Reverse Polarity with Generator

[Vincentc]

I ran the generator today for the first time with the inverter switched on. With the generator running, the reverse polarity lights on the breaker to the inverter and ones on the sub panel came on. There are no polarity issues when the shore power feeds the inverter.

Until I wired the inverter, there was no polarity indicator other than the polarity light for the shore power. This generator was installed 6 years ago by the PO.

Other than an improper generator connection, is there an explanation for the polarity lights to come on?

Thanks,

 

[gbharrington]

Is it an inverter/charger?

 

[SKYCHENEY]

Get out your multimeter. It should be pretty easy to check it.

 

[MikeP]

Since it seems to have started with the installation/use of the inverter, the inverter-related connections are the ones I'd check first. I assume that the inverter is "sharing" the circuits with the genney/shore power circuits, right? That is, when the shore/genny is running, circuit X receives power from either of those and when the genny is not running/shore is disconnected, the inverter runs circuit X.

If so, does the inverter take up the load automatically (pass-through) or do you turn it on when you want it to operate the appropriate circuits?

 

[Vincentc]

I wonder if the inverter install is a cause or a coincidence since until the install, I do not think there was anything to indicate reversed polarity for the generator.

It is an inverter / charger.
The AC feed for the inverter comes after the selector switch for shore power or generator and leads to a 30 amp breaker which allows me to shut off the AC to the inverter. The inverter passes power thru to a sub panel for the port, stbd, and refrigerator outlets. That same AC line also feeds a rotary switch allowing me to take power directly from the selector without passing thru the inverter.

There are no polarity issues indicated when running off shore power or passing shore power through the inverter, and no issues when running off the inverter.

With the generator running, there are polarity warnings both on pass thru and direct with the inverter turned off.

Thanks

 

[Vincentc]

The Mystery Expands,

I used a digital multimeter to check voltage at the main ac switch.

I removed the inverter from the circuit:

off shore power

Hot to Neutral = 123 volts
Neutral to Ground = 0.4 volts
Hot to Ground = 123 volts


off Generator

Hot to Neutral = 118 volts
Neutral to Ground = 49 volts
Hot to Ground = 69 volts

Makes no sense to me

 

[Pete]

Sounds like the generator ground is not connected. When the generator was wired one wire off the generator AC output should be grounded to polarize the output. I suggest you get the generator manual out, look up the electric hookup instructions, focus on the grounding required, and modify your setup as needed. If it is the original Hatteras installation, something is loose or corroded in the grounding at the generator.

Pete

 

[MikeP]

Agree with Pete - Your measurements indicate, contrary to what I thought earlier, that there's a genny connection problem. Sort out the genny connections and then re check polarity.

I've have a fairly long suggestion partially written re the inverter setup but if the above solves the problem then no need to go further.

 

[Pete]

Just one additional item, the polarity light. These indicators are just a light bulb with one lead on the green wire ground and one on the white wire neutral. Since your white wire and ground (bonding system) are not properly connected the 49 volts you are reading cause the light to be on. Bottom line, the polarity light problem will also be fixed when the grounding is corrected.

Pete

 

[Vincentc]

I've looked at the generator ground and the green wire is attached to a connection next to the 12v starter connections and leads under the generator rather than with the black and white wires leading aft to the ac panel.

I will try to check and see to what and how well the ground wire is attached under the generator.

Without opening things up I cannot see how the wiring to the AC panel is connected.

The rating plate for the generator states 120/240 volt and 75/37.5 amps.
As best I can tell, there are no 240v circuits on the boat.

The generator is a 2008 9kw Cummins/Onan purchased by the previous owner and installed by a dealer in Orlando, FL

thanks

 

[Pete]

Vincent,

Since you know the company that installed the generator, I would suggest contacting them and telling them you have a "floating neutral" problem with the generator and inquire if they can tell you where the neutral should be tied to ground. A lot easier than tearing things apart, and hopefully they have a consistent way they wire replacement units they can explain.

Pete

 

[Vincentc]

Pete,

Good suggestion.

I will try that.

thanks

 

[Vincentc]

I spoke to the selling/installing dealer, who is in Bradenton, FL not Orlando, but in any case a long way from Pascagoula, Mississippi. I was told that it is wired according to the diagram posted inside the generator cover.
Yesterday I pulled the cover and looked at the diagram.



