Hmmm - incorrect inverter connection

[MikeP]

I just discovered that I must have incorrectly wired my Outback inverter several years ago though frankly, I find that very difficult to believe...

Today I was going to add the 120vac davit hoist to the inverter circuit so I wouldn't have to turn on the genny to lower the davit while anchored out.

So I did that but the davit wouldn't operate using the inverter; worked fine on shore/genny. So I did a bit of circuit testing and found that when the fridge and other components are running off the inverter, there is no voltage between the hot (black) wire at the breaker and the neutral (white) wire buss. BUT there is 120vac between the ground (green) wire buss and the black wire/breaker. When running on shore/genny, the circuit is correct - 120vac between black/white and 120v between black/green. So it seems I totally spaced out when I installed the wiring to the inverter since I can't think of any other possibility. I certainly don't claim to be incapable of making such an error but...well, yeah, I actually DO think I'm incapable of such an error!

Anybody think of some other way this can happen? I'll be checking the wiring later today.

 

[MikeP]

I think I found the problem though I don't see any way to fix it...

The instructions for the inverter (later set than the ones supplied with my inverter are a bit clearer) state:

"The NEUTRAL IN and NEUTRAL OUT conductors should not be common (connected in any way) prior to connection with a Mobile FX"

Since all neutrals (white) are connected to the boat's neutral buss, how the heck can you ever have two neutrals that are not "common"?

 

[MikeP]

Now I'm even more confused...

One of those 3-prong neon plug-in circuit testers shows that the wall sockets/wiring is correct whether on the genny, shore, or inverter power. That's good!

BUT on the inverter the 120vac circuit within the breaker panel is active (voltage present) between the breaker and the ground (green) not the breaker and the white (neutral). So how the heck is it possible that the circuit switches from using the white as a neutral to using the green as a neutral WITHOUT the wall socket showing an error. The circuit tester is capable of displaying a reversed ground/neutral but it shows everything to be OK. SO it's CORRECT at the wall socket with the inverter on but WRONG at the breaker panel.

I thought I was pretty good at elec work but I'm stumped...

 

[Pascal]

Inverters automatically bond neutral to ground when inverting. Could there be a problem with the switching circuit in the inverter? I don't see how instead of connecting B to G, it transfers B to G

maybe a call to manufacturer would answer that question

as to neutrals, well there is conflicting info. When I installed my freedom 30 xantrex confirmed that neutrals need to be split. So I set up 3 meutral bus: inverter powered circuits, non inverter powered circuits and 220v. Time consuming...

When i installed a magnum 40 on another boat i captain magnum said it was not necessary... And since again inveters bound N to G then all Neutrals will be connected anyway so I'm not sure why neutrals should be split.

 

[REBrueckner]

I have the same thought as Pascal, but that doesn't explain why the davit doesn't work. This kind of problem is the reason I was reluctant to connect my own inverter to the entire ac system.

For trouble shooting, I'd suggest disconnecting the inverter from all other ac circuits except the davit...and start working the issue from there...if it doesn't work, find out why.

It's baffling that the davit worked when properly wired to your genny/shore circuit but doesn't work now connected to the inverter....one check would be to turn off all ac power and check resistance between each circuit...blk to blk, wh to wh and gr to gr,,,each should be zero as should be wh to gr on the genny/shore*, and wh to gr on the davit....

* unsure if this is true if you have an isolation transformer...been too long since I had one to remember....

 

[MikeP]

I just returned the circuits to the way they were, davlt not connected to inverter. I may do some more complete troubleshooting but my time on the boat is over on Sat and I don't want to get too involved with another project that might be incomplete when I leave.

Although I generally don't do this sort of thing, I may just leave it alone since everything works perfectly as is and running the genny to lower the dink isn't a big deal. It's been so hot/humid here lately that when we were out the genny was on from when we left the dock to when we returned so the ac could run the whole time. Hey, if we wanted to camp out, we would have bought a tent, not a Hatteras 53MY!

 

[Pascal]

It s hard to understand without knowing how the inverter is hooked up, if i remeber correctly you are not using the inverter built in transfer switch but the orginal relays that were installed on the boat by hatteras or an early owner, right?

 

[MikeP]

No. I originally used the PO relays but two years ago I switched the setup to use the inverter transfer switches and I removed the relays installed by the PO. It works beautifully but, as I said, I'm a bit confused by this at the moment, especially since the neon circuit checker says everything is OK with shore/genny/inverter power...

