Outback Radian 8kW or MPP Solar pair for 13kW?

[JustPractical]

I used iron ridge 1000 in 24’ lengths
I bought them from my electrical supply house with all the parts necessary I just drove over and picked it all up .
Dropped a skid of panels in the back of the truck and strapped the 24’ bars to the roof .
I’ve never really had any one recommend the more the Merrier for solar panels .
I’ve seen 18 300 watt panels on a quote for a system with a fm 80 .
I know I have 15 panels and my not pass inspection because I’m over the 4000watts specked by the manufacturer .


Hmmm this is a very interesting idea
I was thinking about ground mounting 12 or 15 more panels to my system for winter so I can clean off the snow.
I only get 2000 watts max in the winter so in theory I could double my array and still be under the 4000watts max for a fm 80 .
I only charge with 3 strings 2700watts of solar 6 months out of the year now , but in the winter it’s really gloomy .
I could just turn off the extra panels if I don’t need them .
I guess that the inspector would not like the idea . Your thoughts ?

The iron ridge 1000 says it can go with supports every 12'?!?!? That would be sweet. I would just spook that the wind might pull them off the roof...
How far did you space out your supports?

 

[Hedges]

Hmmm this is a very interesting idea
I was thinking about ground mounting 12 or 15 more panels to my system for winter so I can clean off the snow.
I only get 2000 watts max in the winter so in theory I could double my array and still be under the 4000watts max for a fm 80 .
I only charge with 3 strings 2700watts of solar 6 months out of the year now , but in the winter it’s really gloomy .
I could just turn off the extra panels if I don’t need them .
I guess that the inspector would not like the idea . Your thoughts ?

Some vendors say extra wattage is OK.
Spec typically gives max Voc (including adjustment for cold), max operating current, and max Isc allowed.
If you can show Isc isn't exceeded, that might satisfy him. For instance some Sunny Boy spec max 10A max operating current, 18A max short-circuit current. You could have sum of Imp well over 10A but sum of Isc under 18A.

 

[Hedges]

The controllers are ul listed and rated for 4000watts i think that is a problem

And they will never put out over 4000W.
It is normal to put in more than 4000W (STC) because PTC output is less. Some SCC/inverter spec sheets to list maximum array wattage.
With two PV strings oriented differently, they produce power at different times. Peak wattage is not the sum of peaks of each array.
I think if you keep Voc and Isc within spec, an inspector (or plan reviewer) ought to accept the multiple orientations.

 

[BMcL]

will you wire those all in parallel? I had *thought* I read it's not good to put more than 5 batteries in parallel (but I've also read you're not supposed to step on a crack in the sidewalk...)

Yeah, they have to be in parallel to maintain 48 volts. The most I would buy is 3 to 4 sets of 16s 280AH batteries.

 

[Wellbuilt]

There just isn’t ?‍ No one has that that I know of , that is why we have to figure out how cold it gets .
I turn off my system when I’m not there , some times I’ll leave one string of solar on if I don’t have time for the battery’s to charge to full .

The iron ridge 1000 says it can go with supports every 12'?!?!? That would be sweet. I would just spook that the wind might pull them off the roof...
How far did you space out your supports?

It depends , the rack would hold up but the feet hold the rack down in the wind would pull out .
The engineers had a Specified lay out like this
a foot on each end then a foot at 16” into a beam
Second row starts at 32”
3rd row at 48”
4 row back to 16”
this is standard in my area even for grid tie systems .

 

[Wellbuilt]

And they will never put out over 4000W.
It is normal to put in more than 4000W (STC) because PTC output is less. Some SCC/inverter spec sheets to list maximum array wattage.
With two PV strings oriented differently, they produce power at different times. Peak wattage is not the sum of peaks of each array.
I think if you keep Voc and Isc within spec, an inspector (or plan reviewer) ought to accept the multiple orientations.

Cool I mite try this .
I’ve been building my place since 2014 and a lot has changed with the permitting for solar in my area .
I hope I don’t get a hard time for my final inspection .

