Computer Room Cabling

[gmgerry]

I am consulting on a project for a data center. The electrical contractor is stating that he is allowed to to install whips to the IBM equipment under a raised floor using only rubber coated cords not conduit or flex. Also I am being told that the computer room is not required to be a fire rated room.

Any case studies on this subject would be great. Thanks

 

[bennie]

Re: Computer Room Cabling

Yes

 

[iwire]

Re: Computer Room Cabling

Go to NEC 2002 Article 645

If you meet the conditions of 645.2

1)Disconnect
2)Separate HVAC
3)Listed Equipment
4)Limited Occupancy
5)Firerated

You can use this article to determine wiring methods, if not you must wire the space like any other.

If it meets these requirements flexible cord would be limited to 15' 645.5(B)

[ April 03, 2003, 07:56 PM: Message edited by: iwire ]

 

[gmgerry]

Re: Computer Room Cabling

Bennie, what do you mean by ...yes.

 

[bennie]

Re: Computer Room Cabling

I'm sorry gm. I was being a smart ... I meant yes to the whips and yes the room does not needing a fire rating.

[ April 03, 2003, 08:49 PM: Message edited by: bennie ]

 

[iwire]

Re: Computer Room Cabling

If you want to treat this space as a "Data Room", it will have to be fire rated along with the other requirements of 645.2 or it is just another room in the building that happens to have a raised floor, which would mean rubber cord could not be a fixed wiring method 400.8(1)

 

[gmgerry]

Re: Computer Room Cabling

I see were iwire stated fire rating. I confirmed that with a copy of NFPA 75 I just bought. It also states that under a rised floor is a plenum the cabling must be in conduit.

 

[gmgerry]

Re: Computer Room Cabling

I have gotten more info uout of these responses than the local contractor and inspector. Is there any sites that help with data center designs? Thanks again.

 

[bennie]

Re: Computer Room Cabling

Gerry, ignore my responses. Bob is better versed than I.

I was basing my statement that most walls are steel studs with both sides covered with 5/8" sheetrock.

 

[iwire]

Re: Computer Room Cabling

This might help, it is from the Mike Holt Free Stuff page.


FIPS 94 - Electrical Power for Computer Installations (1-23-99) (7 MB winzip file)

 

[ron]

Re: Computer Room Cabling

gmgerry,
Keep in mind that NFPA 75 is not a code referenced standard. It is just a standard. If you wish to utilize the leniencies permitted by 645, then you must comply with 645-2 first, then you can move further in the article to take advantage of the leniencies (as compared to the first four chapters of the code).
Also, there are engineering firms that specialize in data center design. It is very different that consulting on an apartment/office building or school. So, since I am very close to a firm of this type except in small quantities.

 

[bennie]

Re: Computer Room Cabling

ron, and Bob: Glad you jumped in, I was over my head

[ April 03, 2003, 10:15 PM: Message edited by: bennie ]

 

[dereckbc]

Re: Computer Room Cabling

GMGERRY, I do a lot of these designs, and as Bob stated if you met the requirements of 645.2 you can use a flexible cord upto 15 feet, otherwise not. If the room is not fire rated, you do not meet 645.2.

Most telephone and data center do not want to take advantage of 645.2 for one reason. The disconnect requirement. It means you have to install a button at all the entrances when pushed it will shut down all power to the area. This includes battery and UPS. Great idea for fire departments, bad idea for disgruntled employees or idiots who think it is a light switch.

 

[mikeackley]

Re: Computer Room Cabling

First of all, dereck, great summary.

gmgerry: My 2-cents. All, some, but not none of the advice above may apply to your particular ?data center ?. You really need to give us more descriptive information about this facility for any help or advice beyond that already given. I haven?t been involved in design like dereck or ron but I?ve sure worked in a lot of centers. Fire rated 6-story hummers, 75,000 sq. feet of raised floor space, all of which was classified and used as a HVAC plenum. Highly sophisticated UPS systems, diesel or gas turbine engines spinning back-up generators. Disconnects ? no way! Conversely, on the other end of the spectrum I?ve worked in so called ?data centers? (that?s what the customer called them) that were really nothing more than closets with a 6? X 3? X 2? rack of desktop towers, a few modems, maybe a router or two, a Radio Shack UPS system, a couple of 120-volt circuits with 50 sq. ft raised floor not used or classified as a plenum. You probably have a good idea where along this continuum your data center falls, but we don?t.

I?d be very wary placing much stock in the FIPS 94 doc. referenced above. This is circa 1980/82 material published in 1983. Just think about the technological advancements that have taken place in the computer industry during the past 20+ years. I?ll see if I can?t find something more current for you to use, replying later with a posted link.

[ April 04, 2003, 01:22 AM: Message edited by: mikeackley ]

 

[iwire]

Re: Computer Room Cabling

Dereck, I was hoping you would jump in, I wish more people would do what you said and stay away from the Disconnect buttons.

