Grounding a DC solar system to the house ground

[mtt04]

As I believe there are no stupid questions I'll ask this one.

I'm putting solar in our shop and it already has a 100 amp grid service installed with a grounding rod.

I will ground the array and all components but I was thinking.

It is proper to ground a DC system to the existing AC grounding rod already in?

Or should I put in a separate DC grounding rod and tie them together to complete a grounding system?

Your thoughts are appreciated?

 

[Peteronline]

I will certainly follow this posting because I have a similar question as can be seen below.
This Link
This apparently got stuck to which I still have no answer.

 

[mtt04]

My sense is that a separate rod should be used but bonded with the other AC to complete earth ground.

But I'm gonna wait for feedback.

 

[SCClockDr]

There are two grounding scenarios.

1. The usual hot, neutral, ground kind.
2. Lightning protection.

In the both instance local building codes & inspectors will dictate what to do.

Personally the 2nd instance should be kept separate from the first. If there is an existing lightning protection system it should be used if in serviceable condition. Local codes may differ from this understanding but my reasoning is that if lightning should strike a panel I would want that kept far away from my circuits.

 

[offgriddle]

Tie everything together to your earth ground rod.

 

[oldcat]

this is what don't make sense if you tie your 12 volt system with you house ground rod and something else got hit it blow it all up.

 

[Donald Siegel]

I know very little on this subject but will reply with what I read about this. If you have two separate ground systems close together there is a potential for the burst of electricity to start channeling down one ground system giving it more resistance than the second one as the ground gets less neutral absorbing those electrons. Soon the second ground system is the better path so it arcs from one ground system to the second one burning everything between them hence the need to join or bond the new ground poles to the existing ground. It’s apparently better to add more ground poles to give the excess electricity more paths to ground but have them joined or bonded together. Hopefully our electricians will correct or verify this simplistic explanation.

 

[oldcat]

yes i see i make sense to bond thim.....

 

[offgriddle]

In Regards to the Concept of Grounding & Bonding, Neutral vs Ground etc. I have felt the same pain as all of you in the vain attempt to make sense of it all. I have lain awake nights doing endless calculations in my mind, I have wandered the deep forests in a daze while deeply theorizing. Then one day, I just said screw it, ground and bond everything just like the book says and then peace and serenity returned and I started sleeping more than two hours a night, leaving my house, my appetite returned, I even joined a bowling league and I have never looked back. Just ground and bond *everything, and stay with the mob. *Note: Do Not try to figure this rule out or try to argue with me about it because I don't care for I am a broken man over the concept of grounding, but the rule is make sure that you only combine ground and neutral at the main panel and keep ground and neutral seperate in any sub panels that are fed from the main panel. Hey I'm just the messenger.

 

[Rider]

Note: Do Not try to figure this rule out or try to argue with me about it because I don't care for I am a broken man over the concept of grounding,

 

[offgriddle]

I know very little on this subject but will reply with what I read about this. If you have two separate ground systems close together there is a potential for the burst of electricity to start channeling down one ground system giving it more resistance than the second one as the ground gets less neutral absorbing those electrons. Soon the second ground system is the better path so it arcs from one ground system to the second one burning everything between them hence the need to join or bond the new ground poles to the existing ground. It’s apparently better to add more ground poles to give the excess electricity more paths to ground but have them joined or bonded together. Hopefully our electricians will correct or verify this simplistic explanation.

Yes, in regards to multiple ground rods, (poles?), some electricial codes have been changed to required three ground rods, a few feet apart, bonded, (connected), together instead of one ground rod. I assume that the reasoning is to provide a better path to negative earth ground for positive ions, or perhaps vice versa or perhaps movement of electrons in either direction, (I believe that the theory of elrctron movement and direction is still up for discussion to some extent). Regarding bonding everything, it is important to connect all equipment housings, racks & designated ground attachment points together through a sufficient, (preferably copper), gauge ground cable so that all equipment is at the same potential as much as possible, therefore, reducing the chances that any particular piece of equipment will be less grounded in a facility, therefore, more susceptible to voltage surges.

