nec art. 645 2

[GOTWW]

I am starting to battle it out with an FPE about receptacles
under raised flooring, and the following

http://ecmweb.com/mag/electric_cords_fixture_wires/index.html

appears on the scene. Note figure 1, and the following caviot. "not used for environmental air". Plus no mention of 2002 art 645. Was the author dodging a bullet?, Aimed at me? My interpretation of art. 645, with the required underfloor smoke detection and automatic air handler shutdown system, the above-mentioned caviot is not relevant in this case. And that is, Receptacles/plugs are allowed in the underfloor plenum areas, And the (UL) flexible appliance cords (less than 15') do not require plenum rating. It also does not help with table 400.4 does not list plenum rated flexible power cords.

Anybody else got a stance on this?

 

[GOTWW]

and for clarification,
The afore mentioned plugs and cords are for equipment above the raised floor, that connect to the allowed accessable receptacles below the floor through approved openings in the raised floor.

 

[peebee]

It's not quite clear what your situation is: do you have a plenum floor or not? Are you building your room to meet 645? And what is the problem -- your inspector won't let you put receptacles under the floor?

If you don't have underfloor air (the floor is being installed for wiring only, no air blown thru), you can usually put whatever you want down there.

If you do have underfloor air, you can only put receptacles down there if you are following 645. Some inspectors are not familiar with 645, though, and may give you a lot of resistance on this. And in some jurisdictions, they specifically prohibit underfloor receptacles in plenum areas.

Here in Chicago, if you've got a plenum floor, only hard metal conduit goes in the floor (liquid-tite is permitted up to 6' max, rather pointless). And all receptacles are installed above the floor, or flush-mounted in Wiremold-type floor boxes. Chicago is an extreme example, though.

For straight NFPA, you can put underfloor receptacles in so long as you comply with 645.

 

[GOTWW]

Yes, it is a 645 room, plenum floor, w/smoke detection etc.. I just do not think the FPE is familiar with the plenum exception of this article. 645 clearly states the underfloor outlets are acceptable, however is not clear as to what flexible wire type is allowed to be plugged into these outlets. This is a sticky point, as, the automatic reflex for the FPE's is that all these cables shall be plenum rated. I do not know of any "plenum" rated flexible cord and plug assemblies (yet). My interpretation is that these flexible cords need not be plenum rated, just UL listed with the 15' max length restriction. Do you agree?

 

[peebee]

Doesn't necessarily need to be plenum rated, although you can't just use any old cable. . . .

645.5(D)(5)(c) lists tray cable (type TC) as acceptable. Tray cable is easy enough to get.

However, I believe (really not sure though) that most servers come with type DP cords, covered in 645.5(D)(5). Mike Holt and EC&M come to the rescue again -- from

http://www.ecmweb.com/mag/electric_code_quandaries_10/

:
"Q. . . .Must short (30 ft or less) jumper cords or power cords that plug into underfloor outlets be plenum rated?

"A. No, the cords are required to be listed as Type DP (data processing cable). . . . Sec. 645-5(d) requires power . . . cables associated with information technology equipment be listed for data processing rooms and marked Type DP. Type DP cable has adequate fire-resistance characteristics suitable for this environment. . . ."

Strangely, he doesn't mention TC, but it's clearly stated to be acceptable in the Code.

I took a look through NFPA 75, and it largely copies from NEC 645.5(D) regarding this stuff. But the following excerpts from NFPA 75 might help you -- I'm not familiar with the UL scopes & requirements, though, so I can't say for sure:

7.1.1 Equipment and replacement parts shall meet the requirements of UL 478, Standard for Electronic Data-Processing Units and Systems, UL 1950, Standard for Safety of Information Technology Equipment, or UL 60950, Standard for Safety of Information Technology Equipment.

7.1.2 Listed equipment shall be considered as meeting the requirements of 7.1.3.

This site might help (Data-Processing Cable, UL 1690):

http://ulstandardsinfonet.ul.com/scopes/1690.html

-- it seems a lot of cord manufacturers state "UL1690" rather than "DP", but apparently they mean the same thing.

