Controlled Products Systems Group HRG 220-A ST - Manual (Page 56)

Installation and Maintenance Manual
42
Detector Installation Guide
Detector Basics
The vehicle detector passes a sm
all current flow through the ―loop‖ which then becomes an inductive
coil. When a vehicle passes over a loop the detector senses the resultant drop in the inductance, and
actuates the detector output.
Loop Configurations
Configurations differ depending on the application. In parking applications with our HTG 320 operator, a
loop may be as small as 3’ x 6’. In traffic applications employing one of our sliding gate operators, or
swing gate operators, the smallest loop should not be less than six feet square.
Rules to Follow for Security Gate Applications
1. The side of the loop closest to the gate shall be located at least four (4) feet distant from its line of
travel.
2. The shortest side of the loop shall be between six (6) and eight (8) feet in length. The longest side of
the loop shall be between six (6) and twenty (20) feet in length. For applications that need to span a
wide area, use several smaller loops. Do not exceed a maximum of 200 square feet of loop area to
only one detector.
3. In applications with mu
ltiple loops, keep each loop at least six feet apart. This avoids ―cross talk‖. It
is possible to have loops closer together by selecting different frequencies. An advantage of using
HySecurity model HY-
5A detectors is that problematic ―cross talk‖ is not possible.
4. For greater sensitivity and less chance of false calls caused by the motion of the gate, it is better to
use two smaller loops, connected in a series circuit, to one detector instead of one large, single loop.
5. To avoid interference, keep loops at least two (2) inches above any reinforcing steel. Do not route
loop wires with, or in close proximity to, any other conductors, including other loop leads, unless
shielded lead-in cable is used.
6. Loop and lead-in wire should be one continuous piece. Avoid splices, if possible. If a splice is
necessary for any reason, ―pot‖ the splice in epoxy or use heat shrink to ensure that the quality of the
splice covering is the same as the original wire jacket.
7. Use only 14, 16 or 18 gauge stranded wire with a direct burial jacket. Cross linked polyethylene
insulation types, such as, XLPE or XHHW, will last much longer and are less prone to damage during
installation than conventional insulation types. Preformed loops can be used before road surfacing or
under pavers.
8. Twist loose tails of lead-in wires tightly, approximately ten times per foot.