Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Reply
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
 
Thread Tools Search this Thread Display Modes
 
Old 11-02-2010, 07:21 PM   #1
Senior Member
 
William Willard's Avatar
 
Monaco Owners Club
Join Date: Sep 2007
Location: Gilbert, AZ
Posts: 1,399
Generator Ground Wire

How does a generator make a ground? Would be kinda hard to have a 10' ground rod in the ground running down the road -- Bill Willard
__________________

__________________
William Willard is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 11-02-2010, 10:30 PM   #2
Senior Member
 
Join Date: May 2007
Posts: 632
On mobile gensets you don't need an earth ground. What you need is a chassis ground where the chassis of the genset is connected to the RV chassis. On portable gensets with outlets, this connection is via the green 'ground' wire in the power cord. Installed gensets have a transfer switch to take care of this as needed.

If you are using a genset of less than 5kW at 110v with electrical outlets to plug into, you also don't need to have the neutral power lead connected to the chassis ground lead - the power leads can 'float'. It is a common mistake to think that there is a neutral that needs to be connected to the chassis ground. With a 110v genset, there is no neutral although you may have what the code calls a chassis bonded power lead.
__________________

__________________
BryanL is offline   Reply With Quote
Old 11-03-2010, 09:54 AM   #3
Senior Member
 
vermilye's Avatar


 
Join Date: Nov 2006
Location: Oswego, NY
Posts: 380
Blog Entries: 1
Send a message via Skype™ to vermilye
Good information. The only thing I would add is that some Autoformers & built in power conditioners look for the neutral/ground bond & will not allow power to the RV unless it sees it (it indicated that there is no ground).

In that case you may need to tie the neutral to the ground with an adapter or modified plug when using a generator that does not have the bond built in.
vermilye is offline   Reply With Quote
Old 11-03-2010, 10:58 AM   #4
Moderator Emeritus
 
Gary RVRoamer's Avatar


 
Join Date: Jan 2000
Location: Silver Springs, FL. USA
Posts: 18,078
Since both "ground" and neutral are referenced to the generating source, the generator itself is the ground in this case.

With shore power, the generating station (whatever and wherever it may be) has an earth ground, so you connect to it by using an earth ground at the site.
__________________
Gary Brinck
Former owner of 2004 American Tradition
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC
Gary RVRoamer is offline   Reply With Quote
Old 11-04-2010, 10:11 AM   #5
Senior Member
 
William Willard's Avatar
 
Monaco Owners Club
Join Date: Sep 2007
Location: Gilbert, AZ
Posts: 1,399
Then in reality, there is no ground, since the motor home chassis sits on rubber -- If while running the generator, a short occurs, & it goes to ground, is there a chance that it could screw up the 12v system, since it is grounded to the chassis also -- I understand that the multi-plex system is very fragile -- Bill Willard
__________________
William Willard is offline   Reply With Quote
Old 11-04-2010, 12:18 PM   #6
Senior Member
 
Join Date: May 2007
Posts: 632
The confusion here is not unusual as terms are somewhat confusing between common use and technical (as in the NEC) definitions.

First item: an earth ground is different from a chassis ground. On grid tie systems, these two are connected together only at the service entrance. That is because the grid is inherently coupled to the earth ground and it is necessary to 'define' a local point where they connected together for a reference. Note that there is only one point of connection to avoid loop currents within the service area.

Second: a 110v genset does not have a neutral. It may have a power lead connected to [chassis] ground but that is a different thing than an electrical neutral.

If you have equipment that has a problem with isolated power leads such as in a genset situation, you have equipment not designed or intended for off grid use. That is a warning to heed about using equipment in its intended context. (that warning is that you really must know what you are doing and its implications before doing it)

The hypotheticals on this topic often get to be quite a stretch. The code is much more pragmatic. IMHO, the NEC is the best guide and it is different for RV's than it is for grid tied homes. (i.e. don't depend upon a home electrical contractor to understand RV codes).

The note about the DC and AC sharing a chassis ground as a power conductor is only an issue with some equipment, such as inverters, that do not properly isolate their input from their output. Again, read and follow the equipment manuals and know what you are doing.

Since an RV that is in what the NEC considers to be an isolated power system mode where there are no connections to a power grid, there is no earth ground connection anywhere other than where you make it. That means there is no need to make one. The chassis ground is sufficient for safety purposes.

Just as the power leads for a 110v plug-in type genset can be left floating, the chassis ground can be left floating from the earth ground. When wired by code, either of these situations will require a double fault in order to present any safety issue.
__________________
BryanL is offline   Reply With Quote
Old 11-04-2010, 01:21 PM   #7
Senior Member
 
wa8yxm's Avatar
 
Damon Owners Club
Workhorse Chassis Owner
Join Date: Mar 2009
Posts: 22,811
Quote:
Originally Posted by William Willard View Post
How does a generator make a ground? Would be kinda hard to have a 10' ground rod in the ground running down the road -- Bill Willard
The simple answer is: It does not.. And what's more You don't need one.

