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Old 08-25-2012, 08:33 AM
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Default Electricians

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I notice in my main service box the ground (bare wires) are all tied into a bar on the left side of the breakers and the neutral - white wires) are all tied into a bar on the right side of the breakers. BUT then both bars are connected by a maybe 6 guage cable! And there is only ONE ground going out of the box. This is 1990 construction. Is this right?

And if both are the same why do I need a four wire cable from my generator to the box? And is there any big problem if I accidently switched the neutral and ground?

Thanks!
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Old 08-25-2012, 08:36 AM
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This is going to get violent.

Bonding inside the box is normal. The question about your generator gets complicated and I don't think you'll get a good answer here. It is worth doing some research to see if your model generator has a floating neutral, which I believe influences the correct answer.
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Old 08-25-2012, 08:51 AM
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I just did this. Your generator is what is know as a seperatly derived power source. Your nuetral of your house is grounded at the panel. Since the nuetral is unswitched the generator does not need a seperate ground. The ground and nuetral should be bonded together at the generator as well as bonded to the generator chassis.This is internal wiring on the generator, not something you do. Use the two hots and the nuetral from the generator and you should be all set. If you are making your own cord use W for nuetral and X & Y or Z for your hots. The ground lug ends up grounded through the wiring in the generator.

The hots gets fed to your panel through a 2 pole breaker. This breaker if done properly has a plate that blocks it from being turned on while the main is on. The main gets turned off allowing the plate to slide up and allow your generator breaker to turn on. This is extremely inportant so you can't backfeed power to the utility. You can kill someone working on the powerlines. Please be safe.
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Old 08-25-2012, 08:58 AM
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Originally Posted by Flot View Post
This is going to get violent.

Bonding inside the box is normal. The question about your generator gets complicated and I don't think you'll get a good answer here. It is worth doing some research to see if your model generator has a floating neutral, which I believe influences the correct answer.
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Old 08-25-2012, 09:51 AM
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Thanks

I am all set on the generator end - I have been using this for 3 years now. I do have the 4 prong cord from the gen to outlet and 6/3 with ground cable to the box (in case some day I get a 40 amp or larger gen). Just was curious that inside the breaker box they were joined. I sorta thought the neutral went out the lines in the road and the other to the grounding stake at my home.

Whatever I have is totally legal (whole house transfer switch or something - cant run on line and generator at same time - one or the other- wasn't cheap) - thank you. It was just as I was adding another circuit and noticed the wiring inside the box with the cable connecting both bars.

My 4500 Coleman back up to the backup generator is an older 3 wire system. Haven't used that for 10 years - in fact I am gona run it now before I forget! Did all the gas transfers these last two months so I know have all gasoline with stabilizer newer than 6 months. Reday (somewhat) for the next big one. Last year we already had it by now!
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Old 08-25-2012, 10:34 AM
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If you main is in the panel, you equipment ground and "neutrals" are to be connected. If your main is outside at the meter or prior to the panel, your panel is a sub and therefor the grounds and "neutrals" should be isolated. The size of the bonding jumper used (you said a 6 right?) would indicate to me that your service is 100 amps per 250.66 of the national electrical code.

Masters license in Massachusetts.
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Old 08-25-2012, 12:27 PM
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You really need the 4 wires to keep things on the safe side. You could run the generator without a ground...but you shouldn't! At the panel, all your neutral returns are bonded to ground. If you can imagine what would happen if you removed one of those neutrals and measured voltage from the neutral to ground you would have 110v if that circuit had devices on at the time. This would not be true with ground, it would always measure zero (or very close to zero) from ground to ground. So the ground to genny protects the equipment and anyone around the equipment, and the neutral is a return leg to the panel if you run extension cords from the genny.
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Old 08-25-2012, 03:40 PM
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If your transfer switch switches the nuetral you DO need to have 4 conductors and groud the generator.
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Old 08-25-2012, 05:37 PM
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I have never seen a generator transfer switch that switches the neutral. In fact from what I remember from studying for my exam, the only time you can (and must) switch a neutral is in a class 1 hazardous location. The disconnect for a gas pump for example.
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Old 08-26-2012, 04:32 AM
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Originally Posted by Jaw1215 View Post
I have never seen a generator transfer switch that switches the neutral. In fact from what I remember from studying for my exam, the only time you can (and must) switch a neutral is in a class 1 hazardous location. The disconnect for a gas pump for example.
Yes, I agree. The reason I posted that is sometimes used commercial equipment ends up in a house. Most likely he has a normal transfer switch. I see from your earlier post you hold a Masters. I do not so any other questions the OP may have I will leave to you. Electrical safety comes first.
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Old 08-26-2012, 08:01 AM
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Yes I have 4 wires in all circuits except the back up to the back up which has that old 220 plug with the dual horizontal prongs. - and the round one is the neutral. That init runs but is noisy has no wheels an dis old so it may never be used again for the house (hopefully!)

Checked all outlast week - everything is running smooth. Got my son's house set up too..

thanks again this is the real THT Dovkside chat the pros offering their help

r
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Old 08-27-2012, 05:12 AM
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Also chk your genny for an earth ground lug, mine has one. I use jumper cables from the genny ground lug to an old lightning ground stake that was used for an old tv antenae, I also drove a 4 ft piece of copper pipe into the ground almost flush to the ground out back near my shed to run the genny out there if necessary . This guarantees earth ground at the genny.
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Old 08-27-2012, 05:52 AM
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Originally Posted by KeithS View Post
Also chk your genny for an earth ground lug, mine has one. I use jumper cables from the genny ground lug to an old lightning ground stake that was used for an old tv antenae, I also drove a 4 ft piece of copper pipe into the ground almost flush to the ground out back near my shed to run the genny out there if necessary . This guarantees earth ground at the genny.
You should only have one ground on the system, so if you are ground staking the generator and bonding through the main panel ground stake I don't believe that is recommended. That is why sub-panels must have isolated neutral and ground runs back to the main panel. Since the ground stake is returning voltage to earth you can get currents running through the ground from one ground stake to the other. I don't completely understand this though, because your neighbors house would essentially be the same (with their own ground stake etc.).

Anyhow, I think the recommended method is one earth ground point.
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Old 08-27-2012, 05:58 AM
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If you read the manaufacturers installations instructions (blasphemy i know), it will tell you to drive a ground rod and install a wire (probably a #10 depending on the size of the genny) from the lug on the chassis to the ground rod. Again, neutrals and grounds are isolated here as well.. See separate structure in the NEC. The term structure is VERY vague in the definitions.
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Old 08-27-2012, 06:09 AM
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Originally Posted by Jaw1215 View Post
If you read the manaufacturers installations instructions (blasphemy i know), it will tell you to drive a ground rod and install a wire (probably a #10 depending on the size of the genny) from the lug on the chassis to the ground rod. Again, neutrals and grounds are isolated here as well.. See separate structure in the NEC. The term structure is VERY vague in the definitions.
I wonder if that is just a chassis ground and isolated from the electrical (generator ground)? Seems like that is probably the case. I could never completely understand why my sub panel couldn't be earth grounded at the sub panel when it would be no different than my neighbor having a different ground stake since we both pull power from the same place.
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Old 08-27-2012, 09:15 AM
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The reason Is called "Parallel Path". it has to do with electricity seeking the path of least resistance. I am certainly no scientist so I won't attemp a more detailed explanation.
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Old 08-27-2012, 12:57 PM
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I would put the genny close enough to the service entrance so the ground can be connected to the existing ground rod.

A single ground is always better, no chance for any difference in potential.
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