Grounding an inverter

[ottow]

So, I have a eBay inverter (https://www.ebay.com/itm/Power-Inver...QAAOSwAF5UYusW) and while it works just fine for most use it does generate a slight bit of 50hz hum when used with anything audio-related.
The unit has no external ground/earth post, and came with no instructions re grounding.
Opening it up, I am finding that the ground connector in the outlet is not connected at all...
My multimeter detects no connection between the 12v posts and any of the outlet poles, nor the chassis.

I'd like to get rid of the hum if possible, but am not sure how.
Is it even possible?

Thanks,

Otto

[CharlieJ]

The lack of a safety ground (low impedance, redundant return path to the source) makes this a very dangerous piece of equipment.

Recommend you replace it immediately.

[rwidman]

I have to agree with CharlieJ, you have bought something that's cheap enough, but not suited for a boat. The hum in audio applications is the least of your worries.

Buy something that's intended for use on a boat and something that comes with installation instructions. There are several manufacturers to choose from. A look at the West Marine website will give you some choices.

[billknny]

Originally Posted by ottow

So, I have a eBay inverter (https://www.ebay.com/itm/Power-Inver...QAAOSwAF5UYusW) and while it works just fine for most use it does generate a slight bit of 50hz hum when used with anything audio-related.
The unit has no external ground/earth post, and came with no instructions re grounding.
Opening it up, I am finding that the ground connector in the outlet is not connected at all...
My multimeter detects no connection between the 12v posts and any of the outlet poles, nor the chassis.

I'd like to get rid of the hum if possible, but am not sure how.
Is it even possible?

Thanks,

Otto

So, no ground, anywhere??? When you plug in your AC appliances into this fine piece of equipment, the safety ground wire is not connected to anything? Ouch!

That's not just bad that's really dangerous, and needs to be fixed. It's a bit difficult to give you simple instructions on how to do that without knowing quite a bit about your boat's AC and DC systems. Do you have a generator? Shore power? Is your boat bonded? Is this the only inverter aboard? is it hard wired to anything or just used as a portable?

I think in this case you are getting what you paid for. Forget the annoying hum on your stereo, to just make this safe will cost more than you saved by not getting a "real" marine inverter from a company who designs products that are not likely to kill their customers.

[a64pilot]

It could be double insulated like many electric hand tools like drills are, you know the ones with only a two wire plug. Called a “floating ground”
https://en.m.wikipedia.org/wiki/Floating_ground
IF it’s double insulated, it’s not unsafe.
However if it had a 120V ground it could be connecting the AC and DC grounds together, something you want to keep separate on a boat.

On edit, I have never, ever seen anyone ground a portable generator, all I have ever seen used are placed on the deck and plugged in.

[rwidman]

Originally Posted by a64pilot

It could be double insulated like many electric hand tools like drills are, you know the ones with only a two wire plug. Called a “floating ground”
https://en.m.wikipedia.org/wiki/Floating_ground
IF it’s double insulated, it’s not unsafe.
However if it had a 120V ground it could be connecting the AC and DC grounds together, something you want to keep separate on a boat.

On edit, I have never, ever seen anyone ground a portable generator, all I have ever seen used are placed on the deck and plugged in.

A double insulated tool or appliance is not unsafe but a power source that's not grounded and has no provision to ground whatever is connected to it (in this case, his boat) is pretty dangerous.

What you've seen other people do is irrelevant. People who don't know better do a lot of unsafe things. It's not a goal we should try to achieve.

[Frankly]

I would not expect to find any electrical connection between the DC input and the AC output. Would expect to find a ground wire (typically green) connection between the receptacle ground pin and the chassis. ABYC does require that one side of the AC line (called neutral and colored white) be connected to the ground but one of the most popular inverters found on boats (Honda EU 2000) leaves this connection out.

You can make a case for a simple 120 VAC system leaving this ground neutral connection off makes a safer system but sometimes in code making it is just simpler to have a blanket requirement.

Not sure any of this has any relation to your hum issues. Might just be the result of poor filtering or waveshape on low price inverters.

