How far can panels be from inverters in a 48v setup.

[timselectric]

Combiner boxes are pretty, but an added expense.
All that you need are mc4 fuses and mc4 Y connectors. This is what I have on my roof.

A couple of suggestions:
Try to keep all 5 of each string facing the same direction.
And,
It's recommended to install blocking diodes on paralleled strings that face different directions.

 

[Visionguild]

Sorry, I think that I got 250 ft, from another post.
Yes, 10 gauge should be more than fine.

Wonderful. Thank you for your help. I appreciate it. I'm not sure if I'll need a combiner box or not. That's the next step after I get these panels up. I'm using 2 3000k LVM Growatts. Learning about all of this as I go. Thank god for this forum.

Combiner boxes are pretty, but an added expense.
All that you need are mc4 fuses and mc4 Y connectors. This is what I have on my roof.

A couple of suggestions:
Try to keep all 5 of each string facing the same direction.
And,
It's recommended to install blocking diodes on paralleled strings that face different directions.

Ah, good to know about the fuses and connectors. I'll need to order those. So when you say direction you mean just that, like that they're all facing the sun in the same angle, not whether they're same side up correct? Like they don't have to all be set where the tops are all at the 'top' so to speak. Sorry for the newb question, I know it's kind of silly. I have the six you see on the diagram on the smaller shed already installed but with the 'tops' (top being the side the wires are closest to) set so they're close to each other, meaning the upper ones are turned around so the wires are right there easy to connect.

 

[timselectric]

In respect to the sun.

 

[timselectric]

The only orientation that I would advise against is junction box at the lowest point. They are designed to be weather proof, but things happen sometimes.
I wouldn't want water to follow the wires to the junction box. Just in case the seal didn't hold.

 

[Visionguild]

Combiner boxes are pretty, but an added expense.
All that you need are mc4 fuses and mc4 Y connectors. This is what I have on my roof.

A couple of suggestions:
Try to keep all 5 of each string facing the same direction.
And,
It's recommended to install blocking diodes on paralleled strings that face different directions.

In respect to the sun.

Thanks! I thought so. just saw your email about the junction boxes. Duly noted. Thanks. Ok, last question! Take a look at the pic I included, do I just need fuses on the + ? And on the two groups on the left, since I do have two groups in parallel facing slightly different directions, where inline would the blocking diodes go? I'm assuming that's an inline item? Or something that connects? I thought all panels made to function in the US had diodes. No?

 

[timselectric]

Fuses and blocking diodes go on the positive wires.
Fuses are required when 3 or more strings are paralleled together.
Blocking diodes are used on strings that are paralleled with other strings that face a different direction or angle.
The panels have "bypass diodes" built into the junction box. These are different from "blocking diodes".

 

[Visionguild]

Fuses and blocking diodes go on the positive wires.
Fuses are required when 3 or more strings are paralleled together.
Blocking diodes are used on strings that are paralleled with other strings that face a different direction or angle.
The panels have "bypass diodes" built into the junction box. These are different from "blocking diodes".

Perfect. Thanks. So I guess I'm ok on not using fuses then as I'm only putting 2 strings together but I should get blocking diodes for the two that are facing slightly different angles. Would I be getting two diodes? One for each + string coming from each group or just one on them after they're summed with the y connector?

 

[timselectric]

So I guess I'm ok on not using fuses then as I'm only putting 2 strings together but I should get blocking diodes for the two that are facing slightly different angles.

Correct
And one for each positive, before the Y.

 

[Visionguild]

Correct
And one for each positive, before the Y.

Thank you so much for all your help. I can't tell you how much I appreciate it. Good folks on here. Cheers Tim.

 

[Hedges]

I'm of the opinion blocking diodes don't matter.
My measurement showed Voc of a panel in the shade is similar to Vmp of a panel in direct sun. It will not pull down much current if any.
So power loss through diode drop would likely exceed loss through backfeed.

If there is shade, try to arrange panels so it hits equal number of panels in each string. If it is going to hit a diode-bypassed 1/3 section of a panel, that is better than part of all three 1/3 sections.

 

[Visionguild]

I'm of the opinion blocking diodes don't matter.
My measurement showed Voc of a panel in the shade is similar to Vmp of a panel in direct sun. It will not pull down much current if any.
So power loss through diode drop would likely exceed loss through backfeed.

If there is shade, try to arrange panels so it hits equal number of panels in each string. If it is going to hit a diode-bypassed 1/3 section of a panel, that is better than part of all three 1/3 sections.

Ok. Thank you Hedges. yeah, they're all going to be in the sun pretty equally. No real shade around except in the early morning as the sun gets over some trees, but after 10 till about 6pm they'll all be getting equal sun.

 

[onokai]

Are Fuzes needed?
I have two strings 12 panels 400 watt panels in each string going directly into a Sol Arc 100 feet away with only a disconnect switch between on each string. No fuze
tell me the upside and downside of adding a fuze to the positive wires?

 

[OffGridInTheCity]

Wonderful. Thank you for your help. I appreciate it. I'm not sure if I'll need a combiner box or not. That's the next step after I get these panels up. I'm using 2 3000k LVM Growatts. Learning about all of this as I go. Thank god for this forum.

One advantage of 10awg 'PV wire' is it's usually UV resistant - my point is that whatever wire you use on the roof (even if under the panels) that is exposed to outdoors (sun UV) will do better if you get UV rated wire. After all, the panels may last 25yrs and you want the wiring to last the same .

