MPP Solar LV2424 kicks butt!!!

danb35 said:

Sed linked to an ASI breaker on homedepot.com, but they sell directly, and have DC breakers rated at 125vdc/pole. Using a two-pole breaker on positive and negative, according to the datasheet, would give up to 250vdc. Here's an example, a two-pole 50A breaker at 250vdc:

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Quite a difference between 250vdc and 400vdc, but 250vdc isn't nothing.

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My initial system 15 years ago had 24, 12V panels in series with and Outback box that had 6 or seven 15A 150V breakers. Those segmented the 600V string to groups less than 100V each. That was before MC connectors that let me safely mate a high voltage string.

Later I used unfused 30A 600V "heavy duty" visible blade disconnects.

Now I have touch-safe fuse holders for multiple 600V strings, and the inverter has a DC disconnect attached.

I finally got around to testing my system running 240 split phase. (my pool pump) It wouldn't start when I flipped it on - then 1-2 minutes later the pump would spin up and run for a while and then stop after a couple of minutes, then spin up again and stop. Something was not right. To recap my set up I have each inverter feeding one leg of my Reliance transfer switch and both of them feeding one 30amp double pole breaker. Everything was running fine with the single pole breakers. This was the first test of the double pole breaker and my pool pump.

I checked voltage at each breaker point and I was seeing 248 when running and then when the pump stopped the voltage would go to essentially zero - That was weird as it meant the inverters themselves were not providing voltage to this circuit.

I re-read the (Poor) manual on Parallel split phase set up. Mind you reading this manual means looking at the pictures. I found my issue. It was the Grid input feed.

When I originally installed this I had one inverter with plans for expansion. I leveraged what I had in place already for my Grid input side which was on 30Amp circuit. That circuit was feeding a duplex outlet. I was plugging both inverters into that outlet (one 120Volt circuit). Everything was working fine and while charging (30amps to the battery from each inverter) it was never pulling more than 10amps or so on the AC input side.

The inverters however always have awareness of the grid when it's connected as they need to know if the load is too or battery too low they need to be able to pull that power from grid. What was happening was when I flipped on the pump, the inductive load was enough to call for grid power. I found this out by shutting off the grid and forcing it to pull from my batteries and the pump started and ran fine. When it went to pull from the grid it only saw a single 120volt circuit and couldn't figure out to feed a split phase 240Volt circuit with that input. I rewired the grid feed to use a double pole 30AMP breaker in my main panel, and now have two hots feeding the duplex outlet by my inverters. Each inverter is plugged into a different hot. I also now have more input capacity for each inverter- Problem solved

So to summarize, if you're using split phase 240 on the inverter output side, you need two circuits feeding the Grid input side

Mac6792 said:

What was happening was when I flipped on the pump, the inductive load was enough to call for grid power. ... When it went to pull from the grid it only saw a single 120volt circuit and couldn't figure out to feed a split phase 240Volt circuit with that input.

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With the second inverter connecting a grid wire that was 180 degrees out of phase with what it expected, you're lucky it didn't blow itself up. Is it designed to combine inverter output with what comes from the grid, or does the inverter turn completely off and use the grid instead?

My SMA Sunny Island can be programmed for how many amps to pull from the grid (e.g. 15A or 53A max) and if the load is higher it will draw from batteries to supply balance of power needed by the load without tripping a breaker. If it is disconnected from the grid (e.g. due to grid failure), before reconnecting it monitors grid for voltage & frequency within limits, then alters inverter frequency to align phase before connecting grid. If we have a transfer switch between generator and grid on the input, we are supposed to have both disconnected for 5 seconds before connecting the second one. If the switch snaps directly to a source that is out of phase, the wrong FET transistors might be turned on presenting a short across the grid.

So your inverter is able to start the pool pump induction motor without grid present, but that is an overload so it uses the grid if available?

You said the pump stopped after a couple minutes. Is that too heavy a draw, and the battery got low or inverter overheated? No reason to run the pool pump off this circuit unless it can run a reasonable time from battery and PV.

Hedges said:

With the second inverter connecting a grid wire that was 180 degrees out of phase with what it expected, you're lucky it didn't blow itself up. Is it designed to combine inverter output with what comes from the grid, or does the inverter turn completely off and use the grid instead?

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My understanding of what he was saying was that there was no second grid wire connected. Once he connected it, the LV2424 was able to correctly sync to split phase.

When you have grid in, it syncs to the grid. When you don't it produces its own phases. So, it can't sync to split phase if you only have single phase coming in.

