Combiner boxes

[Bluedog225]

I was asking a vendor about a Midnite combiner box. This is the response I received.

I’m trying to figure out if this response makes sense or if I should be taking to someone else. I was under the impression that I’d use wherever combo of strings or parallel needed to get the voltage and amperage needed.


“MNPV12 includes two MNPV6 busbars that can be bolted together to make one 12x busbar. But no one does this these days… Most projects have an MPPT per string or per two strings. No one uses combiners this day and age for modern projects of scale .”

 

[timselectric]

Well, the statement is accurate.
Newer systems (with higher Voltage limits) don't need combiner boxes.

 

[littleharbor2]

As Tim says, The newer higher voltage AIO's and SCC's can eliminate the need for combiners and associated fusing. That being said, LARGE systems and low Voc. controllers still warrant their use in many cases.

 

[Mattb4]

I was asking a vendor about a Midnite combiner box. This is the response I received.

I’m trying to figure out if this response makes sense or if I should be taking to someone else. I was under the impression that I’d use wherever combo of strings or parallel needed to get the voltage and amperage needed.


“MNPV12 includes two MNPV6 busbars that can be bolted together to make one 12x busbar. But no one does this these days… Most projects have an MPPT per string or per two strings. No one uses combiners this day and age for modern projects of scale .”

Another use of calling separate arrays, "strings". Now I will be disgruntled all morning.

 

[DIYrich]

New systems higher voltage and amps.

I have a sol-ark 15k, with 28 panels in 4 strings of 7. About 400v at 10 amps per string. Each mppt has 2 inputs, so 4 pairs of 14 awg wire could be run, or 2 pairs of 10 awg wire. Cheaper to run extra wire than combiner box plus fuses.

 

[Rednecktek]

I guess I'm alone in using combiner boxes then, but my camper has serious shading issues (4p) and my camp has a lower PV requirement (3s4p) so combiner boxes are my thing.

 

[chrisski]

That’s odd. My installer did a combiner box.

Was a midnight solar and fit six dual pole circuit breakers. There’s three different angles of roof the panels are on, so makes sense why they did this.

Combiners make sense to me for different direction setups and for shading.

I wish I could fit all my panels in the south, but it won’t work.

 

[Brucey]

I was asking a vendor about a Midnite combiner box. This is the response I received.

I’m trying to figure out if this response makes sense or if I should be taking to someone else. I was under the impression that I’d use wherever combo of strings or parallel needed to get the voltage and amperage needed.


“MNPV12 includes two MNPV6 busbars that can be bolted together to make one 12x busbar. But no one does this these days… Most projects have an MPPT per string or per two strings. No one uses combiners this day and age for modern projects of scale .”

What SCC do you have in mind? The 150/250V units you'll generally need to parallel multiple strings to get to their rated output

 

[chrisski]

Even with the household PV being limited to 500 V or 600 V, there's only so many panels that can be put on a string, perhaps 10 or 11 panels. That might get you 5 kW.

For a 10 kW or 15 kW installation, what do these Inverters MPPT do? Do they provide multiple MPPTs? Do two strings and not use a combiner box?

I'd feel comfortable using Y Cables with no fuses for 2 strings in parallel with no fuse provided the max series fuse rating is not exceeded for an installation for a few hundred watts, but I would not want to do this for two 5 kW strings, that I's want to do with a combiner.

For my house installation I have two 100 amp MPPTs with 10 kW of panels, so with the right roof, I could get one string for each MPPT, but I don't have the perfect south facing roof. Maybe the bigger AIOs limit you to 5 kW per input.

 

[Brucey]

Even with the household PV being limited to 500 V or 600 V, there's only so many panels that can be put on a string, perhaps 10 or 11 panels. That might get you 5 kW.

For a 10 kW or 15 kW installation, what do these Inverters MPPT do? Do they provide multiple MPPTs? Do two strings and not use a combiner box?

I'd feel comfortable using Y Cables with no fuses for 2 strings in parallel with no fuse provided the max series fuse rating is not exceeded for an installation for a few hundred watts, but I would not want to do this for two 5 kW strings, that I's want to do with a combiner.

For my house installation I have two 100 amp MPPTs with 10 kW of panels, so with the right roof, I could get one string for each MPPT, but I don't have the perfect south facing roof. Maybe the bigger AIOs limit you to 5 kW per input.

Yes the aios generally have multiple trackers and often the primary tracker may have additional amperage capabilities.

 

[timselectric]

Do they provide multiple MPPTs?

Yes

 

[Kornbread]

Even with the household PV being limited to 500 V or 600 V, there's only so many panels that can be put on a string, perhaps 10 or 11 panels. That might get you 5 kW.

For a 10 kW or 15 kW installation, what do these Inverters MPPT do? Do they provide multiple MPPTs? Do two strings and not use a combiner box?

I'd feel comfortable using Y Cables with no fuses for 2 strings in parallel with no fuse provided the max series fuse rating is not exceeded for an installation for a few hundred watts, but I would not want to do this for two 5 kW strings, that I's want to do with a combiner.

For my house installation I have two 100 amp MPPTs with 10 kW of panels, so with the right roof, I could get one string for each MPPT, but I don't have the perfect south facing roof. Maybe the bigger AIOs limit you to 5 kW per input.

Along with the higher voltages and multiple mppts, the newer aio's mppts generally have a lower amperage rating so there's not a lot of room to stack strings up in parallel. With the old growatt I had combiner boxes at all the ground mounts and the deck roof. Now, it's only the breaker in the combiner boxes that gets used as a shutoff/surge protector.

The downsize in pv wire from the arrays to the inverter when going from 150v to 500v, is krazy!

 

[seneysolar]

I was asking a vendor about a Midnite combiner box. This is the response I received.

I’m trying to figure out if this response makes sense or if I should be taking to someone else. I was under the impression that I’d use wherever combo of strings or parallel needed to get the voltage and amperage needed.


“MNPV12 includes two MNPV6 busbars that can be bolted together to make one 12x busbar. But no one does this these days… Most projects have an MPPT per string or per two strings. No one uses combiners this day and age for modern projects of scale .”

In most cases a stand alone MPPT using more than 3-4 full size panels has to start paralleling strings to not exceed 150v- 250v

I do wonder about a scenario with 12 strings going to a single mppt without exceeding its limits. Seems like a very unique scenario. I think multiple mppts would make sense at this point.