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Thread: Computer rooms - EPO's

  1. #1
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    Computer rooms - EPO's

    Sanity check - the requirement for the EPO to shut down all electronic equipment in a computer room (Article 645) does not include lighting correct? And if it does does that include emergency lighting?

    Thanks,

    Mike
    Mike Shields, PE
    Boston, MA

  2. #2
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    Mike you have it correct.
    However as a fellow PE who designs data centers I strongly urge you to re-consider taking the leniencies associated with 645, EPO's are a really bad idea.

  3. #3
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    An interesting response

    And much appreciated though you leave me in suspense. Can you elaborate as to why they are a bad idea? Is it a concern for the data or a safety concern?

    And regardless, wouldn't this be more than a leniency but rather a flagrant violation of the NEC?

    Sounds like interesting stuff. Do fill me in!

    Mike
    Mike Shields, PE
    Boston, MA

  4. #4
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    Sure Mike I can tell you all kinds of horror stories. The bottom line is they can loose billions of dollars in revenue. All it takes is one disgruntled ignorant employee, or a dumb visitor to push the button. Let's not forget about dumbo the technician checking voltages for something unrelated and gets into the circuit, or my favorite a failure and false trip.

    Think about this; an installer sets a cabinet near one of the relays. He accidentally drops the cabinet, or something on the control panel and jars the trip relay. The room goes quite, then you hear OH #%$^. I can go on if you need more. Bottom line is false unnecessary trips. It will happen

    Anyone of these real life scenarios will trip the whole data center off-line. If it happens to be a large one say like Verizon, ATT, etc these facilities run millions of dollars of revenue per minute, so even a short re-start event of say an hour can run into billions, not to mention the losses of customers as a result.

    There is no code requirement that dictates you have to use 645. It is optional by design. All reputable phone companies avoid them like the plague. In my 30 years only two places demanded them and was later removed by court, King of Prussia, and San Jose.

    Maybe Ron or Sam will chime in as they also have Data Center design experience.

  5. #5
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    Mike,
    Article 645 is an "optional" article. There is nothing that says you must build a "computer room" to that article. The only time you must comply with the rules in 645 is when you are taking advantage of the leniencies that are permitted in that article.
    Don
    Don, Illinois
    "It is the first responsibility of every citizen to question authority." B Franklin

  6. #6
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    Mike,
    I agree with what was said.
    The reason that 645 can be considered optional, is in the text of the code section.
    645.2 (2002) or 645.4 (2005) both indicate that the article (645) shall apply if you meet several conditions, such as EPO, certain HVAC items, listed IT equipment, fire separation, etc.
    So if you don't meet those conditions, then the article doesn't apply.
    It is set up so that if you want to use the more relaxed wiring methods later on in that article (645), then the "prerequisites" must be met, such as the EPO, etc.
    Try to avoid 645 and wire the room exactly like any other equipment room.
    For casual reading, take a look at the article below.
    http://www.csemag.com/article/CA6290839.html
    Ron

  7. #7
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    Question

    I think I have probably seen a dozen posts saying "avoid Article 645".

    But I still have two questions.

    1. Exactly what do you loose by not using 645? Power cords running to receptacles below the floor? What about standard Cat 5 and other computer cables? Can they still run under the floor? Or can they run from device to device overhead?

    2. I sometimes design rooms like this. But all the computer equipment and wiring is usually done by the owner or another contractor after the basic room is constructed. How can I avoid 645 when I'm not sure what the owner will install?

    Steve

  8. #8
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    Steve,
    You only lose out on the more relaxed rules that are listed in 645.
    Such as running a power strip cord through the raised floor tile and plugging into a receptacle below the raised floor. Most folks can't use this leniency anyway since they can't find a power strip that has a DP rated cord for entry below the floor.
    Probably the most used leniency found in 645, is that a listed raceway whip from a PDU or RPP can be run below the floor and doesn't have to be secured.
    Another that is used in some jurisdictions is that you can run non-plenum rated communications cable below the floor, even if it is a plenum. Most don't use this one either, since a lot of AHJ's require fire suppression to be installed below the floor when there are "combustibles" (non-plenum rated cable) below the floor. It is funny though, since plenum rated cable is combustible, by because of the name, plenum rated, it is allowed below the floor most times without fire suppression.
    Those are a few.
    You need to make clear to the client that if they don't want an EPO, then they just have to install the infrastructure and equipment like any other office or equipment room.
    Ron

  9. #9
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    Ron touched on something I would like to expand on in reference to running cables under the raised floor. Initially with the cables under the raised floor makes for a very clean room as none of the cables are visible. However the real purpose of the raised floor is to be used for a plenum for positive pressure HVAC distribution.

    Equipment installers are very lazy when it comes to running cables, and have no plans on cable routing, and spend even less time dressing them if they don’t have too. Running under the floor just gives them the excuse to be sloppy. The processing equipment requires a lot of cabling, and over time as the room is filled up, the area beneath the raised floor becomes very congested and will block the air flow causing hot spots through out the room. Now couple that with cable mining, it is not possible with the chaotic install method when ran under the floor.

    The real solution is an engineered structured cabling system complying with Bellcore Network Equipment Building Systems (NEBS). This evolves installing multi level cable racks and raceways to facilitate the various cable groups used. This typically includes three ladder type cable racks or optical troughs installed centered above and running parallel to the equipment line-ups segregated by signal type (alarm, telemetry, signal, optical, dc power, and ground). Further more installation practices should be put into place and strictly enforced as to how and where cables are installed. Basically the cables have to be formed and laced in such a manner you can place your finger on the cable and run it along the entire length of the route with out any cross-overs, twist, or divers.

  10. #10
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    Very interesting stuff

    For some reason I stopped getting instant notification on this string. I want to thank all for this very interesting conversation. Sounds like I should not only look at EPO's but also the wiring method we use for under the raised floor. We call for UL listed as an assembly, Liquid Tight Flex. I believe, this application requires the EPO. Incidentally, the one thing that we do to protect against accidental triggering of the EPO is to provide a cover like those that are used over FA pull stations where there is a concern for kids pulling them for kicks. In this way, it would take more than someone leaning on it, or something falling on it, etc. Still, the point is taken.

    thanks,

    mike

    Thanks again,

    Mike
    Mike Shields, PE
    Boston, MA

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