Stray Current found - need fix advice

[Bowdrie]

Perhaps I've missed something over the last 3 pages.
Kind of wondering where the DC is coming from, and how is it getting on the water-cooled heat exchangers?
All the parts are interconnected with copper tubing, so if one part is energized than all should be.
But those 12V units don't run on DC, they actually run on, (IIRC,) ~24V AC.
The "black box" inverts the DC to run the compressor and feeds DC to run the fan.
It's been many years since I worked on one of those units, but I'm not seeing any particular reason there should be any DC on the compressor>condenser>line to water heat exchanger unit>line to evaporator>line back to compressor.
Maybe some electrons have gone rogue and have leapt off the path of the straight and narrow.

[Fuss]

Originally Posted by s/v Jedi

You seem to have missed that the OP has a silver chloride reference cell. This means that there is no room left for speculations as factual measurements are clear.

everyone should have one of these… I have an aluminium boat… i sometimes see aluminium boats with anodes over the side in case some steel boat eats them…. this just means they got bad advice and didn’t do their homework.

[s/v Jedi]

Originally Posted by Bowdrie

Perhaps I've missed something over the last 3 pages.
Kind of wondering where the DC is coming from, and how is it getting on the water-cooled heat exchangers?
All the parts are interconnected with copper tubing, so if one part is energized than all should be.
But those 12V units don't run on DC, they actually run on, (IIRC,) ~24V AC.
The "black box" inverts the DC to run the compressor and feeds DC to run the fan.
It's been many years since I worked on one of those units, but I'm not seeing any particular reason there should be any DC on the compressor>condenser>line to water heat exchanger unit>line to evaporator>line back to compressor.
Maybe some electrons have gone rogue and have leapt off the path of the straight and narrow.

I’m not sure if what I had is still current product, but the controllers on my Danfoss compressors took DC input and output a 3-phase AC to the compressor motor. What I do not know or remember is if there was complete galvanic isolation of DC input and if the compressor unit itself was grounded.

I did have trouble with “low voltage” and “no compressor start” errors caused by bad design from Frigoboat with adapters at the DC power connectors on the controller. First thing I did when looking at the bonding lugs of the keel coolers was noting they were a different metal which was red flag #1 and that my amp meter showed dc current between it and my bonding wires so I didn’t connect bonding to it and never really investigated details as I had more projects on my plate

[JoeRobertJr]

I am convinced I need a reference cell. Is this a reasonably priced unit of reasonable quality?
https://www.boatzincs.com/corrosion-...hoCuJ0QAvD_BwE

[s/v Jedi]

Originally Posted by JoeRobertJr

I am convinced I need a reference cell. Is this a reasonably priced unit of reasonable quality?
https://www.boatzincs.com/corrosion-...hoCuJ0QAvD_BwE

Yes, I think it’s the one we all have. The manual is as important as the cell itself

[s/v Jedi]

I need to add this: you also need a really good multimeter. Probably not the one you have aboard now.

If you can afford it, get this one from the EEVblog: https://www.amazon.com/gp/product/B01JZ1ADCO
I even found a great case for it:
https://www.amazon.com/gp/product/B07147SS96

If that is not in the budget then here is a cheap alternative that I trust to the mV level (because I checked it against the good one listed above, which you should get )
https://www.amazon.com/gp/product/B076GZK62B

[Oceanride007]

Bowdrie, it doesn't make sense to me how turning on the refrigerator, makes the Bonding wire network more negative, surely any leakage current would make it more positive.
Regarding your other matter, about any DC leakage, all motors (all circuits) will have a small leakage current, they should all be in the many Megohms, but my point earlier is that in my experience Fridge compressors often have much less resistance than 1 Meg ohm, for example any house that has a new earth leakage devise installed, if it trips its often the refrigerator at fault.

[Bowdrie]

Originally Posted by Oceanride007

Regarding your other matter, about any DC leakage, all motors (all circuits) will have a small leakage current, they should all be in the many Megohms, but my point earlier is that in my experience Fridge compressors often have much less resistance than 1 Meg ohm, for example any house that has a new earth leakage devise installed, if it trips its often the refrigerator at fault.

What I posed was, how can there be DC leakage on the system when NO DC is applied to the compressor.
They run on AC, like Jedi said, 3 phase AC.
DC is only applied to the "black box", and it supplies the fan with DC and the compressor with AC.
It would seem that any DC on the metals of the system would be coming from the black box?
Is the black box metal?
Is it mounted to metal?
Do they "leak" some of the DC applied to them?
Does the black box have anything in it that could be compared to an "autotransformer" type circuit".
Of course it's quite common for the heating element in the boats water heater to leak a few electrons.
I gotta admit, I've never paid any attention to the finer details of the black boxes, they either work, or not.
But I'm learning some stuff from this thread.

[SV Confianza]

Originally Posted by s/v Jedi

Yes, I think it’s the one we all have. The manual is as important as the cell itself

Thanks for the insight on the manual. I’m going to purchase one as well.

[s/v Jedi]

Originally Posted by SV Confianza

Thanks for the insight on the manual. I’m going to purchase one as well.

Soon the sacrificial zinc manufacturers will start complaining about us

[Fuss]

When I bought my boat the zincs lasted 3 months... it took ages to identify all the wiring mistakes but once done, the zincs last nearly for ever