How to test inverter for shore power ELCI failure without ELCI present

[Fredct]

Background: My boat has a Xantrex Freedom HF inverter/charger. It was professionally installed. Here is what happens:

1- At my marina when connected to shore: no problem. Shore electrical is many years old.
2- At other marinas with new pedestals (ELCI-style), shore breaker is tripped after a few seconds, indicating a >30 mA leak between neutral and ground.

Per this forum and others, this problem is usually related to improper wiring of the inverter, mainly the need to separate the pre-inverter neutral bus from the post-inverter neutral bus. In layman's terms: place air con and water heater (which only run on shore power) before inverter. My boat has a common ground and neutral bus for all.

So far so good.

My issue is as follows. With the shore cable OFF, I measure 170 kOhms between neutral and ground (at the connector). This is because the Xantrex bonds the AC neutral and ground when not connected to shore. It breaks that bond after a few seconds when shore power is detected.

To make sure that I correctly identify my problem (improper wiring or inverter failure), I want to simply disconnect the heater and see if I still trip the ELCI. However, my marina does not have pedestals with ELCI!

How can I continue to troubleshoot and test?

 

[Maine Sail]

My boat has a common ground and neutral bus for all.

There's your problem......

 

[Fredct]

I suspect as much but the inverter could be faulty as well. Is there a way to test?

 

[Maine Sail]

I suspect as much but the inverter could be faulty as well. Is there a way to test?

You need to fix the on-board neutral / grounding bond first.

The ONLY TIME AC / Neutral and AC / Ground can be connected on-board the vessel is when you are unplugged from shore power and are either:

1- Inverting

2- Running a Generator

Or, your vessel is equipped with an Isolation Transformer.

 

[Fredct]

So this is my goal then: create a new pre-inverter bus as shown in high level overview. Sounds like there will not be a way to test until i get to a dock with an ELCi equipped pedestal.

 

[dlochner]

So this is my goal then: create a new pre-inverter bus as shown in high level overview. Sounds like there will not be a way to test until i get to a dock with an ELCi equipped pedestal.

Looked at your drawing and I don't see where there is a buss.

When you are plugged into shore power the boat does not have its own generating capacity. The boat is just a big extension cord. However, when the inverter is being used to power the AC outlets, the Boat is now an electric power plant.

On shore power you the white and green wires should not be connected any where on the boat. When the boat is off grid and using the inverter, the white and green wire should be connected.

I haven't researched this, however, I believe there are switches to handle this and there may be some automatic switches that sense when the boat is connected to shore power.

 

[Maine Sail]

So this is my goal then: create a new pre-inverter bus as shown in high level overview. Sounds like there will not be a way to test until i get to a dock with an ELCi equipped pedestal.

Not unless you have the proper breakers and wiring for the air conditioner/heater. Anytime an air conditioner is installed on a boat, and a professional installation is done, there is a second full 30A inlet & AC panel dedicated to the AC or the system has been converted to a 50A service... Your 30A service should not be run at more than 24A and that is when the plug/inlet are in perfect condition. Stack an AC on top of a water heater, battery charger, etc. and your 30A shore power is easily over-loaded and a prime recipe for a boat fire.

 

[Fredct]

I do not have aircon, just a Raritan hot water heater. We never use the heater when inverting (when not connected to shore). From what I figured out, the 3 GFI outlet neutrals + the water heater neutral are connected to a common neutral bus, post-inverter. Same with the ground. When I am disconnected from shore, the inverter bonds the neutral and ground. When connected to shore, the inverter breaks (or is supposed to break ) that bond.

90% of the load is to charge the battery. Ours is a very small boat with a single stater battery and a single house battery.

There is a switch/breaker between shore and inverter.

The GFI outlets have a on/off switch (not breaker - applied to black only). The water heater also has its own on/off switch (also not a breaker, also on hot or black) which we always leave off. I need to check but both circuits may be fused.

Why would I have an ELCI problem when the 3 GFIs and the heater are in OFF position? Regardless of Xantrex recommendation for a separate neutral bus for the heater, wouldn't this indicate a problem with the inverter itself?

It sounds like the simplest way to test is to wait till I go back to a new marina and then disconnect the heater altogether. If that does not work, disconnect each GFI neutral 1 by 1 until the problem is fixed. If that does not work, disconnect ALL neutrals from bus except the inverter neutral. If that does not work, the inverter is faulty or otherwise not installed properly. All of this is not very proactive unfortunately.

 

[Stu Jackson]

On shore power you the white and green wires should not be connected any where on the boat. When the boat is off grid and using the inverter, the white and green wire should be connected.

IIRC, the Freedom I/Cs do this interbnally and it is covered in detail in the installation manual. I know they do, because I have a 1998 Freedom 15 I/C. There are a couple of pages in the manual discussing this.
They also have internal transfer switches.

It was professionally installed.

My boat has a common ground and neutral bus for all.

Could those two statements be mutually contradictory?

