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Electrical panel wiring question


Ryan Corcoran
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I just bought a car hauler with an onboard electrical system similar to an rv.  It has a 30 amp 120v volt panel and a dual battery 12v system also.  I have a Honda 3000w generator for use when no shore power is available.  It does not have a transfer switch, I just plug the shore power cord into the generator instead.  The problem I am having is that when plugged into a gfi outlet it trips the gfi.  Everything works fine when using the generator or a non gfi outlet.  So I took the cover off the trailers 30 amp panel and it has two separate bus bars for the neutral and ground, but they tied it together.  When I separate them, they don't trip the gfi, but I want to know if this is safe to leave it that way both when I'm plugged into shore power and also generator power.  Thanks

Ryan 

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2 hours ago, mptjelgin said:

Here is a good discussion of this issue, with a simple and effective solution:

http://noshockzone.org/generator-ground-neutral-bonding/

Exactly what I would have posted. That is the best explanation for a layperson that I have ever found. It is possible to make this discussion more complicated but there is no need to do so. 

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The tripping of the GFI outlet is a separate issue than the neutral bonding plug for the generator.  Per the original post, everything works fine when plugged into the generator.

The 120 volt panel in the trailer should not have the neutral and the ground bus bars connected within the panel.  The panel should be wired like it is a "sub panel".  In other words, the panel in the trailer is a sub panel to the main panel powering the outlet the trailer is plugged into.  This is why the ground and neutral bus bars in the trailer panel should not be connected because they are already tied together downstream at the main panel powering the outlet the trailer is plugged into.

When you plug the trailer into a GFCI outlet, the GFCI is tripping because of the leakage between the ground and neutral paths created by connecting the ground and neutral bus bars in the trailer panel.  All correctly wired RV 120 volt power panels have separate ground and neutral bus bars.  The car hauler in this instance is no different than any other RV and should also have separated ground and neutral bus bars in its 120 volt power panel.  This will solve the GFCI tripping issue (of course this assumes there is nothing else wired incorrectly in the car hauler).

Specific to the neutral bonding plug for the generator, that is only needed when the generator (with separate neutral and ground buses) is trying to feed power through an energy protection device like a SurgeGuard or Progressive Industries (or similar) unit.  Those devices see the separated neutral and ground as a wiring fault at the source and therefore will not allow power to pass through them to the trailer.  A simple bonded plug plugged into one of the generator outlets will correct the "fault" the protection device sees and the device will then allow power to pass through it to the trailer.  In the above case, no protection device is in use, so there is no need for a bonded plug for the generator.

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Ryan that's an excellent question and of the type often found in RV forums especially having to do with portable generator use and RV panels and GFCI or EMS or testers etc. etc.

One of the first rules concerning secondary power distribution is the concept of SINGLE POINT GROUNDING. That basically means there is to be ONLY ONE Neutral Ground Bond which often occurs at a homes main service entrance panel which is why there the Neutral Buss is bonded to the Ground Buss  BUT FROM THAT POINT FORWARD LIKE AT A SUB PANEL FED FROM THE MAIN PANEL OR IN AN RV'S PANEL FED FROM THE RV PARKS PEDESTAL (or in a trailer panel that's plugged into a home or shop or RV pedestal etc)  NEUTRAL IS SEPARATE AND ELECTRICALLY INSULATED AND ISOLATED FROM THE GROUND.

SOME portable home gensets are often configured to have a FLOATING NON BONDED NEUTRAL while others have a bonded Neutral. In order to achieve the Single Point Ground if the genset has a bonded Neutral then the panel it serves should have separate insulated and isolated Neutral and Ground Busses    HOWEVER   if the Genset  has a floating Neutral then in order that "certain" components (many work fine regardless) or testers or energy management systems or protection devices  (that require a bonded Neutral) to operate  A NEUTRAL GROUND BOND NEEDS CREATED. That can be as simple as taking a plug and wiring a jumper from Neutral to Ground so then the components in question see a Neutral Ground Bond.

There are good safety reasons for floating systems as well as grounded systems and reasons why one genny has a  bonded Neutral while another has a floating neutral but that's beyond this discussion for now.

If a GFCI trips its because there's as little as 5 or 6 milliamps that's flowing OUT the Hot that's NOT returned by the Neutral but that's NOT the same as the concept of Single Point Grounding and floating versus bonded gensets .

SOOOOOOOOOO if its necessary to use protection or management devices that require a bonded Neutral but the genny is floating THEN SIMPLY CREATE A NEUTRAL GROUND. If a trailer or RV or any sub panel is fed from a bonded generator or utility THAT ALREADY HAS A NEUTRAL GROUND BOND  then it needs to have separate insulated and isolated Neutral and Ground.

