wireless technology for better understanding of speech
There have been questions on the EAA listserv about using
plenum-rated wires with active learning (sound field) systems. It can be a confusing
topic, so we've put together this Q&A to help you decide when to use
plenum-rated wire. If you have any questions after reading
this, please contact your local Fire Marshall or feel free to contact our Customer Service department at
800.227.0735 or email
us.
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What is a plenum?
According to the National Electric Code (NEC) a plenum is a "compartment or chamber to which one or more air
ducts are connected and [which] forms part of the air distribution system."
To qualify as a plenum, the space above an acoustic tile ceiling would
have to extend above other rooms in the same building or be open to
ducts connecting it to other parts of the building. The concern is
that during a fire, if there is burning material
in a plenum air space, smoke and fumes can travel through air ducts to
the whole building. For this reason, there are codes to restrict the
types of materials (such as wiring) that can be placed in the plenum.
It's quite common to have an acoustic tile ceiling without having a plenum. If your room-dividing walls extend above the dropped ceiling and seal off the space above, you do not have a plenum air space and so may not require plenum-rated wires. (See illustration.) You can lift up an acoustical tile in your room and peek in to see if your room has a plenum.
What is the code?
According to the National Electric Code (NEC), in plenum air spaces
you must use plenum rated cables, also called Communications Plenum
Cable (CMP).
Plenum cable is only required when cable is installed in a plenum air
space. Materials kept below the ceiling —
including speaker wire, computer cables, telephone cords, etc. — do
not need to be plenum rated according to the NEC.
Remember that even though the National Electric Code may allow non-plenum cable, the final decision is up to your local Fire Marshall. Most cities adopt the national codes as their own without revision, but some cities modify or expand them and require plenum-rated cable in all situations. Regardless of the code or its interpretation, your Fire Marshall makes the final decision. We recommend that you contact your Fire Marshall if you have questions.
Why is the regulation for plenum air spaces but not for
inside the classroom?
It's dangerous to inhale fumes from any burning material.
Speaker wire is no more dangerous than any other plastic item you would find
below the ceiling in a
typical classroom — computers, carpet, power cords, etc. Therefore,
requiring the use of plenum wires
within the classroom itself would have little impact. The regulation
covers the area where it's most critical.
How is plenum wire different from other speaker wire?
Plenum rated coating on wire burns at a much higher temperature and
emits fewer fumes.
What does plenum wire look like?
Phonic Ear’s plenum-rated wire is white and round and has printing
on it. Non plenum-rated wire has clear vinyl insulation and you can see
the copper wires inside.
Do we need to replace all of our speaker wires in the district?
Probably not. The wires in question are only the ones that run through true plenum air
spaces. Cords running through closed spaces or kept below the ceiling
tiles are probably acceptable. We recommend that you replace any wires running above the
ceiling tiles in a plenum air space with plenum-rated wires. If you're
unsure, check with your Fire Marshall.
If I want to replace a wire, how much will plenum
wire cost?
Phonic Ear will replace any speaker wire that you’re concerned
about free of charge even if it’s not running through a plenum air
space. Just call 800.227.0735 then press 5.
Do you want me to send you my old speaker wires?
No. Please don’t.
Who sets the guidelines?
The National Electrical Code (NEC) is a set of guidelines
recommending procedures to reduce the risk of fires, electric shock and
other hazards associated with electrical installations. The code is
advisory in nature, but most state and local building departments across
the country use the NEC as the basis for their own electrical codes.
Some local codes may be more restrictive, so please check with your
local Fire Marshall if you're unsure.
Is compliance with the locally-adopted code mandatory?
Yes. City, county or state codes are
mandatory and enforceable as law.
Does Phonic Ear ship wires that meet the code?
Currently Phonic Ear packages only plenum-rated wire with all of its systems. Even though the
national regulation is specifically for plenum air
spaces only, Phonic Ear will also gladly replace any speaker wire you're
concerned about. Your satisfaction and safety is our top priority.
When did Phonic Ear change to plenum-wire?
Phonic Ear made the transition very recently. Previously, we used normal speaker wires because they were not intended
for use in plenum air spaces. Once we became aware that some of our
customers needed to run speaker wire through plenum air spaces, we made the commitment to change
all of our wires to plenum-rated.
Are the wires on the infrared sensors plenum-rated?
Yes. We have recently changed the wires on our sensors to be
plenum-rated as well.
We offer the NEC quotes here for general information purposes only and cannot guarantee typing or interpretation accuracy. Only the actual National Electric Code should be accepted as the correct version of these writings. Our comments are our own and may differ from actual circumstances in your community. Only the Fire Marshall and/or building inspector in your community can advise you if all of the circumstances detailed in this document apply to you.
Just call 800.227.0735 (US) or 800.263.8700 (Canada) if you have any further questions. We're also easy to reach through email.
homebase: 3880 cypress drive • petaluma, ca 94954 usa