 

[GOTWW]

Talk about hitting the nail on the head!, Thanks peebee, hope I can return the favor someday. Really like the part about the "data" cables not required to be plenum rated. If I throw that one at them, the Inspector and FPE will definately blow a gasket!, or throw a rod through their block!

 

[peebee]

That's kind of the point of 645 -- it lets you put non-plenum rated cable in a plenum area, so long as you do a bunch of other stuff to that area (dedicated HVAC, walls to ceiling, EPO, etc).

If you weren't allowed to put in non-plenum cable, there'd be no point to 645. Why would anyone do all that expensive stuff to the room if there was no benefit? Keep in mind, you COULD design most data centers as normal business occupancies, with walls and HVAC and wiring conforming to normal (but high density) office construction standards. BUT -- in data centers, there's some good reasons to want to run wiring through the floor*. So, 645 permits (but does not require) you to call it an IT space and run your non-plenum wire in the floor so long as you do all that other stuff.

* Actually, I disagree somewhat with that statement about "good reasons to put wiring in the floor". In my humble opinion, wiring belongs overhead on tray systems, and the floor should be dedicated 100% to HVAC. But that's besides the point.

 

[BarryABC]

Question on NEC 645

We are looking to construct a Data Center that will have a full saturation FM200 fire suppression system. The goal is to enable the air conditioning, and hence the computer equipment, to remain on during a smoke condition and FM200 discharge. The EPO will have only a manual activation.

One of the Engineers on the project feels that this is a violation of NEC 645. He states that AC unit mounted duct smoke detectors, must shut down the AC equipment when triggered. (Requirement comes from NFPA 90A for AC units over 2,000 cfm.)

I know of a number of Data Centers that do not shut down on upon smoke alarm. Does anyone know under what conditions this is allowed and where this is described in the code?

 

[RonShap]

Barry,
Your question is somewhat related to NEC 645 and somewhat not.
If you choose to utilize this "optional" article 645, and your jurisdiction follows the 2002 or later NEC, then when smoke is sensed underfloor you need to shutdown airflow. They don't say how you sense smoke under the floor. It could be after crosszoned (two detectors) smoke detectors with alarm verification.
If you have FM200, then you could activate the FM200 on the first detector. The problem is, that by activating FM200, the gas will put every detector in the room, into an alarm condition, thus shutting the air below the floor off. Your best bet is trying to get a permit for the work before the NEC 2002 is adopted by your jurisdiction.

On a separate note, an AC unit only recirculating air within that room does not require fan shutdown, assuming that you're jurisdiction is following the IBC. Although if smoke is below the raised floor, as mentioned before, you have to shut the air flow off below the floor. It's a horrible spiral circle.

If possible, and your center does not need the leniencies permitted by 645, don't do it, and don't shut down the fans that recirc air. Follow the IBC's exception.

 

[BarryABC]

Thank you for your response. We had just started thinking along these lines. Our fire protection consultant felt that if we used Photo-Electric smoke detectors, they would not trigger on a FM200 discharge. In addition the local Electrical Inspector is also willing not to require HVAC shutdown if the Fire Marshal approves the full saturation FM200 system. It looks like we will be able to accomplish what we need.

 

[peebee]

Barry - NEC 645 doesn not require HVAC shutdown -- See NEC 645.2 -- it just requires dampers to isolate the data center from the rest of the building.

Setting off FM-200 with the dampers open would just be a waste of FM-200.

 

[peebee]

However, NFPA 75 includes the following requirement:

8.4.2.1 The power to all electronic equipment shall be disconnected upon activation of a gaseous agent total flooding system, unless the risk considerations outlined in Chapter 4 indicate the need for continuous power.

And the following recommendations:

A.8.1.2 . . . .In other instances where a fire can operate sprinkler heads before discovery by personnel, a method of automatic detection should be provided to automatically de-energize the electronic equipment as quickly as possible. . . . To minimize damage to electronic computer equipment located in sprinkler-protected areas, it is important that power be off prior to the application of water on the fire.

 

[RonShap]

645.5(D)(3) requires shutdown of air below the floor.

 

[peebee]

Oh yeah.

Sorry Barry - you're screwed. No way around 645.5(D)(3). Ignore my other post above.

Nice catch Ron.