Different connectors
Primary, secondary, in-line and CCR-end: four connection points on one series circuit that look alike but differ in what they carry, where they sit and what a fault does.
A series circuit is only as sound as its joints. Wherever cable meets a transformer, another cable or the regulator, there is a connection point, and they are not all equal. The primary connector and the in-line cable joint sit in the loop and carry the full circuit current. The secondary connector sits on the isolated side and serves one fitting. The CCR-end termination is where the field cable lands on the regulator.
That is why the same-looking plug matters differently. A bad joint in the loop can stop every light on the circuit, and a loose or corroded one adds resistance, heats up and can arc. A bad secondary joint normally leaves the loop closed and darkens only that fitting. Whatever the type, the common enemy is water.
Primary connectors, in-line joints and the CCR-end termination carry the full loop current. One poor joint can affect the whole circuit.
The secondary connector serves one light or sign on the isolated side. A fault stays local to that fitting.
| Aspect | Primary connector | Secondary connector | In-line cable joint | CCR-end termination |
|---|---|---|---|---|
| Does | Joins a transformer’s primary lead to the loop cable, in and out, so the series current passes through it | Joins a transformer’s secondary lead to the lead to one light or sign | Joins two lengths of primary cable into one continuous run | Lands the field cable on the CCR output so the loop can leave the regulator |
| Where | In a base can or transformer pit beside the light or sign | In the same can or pit, between the transformer and the fitting | Along the cable route, in a pit, handhole or trench as designed | Inside the CCR cabinet at the power end |
| Carries | The full loop current, the same as every other joint in the circuit | The current of one fitting only, on the isolated side | The full loop current | The full loop current, leaving and returning |
| Made as | A sealed plug-and-receptacle joint that can be separated for test or replacement | A sealed plug-and-receptacle joint, often keyed and sized differently from the primary | A joint made on site and sealed to the maker’s method; not meant to be separated | A terminated cable end, secured at the terminals as the CCR maker specifies |
| How many | Two per transformer (in and out) | One per light or sign | As many as the cable route needs | Normally one pair per circuit |
| If it fails | An open joint can break the loop for every light; a poor contact heats up and can arc | That one light or sign dims or goes dark; the loop stays closed | An open or wet joint can stop the circuit or cause an earth fault | The circuit can lose its output or show a fault at the CCR |
| Watch points | Seating, seals, contact condition, insulation resistance, water in the can | Seating, seals, flicker or dimming, water leakage | Joint quality at install, depth, drainage, insulation-resistance trend | Terminal tightness, cable end condition, labelling, isolation before touching |
What to check on connectors
Match the connector to the job
Check the connector type and size against the design and the maker’s data. Primary and secondary connectors are not interchangeable.
Seating and locking
Check each connector is fully mated, keyed and locked as the maker requires. A half-seated joint is a common cause of heating.
Seals and water
Check boots, seals and the can or pit are intact and dry. Water in a joint lowers insulation resistance long before it opens.
Insulation and continuity
Test to the limits in the procedure and record the values, so a falling trend shows up over the years.
Heat and discolouration
Look for browning, melting or a burnt smell at a joint. A high-resistance contact heats up and can arc.
Isolate before work
Never separate a primary connector on an energised circuit. Isolate, lock out and prove the circuit dead, and treat every lead as live.
Frequently Asked Questions
Q1What are the main connection points on an AGL series circuit?
Four common ones are the primary connector, the secondary connector, the in-line cable joint and the CCR-end termination. The primary connector and the in-line joint sit in the series loop. The secondary connector sits on the isolated side of a transformer and serves one fitting. The CCR-end termination is where the field cable lands on the regulator.
Q2What is the difference between a primary and a secondary connector?
A primary connector joins a transformer's primary lead to the loop cable, so it carries the full circuit current and a fault can stop every light on the circuit. A secondary connector joins the transformer's secondary lead to one fitting, so a fault normally affects that one light or sign only.
Q3Why does a primary connector matter more than a secondary one?
Because the loop is a series circuit, current passes through every primary connector in turn. An open joint breaks the loop for everything on it, and a loose or corroded contact adds resistance, heats up and can arc. The secondary side is isolated, so its faults stay local.
Q4Is an in-line cable joint the same as a connector?
No. A connector is a plug-and-receptacle joint that can be separated for testing or replacement. An in-line joint permanently joins two lengths of primary cable, usually made on site and sealed in the ground. Both carry loop current, so both are weak points to inspect and test.
Q5What limits and requirements apply?
Connector types, ratings, sealing methods and test limits come from the standard, such as the FAA L-823 specification or the relevant IEC requirements, the airport's design and the manufacturer's instructions. Use the requirements for your site, and never separate a primary connector on an energised circuit; isolate, lock out and prove the circuit dead first.
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