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Off-grid tiny house system

para0489

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May 17, 2023
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Aloha everyone!

I have built a tiny house on a trailer and am now building the off-grid system. I am looking for some advice on grounding my system, wire gauge needed in a few places, and any other insight you might find helpful!

My system is as follows:

Victron quattro 24V/5000A/120V inverter charger, 6x 24V/50Ah LiFePO4 Battle born batteries, 150/70 victron MPPT charge controller, 250A victron busbars.

It is wired as such:

Solar array (still to be purchased and installed but will be ~1600W with Q-cell 400 panels on my standing seam aluminum roof with snap-n-rack system)--> midnite solar combiner box with a 30A DC breaker--> charge controller--> positive end (4 awg fine stranded) to 80A ANL fuse--> positive busbar and my negative end (4 awg fine stranded) to my negative bus bar.

Batteries wired in parallel with 2/0 cable--> positive end to battery switch--> positive bus bar. Negative end to 500A/50mV smart shunt--> negative bus bar.

My positive bus bar is then connected to a 400A class t fuse--> inverter. My negative bus bar connects directly to my inverter.

My inverter is then wired to my electrical panel with 6/2 solid core wire.

I plan to use 6 awg braided copper wire to tie my solar panels together and ground them.

But my question is where do I ground from? Is it ok to ground from multiple locations all to one ground? Do I treat this as a floating system since it is a trailer and just bond the trailer and gas lines together with my system? If I ground from one place in my system (the electrical panel, the solar array, the negative busbar, etc.) is my entire system grounded because I am all tied together? Should i use a grounding rod? Should I just bond my electrical panel to my trailer and gas lines and then earth ground my solar system?

What gauge wire should I use to connect my solar strings to my combiner box and my combiner to my charge controller?

Any insight is appreciated!

Thank you!
Dustin
 
All grounding connects back to the electrical panel.
This includes anything metal.
Trailer frame, solar panel frames, inverter, gas and water piping.
I Believe that Victron wants a connection from DC negative to Trailer frame. (Please verify that in your manual)
There should be a ground rod also connected to the panel. (If the trailer is stationary)

Solar circuit wiring size should be based on the circuit requirements. (Check solar panel labels)
And depends on how you configure the strings.
 
This includes anything metal.
Trailer frame, solar panel frames, inverter, gas and water piping.
Just to clarify; So I would pull a ground wire from my electrical panel ground bar and run one long wire that is connected to my metal items: trailer, gas line, copper water lines, inverter, solar array, charge controller, and propane water heater, that will terminate at a grounding rod?

If my propane water heater is plugged into an outlet on my electrical panel it would essentially be grounded as long as my panel is grounded, yes? If so, it wouldn't need to be included in the grounding wire right?

My solar panels spec out at 43.5V and 11A.
 
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Is it not problematic to have DC components and AC components tied together on the same ground wire/rod and connected to my AC panel?
 
Here are some diagrams from the inverter manual. It shows grounding points for both AC-IN locations. If from a shored plug-in on a grounded system that makes sense but if its from being plugged into a generator, where would that ground be satisfied from? I can tie a wire to it from my plug-in wire but is the generator making that in supply grounded?

I do see the ground lug on the metal body, is this the one that should be tied to the earth ground wire?
 

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Just to clarify; So I would pull a ground wire from my electrical panel ground bar and run one long wire that is connected to my metal items: trailer, gas line, copper water lines, inverter, solar array, charge controller, and propane water heater, that will terminate at a grounding rod?
Doesn't have to be a single wire.
Can be individual wires to each item. Or any combination of items.
If my propane water heater is plugged into an outlet on my electrical panel it would essentially be grounded as long as my panel is grounded, yes?
Correct
Is it not problematic to have DC components and AC components tied together on the same ground wire/rod and connected to my AC panel?
It depends on what the manual calls for.
Victron equipment is designed for mobile applications.
but if its from being plugged into a generator, where would that ground be satisfied from?
You'll have to check the generator manual to see if it has N/G bonding internally.
Also have to check the inverter manual for this.
If neither do, then you can do it at the electrical panel.
If one or the other does, then you will have to figure out the best way to handle it. There should be only one N/G bond at any given time.
 
Doesn't have to be a single wire.
Can be individual wires to each item. Or any combination of items.
Ok, but, all ground wires return to one earth ground rod still?

This is from the inverter manual:

"Ground relay (see appendix B)

With this relay (E) the neutral conductor of the AC output is grounded to the casing when the back feed safety relays in the AC- in-1 and the AC-in-2 inputs are open. This ensures the correct operation of earth leakage circuit breakers in the outputs.
- If a non-grounded output is required during inverter operation, this function must be turned off. (See also Section 4.5)
Not adjustable with DIP switches."

If I am understanding it correctly, the AC-out is grounded unless I have an input on either AC in-1/2. Is that correct? This is essentially saying it is bonding itself to the inverter casing to allow flow back to a breaker further down the line from the AC-out?
 
If I am understanding it correctly, the AC-out is grounded unless I have an input on either AC in-1/2. Is that correct? This is essentially saying it is bonding itself to the inverter casing to allow flow back to a breaker further down the line from the AC-out?
Correct
So, the victron takes care of itself.
Just need to figure out if the generator has a N/G bond.

Ok, but, all ground wires return to one earth ground rod still?
All grounding returns to the electrical panel ground bar. Including the ground rod.
 
In this example they show grounding from the case of the inverter going to the negative bus bar and then from the bus bar to an earth ground. So in this case the inverter and all of the ac-out is grounded to the busbar. And I could tie my charge controller case and racking system to this bar. And then could tie my panel to my trailer frame and water/gas lines.

If both of these grounds led to an earth ground, my system would be entirely grounded and safe?

And if I had a generator on AC-IN that is bonded, that would still leave my grounded system complete?
 

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If both of these grounds led to an earth ground, my system would be entirely grounded and safe?
The ground rod (earth ground) doesn't make your system safe. It makes the earth safe by connecting it to your grounding system. An electrical grounding system starts at the N/G bond.
And if I had a generator on AC-IN that is bonded, that would still leave my grounded system complete?
If the generator has N/G bonding and the victron will pass that through to the loads. Then yes, the system is safe. (While the generator is connected)
 
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