GFCI and Ballast

[TXLAKE]

A friend just bought an underwater fishing light. He ask if the GFCI would protect the circuit. My first answers was yes as long as the GFCI is operating correctly. But the more I thought about it I don't know. This light works off of a ballast with the bulb extended out away from the ballast about 20 feet. The ballast is basically an auto transformer (M57 ballast). So does anyone know if the secondary of a ballast is protected by the GFCI that's feeding the primary.

 

[jumper]

A GFCI cannot provide GF protection of the secondary side of a transformer.

 

[cpinetree]

Hehe, we have installed a number of units like that, the GFI only protects the transformer on the primary side, but since its outside it needs a GFI.
The ones we use usually have a GFI on the male cord cap.

 

[Johnnybob]

If it's an autotransformer, then there is, in fact, a mechanical connection from the primary to the secondary, yes?

 

[GoldDigger]

Theoretically, as long as the transformer is installed as non-SDS, the GF protection should extend to the secondary too, no?

 

[jumper]

If it's an autotransformer, then there is, in fact, a mechanical connection from the primary to the secondary, yes?

Yes.

Theoretically, as long as the transformer is installed as non-SDS, the GF protection should extend to the secondary too, no?

IDK.

Gleaned from google, paraphrased:

The OPs ballast is most likely a Constant Wattage Autotransformer for a 175W Metal Halide ballast.

I have no clue if the GFCI could somehow protect the secondary of this tranny. A normal LV tranny, no. Never put a MH fixture on a GFCI before.:?

 

[GoldDigger]

Yes.



IDK.

Gleaned from google, paraphrased:


I have no clue if the GFCI could somehow protect the secondary of this tranny. A normal LV tranny, no. Never put a MH fixture on a GFCI before.:?

If one side of the secondary neutral is connected to the primary neutral AND there is no ground-neutral bond at the transformer, then any GF current from the secondary can only return to the secondary by following the EGC back to the main bonding jumper and back through the primary neutral.
That will unbalance the primary current and trip a GFCI on the primary side.
But any non-Code ground neutral bond elsewhere in the circuit could prevent this from happening.