I have a pressure washer using a Marathon 2HP 115/208-230v motor with separate start and run capacitors. The motor is currently wired for 115v and using a 35' 12/3 water resistant power cord. It has a GFCI 20A plug and is plugged into a 20A GFCI outlet (I know... redundant). Recently, when flipping the power switch, the GFCI breaker on the outlet would trip. Replaced outlet and the outlet still trips. Plugged it into a non-GFCI 20A outlet and the GFCI on the plug trips. Replaced the GFCI plug with a standard NEMA 5-20P and replaced outlet with standard NEMA 5-20R. With this plug and outlet configuration, the motor starts with no problem and does not trip the GE 20A RT-466 THQL circuit breaker that the outlet (and 2 other outlets) are connected to.

I'm assuming the motor's start capacitor is failing and the duration of the high amperage load at start up is exceeding the capabilities of the GFCI outlet and/or GFCI plug. I'd like to get this fixed so I can at least reinstall the GFCI plug or outlet. My problem is the info on the motor's start capacitor says it's a 460-552µF/165v and there's a 15KΩ/2w bleed off resistor soldered across the 2 spade terminals. Getting a new resistor isn't a problem. My problem is the only capacitors I can find locally are 460-552µF/125v, 400-480µF/165v or 540-648µF/165v.

I don't have easy access to a phone during business hours, but I have emailed the motor's manufacturer and a parts distributor, but neither have replied in a week. So I'm trying to figure this out by myself.

QUESTIONS
1. Are the GFCI breakers likely tripping due to a failing start capacitor?
2. Since the motor is wired for 115v, would the 460-552µF/125v capacitor be the correct replacement?
3. If I should use a 165v capacitor instead, do I use the 400-480µF or the 540-648µF?
4. Would using a 15KΩ/2w bleed off resistor be fine with any of the above mentioned capacitors or should I use a different Ω/w rated resistor?

The actual Marathon motor we have is Model # 056B34F5630 and is no longer made by Marathon/Regal, nor do they have ANY information available for it. All of it's specifications are IDENTICAL to the currently offered 056B34F5319 (G533), but I have not found any information on what start and run capacitors are used on this model either. I have no idea if it will help, but I've attached the Certification Data Sheet and wiring schematic for the G533 motor.

I apologize if I included too much useless information, but it's a very expensive pressure washer (at least to us) and I wanted to make sure all the specifics were covered so I don't damage it. Any assistance would be GREATLY appreciated!

 

The capacitor on 120v is usually higher μf than on 240v, they are usually not super critical especially for start caps, and in any case the tolerance on bipolar electrolytic's is high.
I would not suspect a capacitor to trip a GFI.
You may have to megger the motor.
Max.

 

Thanks, Max.

Ugh. Not the answer I was hoping for, but ya can't blame a guy to be hoping for a simple solution. I'm figuring if it is an issue on the motor's insulation, it's going to end up not working sooner than later. Is this something that would be related to the magnetic core being damaged or the winding? Not having a megger meter, I'd have to take it to a local motor shop to run the test. Just getting the motor out of it's location is huge pain. Can't really just "yank it out". Sigh.

With a replacement motor costing about $350, I'm guessing it might be easier to just run it until it quits and replace it rather than getting it rewound or refurbished.

 

Replaced the GFCI plug with a standard NEMA 5-20P and replaced outlet with standard NEMA 5-20R. With this plug and outlet configuration, the motor starts with no problem and does not trip the GE 20A RT-466 THQL circuit breaker that the outlet (and 2 other outlets) are connected to.

I will toss out something for thought and this may be way off base. Something to consider is the possibility of leakage on the part of the motor on start. It takes very little delta current to trip a GFCI and if you have a grounded metal frame motor it would not take very much inductive leakage on start to trip the GFCI. I only mention this based on what you mention. For the most part when a start or run capacitor fails they fail, that has been my observation anyway. Why the problem never surfaced before I am not sure but I have seen leakage in motors trip a GFCI before.

