Hot Tub GFCI troubleshooting

[bmbouter]

Well I got the testo and I tested the shorting underwater light what I believe is correctly this time, pic for amp measurement attached. It reads a stable 0.76 mA and 20V. Notice it also shows a nearly perfect 60Hz signal. Image upload seems to not be working on the forum so here's my pic link: New photo by Brian Bouterse - https://photos.app.goo.gl/hXwTB2GniHrXwvDf9

So that's the kind of power we're working with. It's less than 5mA which explains why the GFCI doesn't trip. Do you agree?

 

[DPG]

Well I got the testo and I tested the shorting underwater light what I believe is correctly this time, pic for amp measurement attached. It reads a stable 0.76 mA and 20V. Notice it also shows a nearly perfect 60Hz signal. Image upload seems to not be working on the forum so here's my pic link: New photo by Brian Bouterse - https://photos.app.goo.gl/hXwTB2GniHrXwvDf9

So that's the kind of power we're working with. It's less than 5mA which explains why the GFCI doesn't trip. Do you agree?

That looks like a more realistic figure.

 

[Lucien Nunes]

What is the meter actually measuring there? Pool water to true ground? Clearly that current wouldn't trip.a GFCI and isn't likely to be harmful, but I'm still not sure what it represents. Aggregate leakage from the whole electrical system? Leakage across the lighting transformer? Difference between supply ground and true ground? We're only seeing the symptom, not the cause. Insulation tests and differential leakage tests will locate its source...

 

[pc1966]

Certainly that reading looks more realistic, though as Lucian has said, it is not clear exactly where you are measuring this (i.e. what is each probe connected to)?

 

[bmbouter]

I should have given info about how the test was conducted in addition to the data observed. Thank you for teaching me this lesson also.

The test performed was with 1 probe in the water itself, and the other in the dirt/earth next to the tub. The dirt is very dense, so I believe it provides direct, low impedence conductivity to the earth.

 

[Lucien Nunes]

It depends what you are comparing it to. There could still be many kilohms or tens of kilohms between your probe and true earth, insignificant when taking a voltage reading, significant when measuring current and barely conductive at all compared to the main ground connection.

But the law of diminshing returns sets in about now. You have some measurements that imply there is some leakage that might be worth investigating, albeit that the leakage only occurs via the present path when the insulation of the underwater lights is compromised. If you want to trace its source, then tests of a more specific and targeted nature are required. I can come up with about half a dozen completely different explanations for your 20V and 0.76mA, but with a dozen other tests I could prove or disprove each theory, in a logical sequence. We don't have much info (not being there with you) and you don't have much test equipment, so I am not sure how far we can help with that. It might be the time to get a service agent or electrician skilled at fault-finding to give it a proper series of tests.

 

[pc1966]

The test performed was with 1 probe in the water itself, and the other in the dirt/earth next to the tub. The dirt is very dense, so I believe it provides direct, low impedance conductivity to the earth.

You would be surprised by how hard it is to get a genuinely low earth rod impedance!

Even so, the test you did implied an impedance of around 26k but a portion of that could be the test probe in to the ground. That would make little difference to the 20V you see, but might impact on the current you observe. Same goes for the size of the conductive object in the water, if you have a foot or two of bare wire in the water it would be better connected to the source.

I would be reluctant to suggest you drive in an earth rod for the sake of it as you might just hit a buried cable/pipe, but you could try using a long wire to an internal (power supply) earth, or something like a metal water pipe entering the building.

But as already said, you have shown readings that are more in keeping with the failed low voltage light than a leak from the AC power itself.

 

[bmbouter]

I had an electrician company that deals with hot tubs specifically come out, and they confirmed the tub, GFCI, and electrical disconnect are all wired correctly. Also the wires going through the hole now have a grommet.

Unfortunately this hot tub electrician could not perform the earth leakage current test, perform RCD trip time measurements, or perform the insulation resistance test. It's frustrating to understand these tests, yet when I asked about them they say things like "what is that" or "that sounds complicated".

Thanks for all the help from this forum!