From everything we've seen so far, the LV2424 is very smart and does a great job of syncing to grid input and, as we learned from Mac, does a decent job handling human error in configuration. This is also good to know because, in theory, there are other reasons this could happen, such as one of the grid inputs later becoming disconnected (e.g., mouse chewed it?)

erik.calco said:

My understanding of what he was saying was that there was no second grid wire connected. Once he connected it, the LV2424 was able to correctly sync to split phase.

When you have grid in, it syncs to the grid. When you don't it produces its own phases. So, it can't sync to split phase if you only have single phase coming in.

From everything we've seen so far, the LV2424 is very smart and does a great job of syncing to grid input and, as we learned from Mac, does a decent job handling human error in configuration. This is also good to know because, in theory, there are other reasons this could happen, such as one of the grid inputs later becoming disconnected (e.g., mouse chewed it?)

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What Erik Said. The induction load wanted to pull from grid for support. It was looking for Split phase from the grid to power that load. There was only one circuit attached. Per Hedges post it would be nice to be able to tell it to pull from my Lifepo4's instead as it seems they can support it but I haven't found a configuration that will do that.

One of the biggest challenges with these MPP Solar units is determining expected behaviors due to the poor manuals. It requires testing different configuration settings and combinations to see how they affect things.

Driving induction motors can be a problem for a couple reasons. They draw massive current when first starting. Depending on load, current drawn is out of phase with voltage and higher than necessary for the power produced. Current is also pushed back into the source. For the grid that gets consumed by other loads and there is just some excess IR drop. For an inverter the current needs to go somewhere, ideally back into capacitors on the DC side, but could do nasty things to the semiconductors instead.

An amplifier or power supply can be anything from "one quadrant" (I drive voltage and current, delivering power only) to "four quadrant" (I source or sink current in or out of phase with voltage, both polarities, delivering or receiving power.)

Here's an article on large AC motors:


And a graph from that article:


The graph shows several large motors loaded to about 50% of capacity, and power factor ranges from 62% to 90%. 100% would mean current is in phase with voltage, just like a resistive load. Less than 100% means the motor is shoving current back into the source during part of the AC cycle.

Your inverter only running the motor for a few minutes sounds like a problem. Did the battery voltage drop too low in that short a time and so the inverter switched back to grid? If not, could be a more serious issue like overheating. Could be reactive power due to power factor shoving out of phase current through the transistors. Or just excessive current due to power factor. Better figure out what's going on before something gets damaged.

@Hedges I was measuring my loads which included Power Factor (PF) before I brought my LV2424 online. My computers and their UPS (all computers run on a UPS) ran well into 90s, typically near 94. But, what ran low, often in the 60s, were things using AC to DC adapters, like my networking gear. Fortunately, they only represent a small % of my load, as they are relatively low power devices. But, I found that interesting as I've never heard anyone mention that.

erik.calco said:

@Hedges I was measuring my loads which included Power Factor (PF) before I brought my LV2424 online. My computers and their UPS (all computers run on a UPS) ran well into 90s, typically near 94. But, what ran low, often in the 60s, were things using AC to DC adapters, like my networking gear. Fortunately, they only represent a small % of my load, as they are relatively low power devices. But, I found that interesting as I've never heard anyone mention that.

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Yea, it is something only an EE would think about. I don't even deal with motors professionally, but I'm aware of power/utility issues.

Cheap AC adapters are nasty. Instead of simulating a purely resistive load (like high end models might), they just use diodes to charge a capacitor, which only draws current during the peak of a sine wave. I visited a factory in Guadalajara where X-Box was being manufactured. With many of them plugged in for testing, the AC line voltage had peaks of the sine wave flattened.

UPS can be on-line or off-line. If off-line and just passing through, then you were seeing the computer supplies, however they behave.

Can you measure power factor of a 1 or 2 horse induction motor to represent Mac6792's pool pump? If you have something like an air compressor you could see the change in PF from light to heavy load as pressure rises. Only representative if you have one with an induction motor. The cheaper ones I've bought from Harbor Freight may be brush-type, I'm not sure.

I'm about to get all my cables to connect my Hybrid LV2424 this weekend. I did notice I don't have a disconnect between the MPP and the PV. I saw some talk earlier in the threads about how to disconnect. I'll be using (2) Sunpower T5-SPR-318E 318w panels to start and added another 6 panels later.

If these are my specs what should I be doing for a disconnect and can someone share links.

You could use a combiner box like one of these, or roll-your-own enclosure, and DC breakers:


https://www.altestore.com/store/enc...akers/din-rail-mount-circuit-breakers-p40906/

Up to two strings it could be a switch and no fuses, or a breaker of about 20A with both strings going to it.