Here is why

In your home, the neutral, for several reasons is bonded to GROUND at the service entrance.. So is your next door neighbor's and his next door neighbor's and so on.. This dates back to a time when due to a copper shortage they ran only one wire to your house.. the neutral WAS the ground back then. Though that has changed today.. I've had it happen in my house where I developed a neutral fault and the ground had to be used as "Neutral" Kind of dangerous. The Power company quickly replaced my drop.

Back to topic

Since neutral is bonded to ground.. If say the drill, or shaver you are holding develops a "HOT to Case" short.. YOU become a path to neutral/return/ground. And that is not something YOU wish to be.

So the 3rd wire safety ground was developed.. IT helps to protect YOU from shock


There is another method some 2-wire devices use to protect you.. IT is called "Double insulation" In this type of device you have no metal parts to touch. (As a general rule which is sometimes broken)

With a Generator providing the power.. The neutral is NOT (Necessarly) Bonded to ground. There is, after all, no need to do this.

Thus, you are protected Much like the "double insulation" nothing you touch is connected to the neutral.. Thus if you come in contact with the HOT, you don't get .... Killed.

NOTE: often in this type of hook up you will see sixty volts neutral (or hot) to ground... This is normal, though the voltage is enough to darken your skys.. The current is not enough to do serious harm (I do feel it, very annoying, but I can actually work through it if I have to.. I Usually grab an insulated tool though when this happens) so it's fairly safe.

So the reason a generator does not need to be grounded is.. It is safe without the ground.

Oh, another reason for the neutral/ground relationship in power mains.. Lightening protection. (Well resistance)
__________________
Home is where I park it!
wa8yxm is offline   Reply With Quote
Old 11-04-2010, 10:20 PM   #8
Senior Member
 
Retired and Happy's Avatar
 
Join Date: Feb 2004
Location: Stone Mountain, GA
Posts: 941
Not sure I understand this...
"Second: a 110v genset does not have a neutral. It may have a power lead connected to [chassis] ground but that is a different thing than an electrical neutral. "

I am experiencing a problem in my 30 A circuit (but not the 20 A circuit) that my little yellow tester says is an open neutral. If I don't have a neutral, how can I have an open neutral? Do I just have a loose wire somewhere from the generator to chassis, or do I have a problem inside the generator?
__________________
Ken, Judy, and the Angels--2005 Fleetwood Southwind--2008 Cargo Trailer--2003 EZGO Golf Cart
Retired and Happy is offline   Reply With Quote
Old 11-04-2010, 10:53 PM   #9
Senior Member
 
Join Date: May 2007
Posts: 632
re: "I am experiencing a problem in my 30 A circuit (but not the 20 A circuit) that my little yellow tester says is an open neutral. If I don't have a neutral, how can I have an open neutral?"

your little yellow tester is intended for household outlets where the power is from a 240 volt split phase grid (company power) connection, not for an outlet powered by a 110v genset. It is not intended to test portable gensets.

It is entirely appropriate for the little yellow tester not to show any voltage between either of the hot leads and the chassis ground and to have only one indicator (of the three on the tester) showing voltage between the two power leads. What that is telling you is that both power leads are isolated from the chassis ground. That is OK for a portable 110v genset that uses plugs.

in a 240v split phase, neutral is the halfway point between the two leads that are 240 volts apart. That point is what gives you two 110v sides in your house wiring (or in 50 amp RV service).
__________________
BryanL is offline   Reply With Quote
Old 11-05-2010, 10:08 AM   #10
Senior Member
 
vermilye's Avatar


 
Join Date: Nov 2006
Location: Oswego, NY
Posts: 380
Blog Entries: 1
Send a message via Skype™ to vermilye
Quote:
Originally Posted by Retired and Happy View Post
I am experiencing a problem in my 30 A circuit (but not the 20 A circuit) that my little yellow tester says is an open neutral. If I don't have a neutral, how can I have an open neutral? Do I just have a loose wire somewhere from the generator to chassis, or do I have a problem inside the generator?
In a home the neutral is bonded (connected) to the ground at the service entrance. This connection is what the 3 lamp testers look for to determine if the neutral or ground is open. Since this bond or connection does not exist in many 120v generators, the tester reads a error.

The term neutral, at least as far as the NEC is concerned only exists in a dual voltage system. In a 120v generator you may bond the white wire to ground, but that doesn't make it a neutral. Code calls it the "identified conductor" and requires that it be bonded in generators over 5000 watts & dual voltage systems.

As to the need to bond the identified conductor - there are good reasons to bond, as well as good reasons not to bond. Check This OSHA Document and This PDF for some interesting discussions of the advantages/disadvantages & requirements for bonding & grounding.