[foggysail]

The so called safety ground on your inverter would only ground the inverter’s case. Most inverters today that I am familiar with do not use a power transformer to output the ac voltage produced by it AND DO NOT HAVE THE GROUNDED CONDUCTOR found with distributed ac power by utilities and the inverter’s outputs must be isolated from external grounding

[donradcliffe]

The howling wolves don't realize you're in Europe, and they do wire differently over there.

[rwidman]

Originally Posted by donradcliffe

The howling wolves don't realize you're in Europe, and they do wire differently over there.

Dude! Being electrocuted is the same worldwide.

BTW: The inverter is made in China.

[hellosailor]

There is no "earth ground" on a boat, since the boat is unattached in the water. The OP can find many references on the internet dealing with the pros and cons, the reasons why one should or shouldn't try to actually "ground" equipment in this use. Some directed at marine users, more directed at portable theatrical (movie, etc.) location lighting equipment. There ARE valid reasons to go both ways.

Staking the "ground", the negative side, to the AC side's ground or neutral, or a real ground rod, may get rid of the hum, but that carries other hazards. The user needs to make their own decision about what is best for their use, and the people who may contact it.

For audio filtering, a relatively high impedance ground path connection or filter might do that trick. If it was easy, there would be audio engineers all over the place.(G)

[sailorchic34]

In order to be electrocuted you have to be part of a current path. Birds can sit on a 12kva power line as there is no current path. With an inverter or inverter generator aboard a fiberglass boat, coming in contact with one side of the circuit generally will not cause a shock. Why, because the inverter is not ground referenced.

That is there is not a circuit path from either leg of the inverter to ground. At most there is a sort of path to dc ground in non transformer inverters. This is unlike shore power, in the USA, which is ground referenced. That is there is a current path from one "hot" leg to ground or earth.

On shore power there is an earth ground reference so there is some danger, Lots on a metal hull, far less on a fiberglass hull as a wood floor tabbed to a fiberglass hull acts as an insulator.

Of course ABYC says that ac ground should connect to dc ground. Myself I personally believe that creates more issues then it solves and I personally choose NOT to connect AC ground to DC - . YMMV

[zboss]

Let’s simplify this... what is the majority of grounding situations for the majority of inverters on boats? Where do you run the ground to... if read a few inverter manuals and they generally say run to the engine block but a few just have a diagram with a grounding symbol and no clear instruction on where to run the ground.

[billknny]

Originally Posted by donradcliffe

The howling wolves don't realize you're in Europe, and they do wire differently over there.

Some us do understand that 220V is used on a European boat. Some of also understand that a safety ground is used in Europe as well. People there don't like to die either.

Maybe you could explain to us how European wiring standards eliminate the need for a safety ground?

[billknny]

Originally Posted by sailorchic34

In order to be electrocuted you have to be part of a current path. Birds can sit on a 12kva power line as there is no current path. With an inverter or inverter generator aboard a fiberglass boat, coming in contact with one side of the circuit generally will not cause a shock. Why, because the inverter is not ground referenced.

That is there is not a circuit path from either leg of the inverter to ground. At most there is a sort of path to dc ground in non transformer inverters. This is unlike shore power, in the USA, which is ground referenced. That is there is a current path from one "hot" leg to ground or earth.

On shore power there is an earth ground reference so there is some danger, Lots on a metal hull, far less on a fiberglass hull as a wood floor tabbed to a fiberglass hull acts as an insulator.

Of course ABYC says that ac ground should connect to dc ground. Myself I personally believe that creates more issues then it solves and I personally choose NOT to connect AC ground to DC - . YMMV

I think you are confusing things... like the difference between the netural wire in the AC circuit and the safety ground.

A safety ground is most certainly still needed on a boat. There are several ways to rig it depending on how the boat is wired, but to say that it is not useful or needed it is NOT true.

My boat has AC safety ground connected to the bonding system, NOT to the DC negative (which floats separate from the bonding circuit). Other boats are wired differently.

By your logic it would not be possible to be shocked by holding the hot wire output of a 220V inverter while standing in a wet bilge. Do NOT do this experiment at home!

In the case of this inverter it might be correct to connect the safety ground to the inverter neutral. That is "ground reference" for the inverter. But to have it connected to NOTHING is by no means correct.