GFCI at a lower voltage.

[jpl5085]

Can a GFCI 120V Class A (5mA) be used at 24VAC? I am using as a pass-through device for downstream protection in a control panel.

 

[busbar]

There’s a novel Leviton GFCI that may do the job. See:

http://www.leviton.com/pdfs/6895gfci.pdf

It needs external 120V power but the protected circuit wiring (24V in your application) passes through a molded-in current transformer. It has to be used with an external contactor to disconnect the protected circuit for a ground fault, though.

 

[gordonl]

A typical GFCI uses 120V from the circuit as supply power for proper operation so you couldn't use an off the shelf residential on 24VAC.

See the following for an internal schematic:

http://www.codecheck.com/gfci_principal.htm