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Old 03-20-2019, 10:02 AM   #1
Mini-Skoolie
 
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Red face Switches and Grounding Questions

Let me start by saying that I have been reading ALOT on this forum about electrical and have come to learn that being an electrician is not anywhere in my future

I have scoured this thread, as well as this one, been reading here and a few other places.

I have purchased the majority of what I need for my electrical system. The solar panels are mounted on the roof. The inverter and charge controller are sitting in the opened box ready to be installed. I have 5 feet of red and black 4/0 gauge wire as well as some 10, 6, and 8 gauge wire for other parts of the system. I have all of the wires ran for appliances and outlets as well. I have built an airtight battery box for my flooded lead acid batteries that vent to the outside of the bus. Now comes the scary part. Making it live

Here is a diagram of my plan to set up everything. Please note the connectioin of the DC and AC circuits to the batteries is a little screwy because of the website I was using



Here are where my questions come in. I know that my inverter has a ground-neutral bond internally. I know that under no circumstances can the inverter and shore power be grounded at the same time( right?!?!).

The inverter has a grounding lug that I was going to attach to an installed bus bar on the chair rail. The shore power plug also needs to be grounded. Can I ground them to the same bus bar and use my master switch to cause a break in the circuit between the inverter and the AC distribution panel to remove the double ground? If not how should I approach the need of both the inverter and the shore power plug both needing to be grounded?

Next question, I have an extra grounding bar. Is there a need of one in the DC circuit?

I feel like i am missing a fuse somewhere. Possibly between the charge controller and the batteries?

Do the batteries need to be grounded as well?

I know that this is alot of questions and some of them maybe stupid, but I know that I am no where close to being an expert in this and would like the opinion of some people who have done this and have experience. Thank you for your time!
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Old 03-20-2019, 05:47 PM   #2
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I've only got a few minutes so will touch on a few things. Please don't consider this a 'complete' response. Hopefully enough to get things rolling...

Given the way you have things wired, I will assume that your inverter does not have an internal transfer switch. A transfer switch (internal or external) is not 'required' but, IMO, it the best approach - and not even all that expensive. Manually switching things will work - until you forget or someone attempt to 'help' (or whatever). A transfer switch avoids all that (something like this: https://amzn.to/2Fh25lR).

A fuse/circuit breaker between your solar panels and charge controller is needed as is one between the charge controller and battery. Using circuit breakers is handy as they can also (easily) serve as a switch when needing to power things down.

When dealing with both AC and DC, the term "ground" can become a bit confusing. With DC, you actually have a positive and negative lead. With AC, you have a 'grounding wire' (plus hot and neutral). That sometimes helps folks, sometimes not...

I'm not sure I understanding your 'grounding' questions so better let someone else take a shot.

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Originally Posted by travelgravel View Post
Do the batteries need to be grounded as well?
See the above on 'grounding' confusion. A DC component must have a closed circuit (a lead for both positive and negative (to the battery in this case)). You can choose to use your chassis (for example) as a negative buss and then the batteries and all components (negative) are connected to this buss. However; that is often NOT recommended due to poor connections and loops. Regardless, all of the installations with which I am familiar connect the house battery bank negative to the chassis.
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Old 03-20-2019, 06:56 PM   #3
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JDOnTheGo Thank you for your response! My inverter does not have an automatic transfer switch. I just ordered a transfer switch based on your recommendation. I will also get some breakers between the panels/charge controller and the charge controller/batteries.

From your last paragraph you are saying that some people only run hot(+) wires to their appliances i.e. water pump and the negative to the chassis of the bus? What I have done is run both hot(black) and negative/neutral(white) wires to all of my appliances and was going to attach those to my 12v fuse block which would then be attached to my batteries with some 6 gauge wire. Is what I have done the more correct way?

In response to the transfer switch I assume that it takes in the hot, neutral, and ground from both the inverter and shore power plug and outputs those into a single output of hot, neutral, and ground? Then this runs to the appliances. Where does the breaker box/Distribution panel factor in? Also does that ground that comes from the transfer switch need to be grounded to the bus bar or does the transfer switch itself get grounded to the bus bar?

Thanks again for your response!

*edit* I'm not sure how important it is but I forgot to mention that all outlets in the bus are GFCI outlets as well as the outlets on the inverter. I did not spring for GFCI circuit breakers in the breaker box. Should I?
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Old 03-21-2019, 02:34 PM   #4
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Quote:
Originally Posted by travelgravel View Post
From your last paragraph you are saying that some people only run hot(+) wires to their appliances i.e. water pump and the negative to the chassis of the bus? What I have done is run both hot(black) and negative/neutral(white) wires to all of my appliances and was going to attach those to my 12v fuse block which would then be attached to my batteries with some 6 gauge wire. Is what I have done the more correct way?
Yes. I'm a red=positive, black=negative wire guy but the wire color doesn't affect performance. Running the negative back to the battery negative is best practice. This can be done with one or more hops thru buss bars (and appropriately larger wires/cables depending on the current that is being carried). This is also true of the positive. Sometimes in our very long buses, it is easier/better to run a large gauge wire (positive always fused, to protect the wire) from battery to a fuse block/circuit breakers located near the accessories/components and then branch off smaller gauge wires from there.