 

[JustPractical]

There just isn’t ?‍ No one has that that I know of , that is why we have to figure out how cold it gets .
I turn off my system when I’m not there , some times I’ll leave one string of solar on if I don’t have time for the battery’s to charge to full .


It depends , the rack would hold up but the feet hold the rack down in the wind would pull out .
The engineers had a Specified lay out like this
a foot on each end then a foot at 16” into a beam
Second row starts at 32”
3rd row at 48”
4 row back to 16”
this is standard in my area even for grid tie systems .
View attachment 70309

Meh. Did not know it was a best practices to stagger the feet. Makes a load of sense (reduces chance of failure), BUT...more potential for me missing a rafter. It is the part of this project I have the most worries over - I just imagine myself drilling loads of pilot holes that miss. Thanks for the drawing.

 

[BMcL]

Hmmmm I would look at there all in one system for 7k $ ish it gives you 2 fm80s a mate fndc power monitor and all the wiring , switches / breakers all ready to go .
You just hook up your battery’s , hook up your solar , hook up your ac out and genarator /grid input .
The unit comes tested and ready to go .
When I bought my system a out back flex power one it was cheaper then if I bought every thing and Assembled it myself .
where ever you buy make sure they have good tech support it’s more important then the price.
If I had internet I could have a engineer from Arizona wind and sun log into my system and trouble shoot and adjust settings , The guys are good .

Agree but I worry that 8000 kw isn't going to be enough. Seems like if I need two 8kw radians that it would be far cheaper to follow one of Will Prowse's videos (like the double LV6548 setup) and wire everything up like he did.
I'm sure two 8kw radians would be overkill for me and I wouldn't have to worry about capacity. Just need lots of batteries.

 

[Wellbuilt]

Agree but I worry that 8000 kw isn't going to be enough. Seems like if I need two 8kw radians that it would be far cheaper to follow one of Will Prowse's videos (like the double LV6548 setup) and wire everything up like he did.
I'm sure two 8kw radians would be overkill for me and I wouldn't have to worry about capacity. Just need lots of batteries.

Hey I would not want any one to have to live like a cave man , but you could use less power .
Maybe take some battery inverter cash a get a wood burner ?
And supplement your heat, you will need a ton of battery’s to run the heater over nite .
I havev430 ah 48 volts i use 10% of that over nite but I don’t run big loads over nite .

 

[Wellbuilt]

Meh. Did not know it was a best practices to stagger the feet. Makes a load of sense (reduces chance of failure), BUT...more potential for me missing a rafter. It is the part of this project I have the most worries over - I just imagine myself drilling loads of pilot holes that miss. Thanks for the drawing.

I don’t remember what type of roof material you have it the holes are easy .
Look in the attic and find the beams ,
just drill one hole next to your first bean where you want to start from the inside out .
Check the framing and make sure of the spacing .
Most homes are 16” or 24” on center .
use your tape to mark out the beams , then use a big nail and hammer down and find the beam .
I even make a few holes to get the bolt in the center of the beam .
I drill the hole for the lag bolt .
Full the holes with polyurethane roof sealant ( supper sticky stuff )
lift the shingles and slip the flashing in .
Easy peezy .

 

[BMcL]

Hey I would not want any one to have to live like a cave man , but you could use less power .
Maybe take some battery inverter cash a get a wood burner ?
And supplement your heat, you will need a ton of battery’s to run the heater over nite .
I havev430 ah 48 volts i use 10% of that over nite but I don’t run big loads over nite .

I do have a propane fireplace that heats the house on the low setting. Ran it for a week when it got down to 9 degrees (unusual for Nashville) and the heat pump never ran.
It's possible the 2nd 8kw radian wouldn't be needed most of the time. It's a shame Outback doesn't have a 12kw model.
That would work for sure.

 

[MrM1]

OK, so the more panels the merrier. I was aware of not going over Voc, and I assumed going over the watts would also cause problems. Makes more sense that it would just not take what it can't use.

