I've been told that I should keep my ground for my system separate from the regular house ground. So I drove in my 8' long ground rod.

I was going to run that wire to my board that has my components on it, to a ground bus bar. Then ground the controller, inverter and battery to that.

Is there any reason why this common ground for everything would not be OK? IF I should only ground my controller to that, what options do I have to ground the other items?

IT seems to me that using the common ground should be OK, but I've heard otherwise, that it can cause issues, but that doesn't make sense, since it all goes to my rod anyhow.

I did pick up some wire for the ground, 6AWG. Was going to get 8 but they were out and offered the 6 at the same price so I figured that extra thickness can only be good...

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Hello Dave:

(Why do I hear HAL in my mind as I write that?)

I am a retired IT infrastructure engineer and have some experience with grounding. My disciplines include designing joint communications systems for computers and telecom in multiple closet multiple story buildings in a campus environment and grounding is one of the most misunderstood (and neglected) functions in building communications systems. I am just starting to assemble my own solar system so I thought I would do a little reading so that is why I am here. I am a neophyte when it comes to solar systems so my opinion is based on what is necessary for communications systems. The same principles will apply to solar systems.

We are discussing modern 3 wire electrical systems for commercial power. The neutral side of the commercial power is not a ground and never should be considered as one. The neutral side of the commercial power should never be connected to ground. Some of our older structures still use a 2 wire power system and that can be dangerous.

Your thoughts concerning grounding are both intuitive and accurate. Yes, your solar system grounds should be separate from your commercial power system. Commercial power grounding systems are based on safety concerns, and little else. What may work OK for commercial power is not always acceptable for other types of systems and they should be completely separated except for one single bonding site. I will cover that below.

I need to do a little guess work about what you are building, but I think I might be able to answer some of your questions. I am assuming that all of your components are located at a single location.

And Yes again each separate device should be separately grounded to a common point and a “busbar” is the best idea. Do not “daisy chain” any devices which means do not ground box #2 to the busbar and then ground box #5 to box #2. Run the #6 (or heavier) wire directly from the busbar to the ground rod like you discussed. The metal frame for the panels should also be grounded. The first device out of your inverter should be a Ground Fault Interrupter (GFI) grounded to your ground system. It is a cheap but effective safety feature for you and your family. All power should go through that before it goes anywhere else.

Now here is the sticky point. If you are using your solar system to run something like a “stand alone” shed or backyard observatory like me, you should not have a problem as long as there is no commercial power used at the same location. If you are using your solar system to power some “solar stuff” anywhere close to where there is commercial power also being used; you have just established two separate grounding systems in one location. It may not be, but that can become dangerous and the potential problem needs to be eliminated up front.

If you have the condition of both systems operating in one place you will need to bond your commercial power and your solar power together but only at the ground rod. That way there can be no “difference of potential” between the ground systems and they must be one and the same for safety purposes, but what is happening in the commercial power system is not going to interfere with your solar system.

I am also a “Ham” radio operator and my computer desk has a separate but bonded ground system for my scanners, receivers, transmitters, amps, antenna array, computer and all of that stuff.

If you have any other questions please do not hesitate to ask.

Ken

Thanks for that in-depth reply.

My solar is "stand alone". The ground-rod is dedicated to the solar only. The ground rod for my house's commercial power is on the opposite side of the house. They are not conected in any way.

My intent for solar is to run a power strip to my entertainment area (TV, router and AT&T U-verse box) and my desk (one light, laptop and charging station for phones. There will be one line run for a lamp that has a 60 watt equivalent LED bulb. I also am running a line to my freezer and fridge. The TV etc and desk will be run every few nights so the batteries get some use and don't just sit. After testing the lines, the freezer and fridge will be there only for use during an emergency if I am in danger of losing $1,000 worth of grass-fed beef!

So what I hear is run my ground to a bar where my charge controller and inverter is. Connect each of those thing to that buss bar.

Gotta go to the pool party now...

Yes, anything with a metal chassis connects to the ground bus.

Also, don't forget the GFI unit. Becoming a human conductor my be exciting but it is never fun.

K

So from my inverter, I plug in a GFI power strip, and plug stuff into that only, correct?

Yes, as long as the inverter has 3 wire grounded outlets and its outlet ground is connected to your common ground busbar. I do not know about the inverter you chose, but it wold be wise to verify it with an ohm meter.

With that arrangement any 110 volt shock or fault problems fed by your solar system will trip the GFI breaker before any damage or pain can happen. Depending on the load you eventually place on the solar system you may need more than one GFI power strip.

Also, you mentioned a freezer and / or a refrigerator (also applies to a UPS). Their demand for power in their "start" sequence is sometimes three or four times their power demand in their "run" mode. Two of those items plugged into a single 15 amp power strip probably run fine but will trip the breaker if they both try to start at the same time. Calculate your power strip loads based on the start current demands of your devices and it should work well without any nasty surprises.

The inverter does has 3 wire grounded outlets... Ordering my bus bar tonight. I may have this thing up and running this weeked...

 

Way cool!

Before you connect the inverter to anything or anything to it - just out of the box, grab an ohm meter to verify the ground on the inverter power outlet is grounded to the inverter frame. When it comes to power, do not assume anything.

Set the resistance scale to RX1, put one probe on the outlet ground and the other to the inverter frame and the meter should read 00.0 or 00.1 (almost nothing). Reverse the leads and do it again. It should still be the same. If you have anything but almost "zeros" a little creative wiring will be necessary.

Please let me know how it works.

Will do. I've never measured Ohms but I think my meter ($6.00 Harbor Frieght special) should do that.

D:

I have a couple of those myself and it will work well enough. I am assuming it is a Harbor Freight Cen-Tech P35761. I will discuss that one to start.

First, test the ohm meter itself. attach the black test lead to the COM (common) (bottom) jack and the red one to the "V (ohm)mA" (middle) jack at the bottom right of the meter. Rotate the dial into the ohm (it is a funny little "omega" symbol that I do not have on this keyboard - looks like a "C" turned on its side with the opening pointed down) range and set it to the lowest number on the scale at the bottom - "200." That indicates you are measuring an expected resistance between zero and 200 ohms. The omega symbol stands for resistance in electronics math.

Anyway, when you turn the meter on with the leads apart it will read a "1" in the far left digit position. When you hold the leads together the numbers will bounce around for half a second or so but should settle down at something like "00.4."

That is some thing like what you want to see between the inverter chassis and the ground connection in the power outlet.

Avoid leaving your meter in the resistance (Ohms) ranges and using it in a circuit with voltage flowing in it. That will damage the meter.

K

The ohm reading instructions didn't work. My meter never stops jumping about. I made sure my hands were not touching the leads and it still never settled down.

Hi Dave:

I am placing my next reply up here because this webpage did not generate a reply tab below your last message.

I think you might have some coating or oxides on your testleads. When trying to read very low resistances it doesn't take much gunk to confuse the reading. 

Rotate your leads in the meter sockets about a half dozen times and then push them in and out about as many again. That should give you a good metal to metal connection in the sockets. 

set a clean penny on your desk and push the test leads down into it vertically while applying some strong pressure.

Watch the meter and see if that gives you some zeros.

K

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