NEC 250.22(5)

[slushin]

Does anyone know why NEC 250.22(5) specifically says not to ground the secondary circuit of a pool lighting system?

I know that the NEC allows circuits to be ungrounded if interrupting the operation of the circuit would be less harmful than an uplanned interruption of the circuit. This makes sense to me in the case of heavy industrial operations that cannot suddenly be stopped, but I can't understand why the same rules would apply to swimming pool lighting.

 

[slushin]

hmmmm ... guess it doesn't make sense to anyone else either ....

 

[DRWeig]

Hi Sluchin,

It makes sense to me, but the answer is very long and complex. I suggest you look into the UL standards for underwater lighting, the prohibition arises there. They're designed to absolutely eliminate the potential for contact with the water, which is also a mighty good ground in lots of cases. It's a ground that is remote from the electrical system ground, which can cause troubles during lightning or large fault events.

Maybe someone else has more time to give you a more complete answer...

Good on ya,

Goober Dave

 

[wcarter]

Slushin,

Essentially, it is to limit how much current can flow to ground. If you do not have a direct return path, IE a ground connection, minimal current will flow (the amount that will is due to capacitive coupling). IE if your supply line faulted and went to ground, it will try and return to its source through any and all possible paths. So if you eliminate the path of return and maximize the resistance, minimum current will flow. I=V/R.

There might be additional thoughts into this, but I believe this is the essential thoughts behind this.

 

[Compositepro]

I would say that is because if you have a hot and neutral, and the hot wire comes in contact with water, current will flow through the water to ground. Swimmers are in this ground path. Current flow through the water will not be enough to trip a breaker in the event of this ground fault, which is the reason for having hot and neutral wires. GFCI will still work. Metal parts would still require a ground wire.