Grounding

I was hoping someone could help me understand where to ground. I'm about to start some wiring on a travel trailer and I am not sure where to ground. I wanted to go with some DC and leave minimal things to run on AC but I am not sure how to ground this when using both. I'll be using solar and a generator, never hooking into shore power with this travel trailer. This whole thing is custom made so I'm not working off any existing wiring.

In a typical house wiring, I know the neutral and ground are tied together and grounded to a pipe outside. In a strictly mobile DC system it would be grounded to the chassis. However, I've read some things which have given me a moment of pause. Some things I've read have said to ground the negative terminal of a battery bank to the chassis. At the same time I've read not to ground the DC side of an inverter.

With a battery bank powering some DC lighting and some AC electronics, do I ground the DC side to the chassis or only the AC side?

Comments

  • mike95490mike95490 Solar Expert Posts: 9,362 ✭✭✭✭✭
    Re: Grounding

    The manual for the inverter will be your friend. Most mod-sine cannot be grounded. Most pure sine should be.

    And then - trailers frame/chassis, is not designed to be a current path, you still need to have power and return wires for both DC and AC
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
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  • Mustang65Mustang65 Solar Expert Posts: 42 ✭✭
    Re: Grounding

    The Jayco Eagle and it has the negative battery connection grounded to the frame, next to the battery box. It also has a 10AWG ground wire running from the battery ground point to the trailers battery controller. There is an 8AWG wire running from the positive terminal of the battery directly to the trailers charge controller (through a 30Amp Fuse). I have added a 250 watt solar panel and that is connected to a MorningStar MPPT60 (through a 30amp fuse) and the MPPT60 connects directly to the batteries (w/30 amp ANL fuse). I also have a 1500Watt PSI inverter that is connected directly to the batteries (300Amp ANL fuse) with the AC side wired to a female 30amp RV outlet, that I installed inside the shore power cable storage area. When I want to use the inverter I plug the shore power cable into the RV outlet that is connected to the inverter. 120VAC at all outlets. Prior to wiring, I contacted MorningStar and the Inverter's MFR to insure that I was correct in setting it up this way. Has been working great for about a year now. I plan on running an 8AWG cable from the trailers charge controller's negative connection directly to the batteries.
    Don
  • BB.BB. Super Moderators, Administrators Posts: 32,018 admin
    Re: Grounding

    Yep, that way will work well...

    Question on the charging of the trailer from the vehicle. Is this something you are going to because it is "free", or do you need the power from the vehicle when towing to recharge the RV?

    In general, it is difficult to get very much charging current through the DC wiring (maybe 10 amps or so?). Also, the vehicle typically charges to ~13.8 to 14.2 volts while the typical deep cycle storage battery would like around 14.5 to 14.75 VDC (flooded cell).

    If you really need to get a goodly amount of energy from the two vehicle, you probably need a DC to DC battery charger or an 120 VAC inverter installed in the car and use the AC to DC battery charger in the RV to get the batteries quickly/properly recharged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Mustang65Mustang65 Solar Expert Posts: 42 ✭✭
    Re: Grounding
    BB. wrote: »
    Yep, that way will work well...

    Question on the charging of the trailer from the vehicle. Is this something you are going to because it is "free", or do you need the power from the vehicle when towing to recharge the RV?

    In general, it is difficult to get very much charging current through the DC wiring (maybe 10 amps or so?). Also, the vehicle typically charges to ~13.8 to 14.2 volts while the typical deep cycle storage battery would like around 14.5 to 14.75 VDC (flooded cell).

    If you really need to get a goodly amount of energy from the two vehicle, you probably need a DC to DC battery charger or an 120 VAC inverter installed in the car and use the AC to DC battery charger in the RV to get the batteries quickly/properly recharged.

    -Bill

    Do I really need the tow vehicle to supply charging power. That depends on if I am running the refrigerator on 120VAC or gas. Normally, I run it on 120VAC, as we do not like pulling into a gas station with the fridge in LP mode (open flame), then the answer is yes. Could I just run the fridge only off of the solar panel during travel? If it was a totally clear day and the sun shinning brightly, the solar panel handles the load/charge perfectly. Unfortunately, during our travels is seems to be mostly cloudy, so the truck supplies part of the power.
    I have a 200+ amp alternator in the truck so if it needed up to 30 amps, there would should no issue. I have the equalization cycle set to "MANUAL", so that I can disconnect all the electronics from the circuit before starting the cycle.
    Working great so far.
    Don
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