What is CCR isolation?
Separating a constant current regulator from its supply, its control path and its series circuit, so it cannot be energised during work.
CCR isolation separates the constant current regulator from every connection that can energise it. The sequence is: switch off the CCR, isolate the input supply, isolate the control path, isolate the output to the series circuit, then prove dead and earth before work begins.
The order matters. A series circuit is built to carry a set current, so it is never opened while the CCR is delivering current: the CCR is switched off first, then the output is isolated. Selecting off at a control position is not isolation, because control can come from the local, remote or tower position, and the unit can hold charge until it is proved dead.
Frequently Asked Questions
Q1What does CCR isolation mean?
Separating the constant current regulator from everything that can energise it or be energised by it: the incoming supply, the control path and the output to the series circuit. Each connection is opened at its own isolation point, then the CCR is proved dead before work starts.
Q2Why isolate the output as well as the input?
The output connects the CCR to the series circuit. Opening it keeps work on the CCR separate from the circuit, and work on the circuit separate from the CCR, so neither side depends on the other being dead.
Q3Why switch the CCR off before opening the output?
A series circuit is built to carry a set current. Opening it while the CCR is delivering current can produce a dangerous voltage at the break, so the CCR is switched off first and the output isolated afterwards.
Q4Is selecting off, or local control, enough?
No. A brightness step or a control selection can be changed from another position. The CCR must be isolated at the supply and output points, with the control path isolated too, and then secured with lock-out tag-out.
Q5Can a CCR still be hazardous once it is isolated?
Yes, until it is proved dead. Internal components can hold charge for a time, so the discharge time and testing method in the manufacturer’s manual must be followed before anyone opens the unit.
Q6Who decides the isolation points?
They come from the airport’s permit-to-work and isolation procedure and the CCR manufacturer’s documentation, because the layout of the isolators, the control wiring and the output connections differs between installations.
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