Why is my power washer's GFCI plug tripping and getting hot?

[russ_watters]

I have a small power washer with a two-wire cord and GFCI plug. My outdoor and garage receptacles are on a "house GFCI" circuit, wired in series to one GFCI receptalce.

Yesterday I tried to use the power washer and the plug GFCI would instantly trip when plugged-in and instantly re-trip when reset. It did this when connected either to the outside GFCI receptacle or to an inside, non-GFCI receptacle. And it also got noticably hot.

I took apart the plug (which it was most decidedly opposed to) and found perhaps a little evidence of past water intrusion, despite having a rubber seal. Fine. So I bought a nearly identical plug at Lowes to replace it. I say "nearly" identical because despite an identical body, the new one was three-wire. Same problem.

Should 2-wire vs 3-wire matter? Or, backing-up; I'm having trouble even wrap my brain around the idea of a 2-wire GFCI: since the purpose is to detect an imbalance hot/return, doesn't the ground represent an addtional failure mode and safety that it should have?

With no alternate return path and the power washer not even turned-on (so it was dry), I can't imagine where power might be leaking to cause a trip. Any ideas?

Deciding I a was well-protected by the house GFCI (reasonable assumption?), I replaced the plug with a non-GFCI plug and everything worked fine. I also have a digital power monitor on my house and noticed no change in power draw when I plugged it in, so I'm reasonably confident there was little or no leakage.

Am I missing a danger here?

 

[russ_watters]

Erhmfh; After googling and reading a few stories about people being electrocuted by faulty pressure washers I'm going to toss mine in the trash. I'd still like to understand better what is going on though...

 

[berkeman]

Should 2-wire vs 3-wire matter? Or, backing-up; I'm having trouble even wrap my brain around the idea of a 2-wire GFCI: since the purpose is to detect an imbalance hot/return,

The GFCI detection circuit for 2-wire just looks for an imbalance in the currents in the Hot and Neutral wires. If there is an imbalance, it is assumed to be leaking to Ground.

So I bought a nearly identical plug at Lowes to replace it. I say "nearly" identical because despite an identical body, the new one was three-wire. Same problem.

That's weird. Maybe a problem in the power cord near the receptacle that you replaced? When you replaced the Lowe's GFCI receptacle with the non-GFCI plug, how much of the cord did you cut off?

 

[berkeman]

Maybe also get one of the electrical socket testers and see if the sensitivity level of the Lowe's receptacle is the same as your in-house GFCI. Maybe the in-house one is less sensitive, and the pressure washer did have a slight path to ground that tripped the more sensitive GFCIs...

https://images-na.ssl-images-amazon.com/images/I/41xgYJ1keXL._SL500_AC_SS350_.jpg

 

[Averagesupernova]

So the GFCI was in fact part of the power washer and was getting hot but when replaced with a non GFCI plug and plugged into a GFCI receptacle everything went along fine? Sounds like a bad part of the power washer. If I were you I would replace the cord with a 3 wire and just plug it in the garage GFCI receptacle. That will offer better protection than what was originally there.

 

[russ_watters]

That's weird. Maybe a problem in the power cord near the receptacle that you replaced? When you replaced the Lowe's GFCI receptacle with the non-GFCI plug, how much of the cord did you cut off?

Zero. The plugs were literally identical except for the missing wire, including that they had a separate compartment for making screw-connections to the wires (in addition to the not quite tamper proof electronics compartment). I did find that odd, but it meant all I needed to do was loosen the connections, pop the grommet out of the old GFCI and pop it all back into place in the new one. The old grommet fit in the new plug and the wires were already stripped and bent to go back into the same screw connections they were in on the old plug.

 

[russ_watters]

So the GFCI was in fact part of the power washer and was getting hot but when replaced with a non GFCI plug and plugged into a GFCI receptacle everything went along fine? Sounds like a bad part of the power washer.

Yes, and that's what I was thinking: internal problem in the washer, not quite serious enough to trip the house GFCI (which I am certain works because it has tripped in the past).

If I were you I would replace the cord with a 3 wire and just plug it in the garage GFCI receptacle. That will offer better protection than what was originally there.

