[GRLUG] Plenum Cable

[mooselikebriard]

Also, it is against code to use the ceiling grid wires for support.
 Everything above should have it's own support.  Many inspectors will let
this slide, however.

The drop ceiling tiles themselves do not have to be sealed.  A plenum air
space uses the entire area above the drop ceiling for return air.  A
non-plenum space utilizes duct-work for return air.  Look up inside the
return air grates (the ones without the diffuser.)  If you see ductwork, you
can use non-plenum cable.

On Thu, Jul 28, 2011 at 3:58 PM, Adam Tauno Williams <awilliam at whitemice.org
> wrote:

> 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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