This from Signature Solar as an email to me As to OverPaneling the Growatt 12kw and how the two PV inputs work for the MPPT SCC (PV1 and PV2).

(Me) Page 10 of the Manual - Indicates There are 2 PV input connections for the 12k version, but there is very little or no explanation of why or how they are used. I assume this has to do with MPPT tracking? Are there MPPT settings in the charge controller section of the control parameters? Not finding much about this or Array arrangement.
These models are essentially 2 6kw units combined into one. Each MPPT controller can handle 7000W from the array and the settings will be determined by total input.

8. We want to over panel the setup, but the manual in the specs only lists the inverter is rated for a 7000w array. Why is this a limitation? If we keep the array input under 250vdc wouldn't any over current just simply not be used? We would like to over panel because we have seen about a 15% drop off in rated power from an array on average here in FL on other off grid systems. Would like to build out a 8000w or 10,000w array for cloudy days, and to maximize power harvest in the mornings and afternoons.
As long as you do not exceed the VOC/VDC you can have more than 7000W of power generated from your panels, however it will not be inverted so it will be wasted.

 

[Wellbuilt]

I do have a propane fireplace that heats the house on the low setting. Ran it for a week when it got down to 9 degrees (unusual for Nashville) and the heat pump never ran.
It's possible the 2nd 8kw radian wouldn't be needed most of the time. It's a shame Outback doesn't have a 12kw model.
That would work for sure.

i would go that way just plan on heating with propane in a emergency ?
It sounds like a no brainer .
8k is a lot of power , a sub pump running all nite will be a battery issue not really a inverter problem .
at least you are down south where it’s sunny ?
I’m about to get buried in snow again , it’s like some one turns off the sun here .

 

[BMcL]

i would go that way just plan on heating with propane in a emergency ?
It sounds like a no brainer .
8k is a lot of power , a sub pump running all nite will be a battery issue not really a inverter problem .
at least you are down south where it’s sunny ?
I’m about to get buried in snow again , it’s like some one turns off the sun here .
View attachment 70393

Nice looking place ! Deer season ?
Does the Outback Radian keep a record of power demand ?
I could add appliances slowly over months to the panel and see if I was safely under the 8kw redline.

 

[Wellbuilt]

Deer rifle season is coming , bow season is now .
I can just get my deer standing on the porch I live in the woods ?
sure thing the mate keeps a record of every thing .
I don’t think you will have a problem
a sub pump can draw a lot of power ?
Your well draws a lot of power .
A/c draws a lot of power .
Are you going off grid? Or is this a back up system ?

 

[newbostonconst]

Nice looking place ! Deer season ?
Does the Outback Radian keep a record of power demand ?
I could add appliances slowly over months to the panel and see if I was safely under the 8kw redline.

Optics RE is the utility to do that type stuff but I have never used it.

 

[BMcL]

Deer rifle season is coming , bow season is now .
I can just get my deer standing on the porch I live in the woods ?
sure thing the mate keeps a record of every thing .
I don’t think you will have a problem
a sub pump can draw a lot of power ?
Your well draws a lot of power .
A/c draws a lot of power .
Are you going off grid? Or is this a back up system ?

I will be totally off-grid to avoid government regulations. It is primarily for backup.
I'm in a subdivision so no wells are allowed.

 

[Hedges]

Got any hillsides that happen to have water seeping out, causing problems?
Where I come from, "Wells" require a permit and licensed well-drilling contractor. "Dewatering points" do not.

 

[SolarPrep]

Agree but I worry that 8000 kw isn't going to be enough. Seems like if I need two 8kw radians that it would be far cheaper to follow one of Will Prowse's videos (like the double LV6548 setup) and wire everything up like he did.
I'm sure two 8kw radians would be overkill for me and I wouldn't have to worry about capacity. Just need lots of batteries.

Outback inverters can be cross-stacked. You can add a 4k unit to an 8k unit, if your don't need two 8k units.

 

[BMcL]

Outback inverters can be cross-stacked. You can add a 4k unit to an 8k unit, if your don't need two 8k units.

That's good to know . Thanks