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Old 26-08-2014, 03:45   #166
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Re: Inverter Dying?

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It's connected together through a breaker. I describe it in a previous post. My main is three Breakers controlled by one switch. And it does not look like the breaker panel has been modified in any way
A triple breaker does not connect neutral and ground but switches them to their respective buses. These buses should not have any interconnection.

A house is static after initial construction, no changes are regularly made to the wiring. If it is correct when built it will stay that way.

A boat that goes anywhere is plugged into the source in any number of marinas, any of which can be badly wired, This can include no ground connection to shore and the possibility of reverse polarity. In North America ABYC calls for the AC ground to be connected to the DC negative bus for safety reasons. While this is debatable it is done this way on virtually every boat in North America by the builder. If you were to plug into a reverse polarity shorepower connection and had the ground and neutral connected on the boat the neutral would become hot as would the DC system. That is why it is dangerous.
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Old 26-08-2014, 03:50   #167
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Damn one more thing to add to my to do list. luckily I'm at anchor so I can push it off for a while. Edit: I don't think it's possible for me to write post without editing it. but did you read my previous post? the ground goes directly from shore to the bus bar from the bus bar to the top the circuit breaker. from the bottom of the circuit breaker to the top of the neutral circuit breaker. so I would think if neutral was hot the breaker would blow. And maybe that's its whole point
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Old 26-08-2014, 03:54   #168
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Re: Inverter Dying?

I watched one of the videos and it doesn't relate to a boat's proper wiring.
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Old 26-08-2014, 03:58   #169
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Nope not about boat wiring it all. Just ways an inverter can be dangerous
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Old 26-08-2014, 04:00   #170
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Re: Inverter Dying?

All wiring can be dangerous if done incorrectly.

If one is not sure they should hire a professional.
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Old 26-08-2014, 04:12   #171
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Old 26-08-2014, 05:35   #172
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Re: Inverter Dying?

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Originally Posted by transmitterdan View Post
I like your idea of asking others about this. Here are a couple of test question for the EEs
I won't do that. It would be rude. "Would you do me a favor and review this? Oh, take this test first."

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Well I'm not an engineer, only a technician, so my decision would be to replace the bulb with one with a smaller wattage rating.

What do you think of that solution?
Very practical. The scenario transmitterdan proposes is the basis for many light dimmer circuits, especially those that use LEDs.

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Fluke make high quality true RMS clamp-on meters as do other test equipment manufacturers. They will be disappointed to learn here on the internet that they are selling expensive equipment that provides misleading results to those poor unsuspecting "scientists" who don't understand their tools.
Companies like Fluke and Agilent and others will be the first to tell you that RMS meters will read wrong for non-sinusoidal waveforms. If I recall correctly a square wave with 50% duty cycle (not the PWM we have been discussing for an inverter) will measure almost 50% low due to the waveform crest factor.

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You mean the scope with the "AC/DC" switch on the front? If you switch an oscilloscope to the "AC" coupling position what you see is exactly what it says.
The choice of AC or DC coupling is simply to determine what portions of the signal you see. With AC coupling you will only see the AC component and time variant DC as long as the variation is fast enough to pass through the capacitive coupling. With DC coupling you will see both the AC and DC components.
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Old 26-08-2014, 06:52   #173
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Re: Inverter Dying?

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I won't do that. It would be rude. "Would you do me a favor and review this? Oh, take this test first."
It's a really easy question for the however many EEs here that all disagree with me.

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Companies like Fluke and Agilent and others will be the first to tell you that RMS meters will read wrong for non-sinusoidal waveforms. If I recall correctly a square wave with 50% duty cycle (not the PWM we have been discussing for an inverter) will measure almost 50% low due to the waveform crest factor.
These company's marketing teams will be disappointed to hear this as they will have to now rewrite all their sales literature. The current we are discussing is not square wave as no inverter draws square wave current from the battery. Fluke and Agilent claim exactly the opposite as you believe. They put RMS circuitry into their meters precisely so they can measure true RMS with high crest factors. I suspect you are thinking of older meters that measure AC by rectification (like Simpson 260) and these meters do not give accurate results for high crest factor currents. The crest factor of the battery current is within the limits of any good Fluke handheld clamp-on meter.
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Old 26-08-2014, 07:21   #174
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Re: Inverter Dying?

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............ Edit: and just curious why is it mandatory for houses to connect the ground and the neutral where electricity enters the home but on boats it's dangerous. ........
When a boat is connected to shore power the ground is at the service entrance to the marina or home where the shore power originates. This is the "source" The ground and neutral are connected together at that point. Connecting them together at the boat creates two neutral to ground connections.

Once you disconnect the boat from shore power, you need to connect the ground and neutral together at the inverter or genset. One of these now becomes the "source".
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Old 26-08-2014, 07:49   #175
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Great explanation. So I guess my main breaker is wired the way it is, is to" break" If the neutral is hot
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Old 26-08-2014, 10:00   #176
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Re: Inverter Dying?

Rwidman is right about connecting neutral and ground at source. But this is a US thing and many boats in other countries don't connect neutral to ground for onboard generated AC power. I don't wish to debate this since it was covered extensively in another thread. I just wanted to point out that there are different recommendations in the world so don't go nuts when you find a boat with isolated neutral. There are lots of them in the world.
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Old 26-08-2014, 11:04   #177
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Re: Inverter Dying?

Thanks for these comments. I may relocate the 1000 watt inverter to about 3 feet from fuse although I use pretty small loads. This would reduce the length of the wire from 8' to 3'. Would #1 wire or #2 wire be OK for 3'?
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Old 26-08-2014, 11:23   #178
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Re: Inverter Dying?

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Thanks for these comments. I may relocate the 1000 watt inverter to about 3 feet from fuse although I use pretty small loads. This would reduce the length of the wire from 8' to 3'. Would #1 wire or #2 wire be OK for 3'?
You must count the length of the cable from the battery to the fuse in your calculations. Also, the negative cable.

Your best advice is the manufacturer's instructions as to cable size and length.

In general, the DC cables should be as short as possible. The AC cables can be any reasonable length just like they are in your house.
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Old 26-08-2014, 11:26   #179
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Re: Inverter Dying?

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...I may relocate the 1000 watt inverter to about 3 feet from fuse...
3' from the batteries is what I would shoot for.
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Old 26-08-2014, 11:38   #180
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Re: Inverter Dying?

The actual distance is not what counts... it's the length of the wire... so...new location is maybe 25" from batts... but the wire distance (guessing from memory here) would be 30" from

12v -
24" to neg disconnect switch
4" to neg buss
38" to inverter
66" +/-

12v +
22" to pos buss
12" to fuse
36" to inverter
80" +/-

Best I can do!
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