Yes. And your consultant must know local practices as well. If you are
building a facility in Fairfax County, Virginia (a major technology suburb
of Washington DC), avoid, in your plans or anything the building inspector
may see, the term "computer room." "Communications room," "network room,"
etc., all prevent the problem: if they see "computer room," they will
demand a mainframe-style central emergency power off control, which greatly
increases electrical wiring cost.
The psychology of dealing with building inspectors would fill an entire
book, however this is a good example of understanding the "Why." If building
inspectors and computer room designers were logical, they would realize
why this requirement exists. They would also realize when the requirement
didn't apply.
Building inspectors cover an incredibly wide range. At the low end, you
really would have to delve into plant psychology. I'd say mushroom
management applies at times, but I've never encountered a carnivorous
mushroom with delusions of self-importance. At the other end, Emory
Rodgers, the head of code compliance in Arlington County, where I live,
next to Fairfax County, is a delight to work with, is an active participant
in evolving building codes standards, and actually believes his department
should help get the job done, safely.
The reason why the requirement exists is computer room wiring often doesn't
meet all the safety and fire retardation requirements of normal occupancy
space because the entire computer room is treated as if it was a restricted
access area and fire retarding space. Hence the requirements for a seperate
HVAC system, fire-rated walls, and a single disconnection means (i.e. EPO)
for the entire room INCLUDING the UPS(s). On the other hand, if you followed
normal occupancy wiring practices, one would expect the space could be
treated as normal occupancy space by the building inspector. I know, that's
not how inspectors think.
I'm not sure eliminating the EPO would really be cheaper. Its not simply
a matter of eliminating the EPO, but also replacing much of the raised
floor cabling with conduit, plenum rated cable, and other changes.
In some of our local codes, they don't have any requirement for raised
floor, but a great fascination with EPO. Over the years, certainly in
networking areas, I have come to prefer overhead cable tray as much easier
to maintain.
Some urban archaeologist is going to take up a research project that
investigates why certain artifacts predominate under raised floors. In
various mainframe data centers I have recabled, there was always one sort
of discarded item that seemed to predominate under the floor. Soda cans I
could understand. Beer cans I could understand. But huge numbers of pocket
combs? Razor blades? I have no clue, but only can report.
In a more directly relevant way when talking about experience, people
really need a high index of suspicion when untangling cables that have
formed the usual tangle under a raised floor. There definitely may be a
shock hazard. The worst combined hazard I ran into personally was when I
started tugging on what appeared to be a black PVC cable, different, so it
seemed, only in color from most other cables.
As I pulled the black cable, and moved other grey ones, I began to feel it
come free...and then suddenly discovered my pants were soaking wet.
Ignoring my associates' rude comments about toilet training, and feeling
rather at risk for electrocution, I discovered that what I had been pulling
was actually a flexible drain pipe from one of the air conditioners, which
had been loosely stuck into an underfloor drain.
Do think of underfloor drains. They are your friend. In close to 30 years
of working with computer rooms, with all the emphasis on fire protection,
I've never had a computer room fire. I have, however, had several major
floods related to fire protection -- a couple from water running downhill
from a fire fought on a higher floor, two from burst sprinkler lines
(improperly protected from freezing), and more from ordinary plumbing
emergencies such as clogged and overflowing toilets. Putting equipment on
high, rather than low, floors can protect it.
Not
just power cables, but also communications cables, such as the cable
connecting a disk cabinet to the CPU cabinet. And worse, from the building
inspector's point of view, having some assurance someone won't install
some cable next week without having it inspected.
Another local factor that MUST be considered in certain cities, and can be
far worse to deal with than building inspectors, is the local electrical
union. Some are great craftsmen and incredibly helpful. But there are
also cities where a union may perceive the data people running low-voltage
circuits as under their jurisdiction...and cables have been known to be
cut. Some of my New York friends have worked out very specific personal
procedures to get on good terms with the shop steward Local 3 of the IBEW
before starting a specific project.
I realize in most offices there are more computers on people's desktops
than in the computer room. At this point I get to critize designers for
how they think. Electronic equipment is spread throughout the organization,
and the infrastructure to support it can't be limited just to the computer
room. But the building codes are always going to be playing catchup, so
designers and inspectors have their negotiating work cut out for them.
Wasn't thinking of MILSTDs as much as some of the DISA documents, and often
relating to base practices. The DoD manual on grounding, bonding, and
shielding is excellent.
This was precisely the one I was thinking about. Since the IEEE Emerald
book was published in 1992, gounding, bounding and shielding practices
for electronic equipment have been getting updated. There is a LOT of
techno-babble floating around about computer room grounding (pun intended).
Make sure you have the updated manual. There are some old ideas about
practices such as isolated grounds for electronic equipment which are
dangerous, and have been revised/clarified in the updates.
I wonder if any of the TEMPEST manuals have been declassified? THey never
were at a terribly high level, and had some very nice general engineering
in them. Now, full disclosure here -- I am NOT an electromagnetic
compatibility person, and, when it comes to working on hardware, I tend to
think of myself as an eletrostatic discharge waiting to happen. As I
remember, DoD had created a special technical slot for their grounding and
bonding expert, Bill Bergman if I remember correctly -- don't know if he's
still around or might have retirred.