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Old 01-01-2021, 11:56 PM   #1
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Brand: Thor Motor Coach
State: Colorado
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THOR #21686
Wiring for an inverter

I just purchased a 2019 Thor Windsport 29M and it has a WF-5110R 1000W Inverter that is not working. Today I chased the issue down to a lack of 12 V at the input of the inverter. I found that the black/negative wire to the inverter goes under the cab and then is just dangling there, not attached to anything. Yikes.



My question is does the negative cable NEED to go back to the battery negative terminal or can it be grounded right to the chassis? The Thor diagram below shows it goes back to the negative terminal, but is that necessary? Does not grounding it to the chassis frame achieve the same thing?

Thank you!

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Old 01-02-2021, 12:34 AM   #2
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THOR #15553
Quote:
Originally Posted by SeanInColo View Post
I just purchased a 2019 Thor Windsport 29M and it has a WF-5110R 1000W Inverter that is not working. Today I chased the issue down to a lack of 12 V at the input of the inverter. I found that the black/negative wire to the inverter goes under the cab and then is just dangling there, not attached to anything. Yikes.



My question is does the negative cable NEED to go back to the battery negative terminal or can it be grounded right to the chassis? The Thor diagram below shows it goes back to the negative terminal, but is that necessary? Does not grounding it to the chassis frame achieve the same thing?

Thank you!
you do not want to use the chassis as a conductor.
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Old 01-02-2021, 12:38 AM   #3
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THOR #6411
Quote:
Originally Posted by SeanInColo View Post
I just purchased a 2019 Thor Windsport 29M and it has a WF-5110R 1000W Inverter that is not working. Today I chased the issue down to a lack of 12 V at the input of the inverter. I found that the black/negative wire to the inverter goes under the cab and then is just dangling there, not attached to anything. Yikes.

My question is does the negative cable NEED to go back to the battery negative terminal or can it be grounded right to the chassis? The Thor diagram below shows it goes back to the negative terminal, but is that necessary? Does not grounding it to the chassis frame achieve the same thing?

Thank you!
The inverter manufacturers recommend the inverter be grounded to the chassis by a nude (non-insulated) 8 awg copper wire. Thor usually routes the negative cable of the a 1000 watt inverters directly to the chassis. The inverter manufacturers recommend the negative cable go directly to the chassis house battery bank. Number 4 AWG 9 strand cable is usually used for the cables of 85 amps or so max.
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Old 01-02-2021, 12:53 AM   #4
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THOR #20289
Do not ground the negative wire to the chassis. There is a safety ground that can be wired to the chassis frame. It is not the same as the negative.

David
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Old 01-02-2021, 01:06 AM   #5
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Without the second ground to the frame my xantrex won't come on. It has some sensor in it.
(I think that's right)

If you want to attach it to the frame temporarily to see if it all works, that would be OK.
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Old 01-03-2021, 03:53 AM   #6
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Are we saying that when 12vDC source is needed we should not use a ground from the frame?

i.e. I want 12vDC for a macerator pump in my wet bay. Because of proximity and ease of wiring, is it safe to connect the 12vDC positive wire to the red post that feeds the generator, and connect the 12vDC negative ground wire to the metal frame of the generator?

I always thought the negative posts was grounded to the chassis / frame anyway?
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Old 01-03-2021, 04:35 AM   #7
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THOR #13932
It will work just fine on the macerator.
It'll even work on the inverter.
But
Galvanic stuff gets involved.
Whole boats are basically eaten from the waterline down if there is a leak on the positive side anywhere. That s what sacrificial anodes are about. The voltage leak likes zinc better than anything else commonly used as building material.

What I did/do:

Speaker wire is available up to about 4guage.
It's bound like, well, speaker wire.
I run positive to a fuse and the negative to a bus bar sitting next to the fuse block or to the negative on the fuse block.

You have to make the positive run, just bus bar the negative right next to it. The wires are bound so you just make one pull... It might even be easier than self tapping the negative into the frame with some wonky run.

Punchline:
Sure you can run to the frame.
But
Galvanics
Loose damn 'forgot where I put it' self-tappers God knows where.
Corrosion like the 'headlight/tail lamp posters are running in to.
Speak to not doing it.
Run10guage speaker wire that is bound and color coded.
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Old 01-03-2021, 01:12 PM   #8
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Quote:
Originally Posted by dkoldman View Post
Are we saying that when 12vDC source is needed we should not use a ground from the frame?

i.e. I want 12vDC for a macerator pump in my wet bay. Because of proximity and ease of wiring, is it safe to connect the 12vDC positive wire to the red post that feeds the generator, and connect the 12vDC negative ground wire to the metal frame of the generator?

