GFCI and pressure washer

[rccola777]

Here's the story. I have a low-end Ryobi pressure washer with a GFCI module built in to the end of the cord where it plugs in. Unit quit working and I determined the GFCI was bad and replaced with a new one. All is good, but after installing the new GFCI, it made me ponder something. There was no ground wire going from the GFCI to the pressure washer, just hot and neutral. My understanding of how GFCI works is that current has to flow between ground and hot in order to trip it. Am I missing something?

[Monkeh]

Here's the story. I have a low-end Ryobi pressure washer with a GFCI module built in to the end of the cord where it plugs in. Unit quit working and I determined the GFCI was bad and replaced with a new one. All is good, but after installing the new GFCI, it made me ponder something. There was no ground wire going from the GFCI to the pressure washer, just hot and neutral. My understanding of how GFCI works is that current has to flow between ground and hot in order to trip it. Am I missing something?

Your understanding is more or less correct but leading you to the wrong conclusion.

GFCIs operate when the current flowing in line and neutral is not equal, which means it's taking a different path back to the source. This could be the ground wire, the neutral (or line) of another circuit, or anything adequately conductive in contact with the literal ground (like a person). No actual ground wire is needed for that.

[Gregg]

The GFCI only senses imbalance between the line and neutral conductors to the device.  If a ground were provided, the GFCI would not connect to that ground in any way.
Think of what happens if you put a clamp meter around both the line and neutral of a device drawing current….the two should cancel and the clamp meter should read nothing if everything is working properly.
However if there is any leakage of current downstream of the GFCI, it should sense that via the imbalance and trip the power at a pre set parameter

[rccola777]

Thanks all, that makes sense now.