 

[Dan Mapes]

As far as why are they separate at the inverter? Perhaps they want to provide a double pole disconnect. Could be an open neutral in the davit or some other line?
If you measure at the breaker with the breaker on, and the davit inoperative, I would expect to read 120v across the black/white and black/green. Since it is only on the black green, I am thinking there is a bad neutral somewhere.
Try a continuity test between the davit and neutral at the breaker box. Did you install a separate breaker box for the inverter? I did. This way I did not need another slide breaker to isolate shore/inverter/genny.
Alternatively did you try a voltage test at the davit controller input? If it is good there but not at the cb box, it sounds like an open wire the inverter refuses to tolerate, and that the grounds are not common between the inverter and cb box. Light that out also?
Is the davit going into a separate breaker box somewhere?

 

[SKYCHENEY]

Mike,
Forget the whole subpanel setup and the automatic switching. Just treat the inverter as another generator and manually switch it to run the whole boat. I put a slide breaker in for mine(gen or inverter), but if you have a space on a rotary switch for "gen 2" that will work too.

With the above setup, you can run any 120v circuit and you will never have to add other items to your subpanel.

 

[Pascal]

automatic switching is really easy and so is a sub panel set up. all you really do is split the ship service panel in two groups, one that's not inverter power (charger, water heater, etc...) and what it. add a 30amp breaker to the first group, run that to the inverter, then back from the inverter to the second group (obviously with the tie bar cut in between the group...). you just need to re arrange the breakers as needed to move the charger, water heater, etc.. to the top

easier than actually replacing rotaries to 3 position rotaries...

Mike, i can't help but wonder if it's not somethign real simple, like you're checking voltage on a Neutral but that's not connected to the inverter output...

 

[MikeP]

The inverter output neutral goes to the same neutral buss bar that every other neutral wire on the ac system connects to. I realize that per Outbacks intstructions it appears that the neutral output from the inverter should go to a separate, isolated neutral buss and that the inverter-driven items have their neutrals connected to that buss bar instead of the common neutral buss bar...

Sky, Yes, I considered doing that. The only reason I didn't do that in the first place was out of concern for overloading the inverter if someone accidentally, or simply forgot, and turned on an ac unit or whatever. But apparently it hasn't caused you any problem at all so maybe I'll think about it again.

 

[Pascal]

You shouldn't be able to overload it as it should have an input breaker (at least the magnum and freedom do).

Plus your input line should be protected by a breaker at the panel anyway

you need this so that if 2 guests plug blowdryers ate the same time in outlets you ate protected

 

[SKYCHENEY]

Mike,
The inverter will not allow an overload situation. It will just shut down. No matter what you put on a subpanel, there will always be something that you want to run that is not on it. Just my .02

 

[Pascal]

what i do is put all lights and all outlets on the inverter, as well as fridges, ice markers, etc... the only thing you dont' want to put on are waterheaters, battery chargers, stoves, ovens (Microwaves are ok).

then depending on you needs you can turn off a couple of things... if you want to increase battery time, you can turn off the icemaker for instance but on days where you'll be out for a shorter time, you cna leave it on. maximum flexibility.

the only downside about using built in transfer switches, vs feeding thru a rotary is that if you need to service the inverter you have to jump the passthru wires... or if the switches fail, then you may be left with no power at all until you jump the wires.

 

[MikeP]

All fixed and davit now running on inverter circuit...

Actually there was nothing wrong with the other circuits at all. I FAILED to notice the SEPARATE isolated neutral buss for the inverter circuits that was already installed in the panel by the PO for the original 1980 inverter. When I installed the Outback, I didn't really add anything to the panel, I just installed the OB to the same wires that had been connected to the oem inverter. When I added an inverter circuit to the master stateroom, I just extended an existing inverter circuit so I never actually got into the panel for that purpose...

The fridge circuit and others that seemed to be incorrectly wired were not, they were already wired to the isolated neutral buss. And as soon as I moved the davit neutral to that buss, it worked perfectly on shore/genny/inverter just as the other circuits did.

Yeah, the small isolated neutral buss was there in plain sight yesterday but for some reason it just didn't register since it is right next to the regular neutral buss and white wires go to both - I just thought it was part of the regular buss.

 

[SKYCHENEY]

Pascal,
The newer (80's)boats have electrical systems that are much more complex than your boat. For example, I have 3 subpanels that can be fed from different sources such as one of the 2 50amp 220v services on either side of the boat, one 50amp 120v inlet on either side of the boat, or one of the generators. This switching is very flexible and allows for using different sources to feed one, two, or all subpanels, but it also makes it very difficult to isolate what you might want on an inverter to just one subpanel. Some of the lights and plugs are on ships service 1 and some are on ships service 3. All panels are in different locations and all have both 120v and 220v loads.

This setup just makes running an inverter as an additional "source" much easier as it is just treated the same as having a second genset. If I had just one panel in my ER as you do, I would probably have done it differently.

Mike,
Glad to hear you figured it out and at least it was an easy fix.