 

[Steve_S]

I can only relate what I was directed to do with my off-grid installation and may apply to you as well BUT always refer to local codes, regs & rules as they vary depending on where you are. Especially if you want top grid connect or have insurance (gotta have that certificate).

My panels were grounded separately as they are 50' from the powerhouse but at the combiner there is also Lightning Protection installed.
My powerhouse AC Panel, DC Panel and gear are all grounded to the 6" Well Casing that goes 25' deep (10 of which is in granite). The Powerhouse is 75' from the Cabin with AC lines running in conduit under ground, the "Cabin" sub-panel is independently grounded to a large ground plate buried 2' deep and 2' away from the side of the building. *NB* This was a point of 'discussion' and was determined to be optional and included the provision that the DC system must also have lightning protection on it's own panel as well. Luckily, using a Midnite E-Panel, made it simple to accommodate. But geez the Lightning suppressors are not cheap !

 

[mtt04]

This is why I dreaded asking the question.
DIY installations are very fulfilling except when it comes to doing to the right thing when no one really knows what the right answer is.
Because I believe there isn't one for this. Two grounding rods bonded has been the norm for decades.

NEC "code" is a bunch of electricians with nothing to do sit around a table and say "What can we change to keep our jobs" .
It's like bureaucracies - without change they are not necessary and thus get laid off

It is not a criticism just a fact.

My two rods are now bonded as I thought I should do.
Thanks Everyone.

 

[offgriddle]

I can only relate what I was directed to do with my off-grid installation and may apply to you as well BUT always refer to local codes, regs & rules as they vary depending on where you are. Especially if you want top grid connect or have insurance (gotta have that certificate).

My panels were grounded separately as they are 50' from the powerhouse but at the combiner there is also Lightning Protection installed.
My powerhouse AC Panel, DC Panel and gear are all grounded to the 6" Well Casing that goes 25' deep (10 of which is in granite). The Powerhouse is 75' from the Cabin with AC lines running in conduit under ground, the "Cabin" sub-panel is independently grounded to a large ground plate buried 2' deep and 2' away from the side of the building. *NB* This was a point of 'discussion' and was determined to be optional and included the provision that the DC system must also have lightning protection on it's own panel as well. Luckily, using a Midnite E-Panel, made it simple to accommodate. But geez the Lightning suppressors are not cheap !

I like the idea of using your steel, drilled well casing as a ground point. ,If I may ask, what is a "combiner", used for?

This is why I dreaded asking the question.
DIY installations are very fulfilling except when it comes to doing to the right thing when no one really knows what the right answer is.
Because I believe there isn't one for this. Two grounding rods bonded has been the norm for decades.

NEC "code" is a bunch of electricians with nothing to do sit around a table and say "What can we change to keep our jobs" .
It's like bureaucracies - without change they are not necessary and thus get laid off

It is not a criticism just a fact.

My two rods are now bonded as I thought I should do.
Thanks Everyone.

I never thought I'd say this, but basic, practical, electricial codes are simply rules to follow that are for the most part based on knowledge and practice essential for the sake of safety. ~ Regarding the bunch of electrician types, I have worked for and with a great many of them. On a very few ocassions I have discovered a person performing in the capacity as an electrician that I would best describe as a, "hack", aka as a person who for a variety of reasons should not be performing such work. Of the electricians that I have worked with, while I found most of them to be dinks, (and dinkettes), which by the way has become the culture most typical of government monopoly raised, USAmericans in the workplace, (but I digress), I have found the vast majority of electricians to possess the highest degree of integrity regarding the quality and safety of the electricial work that they perform.

 

[Steve_S]

I like the idea of using your steel, drilled well casing as a ground point. ,If I may ask, what is a "combiner", used for?

My Solar Panel combiner which ties the 2 strings of panels together before going to the Powerhouse.

 

[offgriddle]

Good to know that, thank you!

My Solar Panel combiner which ties the 2 strings of panels together before going to the Powerhouse.