[GRLUG] Plenum Cable

[Adam Tauno Williams]

On Thu, 2011-07-28 at 15:20 -0400, Michael Mol wrote:
> On Thu, Jul 28, 2011 at 3:11 PM, Benjamin Flanders <flanderb at gmail.com> wrote:
> > We are moving a closet shortly and I will need to string some more
> > cable.  With that in mind I was going to buy some cable and came up
> > with a term that is new to me, "Plenum".  It turns out that the
> > airspace above a drop ceiling could be a plenum, and if such, the
> > cabling that resides up there is much more expensive.
> > Wikipedia provided an explanation of what a plenum is, but my question
> > is is there a test to know if the airspace up there is a plenum?
> Rule of thumb: if it's open to the HVAC system, you'll want plenum.

Yep.

> > I
> > believe that it is a somewhat sealed airspace, but the drop ceiling is
> > old and not really sealed.  Should I just call the fire inspector and
> > ask him?
> Not really useful as a CYA. Fire inspectors' knowledge of the fire
> code is hit and miss. One fire inspectors' good-faith statement isn't
> certification against another's.

Position of the cable matters to the fire inspector as well; cable
cannot 'lay' on the suspended ceiling.  It has to be secured up and away
from the tile & grid.  I've inherited a couple of sites who have been
cited for this.

> >  Anyone else have this situation?  We do have non-plenum
> > cable up there right now, but my concern is that my predecessor didn't
> > know about the law either and we might have to recable the whole
> > office.
> >
> > Also, on a related note should I look at getting cat6 vs cat5e?
> Not especially. As has been discussed in the past, while Cat6 is
> *designed* to be able to handle gigabit signals, cat5e has improved
> dramatically simply through better testing on the manufacturer end.
> We're using gigabit over cat5e throughout our office. At home, I'm
> running gigabit over cat5e, and gigabit over cat6, and I can't say
> I've noticed a difference. I'd need to get my hands on a high-end
> cable tester to make any kind of judgement.

+1 on just using Cat5.


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