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Old 12-14-2012, 11:45 AM   #1
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Help solve my inverter mystery

I recently watched my sunforce 1000-watt pure sine wave inverter go up in smoke and I'm baffled about the reason. I replaced the inverter and I'd really like to avoid a repeat.
Here is the setup:
the inverter is installed in the front storage compartment of my TT. It is wired to the battery bank via two bus bars, positive and negative. Positive lead has a catastrophic 120A fuse installed inline. The inverter is grounded to the trailer frame.
Inverter output goes directly to a dedicated outlet in the trailer. It is not connected to the trailer AC wiring in any way.
I use the inverter to run a HD TV and satellite receiver or blu ray player. Nothing else.
Worked fine until I fired up my generator after a cloudy day left the battery bank a little low.
The generator was plugged into the 30A trailer connection.
When I flipped the remote to turn on the inverter, it fried itself.
Now, the inverter had no direct connection to the generator output. The only thing they have in common is the converter connection to the battery bank. Yet the fuse in the 12V line to the inverter didn't even get warm.
Could it have been a coincidence? Am I missing something?
I dont dare repeat the steps for fear of destroying the brand-new replacement inverter.
Any ideas?
Thanks in advance for the help.
Dave in quartzsite
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Old 12-14-2012, 10:46 PM   #2
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This article shows you hook your cables directly to the battery, not grounding through the frame.
I am not sure if this caused your first one to fry or not. I just followed what the video said.
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Old 12-15-2012, 06:27 AM   #3
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one question, is the inverter grounded to the frame in any way? Other than the battery negative. Like the ground on the outlet.
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Old 12-15-2012, 08:03 AM   #4
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Ditto on "do not ground to the frame"
The black cable must go directly to the battery bank.
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Old 12-15-2012, 10:40 AM   #5
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Quote:
Originally Posted by herk7769 View Post
Ditto on "do not ground to the frame"
The black cable must go directly to the battery bank.
. It is wired to the battery bank via two bus bars, positive and negative. Positive lead has a catastrophic 120A fuse installed inline. The inverter is grounded to the trailer frame.


Sounds to me he wired it properly, +ve and -ve to the battery bank via bus bars and the inverter itself is grounded to the frame which is standard practice. If you look at Xantrex Inverters as an example they recommend using 10 gage wire to ground the inverter.
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Old 12-15-2012, 10:53 AM   #6
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Sorry if I didn't make myself clear. The inverter is connected to the battery bank via a bus bar and two 4 ga cables. The frame ground connects to the grounding terminal on the inverter with 10 ga as per the manufacturers specs. Negative cable is not connected to the frame.
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Old 12-15-2012, 11:45 AM   #7
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Originally Posted by Realrotor View Post
Sorry if I didn't make myself clear. The inverter is connected to the battery bank via a bus bar and two 4 ga cables. The frame ground connects to the grounding terminal on the inverter with 10 ga as per the manufacturers specs. Negative cable is not connected to the frame.
I see.

How are the circuits you power from the inverter powered when running on generator?

If you hook the top two terminals of the duplex to the camper's AC circuit and the bottom two terminals to the inverter's AC output; nothing bad will happen as long as BOTH are never used at the same time.

Powering up the inverter while there is a higher potential on the output side will force juice to flow backwards through the inverter, letting the smoke out.

Could this be happening?

A solution would be to clip the tie metal between the top and bottom of the duplex, making the top outlet "house power only" and the bottom outlet to be "inverter only."

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Old 12-15-2012, 12:00 PM   #8
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Originally Posted by herk7769

I see.

How are the circuits you power from the inverter powered when running on generator?

If you hook the top two terminals of the duplex to the camper's AC circuit and the bottom two terminals to the inverter's AC output; nothing bad will happen as long as BOTH are never used at the same time.

Powering up the inverter while there is a higher potential on the output side will force juice to flow backwards through the inverter, letting the smoke out.

Could this be happening?

A solution would be to clip the tie metal between the top and bottom of the duplex, making the top outlet "house power only" and the bottom outlet to be "inverter only."

view Image

Thanks for the suggestions. I doubt that is the answer, though.
The inverter output goes into a dedicated line that runs to its own duplex outlet in the trailer. The generator powers all the other outlets. The inverter outlet is dead until the inverter is switched on.

There is no connection between these two AC circuits. Yet I can't run both at the same time. Voodoo electronics?

The only common connection is the charging circuit to the battery bank. It also shares this with my solar system. So why does a 12-volt feed from the converter fry the inverter, but the 12 volt feed from the solar regulator does nothing? And why didn't the fuse blow?
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Old 12-15-2012, 12:16 PM   #9
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So why does a 12-volt feed from the converter fry the inverter, but the 12 volt feed from the solar regulator does nothing? And why didn't the fuse blow?
I can answer the second question. The feed side fuse is designed to protect the battery from a short circuit in the inverter (not the other way around).

If the feed wires were directly wired to the battery and the ends were somehow shorted the current would be so great it most likely would start a fire or blow up the battery. The fuse is designed to sever the connection between the battery and the inverter if that happens (and sized so "normal use" will not).

As to the first part of your question, I am at a loss right now. You have wired it correctly as far as I can determine and it could be (as much as I hate them) a coincidence.
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Old 12-15-2012, 01:07 PM   #10
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how is the ground terminal of the outlet grounded?

also, unless your inverter batteries are isolated from the camper battery, the negative IS tied to the frame, and IS grounded when plugged into the shore power.

Here's what I'm getting at. I installed an inverter that say explicitly that the inverter is not to be grounded on the neutral side as it was already grounded thru the battery negative. Doing do would cause the inverter to self destruct. Possibly, somehow, maybe yours is similar, and when you plugged into shore power, the neutral became grounded. I dunno.

I did find out why it says not to ground the neutral side of the inverter. The inverter puts out 65 volts on both the hot leg, and the neutral. Anything plugged across would "see" 120volts. I found this out quite accidentally. I installed a flip-flop switch on the hot leg of a circuit. We wanted to be able to change from shore to inverter easily. Well, after installation, we tested the inverter part, ok. then I went to plug into the shore power, I happened to wipe off the plug end and was shocked pretty good. Here, because I didn't isolate the neutral of the switch to the inverter, the neutral side of the camper was energized 65 volts to ground. Had I actually plugged into the shore power, I'm certain the inverter would have been destroyed.


This may or may not be your case.
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