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The Critical Nature of Communications Infrastructure Planning
by T Jerry McDonell, PE
In this article we will concentrate on Telecommunications Rooms (TR, also known as IDF Rooms or Communications Rooms). BICSI Telecommunications Distribution Methods Manual contains detailed information on sizing and locating TRs. This article offers practical solutions that may be less stringent than BICSI recommendations.
Communications systems have undergone tremendous changes in the last 30 years impacting our personal and professional lifestyles. Most of you have seen large complex data centers and know that millions of miles of fiber optic cabling have been installed along our roads and streets. But you may not be aware of the in-building infrastructure changes, especially for Telecommunications Rooms (TRs) in the average facility.
Back in the mid 1970’s telecom “closets” consisted of 18” deep double-door spaces stacked on every floor. They had no ventilation and were sometimes located through a door off the men’s room. All of this worked at the time.
Move forward 30 years and we find that communications equipment has increased in quantity, complexity and support requirements. A large percentage of the equipment is no longer located at a telephone central office or data center (both well protected). It now resides here in your facility. And it has become an essential component of your daily operations. 30 years ago when the power went off (losing lighting and AC) you had to decide whether to postpone major events or even send many employees home for the day. That hasn’t changed, though the prevalence of power backup systems has mitigated the problem. Today, losing a communications system (telephone, intercom, network, nurse call, security, etc.) can cause some of the same results. And, in hospitals, losing these systems for even a brief period could have life threatening consequences.
The mechanisms for achieving a robust communications systems infrastructure are still misunderstood by many in the design and construction industry, especially with regard to planning for the ideal TR. The problem is compounded by dealing with these issues too late in the planning process impacting the workflow of functional spaces. And, the effects of a compromised infrastructure might not be initially apparent. This leads to the “we did it this way last time and it worked” philosophy.
There are consequences to cutting corners. You weigh the future consequences against the current limitations and make an educated choice. The following paragraphs will help you understand the reasons for certain infrastructure requests and the consequences of cutting corners. Also, we propose methods to minimize the complexities of the decision process.
Telcom Room Locations and Distance Issues: What does the “100 meter distance to TR” rule really mean? The 100 m rule includes lengths of patch cables, up and down runs in walls/racks, slack cable requirements, etc. This leaves us with around 75 meters (246’) assuming there are no unplanned offsets due to field obstructions. And, cabling is run straight in corridors (not diagonally) for future accessibility. Also, allow some flexibility for changes in the design process (such as adding another bay on the side of the building).
TRs are expensive to build and set up. Rarely is it efficient to locate a TR in available space at the perimeter of a building. By building two well located rooms instead of three poorly located rooms, you can save on construction and electronics costs as well as free up more space for basic functions.
TRs can be located near elevator shafts, mechanical shafts, etc. if at least two sides are free for cable entry. Overhead ducts and pipes should not intrude into the TR. Entry should be off a corridor to allow quick access without extra keys or additional access control privileges. Electrical transformers, large motors, and other emissive sources should be avoided in close proximity to cabling and network electronics. Never share a TR with electrical or mechanical space since entirely different employees and outside vendors must visit the space leaving both types of equipment vulnerable.
Telecom Room Stacking decreases costs and increases reliability.
We are often asked why, since we are dealing with flexible cabling, we need TRs to stack. Some riser cables are as big as 2” in diameter and are not very flexible. Others are small but are easily damaged. And cables run above a ceiling must have a more expensive plenum rating and possibly an armored jacket. Therefore, most backbone installations outside of TRs use 4” conduits with large pull boxes. These infrastructures must compete with piping, ductwork, lighting, etc. in the above-ceiling space.
Another reason for stacking TRs is that it limits exposure to water sources. Stacked TRs will never have toilets above them. The cost to replace water damaged equipment and the loss of communications for an extended period of time can be devastating. Finally, stacked TRs provide a convenient way to enable physical redundancy to backbone cabling by using two stacked cores for separate primary and alternate feeds. This redundancy is essential for high reliability installations.
Telecom Room Sizing: Proper sizing for TRs is affected by early unknowns such as outlet density and the extent of non-network equipment in the room. Though TRs are generally not set up as server rooms, a great deal of equipment, including electronics, may have to reside in the rooms: network switches, local UPS, patch panels, CATV, overhead paging, security, intercom, nurse call, telemetry, satellite, radio, and grounding.
With a combination of freestanding and wall mounted equipment a 10’ x 10’ inside dimensioned room is the minimum required to handle a 3-rack basic setup. High density facilities with 4 or more racks or healthcare facilities with additional clinical equipment may need to be 10’ x 12’ or 10’ x 14’. Though rooms with columns and angled walls can be made to work, the basic clear inside dimension requirements still remain.
Solutions: Here are some concepts to make the planning more effective:
- Treat TRs the same as elevator shafts or stairwells. Show them early and plan functional space around them. If necessary, and within distance limits, move the entire shaft to suit functional layouts.
- Locate TRs near the center of the space to be served, not at the perimeter.
- Call in the services of a telecom consultant early in the project before you commit any space layouts to the owner or end users. Even a few hours of planning with limited information may be sufficient. This can be especailly helpful in uncovering surprise end user equipment affecting TR size or location.
