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I'm setting up electronics in a camper van, and I'm wondering about grounding the 230V appliances powered by the inverter. Is it safe (for me and for the components) to connect the grounding wire for the 230V appliances to the vehicle chassis (which is also a common negative for the leisure and starter batteries.)

If yes, would it then be safe (for the components) to connect the vehicle chassis to Earth, for instance when the vehicle is parked somewhere where it can be plugged into a socket for charging which grants access to proper Earth?

circuit example

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    \$\begingroup\$ You should connect the inverter to the chassis. But you should also run a copper wire directly from the inverter to every 230 V load that has a GND connection. The reason is that sometimes copper wire connections to steel chassis go bad due to corrosion and whatnot. So it is good to make sure the GND path is low impedance. This is my opinion. I did not consult appropriate code or standards to verify that it is a requirement to do it this way. \$\endgroup\$
    – user57037
    Aug 20, 2022 at 23:31

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  1. Yes, this is in fact the safest way - for you and your electrical appliances alike.

Most of these inverters are in fact wired internally input negative to inverter chassis and to inverter outlet ground.

Even if your inverter lacks some of these connections, it is expected to wire it exactly as you pictured, connecting these 3 things together.

You can check for these connections (by reading the documentation of the inverter, by inspecting the internals or by an ohm meter / continuity checker) and wire the missing ones accordingly.

  1. Yes.

In some cases (e.g. when using a generator with a metallic chassis), you may need a separate ground rod in order to avoid dangerous voltages between the vehicle chassis, generator chassis and the real ground. Without it, you may get a refreshing feeling when getting in and out of the vehicle (i.e. a foot on the ground and a hand on a metal part of the vehicle.

When using utility power or doubly-insulated generator (those that look like a plastic suitcases), the outlet grounding does everything for you.

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Yes, it's ok for your appliances to connect to chassis GND. It's also ok to connect your chassis GND to shore power GND when you hook up.

Note that the inverter already connects (-) (battery/chassis GND) to its outlet GND. Check it with an ohmmeter. Thus, not only is the inverter outlet grounded, you don’t have an option for it not to be, because of the (-) wire being grounded. See below.

schematic

simulate this circuit – Schematic created using CircuitLab

When dealing with inverters you need to be careful about three things:

  • Make sure your inverter and shore power are isolated by a transfer switch. Never connect them together.

  • Make sure none of your loads bond GND to neutral, unless your inverter allows it.

  • Be realistic about the kinds of loads the inverter + battery can handle.

The reason is for not bonding neutral is, low-cost inverters are push-pull on both H and N legs. That is, H is 120VAC with respect to chassis GND, and N is also 120VAC to chassis GND. H and N are 180 degrees out, so they measure 240V with respect to each other. You can check this with a voltmeter.

More expensive inverters have a floating secondary, so these will allow a neutral-to-GND bond.

Let's talk about being realistic. In a van, why do you need an inverter, let alone 240V?

Most people want a fridge. But, you can get a 12V/240V type with a Danfoss compressor. It can automatically switch over when you connect shore power. They're surprisingly efficient - mine runs on one 40Ah battery with a 200W panel.

Laptops? These can use USB-C these days. Phone chargers? Plain old USB or USB-C.

Oven? Microwave? Toaster? Running these on battery+inverter would be expensive and dumb in a van; these can be shore-power only thing.

Blender or other small hand appliance? Sure, that might be worth an inverter. But I've also seen USB-C ones (like the BlendJet) that work on USB.

Satellite Set-top box + Flatscreen TV? Yes, these tend to want wall power.

Starlink? Also wall power.

Power tool chargers? Unfortunately, also wall power.

So for the couple of small exceptions you could make do with a fairly small inverter (1000W or less.)

For my pop-up I keep a small 400W inverter for those limited cases, like someone's old laptop. Since then I upgraded my truck, which comes with its own 100/400W convenience inverter outlet in the bed. Kinda lame, but could do in a pinch.

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