I have an AC and DC distribution panel installed in my cargo trailer. And I think I have an issue with my DC side of the panel.

This is my first electrical work of any sort and thought it was going well until I checked voltage at the end of one of my circuits. I had 12v. But no fuses in the distribution panel. I was expecting nothing. I did wire up a small LED light and there was a faint amount of light coming from it. If I put in the fuse, LED lights up with the expected brightness.

Are my expectations about having no voltage incorrect?

If they aren't incorrect, what are some troubleshooting steps I should start with?

The specific panel I am using is a Arterra WF-8930/50NPB Black RV Generator and Component (Distribution Center 30 Or 50 Amp Ac Service - 15 Dc Circuits -) and the manual is here.

  • \$\begingroup\$ Google "Phantom Voltage" \$\endgroup\$ – Kyle B May 10 at 21:42
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    \$\begingroup\$ @KyleB he said it's on the DC panel. There's no capacitive coupling in DC. There are some other phenomena that are also called "phantom voltage" that could happen to DC, but this mostly happens on AC \$\endgroup\$ – user2934303 May 10 at 21:59
  • \$\begingroup\$ Long wires act as antennae and can easily pick up a mA for dim LEDs \$\endgroup\$ – Tony Stewart EE75 May 10 at 22:42
  • \$\begingroup\$ @TonyStewartEE75 But there aren't long wires here and it's DC voltage he's reading, if it was an induced voltage from capacitive coupling it would be AC only. And yes, the LED could light up dimly if there was AC voltage as it acts as an rectifier, but then again there are no long wires: The fuses (which are open) are right at the side of the 12 V output in the panel. The segment of conductor from the fuse to the output have like 1 or 2 centimeters at most. \$\endgroup\$ – user2934303 May 10 at 22:48
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    \$\begingroup\$ I had a DC string of LEDs glow without power from AC induction. @Harper-ReinstateMonica FYI , diodes make good rectifiers ;) \$\endgroup\$ – Tony Stewart EE75 May 11 at 3:39

The manual states that the panel has "blown fuse indicators" - red LEDs that will light when the fuse is blown.

The simplest way to do this is to connect an LED and current-limiting resistor in parallel with the fuse. With a blown fuse (or no fuse) this would allow a small current to flow in the circuit - probably enough to light your test light dimly.

  • \$\begingroup\$ Winner! The dimly lighting LED is in series with the LED on the fuse block. \$\endgroup\$ – Harper - Reinstate Monica May 11 at 0:07
  • \$\begingroup\$ That makes sense. And sure enough, my interior lights have that faint glow when the switch is on. I guess I never looked up when it was dark out. \$\endgroup\$ – Jay Cummins May 11 at 0:10
  • \$\begingroup\$ Finally. I didn't see that part on the manual, but I new that something had to be conducing in there, you should never have DC phantom voltage like what happens with AC. \$\endgroup\$ – user2934303 May 11 at 1:19

Wait, it's on the DC or AC panel?

On the AC panel it would be normal to have a voltage (in a no-load condition) due to capacitive coupling, even if the breakers were open.

You could measure that voltage with a multimeter and it would be usually a small fraction of the full voltage, but possibly approaching the full voltage depending on the situation.

However, as soon as any load was plugged in this voltage would disappear.

But you said it was on the DC side and you said "fuses", so you're talking about the DC side only, right?

Cause there's no capacitive coupling for DC.

Then something else is happening.

  • \$\begingroup\$ That is correct. It is the DC side that I'm having an issue with (at least I think it's an issue). \$\endgroup\$ – Jay Cummins May 10 at 22:26
  • \$\begingroup\$ Let me check how the circuit of this panel works again. If it's DC and there's a current passing through an open fuse slot than something is conducing, it can't be capacitive coupling like what happens with AC. \$\endgroup\$ – user2934303 May 10 at 22:36
  • \$\begingroup\$ @JayCummins just to clarify: What are the sources on the DC side? Just the battery? Or there's a battery + converter? \$\endgroup\$ – user2934303 May 10 at 22:37
  • \$\begingroup\$ Just a battery. \$\endgroup\$ – Jay Cummins May 10 at 23:33

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