Above two strings you could have a breaker per string (something 10A to 20A each depending on what the label on the PV panel says). Or, one switch or breaker sized for all strings, and separate fuses for each string. Those fuses could be DIN use holders in the box, or MC-4 fuse holders.


https://www.amazon.com/Renogy-30-Waterproof-Line-Holder/dp/B00YG2IAQ4

Here is a switch I use (but I didn't pay this Granger price!)


Each pole is good for 30A, 600VDC. My strings are just under 600V for a grid-tie inverter, but yours are much lower (< 150V).
One pole would be enough to disconnect all four of your proposed strings.

You probably only need to fuse & disconnect the positive lead. (Some of my grid-tie equipment needs both positive & negative protected.)

If you go with a box and DIN rails, that'll give you the flexibility to reconfigure different number of strings and different number of inverters. I see many pre-configured on eBay. Here's one that could work for you, 4 strings and ganged 15A breakers:

Hedges said:

Can you measure power factor of a 1 or 2 horse induction motor to represent Mac6792's pool pump? If you have something like an air compressor you could see the change in PF from light to heavy load as pressure rises. Only representative if you have one with an induction motor. The cheaper ones I've bought from Harbor Freight may be brush-type, I'm not sure.

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I had to pick 10 circuits for my critical load transfer panel, and chose to exclude the one my compressor is on to avoid dealing with inductive issues. So, I never measured it.

Nitr0 said:

I'm about to get all my cables to connect my Hybrid LV2424 this weekend. I did notice I don't have a disconnect between the MPP and the PV. I saw some talk earlier in the threads about how to disconnect. I'll be using (2) Sunpower T5-SPR-318E 318w panels to start and added another 6 panels later.

If these are my specs what should I be doing for a disconnect and can someone share links.

Vmp: Voltage at Max Power (V)	54.7
Imp: Current at Max Power (A)	5.82
Voc: Open Circuit Voltage (V)	64.7
Isc: Short Circuit Current (A)	6.2

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I went with a Midnight Solar combiner box I got new on ebay for $68, but only handles 3 strings. You'll need some extra parts if you get the bare one, but it has all the core things you need. Needed ferrules and cable glands, and, of course, midnight solar breakers.

With just one string can use the baby box with 10 AWG. But, you'll run into limits with lower gauge that a combiner box is designed to help you overcome.

Thanks for the feedback. I ordered a fabricated 3 string 15 amp combiner box from Ebay. That should handle everything for this inverter. If I add another in parallel down the road I'll just build one like the ebay box.

erik.calco said:

Midnight Solar combiner box

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Funny how that one is built. The box shows "300V" breakers (note it says, "Enclosure only. Breakers sold separately" so you need to buy breakers too) which are two-pole breakers with a jumper connecting them in series. I've seen 150V breakers from them; this is two of those ganged and connected in series for 300V.

I think Nitr0's setup is going to have strings of 2, 24V nominal PV panels in series, about 80 Voc, so a single breaker per string is sufficient. Here's a 15A 150VDC breaker that probably fits the requirement, assuming his panel with 6.2A Isc is labeled for 15A or larger fuse:


The busbar in that box paralled 3 (double) breakers. That will do for 1 to 3 strings but he indicated he might eventually have 4. Here's one that works with 6 single breakers:


With a different configuration this box could combine two sets of 3 strings for two inverters, possibly two sets of 4 strings.

The box appears to have eight 1/2" knockouts on the bottom. That would fit 4 strings if one wire per gland. You may find 2-hole glands that fit, or one with an oval hole for UF cable would fit two, for up to 8 strings. (I used 3/4" glands with 4-hole.)

With all strings going to one charge controller there is no way to connect the MC4 wrong so long as each string is just two in series. If you expand to multiple charge controllers, color-code the wires so you can disconnect at MC4 before touching wires inside the box and easily get them reconnected correctly.

Hedges said:

Funny how that one is built. The box shows "300V" breakers (note it says, "Enclosure only. Breakers sold separately" so you need to buy breakers too) which are two-pole breakers with a jumper connecting them in series. I've seen 150V breakers from them; this is two of those ganged and connected in series for 300V.

I think Nitr0's setup is going to have strings of 2, 24V nominal PV panels in series, about 80 Voc, so a single breaker per string is sufficient. Here's a 15A 150VDC breaker that probably fits the requirement, assuming his panel with 6.2A Isc is labeled for 15A or larger fuse:

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The busbar in that box paralled 3 (double) breakers. That will do for 1 to 3 strings but he indicated he might eventually have 4. Here's one that works with 6 single breakers:

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With a different configuration this box could combine two sets of 3 strings for two inverters, possibly two sets of 4 strings.

The box appears to have eight 1/2" knockouts on the bottom. That would fit 4 strings if one wire per gland. You may find 2-hole glands that fit, or one with an oval hole for UF cable would fit two, for up to 8 strings. (I used 3/4" glands with 4-hole.)