NOTE I realize a non sparky may not grasp all this and that's to be expected. I worked much of my life as a power distribution design engineer and attended NEC Seminars and could write a paragraph or an entire book on this subject and will try my best to help but dont want to overwhelm you  lol so just say again if a protection device or energy management system requires a bonded Neutral simply create one but if a sub panel that's fed from a main panel (that had a Neutral Ground Bind) is in use, make sure it has separate Neutral and Ground busses..............

Post back any questions and I will try to help

 

John T  Longgggggg retired electrical power distribution design engineer and rusty on the latest codes so no warranty but believe the above still holds true

     

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35 minutes ago, Chad Heiser said:

The tripping of the GFI outlet is a separate issue than the neutral bonding plug for the generator.  Per the original post, everything works fine when plugged into the generator.

The 120 volt panel in the trailer should not have the neutral and the ground bus bars connected within the panel.  The panel should be wired like it is a "sub panel".  In other words, the panel in the trailer is a sub panel to the main panel powering the outlet the trailer is plugged into.  This is why the ground and neutral bus bars in the trailer panel should not be connected because they are already tied together downstream at the main panel powering the outlet the trailer is plugged into.

You are right. I think some of us are so used to the reverse problem that we saw what we expected rather than what is written. I strongly suspect that someone may have connected the ground/neutral in the trailer's panel for the same purpose as the plugs mentioned that article when using a portable generator.  Good catch! 

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Thanks for the info guys. So here is the question at hand now. I disconnected the ground bond, but would it be better to make a plug for the generator, or to add a switch next to the panel to make the feouns/neutral connection when it is needed. Im already adding an outlet there anyway, so pretty easy to use a double box and add the switch 

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5 minutes ago, Ryan Corcoran said:

Thanks for the info guys. So here is the question at hand now. I disconnected the ground bond, but would it be better to make a plug for the generator, or to add a switch next to the panel to make the feouns/neutral connection when it is needed. Im already adding an outlet there anyway, so pretty easy to use a double box and add the switch 

The only time you need the bonded plug for an unbonded generator is if you use one of the protection devices I linked to in my original post.  If you do not use one of those (either portable or hard wired), there is no need for what you are talking about.

 

By the way, I work with a Ryan Corcoran here in CA.  I don't suppose you are him????

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2 hours ago, Ryan Corcoran said:

but would it be better to make a plug for the generator, or to add a switch next to the panel to make the feouns/neutral connection when it is needed

Ryan, the idea of a switch at a panel to make or break the Neutral Ground Bond doesn't set well with me as an electrical power distribution engineer and likely not professional electricians and likely NOT the NEC, IM NOT SAYING IT WONT "WORK". The critical Single Point Grounding Neutral Ground Bond needs to be a reliable dependable and low resistance permanent connection and not something subject to switch contact problems and inexperienced folks.

If you need a Bonded versus a Floating Generator Id hard wire it right at the Generator with heavy copper wire and proper connections. The home made plug bonding method (Neutral jumped to Ground) works and many use it.

REMEMBER most appliances will still function regardless if fed from a floating or a bonded system, but the sophisticated energy management and protection devices will throw an alarm.

HOWEVER if you create a bonded system and it feeds a panelboard like in an RV or a Trailer etc.,  it needs separate Neutral and Ground busses.

Portable genset manufacturers don't know if you're going to use it with a transfer switch with how many poles or to provide emergency backup power or power an RV or whatever and they make them floating and bonded BOTH OF WHICH can have advantages or disadvantages but their lawyers cover their _____ by saying GROUND PER THE NEC.

As a past RV dealer and camper of 47 years I've seen folks use floating gensets and never have a problem UNLESS they have the systems mentioned above. If you do use them then Id suggest a fixed NOT switchable hard wired bonded system. There can be safety differences but again that's goes beyond your question and can get complicated. 

The GFCI system isn't concerned with all this discussion, its simply monitoring current out the Hot versus that being returned by the Neutral and if 5 or more milliamps is returned elsewhere it trips.

Hope this helps and answers your good questions, post back any questions and we will try to help

John T

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4 hours ago, Chad Heiser said:

The only time you need the bonded plug for an unbonded generator is if you use one of the protection devices I linked to in my original post.  If you do not use one of those (either portable or hard wired), there is no need for what you are talking about.

 

By the way, I work with a Ryan Corcoran here in CA.  I don't suppose you are him????

No, I'm from PA.  But funny coincidence. Thanks for the help. I don' use one of the protection devices, but feel like if it is important enough to make a code for it to be bonded in the panel box, then I should try to follow that the best I can.

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8 hours ago, Ryan Corcoran said:

I don' understand why it would be better to use the bonded plug vs a switch

Ryan, I bet down deep you DO understand it. A proper solid dedicated hard wired bond is in my opinion far less subject to worn or loose or corroded or oxidized or burned mechanical switch contacts or  "plugged in" contacts, wouldn't you agree ??????? I'm long retired from engineering practice but I cant recall any NEC approved or in the field practice of using a switched Neutral Ground Bond.

