10 Panels in PV Array Series -- combiner box or disconnect?

[TheHappyNomads]

I'm going to luck out and be able to install my (10) 400w panels in a single series along my carport/garage roof. It's the max sunlight/day and can drop right through the roof to my (2) LV6548's and future battery bank.

Probably a dumb question as a beginner but since I'm installing in a single series I don't need a combiner box, right? If not, what kind of disconnect/overcurrent protection should I install?

Each LV6548 is rated for 6500v so I don't think I'll run into an issue there. I plan on wiring the MPPs together for 240v service.

 

[SHTF Power Anyway]

6500 watts not volts, right? Your problem will be the limitation in the MPPs voltage max especially at lower temperatures.

 

[adobopr]

Each LV6548 is rated for 6500v so I don't think I'll run into an issue there. I plan on wiring the MPPs together for 240v service.

What I found online for the lv6548 is that it has 2 MPPTs that accept up to 250V, and there's a V model (LV6548V) that accepts up to 390V. I think you might be confusing the watts with the volts, and you might actually damage something if you hook up those 10 panels in series together without confirming this.

That being said, if you do split them to 2 Strings of 5 panels because it has 2 MPPTs, you don't need a combiner box either way as they'll each have their own controller. What you most likely want is a disconnect. I personally use circuit breakers rated for 1000V for mine, but there's definitely more sophisticated disconnects out there.

 

[LydMekk]

10 panels in series sounds like way too much for your MPPT.
What does your manual list as max for the MPPT in the inverter?

 

[Shimmy]

I would break up to two strings, one per inverter. With the short runs voltage drop isn't an issue. You do need a disconnect inside for the PV.

 

[TheHappyNomads]

6500 watts not volts, right? Your problem will be the limitation in the MPPs voltage max especially at lower temperatures.

Oh yeah, sorry. Each one is reated for 6500w. I thought that in series panels multiply watts and not amps. Ohhhhhhh voltage adds together so I'd be looking at 480v. Crap.

So either I connect two sets of 5 panels in series to each LV6548 or parallel the two arrays, correct?

Can I achieve 240v AC service from wiring the panels to the inverters in this way?

 

[TheHappyNomads]

I would break up to two strings, one per inverter. With the short runs voltage drop isn't an issue. You do need a disconnect inside for the PV.

And if wiring two separate strings then should I go for a combiner or some other disconnect?

 

[adobopr]

And if wiring two separate strings then should I go for a combiner or some other disconnect?

You want 1 disconnect for each string in this case.

 

[SHTF Power Anyway]

Oh yeah, sorry. Each one is reated for 6500w. I thought that in series panels multiply watts and not amps. Ohhhhhhh voltage adds together so I'd be looking at 480v. Crap.

So either I connect two sets of 5 panels in series to each LV6548 or parallel the two arrays, correct?

Can I achieve 240v AC service from wiring the panels to the inverters in this way?

Though I can't answer your questions because I'm not qualified, I can say I saw your error in thinking because I did the same darn thing. lol

 

[#40Fan]

Oh yeah, sorry. Each one is reated for 6500w. I thought that in series panels multiply watts and not amps. Ohhhhhhh voltage adds together so I'd be looking at 480v. Crap.

So either I connect two sets of 5 panels in series to each LV6548 or parallel the two arrays, correct?

Can I achieve 240v AC service from wiring the panels to the inverters in this way?

You could parallel the two sets of 5 (5s2p) into one port of one inverter, but you'd likely be VERY close to the 250v limit when it is cold out.

4s2p into one port (of one inveter) and buy more panels for the other three ports you have left to fill.

 

[rodrick]

I’m assuming your panels are 48 voc if so 4s2p allowing some room for cold weather voltage increase is probably your best setup

 

[TheHappyNomads]

You could parallel the two sets of 5 (5s2p) into one port of one inverter, but you'd likely be VERY close to the 250v limit when it is cold out.

4s2p into one port (of one inveter) and buy more panels for the other three ports you have left to fill.

If I am understanding you correctly the 250v max is per port on the inverter?

 

[Shimmy]

If I am understanding you correctly the 250v max is per port on the inverter?

Correct, and that is Voc adjusted for the worst-case low temperature in your lcoation. That is why 4s strings are a safer bet; Voc will typically increase by ~0.5% per degree C below 20C, or roughly 0.25V. In Fairbanks, AK that could mean you could only run 3 panels in series, but for most of the world 4 is safe.

 

[adobopr]

@TheHappyNomads If you post a picture of your panel specs we can give you more certain answers on your best string combinations.

 

[Tomthumb62]

I thought that in series panels multiply watts and not amps. Ohhhhhhh voltage adds together so I'd be looking at 480v.

You have this partially right.

Panels in series adds the VOLTAGE.

Panels in parallel adds the AMPS.

Either series or parallel will produce the same WATTAGE. But how they get there is different.

 

[TheHappyNomads]

@TheHappyNomads If you post a picture of your panel specs we can give you more certain answers on your best string combinations.

 

[TheHappyNomads]

Does the spec label help?

 

[adobopr]

Does the spec label help?

Yes. The other commenters here assumed 48 Voc so I think their suggesstions are already up to spec with your panel. I have no experience with using solar panels in the cold (my house is in the caribbean) and have no experience with these Voc fluctuations they mentioned.

Just to be sure, you have the basic LV6548 or the LV6548V? The V has a higher Voc of 390V from what I found on their website.

 

[TheHappyNomads]

Just the LV6458 -- no extra voltage. I'm in Northern CA so we rarely have anything that drops below 40*F even in winter

 

[Supervstech]

Just the LV6458 -- no extra voltage. I'm in Northern CA so we rarely have anything that drops below 40*F even in winter

40F is still an increase in voltage, since stc is 78F
But it isn't much increased
And you don't wanna use "rarely" as your calculation temp, you want HISTORIC low and subtract a few degrees for crazy weather issues...
Figure 0C for the calculations, aand you should be safe, but I would VERIFY with weather data.
If you figure close to the 250V limit and have it spec for 40, then you hit 30, you are going to fry your inverters...