Newb with Small cabin build 100% off grid help with wiring

[Moonshine82]

Have a 540sq ft off grid cabin I’m trying to power I have 8 310w panels 6 100ah sok lifepo4 battery bank and a growatt 3000 all in one mppt/ inverter , need some wiring help I haven’t purchased my cables yet plz any help would be welcomed

 

[Moonshine82]

Growatt 24V SPF 3000TL LVM

 

[Northernchateau]

1st 310 watts x 8 = 2.480 watts, that Growatt is rated for 2000 watt. 2000 / 310 = 6.45 panels
2nd 145volts max / 40.3 voc = 3.5 panels which means you can run 2 or 3 panels in series
3rd batteries can be 3 pr of 2 batteries in series for 24 volts.

If you got a 2nd growatt you could use all your panels plus have 240 volts.

 

[Moonshine82]

For the panels I’m thinking due to cloud cover etc I’ll be under the rating for the growatt, do I run a risk of damage on it if I just use one?
and would you by chance have any diagrams of your recommendations ?

 

[Northernchateau]

For the panels I’m thinking due to cloud cover etc I’ll be under the rating for the growatt, do I run a risk of damage on it if I just use one?
and would you by chance have any diagrams of your recommendations ?

My suggestion is click the above tab " DIY Solar Blueprint" which has many different ways to wire up solar systems.

 

[iamrich]

Have a 540sq ft off grid cabin I’m trying to power I have 8 310w panels 6 100ah sok lifepo4 battery bank and a growatt 3000 all in one mppt/ inverter , need some wiring help I haven’t purchased my cables yet plz any help would be welcomed

Can you give us more details on how you are going to mount the panels, distance to the Growatt, distance to the batteries, distance to the main panel?

I would go with 2 panels in series 4 times (2S4P). You can over panel as long as you don't exceed max voltage (145v) of the Growatt. In this case you will be under 100v even on a perfect day with cold temps, so 8 panels will be fine (I would have gone with 9, 3S3P).

You have a couple options on wiring, you can go a lot of long smaller wires to a combiner box next to the Growatt, or short small wires to the combiner box close to the panels, and one set of thick wire to from there to the Growatt. I used the first option.

I would run 12awg solar rated wire from the panels to a combiner box and then 6-8awg from the combiner box to the Growatt (and put the two as close together as possible). I would use 2awg cables from the Growatt to the batteries and from battery to battery. Finally I would run 10awg 10/2 with ground Romex (or your local brand name) house wire from the Growatt to the main panel. Depending on how your panel is setup, you may need to jump the two "hot" bus bars together in the panel to power both sides since you will not have split phase.

 

[Diysolar123]

cable sizing is all about wire resistance and the amps involved...
wire resistance is a combination of the wire diameter(how much copper), AND the distance involved.

using a pencil and paper layout your measurements...remember that when adding up wire distances its the complete wire path that counts.
for example, two devices 10ft apart connected with wire means you have 20ft of wire.

once you have the wire distances, use an online calculator to get an idea of the minimum wire guage you should consider.
When working out the maximum current draw, I use the surge limit of the inverter, not the "nominal" wattage.

This link here will get you this minimum wire guage number (fyi, I always use a 1% allowable voltage drop)

Circuit Wizard - Blue Sea Systems

NOW, this is in important step...if you think you may need to increase you panels, move them further away, or have a larger load "someday", use the calculator and play around more amps or longer cable lengths.
It is always nice if you decide you need a few more panels becuase there are more slightly cloudy days than you planned for you can just attach them without having to worry about wire.

 

[Northernchateau]

O

Can you give us more details on how you are going to mount the panels, distance to the Growatt, distance to the batteries, distance to the main panel?

I would go with 2 panels in series 4 times (2S4P). You can over panel as long as you don't exceed max voltage (145v) of the Growatt. In this case you will be under 100v even on a perfect day with cold temps, so 8 panels will be fine (I would have gone with 9, 3S3P).

