Telco carriers really like to deploy -48v DC batteries within their racks in the telco room ("Telco Entrance Facility" for TIA-942). NEC 645-10 requires that if you use NFPA exemptions for the datacenter (unfastened electrical whips under the raised floor), then you must link all battery systems larger than 750VA into the EPO circuit.
I'm not keen on doing EPO maintenance every time a carrier places a new battery system within the telco room, and don't know of any facilities that do. I can think of a few options:
run electrical conduit overhead in the telco room (standard commercial electrical wiring, no IT room exemptions)... maybe even do everything overhead. Use a different fire suppression zone from the datacenter for the telco room.
refuse to let telcos bring in batteries; or refuse systems larger than 750VA
ignore NEC and NFPA (seems to be common from what I've seen... lots of >750VA UPSes in raised floor environments)
In case anyone is curious, I'm spec'ing the Telco Entrance Facility to be NFPA-76-compliant, rather than NFPA-75. Power in the TEF is via EMT rather than nonmetallic liquid-tight. There are no power receptacles beneath the floor in the TEF. Non-plenum wiring (e.g. outside fiber pulls) must go overhead when inside the TEF. And of course, this will all be discussed with the AHJ before installation. The goal is: no EPO in the TEF, and each cabinet may contain its ows battery system >750va. And no issues, should someone clever device a TIA-942 audit process.
This poses some challenges in combination with TIA-942, which proscribes transitioning overheard cables from the TEF to underfloor cables in the datacenter. My approach is to minimize under-floor cabling between the TEF and datacenter; use plenum wiring where possible; encase any non-plenum between TEF and datacenter inside EMT (not sure that will really be necessary, but there are some weird cables out there).
So, in a flood, fire, earthquake or other emergency, how will you shut off power to the racks? It seems to me that not having a single means for disconnecting power is inherently dangerous, both to on-site staff as well as to first responders. Most telcos have several hours worth of battery backup. Saving lives, or even mitigating the effects of a disaster by quickly de-energizing the site, should be worth the nuisance of making a new dry contact connection when adding a UPS.
DC batteries in Telco Entrance Facility