Hey I'm NOT saying it doesn't "work" I'm ONLY saying in my engineers opinion it's less reliable and possibly higher resistance then a proper hard wired bond.

NOTE I realize the difference between a  mechanically "switched" bond and the method of using a plug which has a jumper wire from Neutral to Ground  which I find much better then a mechanical switch, but would still prefer more of an internal bond  then a plugged in (possibly dirt or moisture or carbon or grease or oxidation etc.) device.

FYI The sole purpose of the Safety Equipment GroundING Conductors (the bares or greens) which are attached to the panels Equipment Ground Buss is to provide a low resistance dedicated return current path ONLY for fault current. It normally carries no significant current. The purpose of the Neutral and its buss and conductors is the normal return current, its a live current carrying conductor and its insulated just like the Hot conductors while the Safety Equipment Ground (often a bare exposed wire) is often attached to the outer metallic conductive frames of tools or appliances WHICH YOU TOUCH. If downstream after the single point Neutral Ground bond you were to incorrectly re bond the Neutral and Ground (like an RV or trailer "sub" panel) then the Ground between the panels is carrying live current and is no longer a non current carrying conductor.

A typical 120 VAC appliance (NOT an electronic management or protection device)  operates fine REGARDLESS if the source voltage uses a bonded or a floating Neutral. It sees 120 VAC from Line to Neutral so alls well as far as its concerned.

I THINK YOU DO GET THIS !!!!!!!!!!!! This is ONLY very basic and very generic and not 100% accurate or perfect but I'm trying hard to keep it short sweet n simple for a lay person to understand, and that's quite a challenge for an Attorney and Engineer lol so forgive me

Best wishes, God Bless and Happy New Year to all

John T

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13 hours ago, Ryan Corcoran said:

So here is the question at hand now. I disconnected the ground bond, but would it be better to make a plug for the generator, or to add a switch next to the panel to make the feouns/neutral connection when it is needed.

I oppose the use of a switch based on my 40 years of working with people, not design theory. In theory, it really doesn't matter but experience has taught me that people will forget to flip a switch, or just stop bothering to do so. On the other hand, a bonded plug for the generator is far more likely to be remembered and when you remove the generator that bond is gone, even if you forget to do something. I actually keep my bonding plug with the generator when in storage, attached by a nylon cord. 

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2 hours ago, Kirk Wood said:

I oppose the use of a switch based on my 40 years of working with people

AMEN Kirk I likewise oppose it........When Billy Bob or Bubba see that switch they can't resist those type of things lol not to mention a pure "mechanical manual switched" Neutral/Ground bond is simply NOT an NEC approved bonding method to my knowledge, but not to say it couldn't be for whatever reason ???? I learned years ago be cautious and never say never........

Hope you have a Happy New Year  

  John T

 

Edited by oldjohnt
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Points taken, I made up the bonding plug and it works fine. I can understand what you are saying, however I am much more likely to forget the plug than a switch, lol.  I do have a question when it concerns the generator tho.  What if the outlet trips that the bonding plug is in? am I no longer bonded or does it continue to make that connection and only the hot wires are not connected?  I'm a contractor and I use generators every day, and I can tell you from experience that I almost never check the breakers when I start it.

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2 hours ago, Ryan Corcoran said:

I do have a question when it concerns the generator tho.  What if the outlet trips that the bonding plug is in? am I no longer bonded or does it continue to make that connection and only the hot wires are not connected? 

Hi again Ryan, another good question. A single pole 120 VAC Circuit Breaker ONLY opens the Hot, so even if its open the Neutral Ground Bond is still intact.

Even if its not something a professional electrician may or may not use and even if its not a preferred bonding method found in the NEC, that plug method for sure works and many use it.

NOTE portable gensets used  on construction sites have all sorts of safety requirements and GFCI's are found all over. Its one place where a Grounding Electrode may not be required and in certain situations it may actually even be discouraged provided the genset feeds plug and cord connected tools from onboard receptacles,  but all that deep stuff is beyond your question and this forum.

 

John T

Edited by oldjohnt
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46 minutes ago, Ryan Corcoran said:

Now I have to do the same thing to my father-in-laws rv

There's an excellent chance at least his RV panel itself already has the correct separate and insulated and isolated Neutral and Ground Busses,  but if you meant his genset has a floating Neutral and now you wish to bond it for whatever reasons YOURE AN EXPERT AT THAT BY NOW !!!!!!!!!!!!!!!!!!!!! I would expect an onboard unit should already be bonded (configured as a Separate Derived Source) but as far as portables it depends on the make and model. 

Only a few 2017 hours left, were parked in the RV in a church parking lot in Wauchula Florida now HAPPY NEW YEAR

John T

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