Earth leakage problem with Karcher pressure washer

[Piemanpete]

Hi all. Talented amateur here, stage electrician at school 1971 - 74 and have done much DIY electrical work iover the years, including central heating systems. I worked for several years for the residential division of Honeywell Control Systems and wrote many installation and user instructions for heating controls.

I have a Kärcher 520M pressure washer which has given excellent service over the years, but using it to jet a drain problem a few days ago and it stopped working and my wife noticed that much of the power in the house had gone off. The washer has a powerful induction motor.

Our consumer unit is a split system with two RCDs, and the house supply is PME, one of which was off. It reset ok but once the pressure washer was turned on again, off the RCD went. The 13A fuse in the washer's plug did not blow.

A bit of online searching suggested the pump motor's starter capacitor was the likely culprit, a 25ùf device, so I ordered a new one and it came the next day. First time I tried it, the pump twitched into life, but then the power went off again.

It has been suggested that a small water leak between pump and motor could be responsible, but I have been unable to strip the washer down far enough mechanically to investigate, but will persevere. The electrics are pretty well isolated in the control box and there's no obvious way water could have got in and caused an earth leak. I wonder whether the in rush current from the starter capacitor could have triggered an earth leak, but I am reluctant to junk an otherwise serviceable capacitor.

Comments, suggestions much appreciated.

Thanks very much.

 

[Mike Johnson]

It could be the fault is elsewhere and the Karcher is just the straw that cumulatively added to the earth leakage and away went the RCD a bit more investigative work needed to ensure it is the Karcher and not something else.

 

[Piemanpete]

Cheers Mike, I will continue to investigate. I would like to plug it into a PAT tester but can't afford to buy one.

 

[James]

i would start with an insulation test of the pressure washer motor.

 

[Piemanpete]

Cheers James. Can I do that with a multimeter or would it require a Megger?

 

[pc1966]

A multimeter might show any leakage, but not under realistic conditions of 250V+

So if you see < 2M on a multimeter from L+N to E it is definitely suspect, but if not it is not proving all is OK.

It might just be a N-E fault somewhere and the washer's current is enough to imbalance the N path causing a trip. If a N-E fault is suspect, try plugging in a vaccum cleaner to the same socket and see if it triggers the fault. But I would start with the testing of the washer first of all

 

[Piemanpete]

Cheers PC, I will get on it with the multimeter tomorrow, if a bew ice age hasn't started!

 

[littlespark]

Being a split board, it may be just cumulative earth leakage and there’s nothing wrong with the washer.

can you try it on the other side of the board or at another location? (Friendly neighbour?)

 

[Lucien Nunes]

If the motor starts promptly and reliably and is not lacking torque, the capacitor is unlikely to be at fault, and in any case it should not cause earth leakage. The capacitor itself does not cause inrush, it is there to phase-shift the current in one of the two windings. However induction motors of this size typically have a starting current around 3-5 x running current because when stationary they behave like transformers with a shorted secondary winding.

@pc1966 makes a good point that you might have an N-E fault somewhere in your wiring, that does not normally cause a trip because there is very little voltage to drive leakage current through it. But the starting current of the washer might well be one of the highest peak currents that the circuit is called upon to supply, and that might just reveal the N-E fault. He recommends a vacuum cleaner as a substitute inrush-creator to compare, but I wonder whether you have something else with a large induction motor such as a table saw?

Certainly test the insulation with a multimeter, if it is low then you need look no further. However it is not necessarily good just because the multimeter says it's high.

 

[pc1966]

Yes, I should have said a "simple" vacuum cleaner, not one with a fancy soft-start motor control system!

So if you have some larger power tool like a table-saw or similar it might be a better test.

 

[PEG]

Hi,you may need to get the machine IR tested,and go through all the operating modes and functions,to test for leakage.
A common source of such an issue,on similar eqipment,is the power lead & plug. These get abused,twisted and run over....then immersed in water,chemical and goo ?

 

[Piemanpete]

A multimeter might show any leakage, but not under realistic conditions of 250V+

So if you see < 2M on a multimeter from L+N to E it is definitely suspect, but if not it is not proving all is OK.

It might just be a N-E fault somewhere and the washer's current is enough to imbalance the N path causing a trip. If a N-E fault is suspect, try plugging in a vaccum cleaner to the same socket and see if it triggers the fault. But I would start with the testing of the washer first of all

Hi all and thanks for reading my post and taking the trouble to reply, much appreciated. Vacuum cleaner Shark) HAS NO EARTH AFAIK.

Today I managed to get the guts of the washer out of the casing, as someone suggested water ingress could be responsible for the earth leak. Yuck. Grey liquid dripped out of it all over the garage floor. It seemed a bit oily and a bit watery. Do pressure washers contain oil normally? Where and how do you get it in and out - what grade etc?

Now taking the whole thing apart to give it a really good blowout with compressed air and clean off oily bits with paraffin, then look to see which parts need to be replaced. Then electrical testing etc. I have bought a used Metrel multifunction tester (like a Megger) on Fleabay so will see if that helps at all.

Thanks and feel free to pitch in with comments and suggestions.

Cheers.

Now I

 

[Piemanpete]

Being a split board, it may be just cumulative earth leakage and there’s nothing wrong with the washer.

can you try it on the other side of the board or at another location? (Friendly neighbour?)

That would probably mean plugging it in in the kitchen! The washer is usually run on a four way round extension reel, plugged in to a socket by the back door, or occasionally a socket in the garage. If you see what I have written today about stripping the machine down snd the resultant mess, you can see that this isn't wholly an electrical problem.

Thanks.

 

[Mike Johnson]

I have only taken a Karcher to bits once, it was enough, the grease inside was from one of the bearings where the sealed for life face shield had disintegrated through what looked like overheating, these things have a short duty cycle that does not like being run for too long, don't clean three cars one after the other.

 

[Mike Johnson]

Suspect the extension lead, too late for that information to help now you have stripped it down, but extension leads are where you should always start.

 

[Timbo1066]

Hi everyone,
New to the forum as i'm looking for a bit of help if it's out there. I'm sure this isn't the right place to post and please please let me know where I should post it for the best exposure! my issue is different, Once the start switch is made the 13A fuse in the plug top blows almost straight away. It's not instant but very quick. Being apprentice trained I like to strip things down so that's whats happened!. Testing has shown me the capacitor is fine at 40 mic, I can't see any switch assembly to switch out a cap and am assuming its just there to phase shift part of the winding - yes? I know winding resistances are fairly low but I feel these are very low at around 5 and 2 ohms. There are 4 wire coming out of the motor (Red, Blue, Black and Grey) and they appear to have slightly different csa's. I've insulation tested at 250V and I have no insulation breakdown to earth but all the winding's seem inter - connected but not dead short. I don't suppose anyone would have a detailed schematic of the motor windings with resistances would they?

I've got it in my head it's an electrical winding issue but it seems so rare I'm after a bit of support really.

Anyway thanks in advance if there are any takers.

Timbo

 

[Lucien Nunes]

Those winding resistances are not unrealistic. The running current is not determined not by V/R but by the impedance which depends on a lot of factors but is much higher than the DC resistance. In a capacitor-start or capacitor-run motor the two windings are connected together at one end. If the auxiliary winding is for starting only, there will be a centrifugal switch to disconnect it.

There is more to testing a motor capacitor than measuring its capacitance. Many capacitors that are failing still have the correct capacitance, but also an unacceptable amount of parallel leakage resistance which might only show up at operating voltage. So the main test of a cap is an IR test.

Start a new thread about this, post some pics of the terminal box etc and we can guide you through tracing the fault.