HySecurity HTG 320-2, Installation And Maintenance Manual

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Installation and Maintenance Manual
34
Detector Loop Installation Guide, continued
8. Follow this guide for the correct number of wire turns according to the perimeter size of the loop:
10 to 13 lf. = 5 turns 14 to 26 lf. = 4 turns 27 to 45 lf. = 3 turns 46 to 100 lf. = 2 turns
9. This guide is written from a design perspective, but installation workmanship practices are equally
important to insure proper operation and long loop life. The best way to insure a quality installation is
to employ a professional installer experienced with detector loops. A few important practices are:
A.
The slot in the surface should be cut ¼” wide x 1 ½” deep.
B.
The corners of the cut must be at an
angle or core drilled to relieve stress on the wires.
C.
After the wire is installed, the slot must be
completely backfilled with a non-hardening sealer. Note that if the loop wires are able to move in the
slot after the sealer has set, the detector may give false calls.
Detector Logic
HySecurity Gate Operators recommends that vehicle detectors be used for free open and obstruction
sensing logic only. The exception is in parking applications with our HTG 320 barrier arm operator where
a reset detector may be also used to close the gate. In applications employing our swing, vertical lift, or
sliding gate operators, closing logic cannot be used.
Loop Diagnostics
The following tests cannot guarantee a functioning loop, but failure of either test means that the loop is
definitely suspect, even though it may still be functioning at the time.
Test #1:
Resistance of the loop and lead-in wire should not exceed 4.0 Ohms.
Test #2:
The resistance to earth, as measured with a 500V “Megger”, should be 100 Megohms or more. Loops
may function at 10 Megohms or less but will not be reliable (e.g. when the ground is wet from rainfall).
Low resistance indicates broken or moisture saturated insulation. This is common if inappropriate wire
insulation has been used.
See also Detector and Loop Fault Diagnostics on page 39 for additional tests that may be performed with
HySecurity HY-5A detector modules.