 

[Fredct]

@Stu Jackson I am not the owner who got this installed. I know it was professionally installed and I know that I saw a single neutral bus and single ground bus for all 4 A/C circuits. When disconnected from shore, the neutral and ground were bonded, as they should.

When connected to ELCI pedestal with these 4 circuits OFF (on the hot/black wire), the breaker trips within 1 or 2 seconds.

I read elsewhere that the inverter does not break the bond automatically, it takes a few seconds. The ELCI is quicker to trip.

I do not mind the work, I just don't want to randomly change things without being able to test or at least isolate the problem.

One final detail, the green AC bus was jumpered to the DC black bus. These seemed correct with I looked a the Freedom installation guide.

 

[dlochner]

I read elsewhere that the inverter does not break the bond automatically, it takes a few seconds. The ELCI is quicker to trip.

This is likely the issue. ELCIs trip quickly to protect those in the water.

The GFI outlets have a on/off switch (not breaker - applied to black only). The water heater also has its own on/off switch (also not a breaker, also on hot or black) which we always leave off. I need to check but both circuits may be fused.

Are you sure the switch is not a breaker? It is standard on boats to use the breaker as a switch on the main panel.

 

[Fredct]

The switches are definitely switches. They may be fused but i am far from vessel so can't check tonight.

For the ELCI to trip, it must detect a 30 mA current. For there to be a current, there must be a load. If all 4 circuits are OFF, there can be no load from these devices. At that initial moment, the only load is the inverter drawing AC to generate DC. That's what made me suspect the inverter, all things being equal. Again, I am looking for a sure way to test without have access to ELCI pedestal.

 

[dlochner]

At that initial moment, the only load is the inverter drawing AC to generate DC.

Yes, this is the load that is tripping it.

I'm not familar with your inverter/charger, however with my charger (ProNautic) as soon as it is powered up it starts with the full 50 amp charge. That will well exceed the 30 ma.

 

[Fredct]

@dlochner So it draws from shore to charge while the neutral and ground are still bonded. That could be tested on ELCI pedestal by disconnecting the inverter white from the bus.

 

[Stu Jackson]

At that initial moment, the only load is the inverter drawing AC to generate DC.

Wouldn't one "test" be to turn off the inverter?

I use a Link 2000 to control my Freedom 15 I/C. Do you have a remote control panel for your I/C?

Also, I wasn't pointing fingers at you or your PO before, but "professionally installed" when it comes to boat electrics, I have found in my 38 years of boat ownership, is an oxymoron. Except for Maine Sail and one guy I knew in San Francisco, Ryan Schofield.

 

[dlochner]

@dlochner So it draws from shore to charge while the neutral and ground are still bonded. That could be tested on ELCI pedestal by disconnecting the inverter white from the bus.

Chargers have no way of knowing how much charge the battery needs until it tries to charge them. Thus, when the charger is first turned on it sends its full charging capacity to the battery. If the battery is charged, the voltage rises quickly to the bulk voltage and then the current tapers off. The more fully charged the battery, the faster the taper to the float voltage.

With the shore cable OFF, I measure 170 kOhms between neutral and ground (at the connector).

This is also indicative of the issue. There should no resistance, 0 ohms or close to it, between the neutral and ground or infinite resistance (open circuit).

 

[Fredct]

@Stu Jackson I thought about turning off the inverter BUT, here is what happens. 1- shore to boat with in-boat shore AC switch off = GOOD. As soon as in-boat AC switch is ON, the inverter automatically turns on, creating the fault.

@dlochner Yours is a good point. I checked resistance between neutral and ground at 2 places (NO SHORE AC PRESENT). At the connector: 170 kOhms. At the post-inverter neutral and ground buses = 0 ohm. The 0 ohm makes sense because the ground is bonded in that state. The 170 kOhms pre-inverter does NOT make sense.

In fact, now that I write this down, I see that this could be the issue. The ELCI will trip immediately if neutral has path to ground. If we extrapolate, I may have a leak pre-inverter between Neutral and Ground. not sure...

 

[dlochner]

In fact, now that I write this down, I see that this could be the issue. The ELCI will trip immediately if neutral has path to ground. If we extrapolate, I may have a leak pre-inverter between Neutral and Ground. not sure...

Start working backwards from the inverter to the plug, check every connection.

It may be time for a new charger. If you go that route, you may want to go with a plain smart charger like the Sterling/ProNautic chargers. Ditch the inverter, you really don't have enough battery capacity to run much of anything on the inverter.

 

[Fredct]

@dlochner I will do just that.

I am not ready to ditch inverter yet unless faulty. One, I do not want to rewire if i can avoid it. Two, we occasionally run our business from the boat and the limited inverter capacity is enough to power our hotspot.

What i need to do is test the wiring from the in-boat shore power connection to the inverter IN, with a special focus on white and green. more to follow. I will do a diagram first. Of course, boat is very cramped so I anticipate slow progress.

 

[dlochner]

We installed a 150 watt pure sine wave inverter that is separate from the charger. It is enough to charge laptops and small non-usb rechargeable devices. It is wired off the main DC panel and functions independently from the charger and whether we are on shore power.

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