2.4.14.1
Interior Point Sensors
a.
Door and window protection:
Accomplish by one or more of the
following:
(1)
Door and window open detection
(a) Balanced magnetic switches (BMS): Switches shall be [surface
mounted] [and] [recessed] [as indicated] and shall have a minimum
of two encapsulated reed switches. Switches shall activate when a
disturbance in the balanced magnetic field occurs. Provide each
BMS with an overcurrent protective device, rated to limit current
to 80 percent of the switch capacity. BMS shall be rated for a
minimum lifetime of one million operations. House the BMS
components in nonferrous enclosure materials.
(b) Surface mount BMS: House components used in outdoor
applications in weatherproof enclosures. Switch mechanism shall
be internally adjustable so the operating gap between faces of the
switch housing and the magnet housing may be adjusted from 6 to
[13] [50] mm 1/4 to [1/2] [2] inch[es] to accommodate installation
variances. Surface mount BMS housing for the switch element shall
have the capability to receive threaded conduit. Housing cover
for surface mounted BMS, if made of cast aluminum, shall be
secured by stainless steel screws. Magnet housing cover shall not
be readily removable. Protect BMS housing from unauthorized
access by a cover operated, corrosion-resistant tamper device.
Device shall initiate an alarm when cover is opened as little as 3
mm 1/8 inch and shall be inaccessible until actuated. As an
alternative, BMS shall consist of [three] [four] preadjusted reed
switches and three preadjusted magnets. Field adjustments in the
fixed space between magnet and switch housing shall not be
possible. Attempts to adjust or disturb the magnetic field shall
cause a tamper alarm. [Conductors running from the door to alarm
circuits shall be jumpered within a flexible armored cord
constructed from corrosion-resistant metal. Each end of the
armored cord shall terminate in a junction box or other enclosure.
Armored cord ends shall be mechanically secured to the junction
boxes by clamps or bushings. Conductors within the armored cord
shall be provided with lug terminals at each end. Jumpered
conductors and the armored cord shall experience no mechanical
strain as the door is removed from fully open to closed. Switch
circuit shall initiate an alarm if a short circuit is applied to
the door cord.]
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NOTE: Regarding the text below, show a junction box
above each door so that slack in conductors serving
switches cannot be accessed when switch mounting
screws are removed. If building construction does
not permit junction box location above doors,
specify switches to be epoxy glued in place after
preliminary testing.
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(c) Recessed BMS: The recessed BMS shall consist of [two]
[three] preadjusted reed switches and [two] [three] preadjusted
magnets. Field adjustments in the fixed space between magnet and
switch housing shall not be possible. Attempts to adjust or
SECTION 13703N
Page 27
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