Contactor. Proving dead . 3 phase .

[3phase]

When working in a control panel. If I needed to replace a 3 phase contactor do I need to carry out a 10point check to prove dead on just the mains isolator. Or do I need to 10point check the mains isolator and then another 10point check on the contactor before removing.
Many thanks

 

[timhoward]

Treat everything you intend to handle, whatever size and colour, as potentially live until you have proved otherwise.

 

[Moley]

Also, never take anyones word that it has been isolated. Always check for yourself. A lesson I learned the hard way many years ago :-(

 

[littlespark]

Why does it sound like an exam question to me??

As above, if you’re likely to use a screwdriver on a terminal, use a tester first.

Energising coil may not be 230v, but still test.

Mark everything with tape if not already labelled…. As everything is more than likely all the same colour of cable.

 

[R-fur]

Whats a 10 point check? how have i survived nearly 50 years in the industry without knowing this

 

[DPG]

Whats a 10 point check? how have i survived nearly 50 years in the industry without knowing this

The industry standard method of making sure something is dead. Basically test every combination of phases, neutral and earth.

 

[3phase]

The industry standard method of making sure something is dead. Basically test every combination of phases, neutral and earth.

Thanks for reply. I just wondered if I must test the part to be replaced even tho I have tested mains isolator. Thsnks

 

[Moley]

Thanks for reply. I just wondered if I must test the part to be replaced even tho I have tested mains isolator. Thsnks

If you don't check at the item being replaced how can you be certain that you have turned off - AND LOCKED OFF - the correct isolator ?

 

[DefyG]

If only the one source then just the isolator(s) but if unfamiliar with the panel/equipment or likely to have a further source, it wont hurt to double check the contactor too.

 

[pc1966]

Whats a 10 point check? how have i survived nearly 50 years in the industry without knowing this

If you have N cables then you have (N * (N-1))/2 pairs to check to know all are safe w.r.t. each other. So for:

• Single phase (L + N + E) = 3 it is (3*2)/2 = 3 checks
• 3-phase without N (just L1-3 + E) = 4 it is (4*3)/2 = 6 checks
• 3-phase normal (L1-3 + N + E) = 5 it is (5*4)/2 = 10 checks

 

[pc1966]

If only the one source then just the isolator(s) but if unfamiliar with the panel/equipment or likely to have a further source, it wont hurt to double check the contactor too.

Absolutely, the contactor control could be from a totally separate supply, maybe even UPS-backed!

 

[pc1966]

Mark everything with tape if not already labelled…. As everything is more than likely all the same colour of cable.

Also take photos before and after, handy for any reports or problems that might have occurred.

 

[3phase]

If only the one source then just the isolator(s) but if unfamiliar with the panel/equipment or likely to have a further source, it wont hurt to double check the contactor too.

Brill thanks. If I was to double check at the contactor. Would you do the 10 checks again or just check the between the phases. Thanks

 

[pc1966]

Brill thanks. If I was to double check at the contactor. Would you do the 10 checks again or just check the between the phases. Thanks

If a 3P contactor just 6 checks per side, the 3*L and the CPC/chassis.

 

[DefyG]

If a 3P contactor just 6 checks per side, the 3*L and the CPC/chassis.

Also check coil terminals A1 A2 as could be from different source.

 

[3phase]

Thanks for all your help. Totally makes sense now

 

[R-fur]

If you have N cables then you have (N * (N-1))/2 pairs to check to know all are safe w.r.t. each other. So for:

• Single phase (L + N + E) = 3 it is (3*2)/2 = 3 checks
• 3-phase without N (just L1-3 + E) = 4 it is (4*3)/2 = 6 checks
• 3-phase normal (L1-3 + N + E) = 5 it is (5*4)/2 = 10 checks

Thanks pc1966, never heard it called that before.