Stray current/grounding question

[Chtucker]

Today I noticed an issue on my Armstrong that had me mildly concerned at first.

I have a Blue Seas breaker panel for my 12Vdc equipment. The panel has pin head size LEDs to indicate on. I have two VHF radios. They are both wired into isolated ground bus bars that are from the factory.

There is (as there should be) one single ground point on the hull where the main DC bus bar is tied to (marked with green tape on heavy guage yellow). I believe that this is all correct and ABYC.

I noticed that the LEDs on the breakers stay lit when I first turn off the the VHF radio and then the breaker. The circuit is being completed as the VHF radios have a ground through the coax shield. The radar power supply also does this.

I assume that this is no issue. The path of least resistance for the power to the radios/radar is through the power cables. The LEDS probably only stay lit till the internal capacitors drain down.

Hopefully this all makes sense and is no issue. The antennas obviously need the connection to ground...

[Armstrong]

Can you expound on the fourth sentence. The LEDs are staying lit AFTER the breaker is off? I don't care about the VHF being turned off, it's the breaker that completes the circuit. If that's what your saying, your fine.

If something stays on after the breaker is off, that's bad. The way to find out what's causing that is to remove power to one item at a time until the led goes off.

[Chtucker]

That is correct, the LEDs which require very very very little current are being back fed from the radios capacitors after turning off the the breakers and the radios... Has to be in a certain order, turn off radio THEN the breaker.

There is no continuity across the breaker when off, just the pin head size LED stays lit. The circuit is completed because the radios have a connection to ground through the shield on the antenna coax.

The LEDs take milliamperes of current... If you turn off the breaker first, the radios internal power supply drains very quickly and the LED doesn't stay lit.

There is only supposed to be ONE central ground to hull on the boat... I am curios to how the antennas are addressed/is there any concern..

I guess this was less of question than an ah ha moment.

[peterbo3]

"There is (as there should be) one single ground point on the hull where the main DC bus bar is tied to (marked with green tape on heavy guage yellow). I believe that this is all correct and ABYC."


If I am reading this correctly (and that may not be the case) are you saying that that your main (-) cable from your house bussbar is connected directly to the hull as opposed to the (-) post on your battery? Is there another cable from the battery (-) post to the hull?

[Chtucker]

There are a few negative bus bars on the boat none are grounded to to the hull. I don't know "exact" configuration, but there is a single green wrapped in yellow tape wire from a main negative bus bar to the hull. At that same point is a ground, green wrapped with yellow tape wire from my AC electrical system as well.

As I understand things, that is the way things should be done. If I were to remove the green wrapped yellow from the hull, everything DC will work fine as they are separately connected to the negative to the battery.

What caught me off guard was the coax braid and hull connected antenna. There was enough energy stored in the radar power supply and the VHF radios AFTER shutting them off to keep the LEDS lit on the switch panel. If I drained the capacitors on those devices by turning off the panel switch first, the LEDS did not stay on after the switch was turned off. If I turn the radio off, the internal capacitors have enough of charge to power the switch light, the circuit is completed because of the antenna ground to the radios chassis.

[peterbo3]

Is your AC power from an on board hard wired genny, a portable genny or do you just hook up to AC from marina shore power? You also mentioned capacitors. You do not usually find them on a standard 12V DC wiring circuit.
How big is this boat? Could you please post some pics of your batteries plus switches & perhaps the DC switchboard.

[Chtucker]

No AC except for shore power. There are MOST LIKELY (I have not opened them up) capacitors inside the radar power supply and radio, I am sure they step 12VDC down for the circuitry. That tiny bit of stored energy is enough to keep the pin sized LEDs lit up on the Blue Sea switches. They stay lit for a minute or so till the power is drained from either the radar power supply or the VHF radio. If I turn off the switch BEFORE I turn off the radio, the pin sized LED goes out immediately because the VHF radio circuitry self drains its internals.

It is only noticed on the radar and the VHF radios because they have a source to ground (the antennas are grounded). No other devices or circuits exhibit this, because they cannot complete the electrical path once they are switched off.

[peterbo3]

Sounds logical. I also have a Blue Seas switch panel & my leds do sometimes fade after powering off. I had never considered any power drain coming from my ICOM.

[Chtucker]

When you spend a few weekends and whole bunch of nights wiring in a loudhailer, search light, multiple GPS antennas, Class A AIS, work lights, AIS transmit antenna and a wifi extender... You start to panic when your electrical panel does weird things..