Ron

 

More probable is that you got water in the motor. I had an electric PW that just started tripping the GFIC - no matter what I did. Turns out that water had entered the bottom of the motor and was a legitimate ground fault. I had to finish what I was doing with a 3 prong to 2 adapter and continue to mix electricity with water! Then I had to dry out the motor (wasn't easy).

 

Thanks Reloadron & SLK001!

SLK001, that could be a very likely possibility. The "Spray Room" always has a super high RH.

 

More probable is that you got water in the motor. I had an electric PW that just started tripping the GFIC - no matter what I did. Turns out that water had entered the bottom of the motor and was a legitimate ground fault. I had to finish what I was doing with a 3 prong to 2 adapter and continue to mix electricity with water! Then I had to dry out the motor (wasn't easy).

Another good possible and not just water but a small amount of moisture will make a small current path to ground and trip a GFCI.

Ron

 

With a replacement motor costing about $350, I'm guessing it might be easier to just run it until it quits and replace it rather than getting it rewound or refurbished.

With a PW it is possible that it IS a moisture problem in the motor, is there no way you can heat it up externally with some source to see if it will dry out?
Otherwise just a question of time.
Max.

 

Our pressure washer is now plugged into a 20A GFCI outlet and running like new, thanks to all of your great advice! The problem was moisture in the motor housing. We've relocated it in the spray room in hopes of reducing it's exposure to spray mist. I dried it out by taking off the end cap (getting the pump off was too much of a hassle), repeatedly sprayed contact cleaner and then used air to blow it out.

It wasn't without it's setbacks, but the majority of them were self-induced. Finally got a reply from the motor manufacturer concerning the capacitor ratings. They said I could replace the hard to find 460-552µF/165v with a 400-480µF/165v. Of course, replacing the capacitors was moot... until I got a wire crossed while putting it back together. Took pictures of everything and labeled all the motor wires, except the ones for the capacitors. OOPS! The start capacitor survived, but the run capacitor didn't. It was a 50µF/250v. Turns out they're harder to find locally than the start capacitor. Read on a HVAC forum that as long as the µF rating is the same, one with a higher input voltage (370v or 440v) can be used for the run capacitor. So I replaced it with a 50µF/370v. I bought a 400-480µF/165v start capacitor and some 15KΩ/2w resistors just to have as a spare.

Learned several lessons. Though the 400-480µF/165v probably starts the motor with a slight load, it won't start when the PW pressure is turned all the way up. You have to back it off almost completely to start the motor. THEN you can turn the pressure back up. It would work in a pinch, but if I had to permanently replace the start capacitor and couldn't track down a 460-522µF/165v, I'd probably use the 540-648µF/165v instead.

Again, THANK YOU VERY MUCH! YA'LL ARE LIFE SAVERS! Okay... Business Savers.

 

If possible it is always best to start a induction motor off load, this is why air compressors, HVAC etc, have an unload solenoid or some kind of delay that allows the motor to come up to run first.
Glad to hear you got it going.
Also if it is in the start mode too long, it stresses the start cap which is not rated for continuous duty.
Max.

 

Since the pump is direct drive and requires the water feed to be on prior to starting, I try to get the crew to relieve some pressure by pulling the trigger on the wand before starting the motor. We don't operate the PW at it's full pressure, so that relieves some of the start up load as well. Of course, the capacitor failure is solely due to my wiring stupidity. I hope we've addressed the moisture issue by relocating the PW away from direct exposure to spray mist. It took about 7 years for enough moisture to collect in the motor housing and start tripping the GFCI breakers and I hope I'm long retired before it becomes an issue again.

Again, thanks to all of the folks here. I know if I had taken it back to the distributor, they would have told us the motor was toast and since Marathon doesn't make that specific motor anymore (though they make one identical with a different model #), the distributor, preying on the average customer's ignorance, would likely say we needed a whole new PW at $1,500.

 

Just a note on start caps: I put a 5 HP motor on a 1 HP table saw and it was jerking the arbor out of line when it started. I reduced the start cap to 25% of the intended size and stopped tearing up the table saw. Of course, a table saw always starts under a no load condition. This is NOT a suggestion for your pressure washer. It is merely notification that start caps are negotiable under some conditions.