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Old 12-02-2016, 17:21   #46
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Re: How do I connect my new inverter

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Originally Posted by StuM View Post
You are repeatedly demonstrating a lack of understanding about the fundamentals of electrical wiring.

I suggest you refrain from posting further advise until you learn the difference between "resistance, heating and maximum safe current capacity" and "resistance and voltage drop over distance".
I know the difference. However, at this basic level where people are calling cable "170 amp cable" why confuse them with another concept like "voltage"?


Now explain why it's called an ampacity chart instead of a voltage drop chart.



LOL
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Old 12-02-2016, 17:26   #47
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Re: How do I connect my new inverter

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Originally Posted by Dockhead View Post
The sense in which it was true, was acknowledged. But this issue is completely irrelevant to the OP's question. What he cares about is sizing his cables correctly, and that's a question of voltage drop and power loss.

If you want to give the right answer, you have to answer the right question.
My post was a reply to the post I was replying to so it was the right answer.

As for the OP, his inverter should have come with installation instructions and if he has enough skill and knowledge to do this installation safely, the instructions are all he needs to install it.
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Old 12-02-2016, 17:54   #48
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Re: How do I connect my new inverter

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Originally Posted by rwidman View Post
My post was a reply to the post I was replying to so it was the right answer.

As for the OP, his inverter should have come with installation instructions and if he has enough skill and knowledge to do this installation safely, the instructions are all he needs to install it.
Actually, an inverter that small usually comes with a cig lighter plug. It's only a $30 inverter. I had a similar 400w inverter and it came with a cig lighter plug on 2 feet of #10 wire attached to binding posts on the inverter. Just for giggles, I plugged it in, and as soon as I turned on the TV, the low V alarm started squealing.

I replaced the cable with 2 ft of #6 and connected it to the main 12v panel. With a good connection it easily ran the TV, DVD/surround sound amp and a satellite receiver.

The instructions stated, "Plug connector into cigarette lighter socket"...
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Old 12-02-2016, 18:19   #49
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Re: How do I connect my new inverter

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Originally Posted by socaldmax View Post
Actually, an inverter that small usually comes with a cig lighter plug. It's only a $30 inverter. I had a similar 400w inverter and it came with a cig lighter plug on 2 feet of #10 wire attached to binding posts on the inverter. Just for giggles, I plugged it in, and as soon as I turned on the TV, the low V alarm started squealing.

I replaced the cable with 2 ft of #6 and connected it to the main 12v panel. With a good connection it easily ran the TV, DVD/surround sound amp and a satellite receiver.

The instructions stated, "Plug connector into cigarette lighter socket"...
Of course the issue is that the average 12Vdc accessory power socket will have current limiting of 15 A or less, and a 400W inverter at 85% efficiency will need about 40 A to operate at full load.

Not a quality product if their instructions suggest plugging a 400W inverter into a cigarette lighter.

PS, risking burning up a $XXXXX boat over a $30 inverter and being left adrift in your PFD in the middle of the ocean is not a smart plan.

Ramblin Rod
Marine Service Provider
www.sheenmarine.com]
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Old 12-02-2016, 18:27   #50
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Re: How do I connect my new inverter

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Originally Posted by StuM View Post
You are repeatedly demonstrating a lack of understanding about the fundamentals of electrical wiring.

I suggest you refrain from posting further advise until you learn the difference between "resistance, heating and maximum safe current capacity" and "resistance and voltage drop over distance".
Hey Stu...chill! ;-)

He actually has a good point in that just because the calbe has 170A in the advertised name, does not mean that it is good for 170 A under all (or actually almost any) circumstances.

See my post on cable ampacity derating based on installation reality.

Ramblin Rod
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Old 12-02-2016, 19:12   #51
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Re: How do I connect my new inverter

Quote:
Originally Posted by socaldmax View Post
I know the difference. However, at this basic level where people are calling cable "170 amp cable" why confuse them with another concept like "voltage"?

Now explain why it's called an ampacity chart instead of a voltage drop chart.

LOL
It's not. Here are several ampacity charts. No mention of length or valtage drop in any of them:

Ampacity Charts

American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies and wire breaking strength
"Definition: ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge."

https://www.gore.com/IndustrialCable...wirespecs.html

http://www.allenelectric.com/referencedata/ampacity.htm

What you are incorrectly calling an "ampacity" chart IS a "voltage drop" chart or table. See for example:

Voltage Drop Table
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Old 13-02-2016, 04:29   #52
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Re: How do I connect my new inverter

These are the suggested cables for the 400 watt Cobra Inverter

10' 4 gauge but there isn't an inline fuse. (plus 8' 8 gauge grounding cables)

Cobra Power Inverter Battery Connection Cables - Walmart.com
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Old 13-02-2016, 06:18   #53
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Re: How do I connect my new inverter

The basic rule of thumb for an electrical conductor (please excuse the metric) is 10A per 1mm2 cross section for up to 10m. You should however always verify against the device's recommended installation information and be aware that undersized cables result in a voltage drop that, while not likely to dangerously overheat the cable itself, can result in increased power consumption and overheating of the device or failure of the device to operate satisfactorily, depending on how it manages low supply voltage. Needless to say, voltage drop increases as current (load) increases on any conductor.
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Old 13-02-2016, 13:19   #54
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Re: How do I connect my new inverter

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Originally Posted by rwidman View Post
My post was a reply to the post I was replying to so it was the right answer.

As for the OP, his inverter should have come with installation instructions and if he has enough skill and knowledge to do this installation safely, the instructions are all he needs to install it.
Incorrect!

To have the skills and knowedge to do it safely, one would have to be very familiar with the corresponding marine electrical standards.

That the OP is asking here how to do it, is a clear indication he is not.

We have absolutely no assurance in this case that the inverter instructions are compliant with the relevant marine electrical standards, and if it is a cheap off-shore inverter, there is an extremely high risk that they are not.
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