You have a couple options on wiring, you can go a lot of long smaller wires to a combiner box next to the Growatt, or short small wires to the combiner box close to the panels, and one set of thick wire to from there to the Growatt. I used the first option.

I would run 12awg solar rated wire from the panels to a combiner box and then 6-8awg from the combiner box to the Growatt (and put the two as close together as possible). I would use 2awg cables from the Growatt to the batteries and from battery to battery. Finally I would run 10awg 10/2 with ground Romex (or your local brand name) house wire from the Growatt to the main panel. Depending on how your panel is setup, you may need to jump the two "hot" bus bars together in the panel to power both sides since you will not have split phase.

On paper that's 24% over paneled.
Growatt data sheet calls out 2000 watts max.
What happens if the input goes over 2000 watts?

 

[iamrich]

O

On paper that's 24% over paneled.
Growatt data sheet calls out 2000 watts max.
What happens if the input goes over 2000 watts?

As long as the VOC is not exceeded, the controller just clips at 2k watts. Over paneling is very common.

Off Grid, when your battery is full, and you have no load, what does the controller do with all the power being generated by the panels? It just doesn't accept the power from the panels. Same situation with over paneling.

The OP could also adjust the panels so they are not all facing the same direction. 2 facing SE, 4 facing S, 2 facing SW. This would extend the solar day, and likely allow every last watt to be used assuming there is demand from the battery(s) or loads.

 

[Moonshine82]

Can you give us more details on how you are going to mount the panels, distance to the Growatt, distance to the batteries, distance to the main panel?

I would go with 2 panels in series 4 times (2S4P). You can over panel as long as you don't exceed max voltage (145v) of the Growatt. In this case you will be under 100v even on a perfect day with cold temps, so 8 panels will be fine (I would have gone with 9, 3S3P).

You have a couple options on wiring, you can go a lot of long smaller wires to a combiner box next to the Growatt, or short small wires to the combiner box close to the panels, and one set of thick wire to from there to the Growatt. I used the first option.

I would run 12awg solar rated wire from the panels to a combiner box and then 6-8awg from the combiner box to the Growatt (and put the two as close together as possible). I would use 2awg cables from the Growatt to the batteries and from battery to battery. Finally I would run 10awg 10/2 with ground Romex (or your local brand name) house wire from the Growatt to the main panel. Depending on how your panel is setup, you may need to jump the two "hot" bus bars together in the panel to power both sides since you will not have split

Can you give us more details on how you are going to mount the panels, distance to the Growatt, distance to the batteries, distance to the main panel?

I would go with 2 panels in series 4 times (2S4P). You can over panel as long as you don't exceed max voltage (145v) of the Growatt. In this case you will be under 100v even on a perfect day with cold temps, so 8 panels will be fine (I would have gone with 9, 3S3P).

You have a couple options on wiring, you can go a lot of long smaller wires to a combiner box next to the Growatt, or short small wires to the combiner box close to the panels, and one set of thick wire to from there to the Growatt. I used the first option.

I would run 12awg solar rated wire from the panels to a combiner box and then 6-8awg from the combiner box to the Growatt (and put the two as close together as possible). I would use 2awg cables from the Growatt to the batteries and from battery to battery. Finally I would run 10awg 10/2 with ground Romex (or your local brand name) house wire from the Growatt to the main panel. Depending on how your panel is setup, you may need to jump the two "hot" bus bars together in the panel to power both sides since you will not have split phase.

So 2series 4 in parallel? Or get another panel and go 3series 3 parallel? Or just put them all in series

 

[iamrich]

So 2series 4 in parallel? Or get another panel and go 3series 3 parallel? Or just put them all in series

You CANNOT put them all in series using the Growatt 3k.

If you already have the Longi panels you pictured, I would go 2S4P and call it a day. If you haven't bought them yet and can get 250w Trina (or similar) panels instead, I would go 3S3P.