In the area I work most customers go the full Data Room route. To help prevent accidental hits of the disconnect button we use a "Stopper II" cover, just the cover not the pull station.

STI Products

They are made for pull stations but the lettering that says "In case of fire lift cover - pull fire alarm" is easily removed and replaced with "Emergency Power Off"

This will not stop disgruntled employees but most of these rooms are limited access.

More of a problem is the tie in to the fire alarm system, a sprinkler contractor had to pay out a large settlement to one of our customers because they flowed water and tripped the alarm shutting down a major Data Center

[ April 04, 2003, 05:31 AM: Message edited by: iwire ]

 

[dereckbc]

Re: Computer Room Cabling

GMGERRY, here is a list of highlights I use on data centers. Not sure if it is applicable in your situation.

1. Raised floor installed and used as plenum for HVAC supply air.
2. AC, plumbing, fire sensors, signal reference grid (SRG) installed under raised floor.
3. 2 or 3 tier 18? cable racks installed centered over equipment line-ups at 8?-6?, 9?-6?, & 10?-6?, supported from ceiling if possible or from stanchion pole and/or equipment racks otherwise. The cable racks are used to carry the all the signal cables and DC power, and DC grounds.
4. Lights installed centered over walk aisles in between equipment line-ups.
5. Sprinklers system installed as high as possible above all other systems.
6. PDU?s from UPS installed strategically in equipment line-up to keep dedicated branch circuits short so voltage drop does not exceed 3%. No IG outlets. PDU feeder and branch circuits ran under raised floor in approved raceway.
7. Battery breaker bays installed same as PDU except distribution is overhead on cable racks.

Hope this helps, suggest you get a copy of IEEE Orange, BUFF, Emerald, and Green books. And since I was recently laid-off, I would love to help out.

Bob I have used the device you pictured. So far I have only had to design a 645 compliant system in two cities, King of Prussia and Philly. Otherwise I avoid it like the plague.

Dereck

[ April 04, 2003, 11:09 AM: Message edited by: dereckbc ]

 

[ed downey]

Re: Computer Room Cabling

gm,
I ran into this requirement that the mechanical engineer and the ahj in Santa Clara, CA required us to remove all of the computer blue sealtight from under the raised floor and replce it with EMT or fire rated cable. I have never ran into this anywhere else in the country but it is soemthing to keep in the back of your mind and ask the question.

From UMC Chapter 6, 1998 edition 602.2.1 Materials exposed within plenums. Except as required by Sections 602.2.1.1 through 602.2.1.3, materials exposed within plenums shall be noncombustible or shall have a flame spread
index of not more than 25 and a smoke-developed index of not more than 50 when tested in accordance with ASTM E 84.
Exceptions:
1. Rigid and flexible ducts and connectors shall conform to Section 603.
2. Duct coverings, linings, tape and connectors shall conform to Sections 603 and 604.
3. This section shall not apply to materials exposed within plenums in one-and two-family dwellings.
602.2.1.1 Wiring. Combustible electrical or electronic wiring methods and materials, optical fiber cable, and optical fiber raceway exposed within a plenum shall have a peak optical density not greater than 0.50, an average optical density not greater than 0.15, and a flame spread not greater than 5 feet (1524 mm) when tested in accordance with UL 910. Only type OFNP (plenum-rated non-conductive optical fiber cable) shall be installed in plenum-rated optical fiber raceways. Wiring, cable, and raceways addressed in this section shall be listed and labeled as ple
numrated and shall be installed in accordance with NFPA 70.

 

[mikeackley]

Re: Computer Room Cabling

Another example of how these design/installations can be dicy. I've seen the aftermath of a chilled water pipe break (feeding a water cooled computer) flooding a 3' raised floor up over the deck and down to the next floor into the UPS battery room.

 

[gmgerry]

Re: Computer Room Cabling

Here is an update on what came out of a meeting between the architect, builder, elect contractor, customer and myself.

Architect stated that they are meeting the NFPA 101 of 1997 26-3.2.1 which states it is not a hazardous room...boiler room, storage room so it is not required to be fire rated. Also. NFPA 75 1999, 3-1.1 which states that if the whole building is sprinkled; the computer room does not have to be fire rated.

When I got into NEC 645 I was blown out of the water because I was not a PE or Electrical Engineer and had not valid reason to question the NEC. The customer was floored and placed the architect and electrical contractor on notice to document the above and to answer my question on NEC 645.

I would have updated earlier but I was out of service due to the ice storm the came through Michigan this past weekend.

I would like to hear your thoughts or input on this. I feel I'm right here and like a good fight for what's right and safe. Thanks.

 

[dereckbc]

Re: Computer Room Cabling

GMGERRY, your architect is correct in his statement the room does not have to be fire rated. It really revolves on what the local authority will have to say about it. If the local codes mirror the NEC, then to take advantage of the relaxed requirements of 645, the room will have to be fire rated.