One reason you may need to bond the neutral to ground when using a portable generator - as I noted earlier in this thread some RV electrical protection systems look for the ground/neutral bond (like the 3 lamp testers) and if they don't detect it, they shut off the power, assuming that there is an open ground.

All cures for this problem are at your own risk - Although I have never seen the problem, I have seen statements that bonding a portable generator MAY damage the generator.

The solution most often suggested is to build an adapter that makes the bond (ties the ground pin to the wide blade of the receptacle.) A simple way to do this is to make a plug with a jumper between the identified conductor (wide blade) and ground, and plug it into one of the generator's receptacle.
vermilye is offline   Reply With Quote
Old 11-05-2010, 11:38 AM   #11
Senior Member
 
William Willard's Avatar
 
Monaco Owners Club
Join Date: Sep 2007
Location: Gilbert, AZ
Posts: 1,399
WE own a 07, Monaco Camelot, that we purchased new in May, 07 --
The reason I started this thread, is that I tested the AC curcits from the inverter, Magnum, model # ME2012, to see which ones the inverter powered, with the idea that maybe someday, I would install a resdential frig -- All recepts showed open ground (no ground detected) on inverter, but good on shore/gen power -- I posted this question on the iRV2 Monaco Forum, & got good response to my problem -- Internal netural to ground switch not switching in the inverter -- Since this board cost $225.00, & I seldom use the inverter, I see no reason to correct the problem, but, if I do install a 110 refer, would I have a problem with the open ground on the inverter, or would I have to fix the Netural to Ground switch first? -- I can & do, wire resdential homes, & wired many Park Model Homes in a factory setting -- Park Models are RV`s & are wired using a Neutral Buss Bar, & a Ground Buss Bar -- So, I do have some understanding of AC power, just not the inverter, generator part of it -- I appreciate any help, but keep it as simple as possible for this electronics challenged old man -- Bill Willard
__________________
William Willard is offline   Reply With Quote
Old 11-05-2010, 02:20 PM   #12
Senior Member
 
Retired and Happy's Avatar
 
Join Date: Feb 2004
Location: Stone Mountain, GA
Posts: 941
Bill, I know how you feel. My background is as an Electrical Engineer from years ago and a career in Hydropower and IT with the Corps of Eng, but since I retired I have forgotten everything except not to stick my tongue in a receptacle to see if it is hot. I have also had very little experience with the RV/gen setup. It has always worked, so I didn't need to fix anything until now.
__________________
Ken, Judy, and the Angels--2005 Fleetwood Southwind--2008 Cargo Trailer--2003 EZGO Golf Cart
Retired and Happy is offline   Reply With Quote
Old 11-05-2010, 04:21 PM   #13
Senior Member
 
Join Date: May 2007
Posts: 632
Whether you will have a problem trying to run a particular appliance from a power source with isolated power leads (like a portable genset or inverter) will depend upon that appliance.

In most cases, it should not present a problem but there are exceptions and, for those, you may need to fudge things if you want to use them with the power sources that have isolated power leads.

That 'need to fudge' is telling me that I am not using equipment in its intended way and that is a warning I have learned to pay attention to.

I do not like fudging electrical power things so I try to either get a power source that supports connecting a power lead to chassis ground or an appliance that has no qualms with isolated power leads. If I wire things in, I use a transfer switch. Otherwise, I use a cord with the proper plugs and wires.

You've got some of the best and most consistent advice and explanations I have seen on this topic in some of the posts in this thread. John and Jon both seem to have good 'been there, done that' experience as well as expertise. If you want to understand what's happening, I think it well worth time to read what they say here carefully.
__________________
BryanL is offline   Reply With Quote
Old 11-06-2010, 11:25 AM   #14
Senior Member
 
William Willard's Avatar
 
Monaco Owners Club
Join Date: Sep 2007
Location: Gilbert, AZ
Posts: 1,399
Then the answer is a "Definite Maybe" -- Thanks for all your input -- I, & probably several others have a better insight on the operation of the RV, ac electrical system -- I`ve spent the last 3 years getting the bugs out of this coach, & when I thought I had it whipped, I screw around, & test the inverter circuit, which I know nothing about -- At 73 years of age, & been through the "School Of Hard Knocks', I should have known better -- Bill Willard
__________________

__________________
William Willard is offline   Reply With Quote
Reply



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Easiest way to find bad SP wire. max49 Workhorse and Chevrolet Chassis Motorhome Forum 25 06-17-2010 05:36 PM
Wire type for 7.5 kva Generator Dick_Wins National RV Owner's Forum 4 05-06-2010 07:48 AM
Orange Wire to No Where PizzaGuy Monaco Owner's Forum 5 04-04-2009 10:51 AM
Ground Wire gator67 Alpine Coach Owner's Forum 4 08-15-2007 11:32 PM
Hot connection melted wire. TallPaul RV Systems & Appliances 11 07-03-2007 11:12 AM

» Virginia Campgrounds

Reviews provided by


Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -6. The time now is 10:45 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.