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In response to the transfer switch I assume that it takes in the hot, neutral, and ground from both the inverter and shore power plug and outputs those into a single output of hot, neutral, and ground?
Correct.

Quote:
Originally Posted by travelgravel View Post
Then this runs to the appliances. Where does the breaker box/Distribution panel factor in? Also does that ground that comes from the transfer switch need to be grounded to the bus bar or does the transfer switch itself get grounded to the bus bar?
The output from the transfer switch goes to your breaker box/panel. The output from each breaker goes to the appliances/plugs/etc. This way, the wire is protected by the circuit breaker regardless of whether it is powered from shore power or inverter.


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...all outlets in the bus are GFCI outlets as well as the outlets on the inverter. I did not spring for GFCI circuit breakers in the breaker box. Should I?
As I understand it, you don't need both: https://www.thespruce.com/install-gf...reaker-1152797
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Old 03-21-2019, 04:53 PM   #5
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Maybe this was mentioned and I missed it, but does your charger accept a 110 input to charge the batteries? The one we bought (still in a box) takes input from the solar panels, shore power and the alternator to charge the batteries. If that's the case, your 30amp shore power would be on the other side of the batteries.
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Old 03-21-2019, 07:32 PM   #6
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Quote:
Originally Posted by JDOnTheGo View Post
Yes. I'm a red=positive, black=negative wire guy but the wire color doesn't affect performance. Running the negative back to the battery negative is best practice. This can be done with one or more hops thru buss bars (and appropriately larger wires/cables depending on the current that is being carried). This is also true of the positive. Sometimes in our very long buses, it is easier/better to run a large gauge wire (positive always fused, to protect the wire) from battery to a fuse block/circuit breakers located near the accessories/components and then branch off smaller gauge wires from there.
Hmmm, so If I have both the positive and negative wires coming from the battery that are attached to the 12v fuseblock one of those wires can be ran through a bus bar to ground the DC circuit? Does it matter if it is a different bus bar than the one that the AC circuit is grounded too?

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Originally Posted by ermracing View Post
Maybe this was mentioned and I missed it, but does your charger accept a 110 input to charge the batteries? The one we bought (still in a box) takes input from the solar panels, shore power and the alternator to charge the batteries. If that's the case, your 30amp shore power would be on the other side of the batteries.
No, I dont think so. My charge controller only has inputs for the batteries and the solar panels
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Old 03-22-2019, 06:34 AM   #7
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Quote:
Originally Posted by travelgravel View Post
Hmmm, so If I have both the positive and negative wires coming from the battery that are attached to the 12v fuseblock one of those wires can be ran through a bus bar to ground the DC circuit? Does it matter if it is a different bus bar than the one that the AC circuit is grounded too?
I may be reading too much into your question. For an AC circuit, all three wires are connected inside the AC breaker panel. The panel itself is bonded to the chassis. For a DC circuit, the negative wire from an accessory may connect to a buss bar which is then connected to the battery bank negative. Yes, both AC and DC is typically bonded to the chassis.

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No, I dont think so. My charge controller only has inputs for the batteries and the solar panels
If you need to charge the battery bank from shore power, you will need a charger. In the RV world, most of them are listed as "converter/chargers" - some are combined with an inverter (inverter/charger). I've had excellent results with the Progessive Dynamics products (like this: https://amzn.to/2OjpmaV). Like the charge controller, the charger/converter is 'smart' and charges the battery bank appropriate to its SOC (at least three, preferably four stages). As you can imagine, the "ideal" charger varies based on the size of your battery bank, voltage, etc.
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Old 03-30-2019, 02:36 PM   #8
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I've been trying to research this for the past few days and there is a loooot of conflicting information out there, but from what I have finally been able to piece together (please someone correct me if I'm wrong, I don't want people getting hurt):

DC "ground" is the negative, this gets attached to chassis
AC ground gets attached to chassis
AC negative does NOT get attached to chassis, and does NOT get attached to AC ground, you want a "floating neutral"
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Old 03-30-2019, 02:49 PM   #9
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Quote:
Originally Posted by diannetea View Post
I've been trying to research this for the past few days and there is a loooot of conflicting information out there, but from what I have finally been able to piece together (please someone correct me if I'm wrong, I don't want people getting hurt):

DC "ground" is the negative, this gets attached to chassis
AC ground gets attached to chassis
AC negative does NOT get attached to chassis, and does NOT get attached to AC ground, you want a "floating neutral"
negatives should always be grounded. So AC negative is the same as AC ground
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Old 03-30-2019, 03:07 PM   #10
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Originally Posted by o1marc View Post
negatives should always be grounded. So AC negative is the same as AC ground
Thanks, I'm still reading and I think my misunderstanding stemmed from 1. really old threads from various sources, and 2. the fact that I didn't realize inverters will change the ground source when plugged in to shore

Everything I read says to keep the AC and DC grounds separate, but should you also keep the AC neutral and ground separate? So neutral to a bus bar, ground to a bus bar, and then those each would go to chassis?
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