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Old 07-22-2014, 05:59 PM   #1
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Grounding a small inverter

I have purchased a Go Power 150 Watt inverter to run my CPAP machine while boondocked.
This little unit will plug into the cig. lighter outlet near the kitchen booth in the Sunseeker 3010DS. It recommends that the unit be grounded to the chassis. My 2 questions are.....
1. Is there any way to ground it inside without having to run a cable all the way up front under the steps to the coach battery ground. I am trying to avoid night time tripping hazards for other occupants. As this is an occasional use item, I also would like to avoid drilling or permanently mounting the cable.

2. Is it essential that it be grounded if there is no risk of storms or lighting?
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Old 07-22-2014, 06:33 PM   #2
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All of your DC voltage devices are already grounded to the chassis through the converter ground, which is in turn wired to the battery negative through the frame.

I think what the manufacturer is implying is that you ground the case of the inverter with a separate ground to chassis for safety and to insure that the AC output of the inverter has a solid ground reference.

At 150 watts, at 120VAC works out to a total of 1.25A of current. Very low. I would think that the inverter would fry before you would overload any of the existing ground wires on the rv. Sorry....thinking out loud here..

Anyway, to sum it all up...just run a piece of 14 stranded wire from the inverter case to the nearest ground (the 12V socket ground or a nearby light fixture ground wire) and you should be good to go.

As far as lightning protection goes, I doubt that the small inverter would survive that regardless, but to protect the devices that you have plugged into it you could run a plug in surge protector inline before you connect the devices you will run off of it.
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Old 07-22-2014, 07:59 PM   #3
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The reason you want to ground the case is that the outlet has a ground in it, the semi round hole socket. That ground is a safety feature for errant voltage from a faulty appliance. In your situation, it has nothing to do with lightening. Besides, if your rv gets hit, that ground will be the least of your problems.
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Old 07-22-2014, 09:18 PM   #4
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Okay, bear with me I know nothing about electricity, grounding etc.
Are you saying that the socket I plan to plug into is already grounded but that I should ground the case as well? Are you saying that I can just run a 14 strand wire from the case (there is a place on the inverter for doing this) to the ground wire in the same socket? or to the ground wire in the nearest light fixture?
Please do the "for Dummies" version. I am a pretty quick learner but have no background in this sort of thing.
And thanks for responding.

FR service department tells me I have 2 options, ground it to the battery or hard wire the inverter. I figured there must be a simple non permanent solution and that this was the right place to come for an answer.
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Old 07-22-2014, 09:35 PM   #5
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Okay, bear with me I know nothing about electricity, grounding etc.
Are you saying that the socket I plan to plug into is already grounded but that I should ground the case as well? Are you saying that I can just run a 14 strand wire from the case (there is a place on the inverter for doing this) to the ground wire in the same socket? or to the ground wire in the nearest light fixture?
Please do the "for Dummies" version. I am a pretty quick learner but have no background in this sort of thing.
And thanks for responding.

FR service department tells me I have 2 options, ground it to the battery or hard wire the inverter. I figured there must be a simple non permanent solution and that this was the right place to come for an answer.
An even easier option is to just wire the case ground terminal to the negative wire on the plug. In DC voltage, the negative wire is the ground. In the case of your rv, the negative wires of all of the DC (ie the 12V stuff) go back to a grounding terminal strip near the converter, which is in turn wired to the frame of the camper. The negative battery terminal will with go straight to the frame as well, or back to that terminal I spoke of.

The purpose of that case ground is to serve as a ground reference for the AC side, or the output, of the inverter. High end inverters typically have this done for you internally, but your does not seem to per the manufacturer recommendation. For your purposes, a 14 AWG stranded wire from the case of the case terminal of the inverter spliced into the negative wire on the plug that you plug into the 12VDC socket will serve just fine.

Eta...the negative wire on the 12VDC plug, if they are not marked which I doubt, is going to be the wire that is connected to the side blades on the plug. The positive wire is the one that connects to the center post. You can see which one is which pretty easily if you have a meter that has a continuity checker. Just don't check for continuity with it actually plugged in!