I always thought the negative posts was grounded to the chassis / frame anyway?
FYI, the red post wire does not feed the generator. The red post feeds the 12 volt battery. There is a difference between ground and negative. Using the frame as negative is OLD SCHOOL. There is one wire to the frame. You have to run a positive wire to the pump so just run a negative with it.
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Old 01-03-2021, 02:56 PM   #9
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Quote:
Originally Posted by cavie View Post
FYI, the red post wire does not feed the generator. The red post feeds the 12 volt battery.

Cavie,

I got lost here so help me with what I am missing.

The red post I refer to is always hot 12vDC; so I assumed it was the power that fed the generator's starter?


There is a difference between ground and negative. Using the frame as negative is OLD SCHOOL. There is one wire to the frame. You have to run a positive wire to the pump so just run a negative with it.
Sounds like I did Old School wiring, but it was New School for me That is why this thread caught my attention. I connected the Negative lead from the macerator pump for 12vDC direct to the bottom of the Genset (see picture: the red wire running next to it is the positive wire from macerator that goes on to the positive post on genset), I have used several times, it works and all appears well. I didn't think I saw a negative post on the genset, but a screw underneath may have been it, but it was very close to the positive post? My thinking at the time was to wire in a way that negative and positive wires were not so close that they could possibly touch by mishap. I have a dedicated 15 amp fuse for this pump on positive wire. It has full access to the power as if it was direct to the battery; which would have been a lot longer run. I used 10awg wiring; so length was also a concern to reduce heat. I also could have tapped into my Shurflo Water pump; which is in the same compartment bay, but I was thinking to keep it separate as to not be tripping fuses or putting my water pump at risk.

Am I good if I promise to keep the RV out of the lake and not use as a Duck Boat
I need "The Duck's" Approval too
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Old 01-03-2021, 03:21 PM   #10
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Your generator, if it is connected like mine, has the 'negative' going directly to frame. The Chassis battery negative is connected directly to frame. The metal frame of the vehicle provides a conduit for the return to the battery. Auto manufacturers have been doing it that way for years. If every device had to have its return directly to the battery, then the wiring would get out of hand.
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Old 01-03-2021, 03:36 PM   #11
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You'll be fine.
It's a good way to have a headlight or taillamp that works intermittently when everything else is working fine, but if you remember where you ran the ground wire and don't mind occasionally cleaning or tightening a screw, grounding to the frame just isn't a thing which requires worry.
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Old 01-03-2021, 03:48 PM   #12
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THOR #13058
Quote:
Originally Posted by ducksface View Post
You'll be fine.
It's a good way to have a headlight or taillamp that works intermittently when everything else is working fine, but if you remember where you ran the ground wire and don't mind occasionally cleaning or tightening a screw, grounding to the frame just isn't a thing which requires worry.

This is good enough for me, I now have the Duck Seal of Approval
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Old 01-03-2021, 04:06 PM   #13
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A slight aside:
A friend of mine bought an early years suburban bigblock 4x4 for practically nothing.
500 bucks I think.
The guy who sold it had just reached the end of his rope about an electrical problem.
The vehicle would randomly shut itself off while driving down the road.
Some jeep Cherokee do this without anyone knowing why, but this was a suburban.

It took my friend three stalls to find the problem.
When accelersting up a certain %grade a wire would swing just right and ground itself out on the drivers side header. It killed the ignition. Since there was no longer an acceleration the wire returned to its static spot, the sub always restarted as if nothing had happened.

Not being a guy who carries a pocket knife, he just tied a knot in the loose wire.
I kinda remember him getting $3000 bucks when he sold that suburban a bit later.

Punchline:
Forget where or why on a ground or power, and you're in for some intermittent pain.
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Old 01-07-2021, 04:48 AM   #14
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THOR #19813
I see on my Vegas and on Thor's wiring diagram 2 or 3 spots they show for grounds to chassis.
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Old 01-07-2021, 11:19 AM   #15
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Quote:
Originally Posted by dkoldman View Post
Are we saying that when 12vDC source is needed we should not use a ground from the frame?

i.e. I want 12vDC for a macerator pump in my wet bay. Because of proximity and ease of wiring, is it safe to connect the 12vDC positive wire to the red post that feeds the generator, and connect the 12vDC negative ground wire to the metal frame of the generator?

I always thought the negative posts was grounded to the chassis / frame anyway?
you are talking "OLD School"
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