Inverter not accepting Generator Power

I apologize if this is a duplicate, I thought I'd posed but it didn't seem to take.

I'm having an odd problem with my inverter not accepting the generator power to pass through, yet it does accept it to charge the house battery. What's really odd is that it does accept the gen power when we're still teathered to the shore power hook up (i.e. just starting the gen at dock and switching over the main selector). The inverter is a Freedom 2500W with Heart interface and the Gen is an 8kw Northern Lights that is running fine and producing rated voltage. The system was checked by a marine electrician and the wiring itself seems OK, boat was rewired to modern standards and has dual 30A circuits. However since we store on the hard he couldn't start the gen.

I'm suspicious of the selector switch since leaving the shore power cord hooked seemed to make a difference, but the electrician said the switch tested as ok. I'm also wondering if there's a ground fault somewhere since I'm getting galvanic activity based on some rapid zinc deterioration. The problem isn't new, the prior owner just lived with it and cruised extensively just using the gen to charge the house batteries. Any ideas out there?

I suspect this has something to do with the wiring of the neutral bus bar. There should be separate ones for the Inverter and non-Inverter loads. Others on this forum more capable than I am will probably have some good ideas.

Did it ever work right? Has anything been changed on the boat since it did work right?

I don't know if it ever worked. Since it was a professional rewire and gen installation by a Seattle company I have to assume it worked at the start. Unfortunately the owner before me bought the boat and just used it as is and didn't try to fix the root cause of the problem, he just worked around it. As to changes, I'm sure something got changed, the question is where to look.

That's an odd one. Switching to charge and passing through AC typically go hand in hand. Since the boat has always been this way for yours and the previous owners stewardship, I'd look very carefully at wiring starting at the inverter output. It's also very possible that the transfer relay in the inverter is bad. That would probably best fit the symptoms, and just nobody ever bothered to fix it. Oh, but AC works if you are plugged into shore power? Then I take it back. It's sounding more like a wiring issue. But impossible to say without digging into the actual boat.

You know what. I think Jim Cave might be exactly right. I'll bet your gen neutral isn't tied through to the load side, so you have an open neutral on the load side when on gen power, but the neutral is connected to the inverter input, so the charger works. And when you plug into shore power, you get a neutral connection through ground and things start to work, though in a very un-kosher way. Anyway, it's a theory that might be worth chasing down.

Try putting a volt meter across the inverter input's hot and neutral, then across the inverter output's hot and neutral, then across the inverter output's hot and ground, then between the inverter output's hot and the generator neutral.

What do you see?

Thanks!
-Greg

Bill,

One thing to remember when working on a boat with AC and DC circuits.

AC has a "neutral" line which is not a "ground" line. At times people get the two of them connected together, And things may or may not work properly.
You should have a long copper strip running down the inside of the boat that is a ground bonding buss that may have an AC ground or neutral attached to it. If so that could be an issue. If so you would see galvanic corrosion on through hulls. You may even find stray currents in the water by your boat.
Just a thought that may or may not be any help.

twistedtree said:

You know what. I think Jim Cave might be exactly right. I'll bet your gen neutral isn't tied through to the load side, so you have an open neutral on the load side when on gen power, but the neutral is connected to the inverter input, so the charger works. And when you plug into shore power, you get a neutral connection through ground and things start to work, though in a very un-kosher way. Anyway, it's a theory that might be worth chasing down.

Click to expand...

I had a similar issue with the neutral wiring: I wanted the Fuel Polishing system on the inverter side of the panel, so I could operate it whilst traveling and not on generator or shore power. The electrician discovered that it was connected to the inverter side, but it only worked on inverter when the shore power cable was connected. The electrician correctly deduced that the neutral was on the wrong bus bar, which was quickly rectified. Your situation is similar, but...somewhat different.

Jim

Thanks to all for the helpful comments. The only recent change to the boat was addition of the inverter case ground which was missing and identified in the survey. First thing seems to be to investigate the neutral wiring to see if something is amis. I am seeing galvanic corrosion issues on my zincs so that also fits with Captain Lee's comments.

The 2 30 amp inlets should not have the neutrals comingled at all. There should be 2 seperate neutral bus bars. The neutrals and bonding ground should not be connected except when on generator power. The neutral and bonding grounds should only be connected at the power source, when on generator power they should be connected, when on shore power they should not be connected on the boat but they should be connected on shore which is the source of power when plugged into shore power. The professional that rewired the boat could be any worker in the boat yard so I would be suspicious of the rewire until you have it checked by a certified marine electrician that you know to be good. The corrosion issue could be due to the neutral and bonding wiring issue.

A recommendation you may want to consider- Dan Hyde at Emerald Harbor Marine. He understands grounding issues very well.

The inverter ground that was recently connected - how and where may be an avenue of interest.

Last but not least, the Xantrex may be problematic.

Wiring for AC units

Rookie electrical question. When our boat was retrofitted with two air conditioning units by the previous owner , the installers put them on a separate circuit from the original 125A/30 volt input plug (on the side of the boat). The plug-in socket for the AC is 125A/50 volt. The yard where the units were installed said the larger plug and wiring was a contingency for a third unit. Because the 50 amp cord is ridiculously heavy, I've been running them on a 30 amp cord with an adapter for the 50 amp socket. The two units and the pump add up to under 30 amps....seems to be working OK. Any reason to be concerned?