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gharlam avatar image
gharlam asked

BSC Charger trips shore power GFI breaker

I'm looking for some troubleshooting ideas for Jaylee, our 2004 Mainship 430.
Like many, our marina is in the process of updating the electrical system to new pedestals with ground fault breakers.
Over the years, we've had lots of issues at other marinas with the GF breakers. Two years ago, we had the boat evaluated and they found and replaced our original galvanic isolator - the older models were known to "test" the system by crossing the ground and neutral (or similar). Once replaced with a newer unit, the electricians portable test GF unit no longer tripped.
On our next trip to Block Island Boat Basin (with GF breakers), we were OK for a few hours with everything running then the boat started tripping the breakers and we could NOT keep the power on nor isolate a circuit that was causing the issue. We were able to plug into one older pedestal without a GF breaker . . .
Tonight, we went to the boat to do some basic testing to see if we could keep the boat powered. I WAS able to find something interesting. When I powered the boat with our bow thruster battery charger OFF, the breaker did NOT trip. If I turned on that charger within the first 5 seconds or so of turning on the shore power breaker, it WOULD trip the breaker. If I wait a bit more (15 - 20 seconds), I could turn on that charger without tripping. Once the power stayed on, I did turn on virtually everything including the AC.
The charger is a Victron Energy BSC IP67 24/12. It is hard wired to the breaker and the only thing on that breaker. It was replaced last year so it's pretty new. Don't think it matters, but there is a dial type power selector switch near the charger (with just an on and off).
If it turns out that I can plug in with that breaker off and turn it on a minute later, I'm OK. I am concerned that based on history, the next time at the boat, I'll find something different - like I did on Block Island.
I'm trying to figure what to look for with this unit to hopefully fix the problem - if I can. As the unit is sealed, I'm not sure there is much I can do.
Thanks in advance for any thoughts!
Gary
Groundingshorepowerfault
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1 Answer
Trevor Bird avatar image
Trevor Bird answered ·

A couple of thoughts you may consider…

A 30mA RCD can trip at a Maximum of 30 mA and a minimum of 50% of that rating or 15mA. We have found many actually trip in practice at about 20mA. That is perfectly within spec.

Modern equipment has many Electromagnetic Compatibility filters. These filters reduce radio frequency transmission and have capacitors between neutral and active and ground. That means they have a very small amount of ground leakage. It can be about 0.5mA each. Many other devices have leakage as a function of their mains input circuitry and that may be 1 or 2 mA.

The equipment does not have to be on for this leakage to be present. Obviously the breaker feeding the equipment has to be closed but the equipment itself doesn’t have to be on.

What this means is that a perfectly well designed, perfectly safe, normal installation with very many individual items fed from the one RCD can trip that RCD as a consequence of the capacitive currents caused by these leakage mechanisms. It is annoying and even more annoying is that the “smoking gun” can never be found because the tripping is caused by an accumulation of small capacitive currents, not one big resistive leakage current to ground.

You can methodically try to isolate and resolve the issue and you can notice that disconnecting some items can “fix the problem” but the problem isn’t really fixed because no single item is actually faulty. It is an accumulation of very small leakage currents that sum to around 20mA and consequently trip the RCD.

Normally in a house or commercial installation this is solved by spreading the accumulated leakage over a couple of RCDs. That is difficult when feeding a boat from a single marina pedestal.

Regards

Trevor

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Related Resources

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Ground, earth and electrical safety


Additional resources still need to be added for this topic

Faults with Victron equipment are best discussed directly with your dealer - this can be formalised with this support request form.