Controlled Products Systems Group 222X383 - Manual (Page 45)

Installation and Maintenance Manual
37
D0119, Rev. F
Detector Loop Installation
continued
9. Follow this guide for the correct number of turns in the loop;
12 to 20 sq. ft = 5 turns 20 to 60 sq. ft. = 4 turns 60 to 240 sq. ft. = 3 turns
10. 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:
• The slot in the surface should be cut ¼” wide x 1 ½” deep.
• The corners of the cut must be at an angle or core drilled to relieve stress on the wires.
• 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 recommends that vehicle detectors be used for free open and obstruction sensing logic only. The
exception is in parking applications with our HTG320 operator where detectors may be also used to close the
gate. In applications employing our swing, vertical lift, or sliding gate operators, closing logic cannot be used.
Because of their slower speeds, closing logic is a poor choice for security gate systems. Since there are several
ways that the gate may be left standing open and because there is a loss of safety, our circuit has not been
designed to accommodate “detect to close” logic.
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 42 for additional tests that may be performed with
HySecurity HY-5A detector modules.