: cavities above false ceiling or below raised floor, used for

air distribution in the server environment, such spaces are more vulnerable to fire

• Certain regulations and building codes have been put in place that permit only specially rated cables to be used in the plenum to reduce the chance or effect of a fire

• Chose the right type of cables according to building codes to rout in a data center

Ceiling Components • Cable tray (shallow basket), Ladder racks (narrow ladder frame

installed horizontally), both are made of crossed metal bars secured to the true ceiling and configured to align with infrastructure path to be followed.

• Raceways: help in organizing the infrastructure to be clustered over each server cabinet.

• Fire codes are applied on raceways, ladder racks, server cabinets, or infrastructure equipments which in most of them requires around 50 cm distance between automatic sprinkler and any solid objects

Ceiling Components

Raceways Cable Tray Ladder racks

Ceiling Components (Cont.)

Raceway overhead Termination Example—Front View Raceway overhead Termination Example—Back View

Having the data ports above the back of the server cabinet in the raceways would help in connecting them easily while it is not the case with plugging power cables at the front of the raceways

Raised Floor Components• During design phase, we need to identify:

- Floor height- Mechanisms for bringing in equipment- Weight-bearing capacity- Types and numbers of floor tiles- Termination infrastructure- Other subfloor details

Raised Floor Components (Cont.)• Floor Height:

some evaluation factors are tide to cooling issues (server environment size and shape, number of equipment, and how much cold air needs to be channeled in the space) while others are tide to infrastructure (how much infrastructure is routed under the floor)

The simple rule is that the more height you have the more air you can circulate within that space the more effect it has above the floor, and the more infrastructure can be routed under the raised floor

Raised Floor Components (Cont.)• Elevated floor vs. sunken floor

Deciding whether to go with either option should be made early in the design phase

Mechanisms for bringing in equipment• Ramps:

- More popular - Raised floor height and slop determine the ramps length - Ideal ramps, 1.8 M wide with 1.8m of landings at both ends - Many building codes requires handrail on both side- It is recommended to install slip-resistance tread on the ramp- More than one ramp may be required depending on the DC size

and approved building codes• Lifts

- Occupies less space - More expensive

Raised Floor Components (Cont.)

Weight Bearing Ability• Considered by many as the most important element of any DC floor

• Ideally, DC floor should support 2000 pounds or more per cabinet location

• Overall weight bearing ability depends on structure of the building that entail- Thickness & integrity of the concrete slab with bottom floor- steel skeleton with above the ground DC

• Weight bearing ability should be specified during the design phase

Weight Bearing Ability (Cont.)• Other type of loads that needs to be specified:

- Static Loads1. Concentrated or point load: weight applied on small area, area

where pegs or casters for fully loaded cabinets touches the floor2. Uniform or static load: weight distributed over large area, as in

case of heavy boxes or large equipment sits on the ground- Dynamic loads

1. Rolling Load(weight rolled over an area from passing equipment)

2. Affect load (force generated by dropped objects – item weight & falling distance)

3. Ultimate load (breaking point of the floor panel)• It is recommended to apply weight load on ramps or lifts equipped wit

the room

Types and Numbers of Floor Tiles• Floor tiles comes with standard size (2 feet)• Typically made of steel with either wood, concrete or steel at the

core• Types of floor tiles:

Types and Numbers of Floor Tiles (Cont.)

• It is recommended to review the planed floor tiles deployment with the person responsible for room cooling as the more use of perforated and notched panels the harder it is to maintain air pressure

• Use static control tiles to reduce voltage generated by walking people

Types of static floor tiles

Termination Details

• Too many methods are available to terminate electrical outlets and structured cables (end of flexible conduit, stationary raceways, server cabinet…etc)

• The goal is to be flexible, not to restrict access, prepare for growth, and can be reassembled else where

Common Problems

• Poor sizing of tile cut-outs, or placing them in wrong location causing air to escape from notches

• Mistakes with relation to cable type installation (plenum, non-plenum or low smoke/zero halogen)

• Problems with relation to the strength of the raised floor