Looking for help designing an off grid system

[Hedges]

Generator is much more expensive to operate, and bother.
If grid less than completely reliable, then inverter, batteries, PV can provide backup.
PV can be significantly less expensive than grid. At least the panels; balance of system can get expensive.

Inverter systems may actually be less reliable than grid, and don't have a crew backing them. It is good to have a bypass mechanism (transfer switch or interlocked breaker) so you can use grid instead.

What size inverter would you suggest?

It costs you nothing to go ahead and run through the design steps now, so you know where you want to go ... a few calculations, power audit, and such will help you know what an "ideal" system is for your home and needs.

...

The design steps:

1. Go here, and enter in each appliance's values (watts, hours/day you want to run it, etc.):
https://unboundsolar.com/solar-information/offgrid-calculator

2. Go here, using numbers from above, and fiddle with various entries/components, and you'll see in real-time what your system component (inverter, mppt, panel) sizing is:
https://www.altestore.com/store/calculators/off_grid_calculator/

...

Once your initial calcs are done, you can see Will's videos & diagrams for example systems, under "DIY Solar ..." drop-down list at top of this forum. It's a journey, and lots of learning (some of which you've already done), but I think a fun one!

That's an approach to determining what size inverter (and other components) you need.
You also have the old inverter size to give you an idea.

There are 3kW inverters, 5kW, larger. Consider one large enough to run all loads you would ever want at once.
There are cheap imports and well known well built products.
Your budget is a factor too - you can buy an inverter/charger, may also have PV input, from about $700 to $7000, some outside that range.

Especially because I have lead-acid I would prefer one which can blend PV & battery power with utility AC, so battery remains at float/fully charged so long as loads don't exceed programmed grid current limit.

Your lithium can take 5x or so the cycles of my battery. Inverter should have option to allow battery cycling to some DoD, so battery could cycle at night and recharge from PV during the day, not drawing from grid unless consumption exceed production over the entire day.

 

[OffGridForGood]

There is a lot of good advice here, but the replies leave us in the dark too much to be very specific with suggestions:
I have not see a clear reply on the utility supply you have installed: is this 120 2C or is this 240 3C ?All we know is it is 450 feet long, 10AWG.
As Hedges has pointed out, just running your rather low power needs from the utility would likely be lowest up-front cost to just make use of this utility connection, however we know nothing about what the costs are associated with this line, where it comes from, why it may be unreliable, is it 10-cents per kWh or 47-cents, we don't know.
For Inverter recomendations, as noted earlier, there are small 120V single phase units for as low as $700 or as high as $7,000. We have no feed back on what the budget limit/expectations are.

IF your whole system can run 120V single phase, and your on a budget, look at singel AIO like the Growatt or EG4 or MPP-Solar.
IF that 10AWG wire you already have is providing 120/240 split phase (3C+Gnd) AND your on a budget, I suggest the MPP 6048's like I have, since a single unit ($960) will give you 120 and 240 in one single AIO unit at low cost.

IF your not restricted by budget, look at higher tier equipment from Victron, SMA, Fronius, SolArk.
To me, if you feel your loads are met with 3kW output, I would plan on 5-6kW since it seems we only add loads to a system.
Hope this helps lead you in one direction or another.

 

[Zwy]

What 240 loads do you need to run? Fridge, washer, lights - sound like all 120v AC loads to me. Did I miss something?

Yes, you did miss something. His generator is 240V and his current system is setup for 240V split phase.

If you stick to just 120, the standby consumption may be lower, and cost of equipment will be less.

I'd go with a split phase inverter if one really wants the minimum.

In a simple plug and play set up you could use one of the entry level 3kW 120volt (single phase) inverters like the Growatt, or MPP or several others that are more or less re-branded Voltronics inverters. But these are also pretty hungry on stand-by current. If you have the budget, a higher tier Victron 3kW will run less standby, but cost up front x3 or x4. Depends what your budget is.

For all we know he might be using close to 30A per leg intermittently peak currently. I'd recommend an inverter of at least 4Kw per leg.

"My power line is #10 two conductor w ground. It is 450' and I have 120v on both conductors and used the ground as the neutral. At the end of the run I'm using the ground rod as the ground. The source is a 30a split phase breaker."

Not a good idea. If you had used 10-3 with ground it would be ok. The impedance of the ground might mean that ground fault protection will not work, are you bonded on your end? While the earth is high resistance and very low current could flow thru earth back to source, if the neutral becomes open then it could be a problem.

