Is it enough to prove safe isolation on a circuit which is controlled by a PIR on a seperate circuit ?

[Rob678]

Hi Guys currently doing my apprenticeship and looking for some external advice regarding safe isolation.
Situation is a circuit supplying some external street bollard lights and 1 or 2 street lamps. This circuit is fed via a single phase MCB then through a contactor all located in the db. The contactor is pulled in when a PIR sees it’s dark outside. This PIR on a seperate control circuit to energise the contactor coil.
Question is, is it enough to prove safe Isolation just on the circuit supplying the loads ? Or Should safe Isolation also be completed on the seperate control circuit aswell ?
Any help would be much appreciated and you have any references in BS7671 or relevant material that would be fantastic,

thanks guys

 

[westward10]

If you are working on the bollards you isolate the circuit/s for them.

 

[brianmoooore]

. The contactor is pulled in when a PIR sees it’s dark outside. This PIR on a seperate control circuit to energise the contactor coil.

A PIR detects movement of objects that are at a different temperature to their surroundings. A photocell or similar will detect when it's dark outside.

 

[mainline]

Hi Guys currently doing my apprenticeship and looking for some external advice regarding safe isolation.
Situation is a circuit supplying some external street bollard lights and 1 or 2 street lamps. This circuit is fed via a single phase MCB then through a contactor all located in the db. The contactor is pulled in when a PIR sees it’s dark outside. This PIR on a seperate control circuit to energise the contactor coil.
Question is, is it enough to prove safe Isolation just on the circuit supplying the loads ? Or Should safe Isolation also be completed on the seperate control circuit aswell ?
Any help would be much appreciated and you have any references in BS7671 or relevant material that would be fantastic,

thanks guys

A suitable contactor can be used for safe isolation, but to be suitable it must be marked with the specific symbol for isolation and would have to have the ability to be locked in the open position.

Table 537.4 indicates that contactors to BS EN 60947-4-1 are suitable for isolation as long as they are marked with the symbol for isolation. With the caveat in 537.2.4 that devices for isolation shall be selected and or installed so as to prevent unwanted or unintentional closure.

Regulation 462.2 of BS 7671:2018+A2:2022 requires every circuit to be provided with isolation for all live conductors, except those detailed in Regulation 461.2 of BS 7671:2018+A2:2022, which provides exceptions for TN-C-S and TN-S systems where the neutral or PEN conductor is reliably connected to Earth.

Also bear in mind, there is a difference between isolation and safe isolation.