Grounding Puzzle

[sjordanjeff]

Hello!

My project is coming along pretty well. Just got the 110V shore power and 2000 W Inverter going. On shore power all is well. All outlets show wired correctly and WFCO 8725 functions perfectly with onboard battery. First test on the inverter, the outlets show show open on the ground (three prong tester). (all were fine on shore power) So, I'm thinking the only possibility is negatve on the battery and the ground lug on the 8725 should be tied together. When I do that, the three prong tester reads all lights on. That means Hot & Neu Reversed. Aside from this system seems to run fine on the inverter. Outlets will run tools etc no problem. No smoke, no overheating. All seems OK just wondering about those pesky tester lights...
Anyone have any thoughts? Thanks in advance.....

Jeff

[Dale M.]

Umm...... The WFCO 8725 is a AC to DC converter (battery charger)...

I don't think your wiring problem is with WFCO 8725..

What is inverter ( 12 Volt DC to 120 Volt AC) you speak of (make and model)...

Is there a safety ground (green wire) connection on inverter and is it tied common to safety ground (green wire) connections on AC wiring...

Dale

[sjordanjeff]

Dale,

The inverter in my system is a Chicago Electric Modified Sine Wave Converter. 2000Watts Continuous, 4000 Watts Surge. Harbor Freight. I do have the chassis ground on the inverter tied to the neg. terminal on the battery. And the ground on the 8725 to the neg. terminal on the battery as well. As I mentioned in my previous post, it all works fine, It's just the weird lights I get on the three prong outlet tester. Plus I'd like to know that it's right or it will bug me...... Thanks for your comments.

Jeff

[vreihen]

Can you plug the tester directly into the inverter? I don't think that those little tester gizmos are very complex, and I suspect that it could be giving false readings on modified sine wave power. If it shows a problem plugged directly into the inverter, I'd assume that it is the power waveform causing the fault and not your wiring.....

[Dale M.]

Dale,

The inverter in my system is a Chicago Electric Modified Sine Wave Converter. 2000Watts Continuous, 4000 Watts Surge. Harbor Freight. I do have the chassis ground on the inverter tied to the neg. terminal on the battery. And the ground on the 8725 to the neg. terminal on the battery as well. As I mentioned in my previous post, it all works fine, It's just the weird lights I get on the three prong outlet tester. Plus I'd like to know that it's right or it will bug me...... Thanks for your comments.

Jeff

Is the shore power safety ground tied to negative terminal on battery? (since you seem to be using it as common ground point)...

Dale

[sjordanjeff]

vreihen,

You were right on the money sir. Pluged the tester into the Inverter and the dreaded three lights on the tester went ON. Probably due to the cheapo outlet tester....Thanks for pointing out the obvious. I'm

Jeff.

[eamarquardt]

I'm confused.

I got out my tester gizmo and it has the same pattern as this one:



There doesn't seem to be a configuration when all three lights are on at the same time.

Here is a schematic of how the gizmos are wired inside:

http://en.wikipedia.org/wiki/File:Recep ... iagram.JPG

It's nothing but three neon lights wired in a specific pattern. I don't think they would be sensitive to "a modified sine wave" but maybe they are?

vreihen,

You were right on the money sir. Pluged the tester into the Inverter and the dreaded three lights on the tester went ON. Probably due to the cheapo outlet tester....Thanks for pointing out the obvious. I'm

Jeff.

So, are you saying all three lights come on at the same time? I'd test the gizmo on a house circuit, with known wiring defects, but I doubt there is a problem with it.

I'm open to enlightenment.

Cheers,

Gus

[wannabefree]

The observation in the first post is perfectly correct. Ground, on shore power, is tied to the neutral at one point in the system - the breaker panel. That point connects to the real "ground," usually a water pipe or copper rod.

Inverters don't have a real ground. They apply power to line and neutral and leave the ground unconnected. That's what your tester told you. This is considered OK by UL and CSA who put their approval stickers on most of these products. Is it OK? Probably. Look at all the 2-wire appliances you use. They don't have any ground to connect.

[eamarquardt]

The observation in the first post is perfectly correct. Ground, on shore power, is tied to the neutral at one point in the system - the breaker panel. That point connects to the real "ground," usually a water pipe or copper rod.

Inverters don't have a real ground. They apply power to line and neutral and leave the ground unconnected. That's what your tester told you. This is considered OK by UL and CSA who put their approval stickers on most of these products. Is it OK? Probably. Look at all the 2-wire appliances you use. They don't have any ground to connect.

Inverters, I gather, are kinda like isolation transformers where the neutral isn't connected to ground (making it harder, but not impossible, to get shocked). Still confused as to how all three lights are coming on at the same time. Open neutral is indicated by only one light beng lit.

Cheers,

Gus

[sjordanjeff]

Gus/all,

My three prong tester is an AMP brand. I've had it 30+ years. The light patterns shown on it don't match your more modern example. The all lights, or, three light pattern I mention, says Hot/Neu - Rev. That is what I get when I plug the tester into the Inverter. The way my system is set up, I can't have my Inverter and shore power on line at the same time. So when on the inverter, the system has no real ground present. Thanks to all who helped me see through the fog. Best regards, Jeff