Grounding a Portable Generator

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Old 11-03-11, 08:39 PM
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Grounding a Portable Generator

The manual for my small portable generator says it needs to be grounded to a grounding rod.

Do I need to install a new grounding rod just for the portable generator or can I run 10 AWG wire to the existing house grounding rod (so both the house and generator would be connected to one grounding rod)? The existing house grounding rod is probably 15 feet away from where I plan on running the generator.

Thanks!
 
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Old 11-03-11, 09:34 PM
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The manual for my small portable generator says it needs to be grounded to a grounding rod
I dont think it says that. What is the make and model of the gen?

From my understanding the gen uses the ground from the home when you plug it in.

I believe its on job sites where you are powering tools that you use a ground rod.

Could be wrong. I am not an electrician, but just following my gen manual.

Mike NJ
 
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Old 11-03-11, 09:51 PM
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The manual is here - http://www.centuriongenerators.com/M...DFs/0H2583.pdf

On page 6, it says:

2.3.1 GROUNDING THE GENERATOR
The National Electrical Code requires that the frame and
external electrically conductive parts of this generator be
properly connected to an approved earth ground (Figure 8).
Local electrical codes may also require proper grounding of the
unit. For that purpose, connecting a No. 10 AWG (American Wire
Gauge) stranded copper wire to the grounding lug and to an
earth-driven copper or brass grounding rod (electrode) provides
adequate protection against electrical shock. However, local codes
may vary widely. Consult with a local electrician for grounding
requirements in the area.


The generator doesn't connect to the house with a transfer switch or anything. I just run extension cords.

So, does that mean that I now need a ground?
 
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Old 11-03-11, 10:13 PM
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From what I read here no. The frame is the ground because the gen is bonded.

Now I have to read more and see if my gen is correct because I go into a transfer switch.

http://www.osha.gov/OshDoc/data_Hurr..._generator.pdf


Mike NJ
 
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Old 11-03-11, 11:10 PM
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If using extention cords, I would ground it to the house ground rod.

For transfer switches...
Generator Groundig
 
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Old 11-03-11, 11:20 PM
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The rules for grounding a portable generator have changed significantly with the adoption of the latest (2011) National Electrical Code.

Current production of portable generators are required to have the neutral connection of a 240/120 volt output BONDED to the frame of the generator. These generators MAY NOT be connected to premise wiring (house wiring) UNLESS the transfer switch disconnects ALL CURRENT CARRYING CONDUCTORS FROM THE UTILITY SOURCE AND REMOVES THE NEUTRAL-EQUIPMENT GROUND BOND. This means that most transfer panels and transfer switches currently installed do not meet current code. By use of an approved transfer switch the generator becomes a "separately derived source" and has specific grounding and bonding requirements that are different from a "non separately derived source".

The reason for this change is to reduce hazards from "ground fault" occurrences.

For a portable generator with neutral-equipment bond AND used only with extension cords you DO want to run a grounding conductor to a proper ground rod.

My personal opinion is that the hazards from not using a grounding conductor are minimal. Understand that my opinion won't even buy a cup of cheap coffee unless accompanied by a dollar bill.

For generators connected to premises wiring the rules are different and I will discuss them if someone is interested.
 
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Old 11-04-11, 04:43 AM
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Very interesting post Furd. My transfer switch disconnects the two hot legs but leaves the ground connected which is also tied to neutral in the breaker box. I suppose disconnects that meet the new code will get a bit more expensive.
 
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Old 11-04-11, 06:21 AM
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Thanks for the info here, guys but it's a little over my head. Can you please help me and simplify the information?

I said that I don't have a transfer switch but that's not entirely true. I do have a Reliance Controls TF151W single circuit transfer switch that an extension cord can plug in to (link here - http://www.reliancecontrols.com/Prod...il.aspx?TF151W).

It connects to the generator with an extension cord and would only be connected in the winter and not in the summer. This transfer switch does connect to the household wire and I *THINK* it just disconnects the hot wire but I'd appreciate some guidance here.

So, I guess my questions are:

Should I connect my generator to a grounding rod?

If I do need to connect to a grounding rod, do I need to install a new rod or can I use the one that the current utility powered panel connects to (keep in mind, there is a good chance that the generator and panel could both be live and connected to the same grounding rod at the same time if sharing a grounding rod)?

