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Off-Grid Newbie Grounding

vulcan66

New Member
Joined
Oct 30, 2022
Messages
13
Hi all,
New here and been reading through lots of great content. On the topic of off-grid grounding, I went down the rabbit hole and now a little confused.
I currently live in an area where we experience regular power outages. Bought a small honda generator and installed a 1-circuit transfer switch so I could feed power to one 15 amp circuit in the house during power outages. Works great and now would like to expand on it a little. I'd like to have the option to feed that one 15 amp circuit from either the generator or solar. Started putting together a small, backup solar setup which I will house the batteries and components in a small barn behind our house. I'm just wondering about grounding for the panels, charge controller and inverter. Lightning in my area is very rare so don't really know if I even need to address that. I was hoping not to have to drive a new grounding rod for the purpose of grounding this small setup. I'm about 25 feet from the main houses panel to access the homes grounding connection. Since my system does not involve a vehicle chassis and the nearest grounding connection is 25 feet or so, do I just hook up the negative side of the battery to neg bus, run my grounds to that bus and call it a day? Of course I do know about fusing the SCC and the inverter connections, but is there another path to properly grounding a small backup system like this? Appreciate the help.
 
There are a few things to consider

1. If the incoming grid is disabled , ie your in “ island “ mode then most likely your neutral PE bond will be on the wrong side of the transfer switch

In this case you may need to rstablish a local ground and only when thd grid is disabled tie that ground to neutral

Secondly where practical only have one earth point. So if establishing a local earth typically with a ground rod , don’t connect this to your houses PE ground.

In your case yrs as they are close ground the panels to the houses earth wire.

Some people prefer the panels locally grounded for lightening protection. Personally that’s my approach , as typically large exterior metallic structures are not bonded into the house PE network due to risk of lightening surges in PE.

Hence either don’t ground the metallics of the PV or establish an independent local ground.
 
There are a few things to consider

1. If the incoming grid is disabled , ie your in “ island “ mode then most likely your neutral PE bond will be on the wrong side of the transfer switch

In this case you may need to rstablish a local ground and only when thd grid is disabled tie that ground to neutral

Secondly where practical only have one earth point. So if establishing a local earth typically with a ground rod , don’t connect this to your houses PE ground.

In your case yrs as they are close ground the panels to the houses earth wire.

Some people prefer the panels locally grounded for lightening protection. Personally that’s my approach , as typically large exterior metallic structures are not bonded into the house PE network due to risk of lightening surges in PE.

Hence either don’t ground the metallics of the PV or establish an independent local ground.
Thanks for the reply. So currently, I have a 48" grounding rod near the little honda which I tie the honda grounding lug to when using it to feed this one circuit. Seems to work fine and have had no issues. Please forgive my ignorance here, but can I just tie the negative side of my battery to a grounding bus bar that is connected to this same 4 foot rod in the ground and also connect any solar component case grounding lugs to that busbar? Do I need an 8 foot rod. My area is super rocky/tough ground so expect driving an 8ft rod might be a chore. When you say since my panels are close to the house, to ground them to the homes grounding connection, is it okay to run a bare copper wire that distance? I said it is approximately 25 feet, but there is no direct path to run that ground wire. The run would be making a number of twists and turns which I was led to believe is not the best, but I suppose better than nothing. So grounding the panel array to the same rod I've been using for the generator is not a fair option? I kind of think of my little setup I'm trying to come up with as sort of a version of a portable "Jakery Power Station". They never seem to mention anything about grounding rods or any external grounding concerns when using these power stations. It seems like a similar type of thing so I just wonder why there's no mention of it with those setups and how they address grounding on truly portable systems where an earthing rod is not practical (due to portability needs) and you don't have a vehicle chassis to connect to?
 
Don't worry too much about being confused, grounding is quite complex, even electrical engineers will disagree on what is "best". I did not ground the DC side of my solar and my victron multiplus only bonds to ground internally when it "sees" a grid connection. Plenty of people will (strongly) disagree.

If you want to learn more have a look at @FilterGuy resources on grounding he has created a few resources on this, for example https://diysolarforum.com/resources/grounding-made-simpler-part-1-ac-houshold-grounding.157/

The best thing you can do is follow local code.
 
Thanks for the reply. So currently, I have a 48" grounding rod near the little honda which I tie the honda grounding lug to when using it to feed this one circuit. Seems to work fine and have had no issues. Please forgive my ignorance here, but can I just tie the negative side of my battery to a grounding bus bar that is connected to this same 4 foot rod in the ground and also connect any solar component case grounding lugs to that busbar? Do I need an 8 foot rod. My area is super rocky/tough ground so expect driving an 8ft rod might be a chore. When you say since my panels are close to the house, to ground them to the homes grounding connection, is it okay to run a bare copper wire that distance? I said it is approximately 25 feet, but there is no direct path to run that ground wire. The run would be making a number of twists and turns which I was led to believe is not the best, but I suppose better than nothing. So grounding the panel array to the same rod I've been using for the generator is not a fair option? I kind of think of my little setup I'm trying to come up with as sort of a version of a portable "Jakery Power Station". They never seem to mention anything about grounding rods or any external grounding concerns when using these power stations. It seems like a similar type of thing so I just wonder why there's no mention of it with those setups and how they address grounding on truly portable systems where an earthing rod is not practical (due to portability needs) and you don't have a vehicle chassis to connect to?
Run insulated copper wire

Normally external metal structures are not connected into the house electrical ground system as lightning induced ground jumps can cause issues.
 
Separately Derived System - 100% offgrid with transfer switch - no common neutral - use 4 pole switch to separate neutral
 
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