Computer rooms - EPO's

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ron said:
Dave,
The types of raceway permitted are also slightly different when you compare 645.5(D)(2) and 300.22(C)
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I was always under the impression that this was the heart of the advantage of 645.

645.5(D)(5) says cables shall be listed unless they are one of those covered in 645.5(D)(2).

Does this mean you can use the other wiring methods of 645.5(D)(2) (rnmc, enmt, metal and nonnetalic wireway, liquidtight, standard MC cable etc.) in a 645 room when you wouldn't be able to under 300.22.

Are you saying that this expanded use of wiring methods (if I'm right) still doesn't make it worth it?

I know this is a long way to go to finally get to a bottom line question, thanks for your patience.:smile:
 
There are a lot of wiring methods in 300.22(C). the 645 methods are IMHO not worth the liabilities of 645.
http://www.csemag.com/article/CA6290839.html
Human error is the main reason to not use 645. Accidental activation of the EPO means no power or HVAC, or a small smoke condition from ..... maybe one power supply out of 1000s requires shutdown of all airflow below the floor per 645.5(D), YIKES!
 
Ron's Article

Ron's Article

Ron,

Excellent Article. But tell me this, you talk about installing cabling in wire trays above the racks. Missing from the categories of cabling you describe is power wiring. How do you recommend distributing the 120V, 208V, etc required by cabinets, racks, etc?

Mike
 
Correction

Correction

Have been reading all of this stuff and lost track of where I read about the Bellcore Network Equipment Building Systems (NEBS) solution. It was a post by dereckbc.

Dereckbc, same question as above if you please. How do you recommend running your power cabling?

Thanks,

Mike
 
I'm not sure what part you are commenting about, but if not compiling with 645 .... control/communications/IT type cabling follows Article 725, 770, 800, etc.
Raceway (or lack thereof) for those can be found in 300.22 where needed in in the specific low voltage section as mentioned above.
Power wiring follows the methods in 300.22 depending on your situation, like any other equipment installation in any other type space/building.
 
Mike there are a few ways but the most efficient is to install al the AC power distribution (300.22) under the raised floor along with any Signal Reference Ground grid (SRG). The rest goes overhead on cable racks centered over the equipment line-ups.

I urge you to spring for a copy of NEBS. It has tons of eviromental, lighting, line-up spacing, equipment racks, and space allocation info.
 
I can see article 645 for EC's following designs that consolidate all systems under the floor.

When underfloor space is required to house multiple systems, (ie) AC, data, plenum, plumbing, and power, perhaps the fire suppression requirements are also required to be concentrated there.

Fire suppression may cleanup easier, and accidental death insurance may be cheaper if most of that asphyxiating-chemical discharge occurred under the floor.

Venting AC under raised floors does eliminate overhead ducts, and perhaps keeping all these systems off the ceiling offsets enough construction-trade costs, to justify giving the EC's a bit more to make it work underfloor also.
 
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Ramsy,
In many datacenters, air must be distributed under the floor in order to get the heat away from the equipment. Cold air comes up in front of or through the equipment racks and then is returned back to the HVAC system at the ceiling (sometimes above the suspended ceiling) level.

This can be done with a hot aisle cold aisle technique or others.
 
Yah Ron, I've seen that method in existing installations, mostly high rises in downtown Los Angeles, but new data-center installs in my region are consolidating everything under the floor.

The equipment AC units were bolted to and fed from the floor. There may have been small air deflectors or scoops, but no ducts under the raised floor and lots of chilled forced air from those AC units blasting us around under there. I remember being the only JW that could stand hammer drilling, & strapping raceway in front those 40F wind tunnels. I doubt there was any need for a separate environmental air system overhead, and I didn't see any ducts connecting ceiling to floor.

The floors tiles were usually thick, concrete-filled steel plates, and that positive pressure under there would seem to direct any smoke out of the building, and cool the PDU's & other floor mounted equipment from underneath.
 
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ramsy said:
The equipment AC units were bolted to and fed from the floor. There may have been small air deflectors or scoops, but no ducts under the raised floor and lots of chilled forced air from those AC units blasting us around under there. I remember being the only JW that could stand hammer drilling, & strapping raceway in front those 40F wind tunnels. I doubt there was any need for a separate environmental air system overhead, and I didn't see any ducts connecting ceiling to floor.
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If the cooling is done properly from the start there's no need for additional cooling -- what's under the floor is sufficient to keep everything, including the people, quite cold.

The way I've seen it done most of the time is they have a cooling unit that runs on chilled water. It operates as a heat exchanger, sucking in hot air from above the floor, chilling it with cold water, then pumping it back under the floor. Perferated tiles are then used to allow cold air to come up wherever needed, and the notched tiles that allow cables to be brought up from underneath the floor provide additional cold air from below to come up.
 
In a high density datacenter, you can't put everything below the raised floor, because it will block the distribution of cold air.
In a lightly loaded datacenter, everything below the floor is OK, until the owner wants to raised the power density and realizes they can't due to air flow restrictions below the raised floor.
 
ron said:
In a high density datacenter, you can't put everything below the raised floor, because it will block the distribution of cold air.
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Sure you can, go back to page one and read my response. Installers/technicians do it all the time :) That is the beauty of 645, ignorance of the concept generates millions of dollars of unnecessary retrofits making us engineers wealthy and employed.
 
The gas fire suppresion you speak of , what type is it ?
I do remember a gas of of old but not the name -that was disscontiued in my area because of the danger to personel
Most of the data centers I work in have a dry type sprinkler -so that a fire triggering the epo would shut down everything so the water would'nt ruin it-hot it will off it won't .
Most of the raised floors in the newer buildings we have wired are 3 ft. raised, some of the old ones we have added power to have 2 ft. raised.
I am about to wire an expansion to a data center so I find this thread very interesting
 
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