Does it make a difference how/if I connect to a grounding rod depending on if the generator is connected to the single circuit transfer switch or not?

Thanks so much!
 
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Old 11-04-11, 07:38 AM
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Your generator should be properly grounded through the single circuit transfer switch. If it it was installed correctly, the house ground and the generator cord ground will be solidly connected to the metal frame of the transfer switch. The house grounding system is already earthed.

If the generator was completely divorced from the house wiring (e.g. unplug the fridge, then plug it in to the generator), then it would be recommended to connect the generator frame to your home's grounding electrode (rod) using a #10 copper wire.
 
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Old 11-04-11, 08:12 AM
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For generators connected to premises wiring the rules are different and I will discuss them if someone is interested.
So the code changed???? Yes interested please post.

I have neen trying to understand the whole derived/un derived thing and assume its the not the gen but the transfer switch that constitutes derived or un derived.

Generator Grounding


Mike NJ
 
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Old 11-04-11, 10:14 AM
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Originally Posted by lawrosa View Post
So the code changed???? Yes interested please post.

I have neen trying to understand the whole derived/un derived thing and assume its the not the gen but the transfer switch that constitutes derived or un derived.

Generator Grounding
Right. There are two types of transfer switches. One just switches the hots and also provides a connection to the house neutral/ground.

The other also switches the neutral (neutral switching transfer switch), and in that case, the generator would not be connected to the house ground via the neutral.
 
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Old 11-04-11, 10:21 AM
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...and why use a neutral switching transfer switch?

Following from the link below...

["Some portable generators are intended for use on jobsites, and therefore are subject to OSHA regulations for GFCI protection on all receptacles. These "contractor grade" generators have their neutral wire bonded to the ground wire to pass OSHA inspection on job sites. Since home and building main load centers also have the neutral bonded to ground, a loop is created, comprised of the neutral wire and the ground wire. A small amount of current is induced in this loop by the running generator. and since the neutral wire passes through the ground fault sensor, the GFCI senses this induced current and trips the main circuit breaker in the generator.

When using these neutral bonded generators to power a house or building through a transfer switch, the neutral bond wire on the generator must be removed, preferably by a dealer or a qualified electrician. NOTE: After this action, the generator will no longer pass OSHA inspection on job sites. Contact your dealer to determine if the neutral bond can be removed, and we recommend that a dealer perform this task. Honda dealers may refer to Honda Service Bulletin #20 for instructions on removing the neutral bond. Once this is done, no modifications to your transfer switch installation are needed.

If the neutral bond cannot be removed, you have two choices. The easiest solution is to lift the ground wire coming from the generator inside the transfer switch, and secure it with a wire nut, by itself. This eliminates the loop. Your other choice is to install a Switched Neutral Kit (SNK) accessory with your transfer switch, available thru our website."]

See #7
Gentran Corporation: Generator Transfer switches for home & business
 
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Old 11-04-11, 04:00 PM
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When using these neutral bonded generators to power a house or building through a transfer switch, the neutral bond wire on the generator must be removed,
I would assume most portables are neutral grounded correct? I have neen running the gen through the transfer switch with no issues... Ugggg. More crude to worry about.

Sorry. Not to hijack the thread. I will research this and start a new thread possibly.


( Just read the gen it says floating neutral. I will have to look it up)

Mike NJ
 
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Old 11-04-11, 09:42 PM
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Understand that a system that was installed to the code provisions in effect at the time of installation is STILL acceptable. Only newly installed systems need to meet the current code provisions.

Jfinn, your transfer switch is grandfathered under the code in effect when installed. It does NOT isolate neutral from equipment ground and therefore your generator is NOT a "separately derived system" according the latest code definition. Your generator IS "grounded" through the equipment grounding conductor of the extension cord used between the generator and the transfer switch however that conductor is no larger than the current-carrying conductors.
 
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Old 11-05-11, 06:46 PM
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Thanks for all the information and clarification, everyone.

I picked up a clamp and some #4 solid core copper wire (that's all they had) at the hardware store today. I decided that if I'm going to use the generator, I'll just hook it up to the grounding rod no matter if it's connected to the little transfer switch or not.

It's not used frequently and easy enough to hook up so I'd rather over-do safety than wish I had later.
 