The label on the front of the generator indicates that it is set up as 120/240v



The Generator is wired as shown:



The wires going to the breaker and hot wire are labeled "T-1" and T-3" and the "T-2" and "T-4" going to the neutral wire appears consistent with the diagram IF the generator set up as 120v. On the other hand the generator label indicates it is 120/240.

My confidence level in the installation is reduced by the fact that 9kw (75 amps) appears to be run through one half of a double 40 amp breaker. There is no connection to the second 40 amp breaker. As long as we have had the boat, the breaker has tripped whenever we ran both air conditioners at the same time as the stove.

I am going to get back in touch with the dealer who installed it, but would appreciate any insight you may have on this. I plan on having a closer Onan dealer come out and take a look, but I would like to know more about this to better understand what I might be told.

Thanks for your advice.

 

[Vincentc]

A few more facts.

The generator is wired from its double pole 40 amp breaker, shown in the upper right

front:


Back:



to a single breaker which in turn is connected to wiring for both the 30 amp air conditioner panel and the 30 amp ship service panel.



The grounding wire from the exterior of the generator leads to the boat's grounding/bonding strip which runs alongside the port engine stringer. The grounding wires for the two 30 amp circuits are connected inside the generator as shown in the previous post.

The labeling is my addition due to the repeated need to go down and reset the breaker.

Thanks

 

[bostonhatteras]

The single 40 amp breaker serving the entire boat when run on the generator doesn't surprise me. My boat had the air conditioning panel wired through the main A.C. selector switch for running on the generator. I still had to switch both selectors to gen but the feed came off the main A.C. Switch, not a separate feed. Their was no separate and distinct wire run from the generator output to the air conditioning panel selector switch. The set up ran things just fine for me but I wanted it separate so I changed it with two 30 amp breakers off the generator. I assumed hatteras figured you would be using that much less electricity away from the dock. I did think it was a sort of cheap way of hatt to do it. Would another wire run to the panels been that expensive for them? I have a 8kw by the way.

 

[Vincentc]

Boston,

I don't have a problem with the Hatteras wiring. Their breaker has never tripped, it is the 40 amp breaker on the 75 amp generator that sends me down into the ER.

There are two sets of very large wires going from the Hatteras breaker to the two 30 amp panels, each with its own rotary switch on our boat.

Regards

 

[gbharrington]

I have been waiting for the more knowledgeable "sparky" types to weigh in on this, but I do have a couple of thoughts. As far as the labeling goes, I believe it just means that your generator is capable of producing either voltage, depending on your needs.

As far as only one side the double 40A breaker being used, it doesn't make much sense. The wiring diagram for my boat shows a 2 pole 65A breaker (7.5kw gen) splitting into 2 lines, 1 for the main service panel and 1 for the AC panel. Have you considered upgrading to a 80A breaker?

 

[gbharrington]

As I re-read this for the 5th or 6th time, I'm now confused as to which breaker is tripping. The one labeled "Generator No. 1" or the Onan breaker on the gen?

 

[Andy B]

If it's the onan brk tripping what you need to do is run two properly sized jumper wires on the 40 amp brkr across the terminals load side to load , and line to line, if you don't you will never get rated power from the gen.

 

[Vincentc]

Greg,
The breaker on the Onan is that one that is tripping. The breaker labeled Generator 1 has never tripped.

Regarding upgrading the generator breaker. Until I opened things up, I assumed both poles of the double breaker on the generator were being used. I agree with your suggestion regarding using both sides of the double breaker and replacing the single hot wire between the breaker on the generator and the breaker on the bulkhead labeled "generator 1. I do not want to change anything until I find out what I am dealing with, and be sure it is done correctly.

Regarding 120 vs 120/240. I believe there is a difference. As shown in the wiring diagram which I photographed, in a 120/240 setup, two of the 4 wires coming out of the generator are hot, each carrying 120v. As I understand it, but do not claim to know, If they are combined, you get 240 volt, if they are connected separately, one to each pole of the double pole breaker you get 120v on each leg.

I have spoken to the service rep a Dog River Marina who said he could probably send a technician over next week to sort this out for me.

Regards