Eta no 2....just in case...if you are running this inverter in a vehicle (motor home), which is supplying power through an alternator and then through a regulator when running, you will need a hard wire that goes to the frame. This is due to the induced noise (phantom voltage) from the alternator that can be problematic if you ground through the entire electrical system circuitry like I am describing. I did also miss that you stated when "boondocking". If you are on generator power you may have the same issue, though I assume that since you're using an external inverter that this is not the case. If you are running strictly on battery then you'll be fine doing it the way I outlined above.
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Old 07-22-2014, 09:58 PM   #6
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I will be strictly running off the 2 deep cycle RV power while boondocked. I will be travelling during the day and recharging the batteries while the motor home runs.


Don't give up on me yet.
I run the wire from the inverter case to where? I don't have blades on the plug. Do I need to open the wall receptacle to connect the wire? Can you suggest a site that might have a diagram I could refer to? I'm way out of my element but want to learn this.
Thanks for the patience.
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Old 07-22-2014, 10:03 PM   #7
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Awesome you have a pic!

And I see that the wires are color coded so this is easier. Two different ways to do this...

1. Yes. Run a wire from the chassis ground terminal to the negative wire on the socket.

2. Cut the black wire about 6 inches from the inverter and then strip both sides of the cut and twist them back together. Then take the twisted wires and connect them to the chassis ground terminal. Be aware that this option may void your warranty though.

Also, the "blades" I was referring to are the little black prongs on the side of the plug.
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Old 07-22-2014, 10:11 PM   #8
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Okay, its starting to click. I can expose the black wire and connect it to the ground terminal.
Or, I can connect a 14 strand to the ground prong on the plug and run that to the gr. terminal.
Either one will satisfy the grounding requirement.

Thank you.
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Old 07-22-2014, 10:13 PM   #9
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No problem. Glad to help.
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Old 07-22-2014, 10:26 PM   #10
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Or, I can connect a 14 strand to the ground prong on the plug and run that to the gr. terminal.
You will NOT likely find 14 strand wire.

What he meant was 14 GAUGE, STRANDED wire (as opposed to solid wire). The actual number of strands is of little consequence.

You could also use 12 gauge or 10 gauge stranded wire. The smaller the gauge number, the larger the diameter of the wire, hence the greater current carrying capacity.

Tim
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Old 07-22-2014, 10:30 PM   #11
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Thanks for catching that Tim!!
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Old 07-22-2014, 11:04 PM   #12
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Thanks for catching that Tim!!
You are welcome. We electrical guys know, but others may need a little clarification.

Tim
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Old 07-23-2014, 04:49 AM   #13
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DUH, a simple jumper between the ground lug and the negative wire.



The reason for the external ground is that there are certain electrical installations where the battery negative may not be bonded to the vehicle frame or the inverter is used without a vehicle.

BTW, you shouldn't ground the "neutral" of the inverter. Its not like a neutral in a house that is already bonded to ground.
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Old 07-23-2014, 06:23 AM   #14
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Okay, I'm thinking that 14 gauge wire will be too large in diameter to connect to the wing and then be inserted into the outlet.
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Old 07-23-2014, 06:39 AM   #15
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Here is installation manual......
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File Type: pdf Inverter GoPro.pdf (748.8 KB, 46 views)
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Old 07-23-2014, 07:42 AM   #16
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Okay, I'm thinking that 14 gauge wire will be too large in diameter to connect to the wing and then be inserted into the outlet.
No no no. Don't do that! Either cut the plug's black wire like I stated or connect the 14ga to the negative wire on the SOCKET (behind the wall). Don't try to shove anything into the socket with the plug. You can break the socket.
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Old 07-23-2014, 09:08 AM   #17
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Reading the instructions, section 4.4, ..."chasis is ground to negative input" by reading this I'd say don't worry about grounding the inverter.

Something else, on my Inverters, both say "Do not ground the neutral" but in your manual, it says they are bonded in the case. Humm.
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Old 07-23-2014, 09:32 AM   #18
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Dont cut anything, as stated above if its DC, case of the inverter is already grounded/hooked up to negative terminal. If it was going into a house with ac, then you would need to ground it with the ac circuit.
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Old 07-23-2014, 09:36 AM   #19
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Dont cut anything, as stated above if its DC, case of the inverter is already grounded/hooked up to negative terminal. If it was going into a house with ac, then you would need to ground it with the ac circuit.
A little confused by your comments here Kuba...If it was going into a house with A/C....WHY would you need an inverter??
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Old 07-23-2014, 09:47 AM   #20
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Backup power for home appliances etc. For example if you had a bunch of car batteries and wanted an inverter to run any home appliances of the batteries in case power goes out(110-120v AC). You are good to go and have nothing to worry about.
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