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Old 11-13-11, 08:28 PM
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This has been on of the best forums i've had the pleasure of joining in my quest for "how-to" with regards to my new Homelite 5000 generator with neutral bonded to ground configuration. I've poured over so many websites and can finally say I have a pretty good grasp of the issues and hazards involved in the different ways others have set up theirs for home backup and job-site use.One person mentioned in an article that he was in -formed by Gentran that if all else fails to simply lift the ground from the transfer switch comming from the generator and cap it to close the loop- would it not be fair to also not connect the ground to the transfer switch from the generator at all- simply ommit this conductor from the output from the 240 twist on plug-basically just use a 3 conductor cable to the transfer switch from the generator?Wouldn't this in fact prevent the parallel circuit feed-back to the generator?I realize the GFIC protection would not protect the circuits as they were desinged and the generator would also not be a seperatly derived system because the neutal would still be hard-wired to the system neutral through the transfer switch-but it would power the cicuits without triping the GFIC. Correct? What about ground the generator with a rod -mine is in thick rubber wheels and feet. will all this work until i get a new transfer switch that switches my neutral?
 
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Old 11-13-11, 08:45 PM
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I dont know jfinn. You have a bonded gen. I think your looking for trouble with two bond and grounding that generator with a rod. Your completeing the loop so to say...

If your hooking to the transfer switch I thing you need to lift the bond. The transfer switch has the bond. Then If you use as stand alone I would assume you re connect the bond.

Even though code says to bond for stand alone, I read that electricians would prefer a floating neutral in most if not all applications. I read its safer.

But I will need to find that document.

It seems many electricians are not sure. Thats why I posted that OSHA sheet, but here is from the guy that teahes it.


http://oshaprofessor.com/Portable%20...rds%203-05.pdf

Just want you to be safe.

Mike NJ
 
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Old 11-13-11, 09:49 PM
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In my opinion, the safest would be a neutral switching transfer switch, leave the generator neutral/ground bond in place, and connect the generator ground to the electric panel/house ground system.

Then a hot to ground short anywhere including the generator metal frame, then generator breaker trips. (Via neutral to ground bond at generator.)

Leak to ground anywhere from hot, and generator GFCI trips. (Via neutral to ground bond at generator which is prior to the GFCI.)

I don't feel it is safe to leave the generator frame ungrounded or to leave the generator ground disconnected from the house grounding system. And you need that neutral/ground bond at the generator before the GFCI for the GFCI to function. And you need a generator neutral to house ground bond (somewhere) for the generator circuit breaker to function for a short to ground.

With this, you can also use that generator for construction, camping etc.

Q1: So what if someone gets shocked by touching anything metal in the house or the metal frame of the generator? Do you have GFCI protection?

Q2: Or what if a hot wire shorts to ground anywhere including the metal frame of the generator? Do you have circuit breaker protection?

As for going by what "everyone else does", that is not necessarily the best way to do things. Think through various situations which could happen with Q1 and Q2 above, THEN decide which is the best way to do things...
 
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Old 11-14-11, 08:28 AM
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Thanks guys. I didn't realize that my setup had safety concerns. Thanks for pointing out the issues.

I have an email out to the transfer switch manufacture to see what what they can offer for a solution. I'll let you know what they say.

I don't want to modify my generator because I need it to work safely both connected to the house wiring and not connected to the house wiring.

...I bet I'll be installing a different transfer switch soon... Too bad because that little single circuit transfer switch is a pretty cool little gadget.
 
  #20  
Old 07-20-12, 10:35 AM
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Nice Job Bill191

Your explanation is the most consise and accurate information I have yet to find on the internet. There are so many different opinions out there on the proper grounding of generator. I think you are spot on. My only question comes from you telling people to lift the ground in the transfer panel and cap it off. I agree it breakes the ground loop, but now we have no ground protection.

I think people need to understand the differences in how they are going to use a generator prior to purchasing one. Becuse it does effect how you will properly wire the generator.
 
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Old 07-21-12, 01:43 PM
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Right or wrong, I have never grounded a portable gen.
When connected to houses, it has always been the old ungrounded systems. If I should connect it to a modern system, I would have used GFCI and grounded it to the ground in the house.
dsk
 
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