 

[Zwy]

My name is Danny. I'm living in a house that has been off grid for over 30 years. The latest system has been in place since 2015. It was a 12v lead acid battery bank with an inverter/charger and a solar with panels.
The battery bank was 16 250ah 6v golf cart batteries wired seriesD3/parallel. The panels are Siemens 75w Pro 4jf of which there are six. The inverter/charger is a Xantrex freedom sw-12. 815-3012 and the solar charger is a PWM taper charge CC-60E.
This system was in place when I moved here in 2020 so my knowledge of the system is limited. There is a generator that would charge up the batteries when they got low. In 2021 I installed a direct bury #10 wire from a power source 450 feet away. That eliminated the need for the generator for a year.
Our power requirements are lower than most. We cook, dry clothes and refrigerate with gas.
The original batteries are no longer usable. Recently I have acquired 16 280ah 3.2v lifepo4 cells. Unfortunately I feel like a dog whose chased a truck and caught it! What do I do now? Having looked around there appears to a lot of ways to go. I'm hoping to get ideas to aid in this endeavor.
My plan is to make a 48v system and swap the propane refrigerator for an electric one. Any advice on how to complete this project would be greatly appreciated.

What is your budget?

One thing about higher battery voltage is the cable size doesn't need to be large to carry the same watts.

 

[Hedges]

"My power line is #10 two conductor w ground. It is 450' and I have 120v on both conductors and used the ground as the neutral. At the end of the run I'm using the ground rod as the ground. The source is a 30a split phase breaker."

Not a good idea. If you had used 10-3 with ground it would be ok. The impedance of the ground might mean that ground fault protection will not work, are you bonded on your end? While the earth is high resistance and very low current could flow thru earth back to source, if the neutral becomes open then it could be a problem.

A ground rod may give about 25 ohms, will not trip the breaker. If 3-wire (including "ground") is used for L1, N, L2, and ground connection only goes to a stake in the ground, fault from L1 to chassis could still put most of the 120V between your body and earth.

A 2-pole GFCI breaker, you could get away with it. But I'd rather the chassis had copper wire back to neutral-ground bond at source.

If N-G bonded at both ends, neutral open as you mention would electrify chassis without even needing a fault (short).

So my preference is either L1/N/G for 120V, 6A, 720W or L1/L2/G for 240V, 12A, 2880W (in this case use isolation transformer and derive neutral)
That's all the power available without exceeding 5% voltage drop. But over a 24 hour day it is quite a bit. Even 720W x 24 hour is 17kWh, would take a 3.5kW PV array with 5 hours sun to match that. Winter maybe twice that size array.

 

[OffGridForGood]

The inverter/charger is a Xantrex freedom sw-12. 815-3012 and the solar charger is a PWM taper charge CC-60E.

Looking online the Xantrex is a 120V output single phase output inverter based on 12V DC.

This system was in place when I moved here in 2020 so my knowledge of the system is limited. There is a generator that would charge up the batteries when they got low.

No mention from the OP of this being a 120V only or 120/240 output generator. The Xantrex is 120 only anyway.

In 2021 I installed a direct bury #10 wire from a power source 450 feet away. That eliminated the need for the generator for a year.
Our power requirements are lower than most. We cook, dry clothes and refrigerate with gas.

Low loads, 3kw Xantrex has been supplying the loads up until now. The description seems like this is a decent inverter, any reason not to just keep using it and build the LiFePO4 12-volt to just replace the Lead-acid batteries. See if you can add some additional PV to increase ability to charge the new batteries.

 

[Zwy]

A ground rod may give about 25 ohms, will not trip the breaker. If 3-wire (including "ground") is used for L1, N, L2, and ground connection only goes to a stake in the ground, fault from L1 to chassis could still put most of the 120V between your body and earth.

I agree 100%.

A 2-pole GFCI breaker, you could get away with it. But I'd rather the chassis had copper wire back to neutral-ground bond at source.

If N-G bonded at both ends, neutral open as you mention would electrify chassis without even needing a fault (short).

It also passes current thru earth so it would be quite deadly.

So my preference is either L1/N/G for 120V, 6A, 720W or L1/L2/G for 240V, 12A, 2880W (in this case use isolation transformer and derive neutral)

I recommend if this line is used, it is only used as a 120V circuit and using a battery charger like the Chargeverter for charging the batteries.

That's all the power available without exceeding 5% voltage drop. But over a 24 hour day it is quite a bit. Even 720W x 24 hour is 17kWh, would take a 3.5kW PV array with 5 hours sun to match that. Winter maybe twice that size array.

 

[Hedges]

"Low loads, 3kw Xantrex has been supplying the loads up until now. The description seems like this is a decent inverter, any reason not to just keep using it and build the LiFePO4 12-volt to just replace the Lead-acid batteries. See if you can add some additional PV to increase ability to charge the new batteries."

I think MPPT not PWM for lithium.