dmax lover
Portland,Oregon, USA
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MTBob wrote:This question relates to a Northern Lite camper - there is no "frame" to connect to - that would seem like the thing to do, but it's all fiberglass. So, is there a 12 volt negative buss located somewhere else in the these campers? Where do all the other 12 volt circuit negative wires go? I guess I can run the lead back to the negative battery terminal. The charger, of course, has a negative connector. But only two and they are filled and I can't get any other wires in these two connectors.
This has me scratching my bald head.
Bob
On my Northern Lite there is a sticker on the forward passenger side tie down bracket on the camper that says "acts as ground" or something like that... So there is a DC ground path provided by tie downs, etc.
There is also a ground line in the connector from the truck.
jeff
2005 Chevrolet Duramax 3500 SRW Crewcab Longbed (KYB Monomax Shocks, Michelins,Pacbrake Airbags,Hellwig Rear Swaybar)
2006 Northern Lite 9.6 Classic (Torklifts & fastguns)
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Matthew_B
The boonies near Dallas, Oregon
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You should be able to find a 12V negative common. Do not rely on the AC safety ground and certainly do not rely on the AC neutral as the return for DC circuits. The neutral should be fully isolated in an RV.
In my camper the DC common was originally a giant wire nut tying the circuits together. I've replaced it with a busbar for a connection I'm more confident of.
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Matthew_B
The boonies near Dallas, Oregon
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dmax lover wrote: On my Northern Lite there is a sticker on the forward passenger side tie down bracket on the camper that says "acts as ground" or something like that... So there is a DC ground path provided by tie downs, etc.
There is also a ground line in the connector from the truck.
jeff
RIVA requires the "frame" to be connected to the AC ground and DC negative. Since there is no camper frame, many camper manufacturers run an AC ground wire and a DC negative lead to one of the tie down mounts. Most often this is the left front tie down that is grounded.
This ensures there is no way for an AC short to energize the frame of the truck.
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JoeChiOhki
Sauvie Island, OR
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Body grounds exist in some TCs. Arctic Fox had a 8 gauge line that goes to one of the forward tie down brackets to act as a backup ground line through the truck's chassis.
In my old camper there are two separate ground connections to the outside skin of the camper, however these are mainly meant to act as grounds for the running lights / turn signals, though for some reason my heater is grounding through it as well, I'll be taking a crack at that when I pull the bottom of my pantry cabinet to reframe it and use plywood instead off a ultra thin piece of particle board that currently makes up the floor.
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MTBob
Montana
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Matthew_B wrote:dmax lover wrote: On my Northern Lite there is a sticker on the forward passenger side tie down bracket on the camper that says "acts as ground" or something like that... So there is a DC ground path provided by tie downs, etc.
There is also a ground line in the connector from the truck.
jeff
RIVA requires the "frame" to be connected to the AC ground and DC negative. Since there is no camper frame, many camper manufacturers run an AC ground wire and a DC negative lead to one of the tie down mounts. Most often this is the left front tie down that is grounded.
This ensures there is no way for an AC short to energize the frame of the truck.
Yes, the tie down on the left front has a tag next to it saying it is a grounded connection.
I understand from Matts's comments that the AC ground and DC neutral are connected together (though that contradicts some earlier poster's comments). Matts's comments are consistent with the voltage readings I get when measuring from AC ground buss which shows 12/14 volts DC to the DC positive circuits. This tells me that the DC negative lead IS connected to the AC neutral buss (the buss with white wires).
So, am I right that I have two choices? 1) run a separate 12v negative lead from the battery or 2) connect to the AC neutral buss.
I'm leaning towards running a separate wire to the battery neutral post simply because I don't yet fully understand the circuitry between the AC and DC system. I'd really like to get a wiring diagram of the camper... is that possible?
Thanks for all your help.
Bob
* This post was
edited 11/20/09 09:02pm by MTBob *
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MTBob
Montana
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Oh, one other thing. It seems like a insecure way to establish a ground connection to the truck by using the camper tie down as the conductor. The connection relies on the pressure connection between the upper and lower hooks AND it relies on the tie down actually being connected. If this connection to the truck is important - and I assume it is - using the a tie down as an electric circuit seems like a really bad idea.
Bob
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Matthew_B
The boonies near Dallas, Oregon
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MTBob wrote:This tells me that the DC negative lead IS connected to the AC neutral buss (the buss with white wires).
You're treating neutral and ground on the AC system as the same. They're not.
The only place the neutral buss is connected to ground is back at your house service panel. If you disconnect the camper you shouldn't have any continuity between the neutral buss and ground. If you do you've got a ground fault that needs to be connected.
There should be continuity between the ground (green or bare wires) and DC negative. But this shouldn't be used for 12V returns since the purpose of those wires is solely for the safety bonding of the 120V system.
Interconnecting 120V grounds and 12V negative returns is how Norcold ended up with a whole bunch of burned up refrigerators.
MTBob wrote:So, am I right that I have two choices? 1) run a separate 12v negative lead from the battery or 2) connect to the AC neutral buss.
Don't do #2. Connecting anything to neutral other than the returns of 120V circuits sets you up to a bunch of scenarios that can result in fire or electrocution.
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enblethen
Moses Lake, WA USA
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MTBob:
You are still confusing your AC neutral with DC negative/ground.
DO not connect any grounds to your AC neutral. The neutral is the white wire in your AC system.
The ground in the AC system is the bare or green wire.
Bud
Suzuki XL7 pushing Pace Arrow
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covered wagon
USA
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The charge voltage to your camper batteries can be greatly reduced while driving if your DC ground is thru the tie down. I did at test with the ohm meter and found much resistance thru the tie down itself.
I ran a separate ground wire to the truck battery as a test and it increased my charge voltage by almost one full volt at the camper batteries. That is significant.
Would like to add that my tie downs are non corrosive stainless except for the TorkLifts to the truck frame.
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AnEv942
CA
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MTBob: "I understand from Matts's comments that the AC ground and DC neutral are connected together"
What Matt said is correct but not the way your read- KEY WORD is "ground", NOT AC white/neutral bus
MTBob: "So, am I right that I have two choices? 1) run a separate 12v negative lead from the battery or 2) connect to the AC neutral buss."
NO! you only have 1 choice-connect 12v Neg to the neg. lead of battery, either hard wired or AC "ground" buss which should be seperate from AC nuetral buss.
I think Id also just add a bus thats hard wired to -12V. (if theres any confusion or there are white and green/bare wires tied together) youll prob be adding stuff down the road. (Or if you had a 12v chassis ground.)You may have a buss thats already there -12v and it may be shared with the AC "ground" (bare or green ac wire)
IN theory if you connect the -12v ground from say a light to the AC nuetral buss, light shouldnt work. However as your camper has had previous owner(s) that have done some wiring there may be cross connection between AC nuetral & ground. But I would not add to it.
MTBob:-"..using the a tie down as an electric circuit seems like a really bad idea."
If there isnt also a ground wire in your truck plug Id agree and add one.
I know im repeating the clarifications others have stated-but it seems important for MTBob and any others reading this
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