Expedient setup

[Bluedog225]

Here’s my expedient ground mount. I’ve got to get some power to cool the conex before summer. Expansion later.

Plan as follows:

3 panels per string at 38.7 volts. 1.2 temperature safety factor. 139.2 volts on Victron 150/35. Check.

9.26 amps Isc per string. 3 strings. 27.78 amps. Below 40 amp Victron limit. Check.

10 awg “solar” wire to combiner box. Midnite MNPV6 combiner with 30 amp fuses to panels and 30 amp breaker to MPPT. Right?

Victron worthy 10 awg (minimum) fine strand from the combiner box to the MPPT. And from the MPPT to the bus bar.

I have a spare Victron 150/35 and may double this array as a duplicate. Or add one more string of 3 panels. This would still keep me below the MPPT limit of 40 amps.

Any obvious errors here?

Thanks

 

[timselectric]

30 amp fuses to panels

Doubtful that the panels are rated for 30a.
What do the stickers say?

Any obvious errors here?

You didn't mention grounding.

 

[Mattb4]

Nice stout I-beams. If you tilt the I-beams up a bit you will get a better angle for solar production (a sawhorse perhaps?). I would also want to come up with a clamping method to prevent wind from scattering the panels about. Might be as simple as drilling a hole for a bolt and using a washer over the panel edge.

 

[Bluedog225]

Doubtful that the panels are rated for 30a.
What do the stickers say?

You didn't mention grounding.

First, yes on grounding. Will do.

Second, they are 15 amp max series fuse. I’m just wrapping my head around your posts on parallel fusing and multiple strings.

If I understand, one string shortening will send 9 amps to the other strings thereby exceeding the 15 amp limit. Right?

Switch the 30 amp string fuses for 15 amp addresses this, correct?

And keep the 30 amp fuse to the mppt.

Thanks

 

[Bluedog225]

And while we’re are here, with these panels, wouldn’t I need a fuse for 2 parallel? Or am I confused?

 

[timselectric]

If I understand, one string shortening will send 9 amps to the other strings thereby exceeding the 15 amp limit. Right?

If one string is shorted. All other strings will send their current to it.
This is the reason for fusing parallel strings. To protect the shorted string from the rest.

Switch the 30 amp string fuses for 15 amp addresses this, correct?

Yes

And while we’re are here, with these panels, wouldn’t I need a fuse for 2 parallel? Or am I confused?

No
With only 2 strings. There is only 1 strings energy available to a shorted string.

 

[Bluedog225]

If one string is shorted. All other strings will send their current to it.
This is the reason for fusing parallel strings. To protect the shorted string from the rest.

Yes

No
With only 2 strings. There is only 1 strings energy available to a shorted string.

I see. I had it backwards. Of course the current flows to the short.

Still a little confused. If the shorted panels can absorb their own 9.26 amps, and the other string sends them another 9.26, then don’t we exceed the maximum rating of 15 amps?

 

[timselectric]

I see. I had it backwards. Of course the current flows to the short.

Still a little confused. If the shorted panels can absorb their own 9.26 amps, and the other string sends them another 9.26, then don’t we exceed the maximum rating of 15 amps?

A panel can't produce and receive power at the same time.
It's one or the other.

 

[45North]

Texas is about 32 deg latitude so you could use a bit of a tilt, say 32-15=17 deg for summer (32+15=47 for winter and 32 in between, if you want to optimize)
Or just leave'em at 32 deg year-round if you can't be bothered moving 'em.

 

[Gold Country Russ]

Alternate idea: Rotate the panels 90 degrees into 5 rows of 2 between the six I-beams. Drill & tap 24 suitable hole to use standard aluminum edge & mid-clamps. Mount on the container roof with 1.5" X 3" rectangular steel legs welded between the I-beams and the containers 60mm Sq. top roof edge tube. Leg lengths should result in about a 30deg angle from horizontal. Sight the container so panels face due south.

 

[Bluedog225]

Yes. Many plans for later. Needed to throw something down quick.

 

[Nobodybusiness]

Yes. Many plans for later. Needed to throw something down quick.

View attachment 215192

Iron ridge?

 

[Gold Country Russ]

I will be putting 9.6KW (24-400W panels) on a 40' container very soon.

 

[Bluedog225]

Iron ridge?

4” and 3” rigid conduit, double strut, and some rails I got from resort. The name of the post caps isn’t coming to mind just now.

 

[Bluedog225]

A panel can't produce and receive power at the same time.
It's one or the other.

Thanks. It’s not sinking in. I’ll study up some more.

 

[AntronX]

LOL don't fuss over temp setup, it looks fine. Chances of one string becoming dead shorted are non existent unless you short it by mistake. If this is low voltage off-grid setup I would not even bother grounding. I would if it was AIO.

 

[Bluedog225]

Well, the Overcurrent Protection Devices (OCPD) on Solar Arrays resource document seems to indicate that 3 or more parallel string protection must be less than the series fuse rating.

That points to a 10 amp fuse. A 15 amp file is too large.

But the over current protection device needs to be 1.56 of the Isc.

9.26 * 1.56 = 14.4456 amps.

How do I reconcile these?

@FilterGuy

Thanks

 

[timselectric]

string protection must be less than the series fuse rating.

Less is fine, it just can't be higher. If you read the sticker on the solar panel, It says "maximum".
But if you go too low, it could trip/blow during normal operation.

 

[Bluedog225]

These fuses don’t seem to come in fine increments. It looks like 10 or 15 amps.

10 is too low and 15 is too high.

Or an I missing the boat? I’ll have another look tomorrow when I’m clear headed.

 

[Bluedog225]

Iron ridge?

Tamarack post caps. The rest as above.