Why connect a ground cable from cabinet to door of cabinet?

[AgroVenturesPeru]

Am I missing something here? Was it really necessary to do this?

 

[mopat]

Plastic hinges

 

[Jim Burrow]

if there is no mental to mental contact between the box and led, like through mental screws through the hinges, then it doesn't hurt. It's just for safety and no other function.

 

[HighTechLab]

Per NEC, Hinges to not provide a bonding path, gaps can form between the pins during normal operation and your bond is lost, which is a safety hazzard.

 

[MichaelK]

You can attempt a simple test. Just disconnect one of the leads, then check the base and lid with a ohm-meter to see if there is continuity? If you don't see 0 Ω, then you have your answer.

 

[time2roll]

If the lid is energized you may not know it until you lift it up and it becomes isolated. Then you become the ground strap.

 

[Bud Martin]

Resistance read test is not really valid, for example you can have low contact resistance though the metal hinge equivalent to short length of 22 AWG wire but it may not able to handle ground fault current (if front panel is energized) enough to trip the circuit breaker due to contact between front panel and the chassis blown open circuit before circuit breaker trip then the front panel will still be at hot potential, it is one of the reason that safety ground wire must be at least the same gauge as the L and N wire.. this is what I require to use from working with UL lab to get the power product I design to pass UL compliance test.

 

[Supervstech]

If the lid is energized you may not know it until you lift it up and it becomes isolated. Then you become the ground strap.

This.
I have seen FAR too many failed connections contact the doors to switchgear or junction boxes...
If the door isn’t PHYSICALLY screwed to the box, a bonding jumper is required to prevent YOU becoming the fault current path.

however...
In this case it could simply be for shielding...

 

[curiouscarbon]

If the lid is energized you may not know it until you lift it up and it becomes isolated. Then you become the ground strap.

ding ding ding?

 

[Robin Gudgel]

UL requires that any metal part that can be energized that can cause an electrical shock hazard to personnel that is not suspecting that it could be energized must be grounded. That isn't the exact words, but it is something like that. You would not expect a cabinet door to be able to shock you, but if it had plastic hinges or paint on the metal hinges, it may not be automatically grounded. Thus the wire bonding jumper.