Inverter earthing????

Submitted: Sunday, Feb 17, 2008 at 21:30
ThreadID: 54682 Views:5541 Replies:6 FollowUps:6
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I purchased a 150w Powertech Inverter at the C&C Show on the weekend.It has a wingnut on a bolt thread which is for earthing? The instructions talk about driving an earth stake into the ground just like generators tell you to do. Then it says if mounted in a vehicle to use this earth to run to the chassis. Anyway i tested it without the extra earth and it works fine. It's easy enough to run the extra wire. Just wondering why it's recommended when the connections already have a +ve and a -ve connection?
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Reply By: Dunaruna - Sunday, Feb 17, 2008 at 21:39

Sunday, Feb 17, 2008 at 21:39
In your house, the entire electrical system is grounded.

A generator or an inverter has that wingnut connection for exactly the same reason, it is there to protect you in case of a malfunction. If the unit should short to ground it will bypass your body.

I would not for one minute suggest you don't do it, but I don't know anyone who has bothered (including me).
AnswerID: 288039

Follow Up By: Bonz (Vic) - Monday, Feb 18, 2008 at 22:13

Monday, Feb 18, 2008 at 22:13
The reason your house is grounded is because all the "real" electricity is referenced to ground, so if you happen upon "shocko" and you are in contact with the ground then you'll get a belt.

The inverter isn't referenced to anything other than itself, thats half the problem with them cause if yo get across the active and neutral of them then its the little fuse of circuitry inside that'll protect you. I dint see how earthing the thing will make a difference. Mike will know tho.
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FollowupID: 553511

Reply By: Derek from Affordable Batteries & Radiators - Sunday, Feb 17, 2008 at 21:58

Sunday, Feb 17, 2008 at 21:58
Hi Brew

Earth points are common and our own 500W Marine inverters also have this earth bolt. It is best to ground it to the chassis as they can build up some static (Just like plastic shoes on a nylon carpet) not deadly but gives you a fright. Good question as I must answer it at least once a week.

You can see the earthing screw near the fan on the picture below. (LH side)


AnswerID: 288051

Reply By: Paul Grabonski. Vic - Monday, Feb 18, 2008 at 04:02

Monday, Feb 18, 2008 at 04:02
Powertech inverters are quality inverter that are electrically isolated and DO NOT need an earth.
Earthing an electrically isolated inverter increases the danger of electrocution.
Powertech inverters are the house brand of Jaycar Electronics

Inverters that are NOT electrically isolated are junk and dangerous.
Plenty of quick buck rip you off dealers selling dangerous inverters.
AnswerID: 288092

Follow Up By: feral - Monday, Feb 18, 2008 at 08:06

Monday, Feb 18, 2008 at 08:06
If Powertech inverters do not need an earth, why do they provide one and their instructions clearly state how to wire it either to chassis or using a stake into the ground method?

Confusion abounds it seems.
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Follow Up By: Member - Kiwi Kia - Monday, Feb 18, 2008 at 13:47

Monday, Feb 18, 2008 at 13:47
Hi feral, perhaps they should call it "bonding" and not earth connection.
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Follow Up By: Dunaruna - Monday, Feb 18, 2008 at 18:15

Monday, Feb 18, 2008 at 18:15
I must own the ONLY powertech inverter in the world that has a chassis earth wingnut.
FollowupID: 553443

Reply By: Member No 1- Monday, Feb 18, 2008 at 08:09

Monday, Feb 18, 2008 at 08:09
not sure about the need to earth generators

From the office of The Technical Regulator (South Australia)

"Most portable single phase generators supply power to the load via a 3 pin socket outlet mounted on the generator. At the socket outlet from the windings of the generator a live cable ‘out’ is connected to the active pin and a live cable ‘in’ is connected to the neutral pin.

There Is Nothing Connected To The Earth Pin Of The Socket Outlet From The Windings Of The Generator.

Therefore an earth fault on exposed metal of a metal clad appliance which would be normally considered dangerous is safe as there is no return path back to the windings. The winding is in effect isolated above earth. Also it is essential that the frame of the generator is not connected to the end of the winding as this may provide an alternative path back to the winding destroying the technique of isolation. For a person to receive an electric shock, contact between live ‘out’ and live ‘in ‘or (active and neutral pins) must be made. A Residual Current Device (RCD) will not work as a protective device with this technique."

AnswerID: 288100

Follow Up By: Member No 1- Monday, Feb 18, 2008 at 09:22

Monday, Feb 18, 2008 at 09:22
here is full article
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FollowupID: 553359

Follow Up By: Member No 1- Monday, Feb 18, 2008 at 09:25

Monday, Feb 18, 2008 at 09:25
check out my rig page..its much clearer there
FollowupID: 553361

Reply By: Notso - Monday, Feb 18, 2008 at 10:18

Monday, Feb 18, 2008 at 10:18
I think you'll find that the reason they say to earth the thing is because if there is a fault to earth in you appliance that is plugged into the inverter etc, there is no path to earth. So it wouldn't throw a circuit breaker etc. Then if you touch the appliance and create a path to earth it will use your body and you'll suffer the consequences.

AnswerID: 288118

Reply By: Member - Mike DID - Monday, Feb 18, 2008 at 14:35

Monday, Feb 18, 2008 at 14:35
The safety factors from earthing depend very much on the situation - single/many loads; double-insulated/earthed; short cabling/extensive fixed cabling etc

The safest option for an Inverter or generator, is to have it earthed and to use an earth Leakage Circuit Breaker.

If you have an insulated generator and load, then earthing the "Neutral" can actually increase the chance of a fatality. If you contact the "Active" while in contact with earth, and the "Neutral" is not earthed, then no current will flow through your body. If the "Neutral" is earthed you will have 240 volts across your body.

When power feeds multiple houses, retaining insulation of Active and Neutral is unlikely, so for house power, Multiple Earthed Neutral is the only realistic option.

Remember that the 240 volts from an Inverter or Generator can kill you in one-tenth of a second - exactly like the 240 volts at home.
AnswerID: 288145

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