Where Loop Detectors Go on a Slider
Loop placement decides whether a car gets hit, and the correct positions on a slider are not the same as on a swing pair. The layout drawing referenced at Mount Pleasant Sliding Gates Narcoculture shows three loops rather than two, because sliding gates in Mount Pleasant sweep along the fence line and the vehicle sits in a different relationship to the leaf.
The Three Loops
An exit loop sits inside the property and opens the gate for a departing vehicle. A safety loop sits directly in the path of the closing leaf and prevents it closing while anything is over it. A shadow loop sits immediately at the gate line and holds the gate open while a vehicle is straddling it, which is the one most often left out.
Why the Safety Loop Is Placed Differently
A swing gate arcs into the driveway, so the protected area is a sector. A slider tracks straight across, so the area at risk is a narrow band along the gate line and the loop needs to cover that band across the full width of the opening. A loop sized for a swing installation leaves gaps at both edges on a slide gate.
Cutting and Sealing
Loops are cut into the surface with a saw, wound, and sealed with a flexible compound. Corners are cut at forty five degrees so the wire is not kinked. On the coast the sealant is what keeps salt water off the insulation and off the conduit fittings, where rust otherwise starts, and it is the part that fails first, so it deserves inspection rather than being forgotten once the driveway looks tidy.
Interference Between Loops
Loops close together on the same detector card can crosstalk, which shows as one loop triggering when a vehicle is over another. Detectors have frequency settings for exactly this, and setting adjacent loops to different frequencies at commissioning avoids a fault that is very hard to diagnose later.
What Fails and How It Presents
A gate that closes on a car has a dead safety loop, a card fault or a wire broken in the lead in. A gate that will not close at all often has a loop reading permanently occupied, usually from water in the saw cut. Both are testable at the card in the operator cabinet, alongside the photo eye and the keypad inputs, before anybody cuts the driveway open.