Well, I would have to find something in the washer to connect the ground wire to. I suppose I could do that and go back to the GFCI, now with 3 wires and if it still trips, then that would point to a more serious internal fault.

I'm also going to take @berkeman's suggestion and get a receptacle tester.

There is another wrinkle here that has me still leaning toward chucking it (beyond the effort factor): my mother wants to borrow it to clean her deck and her house is 30 years old, and I'm pretty sure the outside circuits are not GFCI protected. So if I were to give it to her, it must have a GFCI plug.

 

[Averagesupernova]

Yes, and that's what I was thinking: internal problem in the washer, not quite serious enough to trip the house GFCI (which I am certain works because it has tripped in the past).

Well, I would have to find something in the washer to connect the ground wire to. I suppose I could do that and go back to the GFCI, now with 3 wires and if it still trips, then that would point to a more serious internal fault.

I'm also going to take @berkeman's suggestion and get a receptacle tester.

There is another wrinkle here that has me still leaning toward chucking it (beyond the effort factor): my mother wants to borrow it to clean her deck and her house is 30 years old, and I'm pretty sure the outside circuits are not GFCI protected. So if I were to give it to her, it must have a GFCI plug.

I certainly won't talk you out of taking care of your mum.
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I also wondered if there were a place on it to connect the ground. Most GFCI receptacles are 5 mA threshold if I am not mistaken. I doubt the GFCI plug that came with the washer is more sensitive than that. Did the GFCI plug you bought at Lowe's get hot as well?

 

[berkeman]

BTW, if it's a resistive fault, you can measure that with a DVM on the Ohm setting. If it's a 60Hz capacitive fault, you won't see that with a DVM.

Well, I would have to find something in the washer to connect the ground wire to.

So with a 2-wire GFCI plug and the washer sitting on dry ground, it still tripped? That's weird, and sounds like a faulty GFCI circuit. Where could the current go?

 

[russ_watters]

Did the GFCI plug you bought at Lowe's get hot as well?

It wasn't plugged in long enough to find out -- I was out of troubleshooting mode by then.

 

[russ_watters]

So with a 2-wire GFCI plug and the washer sitting on dry ground, it still tripped? That's weird, and sounds like a faulty GFCI circuit. Where could the current go?

Yes, I was scratching my head about that too...

...caveat though; I had a rubber hose plugged into it and at least partially charged. The tap was on, but I keep the hose empty, so it was filled almost entirely with air. Seems a long shot, but I suppose it could have been damp enough inside to carry some return current. A very long shot though, since the power washer has a cumbersome/low quality, plastic, removable quick-connect fitting to connect to the hose. That should have been totally dry, but maybe it doesn't take much.

...if I feel like it I might put the GFCI plug back on and plug it in with the hose disconnected to see if it still trips.

 

[Tom.G]

...if I feel like it I might put the GFCI plug back on and plug it in with the hose disconnected to see if it still trips.

Try plugging the GFCI plug into power without reconnecting the wires, just the GFCI itself.

p.s. It's common for them to run a little warm even with no load.

 

[Guineafowl]

Try plugging the washer into a normal outlet and putting an accurate clamp meter around the hot and neutral together. Any net (leakage) current difference will show up.

 

[russ_watters]

Try plugging the GFCI plug into power without reconnecting the wires, just the GFCI itself.

Great/clever idea. Indeed, they both function normally, indicating it is definitely a problem with the washer. Next step will be to take it apart.

FYI, here's what the GFCI plugs look like:

 

[Tom.G]

Next step will be to take it apart.

Well, those sure came from the same factory.

If you have an Ohmmeter, before disassembly check resistance from the power cord (each conductor individually) to the frame of the thing. Both with the switch ON and OFF. That could help localize the problem. A reading below 25kΩ may well trip a GFCI due to capacitive coupling of the frame to the rest of the Universe. (or thru the water source.)

A prime suspect, in my opinion, is moisture in the motor; perhaps because of a bad shaft seal at the pump. Another possible, a dead insect in it somewhere.

Or, before tearing it apart, you could let it sit in direct Sun for a day or two to dry it out.