jsloan@wright.EDU (John Sloan) (05/11/88)
I've seen references on the net to plenum-rated ethernet transceivers but have never read any specific citations. Plenum-rated transceivers could be used in the plenum, the environmental air space above drop ceilings (and other places). Plenum-rated transceiver and coax cable is common. I note that the standard DEC transceiver says on its label very specifically that it is NOT plenum rated, as do the BICC and 3COM transceivers we use. The Cabletron transceiver literature says "conforms to UL 910 and NEC 725-2(b) requirements for installation in air-handling spaces". A quick phone call to our rep had him reading this verbatum over the phone, which wasn't much help. Other phone calls have yielded similar results. A call to our University electrician, who is supposed to know at least the codes, was not of much use. So here I am wasting everyone's bandwidth. Does anyone have specific recommendations, including vendor name and part number? If anyone else is interested, I'll investigate it from there and summerize results. Thanks! -- John Sloan, The SPOTS Group Wright State University Research Building CSNET: jsloan@SPOTS.Wright.Edu 3171 Research Blvd., Kettering, OH 45420 UUCP: ...!cbosgd!wright!jsloan +1-513-259-1384 +1-513-873-2491 Logical Disclaimer: belong(opinions,jsloan). belong(opinions,_):-!,fail.
mark@applix.UUCP (Mark Fox) (05/13/88)
In article <859@wright.EDU> jsloan@wright.EDU (John Sloan) writes: >I've seen references on the net to plenum-rated ethernet transceivers [etc.] > >...Does anyone have specific recommendations... When we first installed our Ethernet cable above our dropped ceiling we also had trouble getting info from fire & building officials. However, we were assured (not sure by whom -- it was 4+ years ago) that it was ok from a legal standpoint to install normal yellow PVC cable in plenums as long as smoke detectors were also present (in the plenums). It certainly is cheaper than installing Teflon cable or using metal conduit (at least in the absence of fire!) Anybody know if this is true today? Any specific building/fire code references available? Thanks. -- Mark Fox Applix Inc., 112 Turnpike Road, Westboro, MA 01581, (617) 870-0300 uucp: {ames,rutgers}!harvard!m2c!applix!mark
edm@nwnexus.WA.COM (Ed Morin) (05/16/88)
I was recently faced with the same problem while installing a network in a building that uses the air space above the ceiling for the cold air return of the air-conditioning system. Since we were ordering Cabletron transceivers, I knew that everything would be ok. However, once we re- ceived the transceivers they had little stickers on them saying (I don't have one with me at the moment) that they could *not* be used in "pleums"! So, I contacted Cabletron. Normally I get terrific service and attention from them, but this fiasco went on for *weeks* trying to reconcile this apparent inconsistency. Nobody seemed to know anything about the meaning of their NEC 725 (?) specification vs. this crazy sticker with an apparent misspelling. It turns out that the transceivers can be put into "air handling *spaces*" (like ceilings), but *not* in actual ducting (i.e. main air supplies, etc.). I guess Cabletron is drawing a distinction between an "air handling" spaces and "plenums"... Ed Morin Northwest Nexus Inc. edm@wa.com
devine@cookie.dec.com (Bob Devine) (05/18/88)
> Nobody seemed to know anything > about the meaning of their NEC 725 (?) specification vs. this crazy > sticker with an apparent misspelling. There are *many* regulations regarding building codes. I suspect what happened here [cable allowed in "air carrying space" but not in "plenums"] is due to a local or national fire code. For a plenum you want to have non-PVC cable so that the toxic fumes caused by a fire burning the cable are not circulated by the plenum. The "NEC" stands for the National Electrical Code. From what I remember, it is Article 800 that controls cabling. Article 800 defines 4 types of cables (this is the entent of my notes, if you want more info you'll have to get the actual regulations): 1. Communication cable = general stuff, probably what you bought 2. Communication riser cable = for use in shafts, is fire-resistent 3. Communication plenum cable = used in plenums, no toxic fumes 4. Communication cable, limited use = for use in noncombustible pipes Bob Devine
jsloan@wright.EDU (John Sloan) (05/19/88)
in article <410190444@nwnexus.WA.COM>, edm@nwnexus.WA.COM (Ed Morin) says: > It turns out that the transceivers can be put into "air handling *spaces*" > (like ceilings), but *not* in actual ducting (i.e. main air supplies, etc.). I'm not sure there's much of a distinction in modern buildings. Many (including ours) use ductwork to deliver air to offices, then use the plenum (the air space above the ceiling) as an air return. Since the fire code is concerned about smoke and noxious fumes from burning materials (particularly plastic), which are the major causes of deaths in fires, spreading to other parts of the building (also making locating the fire very difficult), it would seem to me to be six of one, half dozen of the other. It sounds more to me like Cabletron was trying, not very successfully, to come up with a plausible explanation. Second worry of the day: I recently realized that some of the telephone closets are open to the plenum in the top... i.e. no ceiling. So, like, is that a plenum space or what? Third worry of the day: trying to explain to our new department chair why this is all so complicated ("why can't you just run a cable?" "because I don't want my a** sued off."). -- John Sloan, The SPOTS Group Wright State University Research Building CSNET: jsloan@SPOTS.Wright.Edu 3171 Research Blvd., Kettering, OH 45420 UUCP: ...!wright!jsloan +1-513-259-1384 +1-513-873-2491 Logical Disclaimer: belong(opinions,jsloan). belong(opinions,_):-!,fail.