|
|
|
|
On 04 Dec 2004 15:46:01 GMT, ospam (Leoaw3) wrote:
According to the NEC and it is the *LAW*, snip
The NEC is a bare bones baseline. Most local codes supercede NEC.
NEC still permits aluminum residential wiring (with "approved
devices"), but is now illegal in most areas due to many fires and
deaths attributed to it.
...in plenums you *must* use plenum
cables that are listed as "Type CMP"(Communications Plenum Cable). Article
800-53 of the NEC states: " Cables installed in ducts, plenums, and other
spaces used for environmental air shall be Type CMP". Permitted substitution
for "Type CMP" cables is "Type MPP" cables (Multipurpose Plenum Cable). snip
Thanks for finding the cite in the NEC, saving me some reading while
typing! True, NEC permits use of HVAC ducting as well as in wire
ducts and runways, but many local codes prohibit it. I know it's
illegal in Los Angeles city AND county, but then again, so is BX,
which has been since the 1950s.
The NEC requires that "Type CMP plenum cable shall be listed as being suitable
for use in ducts, plenums and other spaces used for environmental air and shall
also be listed as having adequate fire-resistant and low smoke-producing
characteristics". snip
No IBEW electrician would ever use CMP, even for signal cable, in an
HVAC duct; their training prohibits it on safety grounds. Although
CMP is "low smoke-producing," it also releases noxious PVC gas when it
melts, and that's a major health hazard. I was directly involved with
in a cable fire in a telephone central office many years ago, and the
work force on the involved floors of the complex had to undergo blood
gas tests immediately afterward, and some did get very ill. If the
cable had been in a return air space, the PVC gas could've been
propagated much further than it was. Also, the smoke damage from
burning PVC isn't just soot. It's conductive and very adhesive, and
was responsible for hundreds of thousands of dollars in equipment
repair and replacement in this single incident.
My vote? NO cables in HVAC plenums, period. It may seem like a real
longshot, but remember...if someone screws up and gets 220 on your mic
pair, it melts and causes damage, YOU'RE on the hook for it just as
much as the idiot who caused the failure if you're installation
violates code. If local code is permissive, then you're not liable,
but it wouldn't do much for your reputation.
dB
|