Loop Wire Material - CARLO GAVAZZI LDP1 Manual De Instrucciones

When installing multiple turns in the loop, it is recommended to place the wires like shown in figure
below.
The recommended groove depth is 30-50 mm (1.2-2.0 inches). If the wires are installed deeper than
50 mm (2.0 inches), the detection signal for the Loop Detector is reduced and detection of high bed
vehicles can be compromised.
Note: A common problem for loop failures is wire splicing. It is recommended to use one continuous
wire without any splices. If wire splicing is used, the wires must be soldered. Screw or spring terminals
are not allowed. All wire splices must be insulated against moisture with adhesive-lined heat shrink
tubing or equivalent.

7.3. Loop wire material

It is important to select the right type of cable for the loop wire. If insulating material is not suitable
for the application, the cable jacket can crack or absorb moisture. It is a common problem to have
moisture penetration in the cable jacket, which can cause a wire shorting to ground. This can lead to
conditions where the application works well while it is dry, but starts failing in high humidity conditions
or rain. A cracked cable insulation can lead to similar issues.
Cable recommendations:
• Wire insulating material of Cross Linked Polyethylene (XLPE) is recommended for both cold and hot
sealant.
• Wire insulating material of PVC (TFFN, THHN, THWN) is only recommended for hot sealant and if
the wires are encapsulating completely. Otherwise PVC insulating material is not advised.
• It is important to avoid any voids in the sealing around the cable. This can allow moisture to build
up and cause loop failures.
To troubleshoot broken wires an insulation tester (500 MΩ minimum) can be used. Place one wire from
the meter to the disconnected wire loop and place the other meter wire in the ground. Testing should
be performed with AC voltage.
Measured resistance
100 to 1000 MΩ
50 to 100 MΩ
0 to 50 MΩ
20
Rev.00 - 01.2019 | LDP1/LDP2 Single and Dual Loop Detector | © 2019 | CARLO GAVAZZI Industri
4-5 mm
Road surface
Loop sealant
Loop wire
Conclusion
Loop condition is good
Loop integrity is questionable
Loop needs to be replaced