With all strings going to one charge controller there is no way to connect the MC4 wrong so long as each string is just two in series. If you expand to multiple charge controllers, color-code the wires so you can disconnect at MC4 before touching wires inside the box and easily get them reconnected correctly.

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I called them to get details on options for the breakers and learned some interesting things. The key takeaway is you can use the 150VDC breakers. Here are my notes from that call:

Todd
up to 63A, up to 6 AWG, 150DC
80-100A have external barrel lugs, up to 2 AWG, 150DC

300VDC is same,

panel mount breakers: buy terminal lug, crimp it to end of wire, 5/16”

300VDC, 6 AWG is the largest.

up to 2 AWG on the plate busbar that goes in the breakers (2/0)
negative bus bar in enclosure goes up to 1/0

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If it is a little confusing, it is because he kept jumping back and forth to panel mount breakers until I told him I'm only concerned with DIN breakers. This was months ago, so hard for me to rewrite clearly lol

But the key lesson is that the 3 pronged combiner bar -- their unique feature -- will fit in the 150VDC breakers. You'd just obviously space them a little apart on the DIN bar.

Wanna see a ratsnest?


I presently have 7, 600V strings of various model panels going to two grid-tie inverters. Instead of the MC wires going straight to the combiner box, I've run 12 AWG wire through conduit from several locations in the yard. I plan for more strings at different orientation to spread production over the day.

The box upper left has two strings going through one gland with room (and wires pulled) for two more. Rather than wire nuts, which the inverter manufacturer recommends against due to possible arcing from a bad connection, I'm now using setscrew connectors with plastic caps (one can be seen with cap removed.)

Bottom left is a DC disconnect switch attached to one of the inverters. Wires are 8 AWG from combiner to disconnect for DC, and 6 AWG is used for AC which is slightly lower voltage, higher current.

Combiner box is a ratsnest with excessive length wires for now. After everything has been added and rearranged I'll cut those down. Wires from arrays go to touch-safe fuse holders. They are only to be opened/closed with with no current flow, DC disconnect open. Screw terminals are accessible to DMM leads so I can check all strings are about same Voc before paralleling them by closing fuseholders. Also, with two inverters I can shut one off and confirm the circuit I'm going to work on is showing Voc not the lower Vmp before unplugging MC4 connectors.

I stuffed 600 VDC lighting arresters in this box, at least for now. The AC breaker panel has 240 VAC arresters. These supplement the little ones inside the disconnect provided by inverter manufacturer. I'm in California and the utility transformer is underground. A location like Florida and overhead power lines would have higher likelihood of lightning strikes, but considering these things are only $60 and my inverters cost $thousands I invested in extra protection.

I bought spools of 12 AWG stranded wire in several colors. I added bands of heatshrink to label which rack of multiple arrays they go to, used four colors for the positive wires at each rack, and heatshrink to label which white negative wire goes to each positive.

Hunter937 said:

I don’t have anything going into the unit what so ever. I have 8 solar panels and it gave me a reading of 80 volts when I had all of them plugged in. I was running two 400 watt arrays in parallel getting 80volts. I ended up unplugging two of the panels, leading me to have a total of two 300 watt arrays in parallel but now it is only reading 28volts so at this point I am royally confused. My voltage on my batteries is 26.8 currently

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Could be for some reason it isn't doing MPPT, is just making a DC connection from the panels to the battery, with 1.2V drop across the transistors. The battery voltage is relatively low, probably drawing current the panels produce at that voltage.

Your post was several days ago. What is the battery voltage now? Hope the charge controller didn't fail with transistors shorted and cook the batteries.

Sunny Days said:

Anyone know about repair guides for
The LV2424?
Mine been working great for about 2 years, now its off, if switch it on the screen lights up with no data just blank and last for 3 seconds then its off, no beeps and no fans running.
Cant seem to find anything online.

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You check your batteries? it will do that if the battery is unable to supply the minimum voltage. (I think it wants to see at least 22V?)

madmax said:

You check your batteries? it will do that if the battery is unable to supply the minimum voltage. (I think it wants to see at least 22V?)

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Thanks for the reply! Battery is at 25.5V so its charged, tomorow im opening it up again and completely disasemble it and see what i find.

Sunny Days said:

Thanks for the reply! Battery is at 25.5V so its charged, tomorow im opening it up again and completely disasemble it and see what i find.

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What kinda batteries are you using? It is important to check the battery under load. For me, fully charged is more in the 28v range.

If your attaching a stand alone battery charge to top it off, the voltage may be a little... misleading. It may just be a surface charge.