Grounding

No solar. 15 amp shore or generator to run Genius2 which charges battery(s). Should shore connection be grounded to frame? Should inverter be grounded to frame? Should leisure battery be grounded to frame? When shore available, separate outlets available to run TV etc. If grounded to frame it would be only connection to DC system.

Comments

  • BB.BB. Super Moderators, Administrators Posts: 28,859 admin
    Welcome to the forum SB...

    Grounding is one of the most complex questions out there. And and RV with multiple AC and DC power sources makes it even more complex.

    In general, it is normal to ground the DC Battery Negative Bus to the RV frame. If there is a short circuit from hot (+) to ground, it should pop the fuse/breaker protecting that wire--Rather than making that metal "thing" not.

    In RVs, you may have the metal frame, sheet metal siding, plumbing, electrical boxes, etc... And the grounding among all that stuff being "iffy" (many RVs use plastics and wood studs which support and insulate metal items).

    Assuming you are in the USA (New York?), 120/240 VAC power has the neutral ground bonded to the earth/green wire (in a home, it is usually done in the main breaker/fuse panel for the home). This is done for safety. Both the white and green wires are always at zero volts (ground potential), as well as plumbing, natural gas, many appliances (generally, metal appliances are grounded to the green wire through a 3-prong plug). The idea is that if the Hot wire (Black or Red typically) gets exposed and shorted to metal (like a plumbing pipe or sink), the green wire will short circuit the AC output and trip the breaker--And turn everything off (on that branch circuit).

    With an RV, the AC neutral bonding is provided by the Home/RV Park. When you disconnect the external power connection, your white wire to green wire ground bond is "gone".

    In larger RVs and those more complex power systems, typically, the RV will do the Neutral to Green Wire bonding inside the RV. Typically at the Genset and/or AC inverter. (and the green to white wire bonding is lifted by a relay when shore power is connected).

    This is complicated, and depends on the exact hardware (genset, AC inverter, size of devices, etc.) to know what to do. Typically, from what I have seen, gensets and AC inverters larger than ~3,000 or 3,500 Watts have the green wire and white wire "bonded" internally to the device (I am not an expert, just what I have seen). You can setup relays that will do the auto-bonding/bond lifting as needed.

    Now, back to reality... If you have both a white/green wire bond at the shore power source, and a white/green wire bond "active" in the RV, it will typically trip the ground fault breaker at the shore power outlet--Hence the reason to not do both at the same time (shore power bond + RV bond).

    Other than for safety (very important), there are usually very few reasons why AC ground bonding is done (fluorescent tube fixtures start better/more reliably, spark ignition for gas appliances works, etc.).

    So, assuming none of the above two reason apply to you (neutral/ground bonding of AC power inside the RV), another solution (for safety) is to use ground fault outlets--Especially on the exterior AC outlets, and near the kitchen/bathroom sink. The GFI will trip if there is a short (or person grabbing a "hot wire") and shut of the AC power to that outlet.

    You could, for example, put an GFI on the main output of your AC inverter--But if that tripped, you would lose 100% of your AC power (example, your mixer falls in sink, and your overhead lights go out on a dark night)... So, I suggest that GFI be broken up so that if a power tool trips the GFI, the other circuit(s) are still powered.

    If you have GFI outlets to your exterior outlets (and interior near water outlets), then you really do not "care" what is providing your AC power (shore power, genst, AC inverter in RV)--You are safe. And you can use separate AC outlets for Shore vs AC inverter power, or you can use some sort of relay/shore power transfer switch to power an outlet from either AC inverter or shore power--It is really your choice.

    There is another issue with grounding... You mentioned TV, but HAM radio and folks that listen to AM radio find--Grounding or not of DC/AC power can affect receiver performance. And even things like LED/CFL lighting vs standard filament can be the difference between between a TV receiving signals or not. Generally, ground bonding is not a big factor in RF interference, but it can be a factor in what solutions are used.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • sandebagger2usandebagger2u Registered Users Posts: 2
    Bill, Thanks. Very informative. I'm trying to KISS. It's just a Chevy van. Only have 1 now, but getting another 100ah battery. Genius 2 does a good job of charging battery. So I will leave the shore or generator source unconnected to frame, the inverter connected to - battery and the additional inverter ground connected to ground bus bar. Ground - bus bar to frame. (thru shunt maybe). Not sure but can't live forever.
Sign In or Register to comment.