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trailer brake issue?
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Author:  kd4pbs [ Tue May 13, 2014 9:39 am ]
Post subject:  Re: trailer brake issue?

Understood. The only concern one should have with water in an "electrical system" is corrosion. Since we all solder and heat shrink our wiring splices, it isn't a problem if you have LED lights.

Our multi-kilowatt transmitting inductive output tubes in our transmitters use a multi-stage collector. There's close to 35,000 volts DC between conductors that are immersed in the water that cools the IOT. Guess how it's done... One hint: it's not insulated; there's actually a 35KV potential difference surrounded by mere inches of water.

Author:  rpengr [ Tue May 13, 2014 10:57 am ]
Post subject:  Re: trailer brake issue?

kd4pbs wrote:
If you can show me any water-based solution that will "short out" at 13.8 volts, please let me get in on this deal... it would be a great environmentally friendly replacement for the mercury used in mercury switches.

It is true that pure de-ionized water does not conduct, however, dirty water conducts, and salt water conducts. Go to your nearest Ocean and you will see A LOT of conductive water.

I once saw a boat that had been submersed for 3 hours in salt water. The fuse block was 10" from an aluminum tank (grounded). In just three hours most of the brass had eroded away from the fuse block and caused electrolysis on the nearby aluminum tank. That was at 12 volts.

Author:  LouC [ Wed May 14, 2014 6:04 am ]
Post subject:  Re: trailer brake issue?

Salt water can do pretty destructive things. Lucky for me my boat is on a rotating mooring with no docks/shorepower nearby. There are tests you can do to make sure that you have enough protection when your boat is slipped or moored.

Author:  kd4pbs [ Wed May 14, 2014 12:52 pm ]
Post subject:  Re: trailer brake issue?

Exactly; it's not the water that causes problems, but the impurities contained within. Water itself is non-conductive. We maintain ~12M ohm/cm³ to be able to run those potentials.

Then again, my trailer never sits in water with lights on for any length of time, nor do I put it in salt water.

That being said, it's not the conduction that causes problems, but the resulting electrolysis. Even if the de-i water in our 35KV systems gets too conductive, it doesn't "short" things out; we just end up having no metal left on the collector. For a $20,000 tube, that's not a good thing to have happen.

I'd dunk 500 feet of bare copper wire hooked up to my trailer light receptacle in a heartbeat without worry of damage to the vehicle wiring. All that would happen is a bunch of hydrogen and oxygen, and less wire than what I started with. Even a dead short with an actual good conductor is protected by a fuse, so I can't think of what kinds of problems could be caused to a tow vehicles wiring by backing a trailer in with the lights connected.

Now, for those that take shortcuts and use "tap in" connectors or butt splice connectors (whether heat-shrink or not) commonly supplied with trailer light kits instead of solder, then yeah, I can see where there's gonna be trailer light wiring issues causing problems.

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