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  #1  
Old 03-25-2009
GPSGary GPSGary is offline
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Default Chassis ground question

I'm installing a big charger / inverter (Xantrex RS3000) in the stock charger compartment.

The stock configuration had a +12v 1/0 wire running to the battery compartment and a GND 1/0 wire running to the battery compartment ground post.

I'd really like to use the old GND cable for my second battery bank rather than run a new one.

Does anyone see any downside to installing a heavy duty ground point in the charger compartment and using that for the (-) terminal of the charger / inverter? I can get it to the same very large frame rail that the battery compartment GND point is on.

Note: I am NOT proposing to tie any of the AC grounds to this point ONLY the charge (-).

Regards,
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Old 03-25-2009
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Gary,

How long of a run is it from your inverter to the batteries?? If it is as long as mine is (inverter in compartment opposite original charger location) 1/0 cable isn't big enough for your needs. Also what do the instructions say about using a frame ground instead of a ground back to you battery bank?? I suspect they say to run all the way back to the batteries. My Xantrex 2500 watt inverter has power and ground run back to the batteries using 4/0 marine grade individually tinned stranded wire, alittle extreme, but it works very well. There is a wire gauge chart on the W-L Yahoo forum for calculating wire size for current requirements vs. length too. Keep in mind your inverter will draw something like 300 amps off your batteries at times. When it comes to wire, bigger is better than not big enough
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Old 03-25-2009
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Here's some info from the RS manual

Table 3 Recommended DC Input Cable and Fuse Size
Maximum DC Cable
Length: Battery to
RS3000 (one way) 10 feet
Total Length (two way) 20 feet
Minimum Recommended Cable Size No. 4/0 AWG
Maximum Battery Fuse or Breaker 400A class T
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Old 03-25-2009
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I installed the Xantrex in the right front compartment, which provided the shortest DC cable run to the batteries. It did, however, provide the longest AC run to the breaker panel. I used 8 guage romex wire for the run from the panel to the Zantrex and back.
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Old 03-26-2009
mynavion mynavion is offline
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I did the exact thing and in addition I used "sealtite" flexible conduit for the run from the right front compartment to the breaker panel. This really protects the wiring from any road debris.....


Quote:
Originally Posted by gcyeaw View Post
I installed the Xantrex in the right front compartment, which provided the shortest DC cable run to the batteries. It did, however, provide the longest AC run to the breaker panel. I used 8 guage romex wire for the run from the panel to the Zantrex and back.
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  #6  
Old 03-26-2009
GPSGary GPSGary is offline
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Default Chassis ground question

I finally called Xantrex tech support and insisted on getting the second level tech support people.

It turns out that the small screw in the side of the unit with the chassis ground symbol is actually tied internally to the (-) DC terminal anyway and Xantrex wants you to tie this small screw to frame ground, so you are automatically making a (-) DC terminal connection to frame ground.

The tech guy also said that there is not technical reason you can't use frame ground for the (-) DC connection only that it might not be very reliable.

Since everything else in this bird is using frame ground, I don't see any downside as long as I do it right.

Regards,
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Old 03-26-2009
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"Since everything else in this bird is using frame ground, I don't see any downside as long as I do it right."

Gary, nothing else in the bus is using 300 plus amps though. Run it all the way to the main ground near the batteries. You won't regret it.
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  #8  
Old 03-26-2009
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I have two 16' 4/0 cables connecting my inverter to the coach batteries. They run on top of the holding tanks then next to the frame rail to the battery compartment. The (+) cable terminates on a fuse holder with 300 amp fuse. The (-) cable connects directly to the battery pack.

The inverter draws large amounts of current when operating and creates a lot of heat in the cables, especially at connection points. If you use the frame as a ground path, you add two more connection points in the circuit - providing two more points of failure and two additional maintenance items.

Xantrex recommends twisting the (+) and (-) cables together on long runs - makes them a little easier to install too.

Good luck,
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