2S4P Longi Panel = Typical 33.3V/10A x2x4 so 67V/40A. Both well within the Growatts specs. If you have a banner day (laboratory type perfect) you might see close to 2800watts, so the Growatt will clip.

3S3P 250w Trina panels (Santan or local). The specs are a lot closer. I typically run at 97-103V and less than 24a on the sunniest of days which is about 2500w.

If you have the option of pointing your panels in different directions, say x3 South East, x3 South, x3 South West it would give you the same amount of power but spread out over more of the day and I think you would be fine using even the Longi's in 3S3P.

 

[Moonshine82]

You CANNOT put them all in series using the Growatt 3k.

If you already have the Longi panels you pictured, I would go 2S4P and call it a day. If you haven't bought them yet and can get 250w Trina (or similar) panels instead, I would go 3S3P.

2S4P Longi Panel = Typical 33.3V/10A x2x4 so 67V/40A. Both well within the Growatts specs. If you have a banner day (laboratory type perfect) you might see close to 2800watts, so the Growatt will clip.

3S3P 250w Trina panels (Santan or local). The specs are a lot closer. I typically run at 97-103V and less than 24a on the sunniest of days which is about 2500w.

If you have the option of pointing your panels in different directions, say x3 South East, x3 South, x3 South West it would give you the same amount of power but spread out over more of the day and I think you would be fine using even the Longi's in 3S3P.

Great thx , yeah I currently own the 8 longi could get another poss. will these need to be fused as well don’t know the math on the short circuit rating etc , if so will I need 8 fuses in a combiner box or just one

 

[Moonshine82]

Panels will be on roof 18-20ft high all hardware and batteries will be in a solar shed by base of 540sqft cabin

 

[iamrich]

Great thx , yeah I currently own the 8 longi could get another poss. will these need to be fused as well don’t know the math on the short circuit rating etc , if so will I need 8 fuses in a combiner box or just one

I would just use what you have then using 2S4P. I would run 4 sets of 12awg solar rated wire from the roof to the combiner box in conduit. The negative wires (black usually) will all go to the negative bus bar, the positive (usually red) will each go to a separate fuse or breaker. So you will have a combiner box with four fuses or breakers (I used breakers). Then you can use the biggest wire you can fit (it should be a short run) from the combiner to the Growatt (I used 8awg, but you have more amperage so 6awg would be better). For panel ground I just used 1 6awg wire and tied all the panels into that.

 

[Moonshine82]

I would just use what you have then using 2S4P. I would run 4 sets of 12awg solar rated wire from the roof to the combiner box in conduit. The negative wires (black usually) will all go to the negative bus bar, the positive (usually red) will each go to a separate fuse or breaker. So you will have a combiner box with four fuses or breakers (I used breakers). Then you can use the biggest wire you can fit (it should be a short run) from the combiner to the Growatt (I used 8awg, but you have more amperage so 6awg would be better). For panel ground I just used 1 6awg wire and tied all the panels into that.

Would you happen to have a link for a diagram for the 2s4p possibly?

 

[iamrich]

Something like this:

 

[Moonshine82]

Will I have to run a ground wire under ground? If so 18”? 24”?

 

[Northernchateau]

Will I have to run a ground wire under ground? If so 18”? 24”?

The light green arrows refer to Earth Ground. Attach them to a ground rod you put in the ground.

 

[iamrich]

I ground everything to one of these:

ERICO 5/8 in. x 8 ft. Copper Grounding Bar Rod 615880UPC - The Home Depot

ERICO copper-bonded ground rods are the highest quality ground rods available today. We use a unique manufacturing process, which includes drawing the steel rod to size before the copper bonding process

www.homedepot.com

 

[Wellbuilt]

I have a question , I thought you should have only one common ground for a system ?
All my grounds wires go to a common ground at the house .
Invert, panels , generator service panel is this correct .
This is my first post here. Hello every one .