 

[timselectric]

Are Fuzes needed?
I have two strings 12 panels 400 watt panels in each string going directly into a Sol Arc 100 feet away with only a disconnect switch between on each string. No fuze
tell me the upside and downside of adding a fuze to the positive wires?

Fuses are only required for 3 or more parallel strings.
The reason for this is that if a string gets shorted. Any other strings in parallel with it, will send all of their power to it. The panels are rated to handle their regular output. So one string in parallel, will send the same amount of power that the string is rated for. But two strings in parallel with a shorted string, will send twice the amount of power that the string is rated for.
Then, it's time for the marshmallows.

With that being said, I have Fuses on all of my strings. Even though it's not require. It's cheap insurance, and helps me sleep at night.

 

[timselectric]

One advantage of 10awg 'PV wire' is it's usually UV resistant - my point is that whatever wire you use on the roof (even if under the panels) that is exposed to outdoors (sun UV) will do better if you get UV rated wire. After all, the panels may last 25yrs and you want the wiring to last the same .

Yes, all of my wiring (underneath the panels) on the roof is PV wiring. I changed over to THHN at the junction box. Then it's ran down to the inverter in flexible metal conduit. (All inside of the attic and walls)

 

[mrzed001]

I'm of the opinion blocking diodes don't matter.
My measurement showed Voc of a panel in the shade is similar to Vmp of a panel in direct sun. It will not pull down much current if any.
So power loss through diode drop would likely exceed loss through backfeed.

If there is shade, try to arrange panels so it hits equal number of panels in each string. If it is going to hit a diode-bypassed 1/3 section of a panel, that is better than part of all three 1/3 sections.

I agree, in a grid-tie system blocking diodes do not matter. If there is any production the inverter will put it to the grid . (except in a blackout)

But in an off-grid system where batteries can be full, and inverter can stop production from PV ... it matters a bit.
If you do not use blocking diodes then you backfeed to the weaker string.

In a 10s2p (400-450Voc 2x8-10A) setup if only 2 panels are in a shade (they will be closed out from the circuit by its bypass diodes) on one string then it is about 80-85Vdc difference (between the strings).
And that will flow back to the weaker string

And your panels "light up" in IR (also heating).

 

[Hedges]

I still say no need for anti-backfeed diodes, even if one string is in a pitch-black room. Because I like to be right.
(many times I'm not. That's how I learn.)

The video demonstrated 14V applied to a solar cell taken from a calculator, and 9 x 4 = 36V applied to another cell (or more likely several cells in series?)
If the applied voltage is only Voc for a given cell or string, the backfeed current is quite low. I expected it to be half of Isc, but it wasn't.
For anything interesting to happen, had to put a 2s string of PV panels in the sun to get decent current through one panel in the dark.

Measuring PV panel performance

I suppose I could buy a solar panel tester like Will reviewed, but that doesn't feel DIY enough to me. Besides, I'm a cheapskate, and I try to do things in the most difficult (and expensive if the equipment wasn't on hand) way. I'm presently working on an underperforming string of Sharp 165W...

diysolarforum.com

So if your array is operating above Vmp because off-grid system doesn't need all the power, there would be some backfeed. I don't think it is any harm, however.

 

[Visionguild]

Fuses are only required for 3 or more parallel strings.
The reason for this is that if a string gets shorted. Any other strings in parallel with it, will send all of their power to it. The panels are rated to handle their regular output. So one string in parallel, will send the same amount of power that the string is rated for. But two strings in parallel with a shorted string, will send twice the amount of power that the string is rated for.
Then, it's time for the marshmallows.

With that being said, I have Fuses on all of my strings. Even though it's not require. It's cheap insurance, and helps me sleep at night.

Hey Tim, this is from a while ago but I am looking to get some fuses per this older discussion. I have a 5S2P set up sending 205 Vdc at 19amps into a Growatt 3000 LVM inverter. I attached the specs for it. I'm wondering what amperage I should get for the fuses. I called the place I bought it and they said the unit won't draw more than 18amps. That's the max PV input amperage. They said it won't harm the unit at 19Amp. That's provided the panels were producing full power too. I hope I'm providing the right info and asking the right question. You had recommended getting mc4 fuses for the + . Should I get 20amp fuses? Thanks in advance for any help you can provide. I appreciate it.

 

[timselectric]

Hey Tim, this is from a while ago but I am looking to get some fuses per this older discussion. I have a 5S2P set up sending 205 Vdc at 19amps into a Growatt 3000 LVM inverter. I attached the specs for it. I'm wondering what amperage I should get for the fuses. I called the place I bought it and they said the unit won't draw more than 18amps. That's the max PV input amperage. They said it won't harm the unit at 19Amp. That's provided the panels were producing full power too. I hope I'm providing the right info and asking the right question. You had recommended getting mc4 fuses for the + . Should I get 20amp fuses? Thanks in advance for any help you can provide. I appreciate it.

The fuse size is determined by the panel specs.
You will be fusing each series string. Not required for 2P, but I think it's a good idea.
Check the panel sticker for fuse size. (Probably 15a)

 

[Visionguild]

The fuse size is determined by the panel specs.
You will be fusing each series string. Not required for 2P, but I think it's a good idea.
Check the panel sticker for fuse size. (Probably 15a)

Hi Tim, so looks like 20amps. I included the panel label below. Also included is a diagram of the set up with where I understand the fuses should go. Look correct? So I need four 20amp fuses for this set up? Sounds like we have similar setups. I also have 6kw of panels going into the two growatts into 2 EG4 batteries. Thinking of buying one more battery actually. Thanks so much again for your help.