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LV6048 won't energize L2 in 240v configuration

Gallophill

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Sep 25, 2021
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I have a brand new MPPSolar LV6048 and have it configured for L1/L2 240v. When my well pump turns on it trips breaker on panel, because inverter spike voltage on L1 but won't energize L2. My electrician has checkd e all connections and everything else seems to be working fine. Any opinions would be appreciated. This solar setup is connected to 2 BigBattery Huskies totalling 10.6 kw. It is backup for power loss for Ag well and barn lighting.

Also, I have S-Energy 310 watt panels. What kind of wattage/voltage can I expect on Full-Sun days, no shadows, clean and at the right angle and direction. Efficiencies?

Thanks for any help.
 
Have you actually tested the output terminals themselves before applying a load? L1 to neutral should read 120V, L2 to neutral should read 120V, and L1 to L2 should read 240V. What kind of load can either L1 or L2 handle independently of each other?

If you perform those tests and you don't see the expected voltages, try first fully shutting down the unit and rebooting it. A full shut-down means completely powering down the unit including first the panels, then disconnecting the battery connection, so it goes stone-cold. After rebooting on battery power ONLY, then reconnect your panel strings.

What is the size and inrush current of your well-pump? My 1hp pump draws 38A at startup, though runs at only 9.5A. That's a starting surge of 9200W. MPP units are high frequency inverters and do not have meaningful surge, so it might just be that 6000W is not enough to start your pump.

How are your panel wired? It looks like your unit requires a minimum of 120VDC for proper functioning. Your panels are supposed to be putting out 33VDC, so you'd need at least four of these panels wired in series to go above 120VDC.1638505521085.png

In terms of output, assume that voltage remains the same for most of the day, but will drop slightly around noon or so as the panels get their hottest. When pointed directly at the sun, I'd expect to see no more than 85-90% of their rated amperage. 95% would be amazing!
 
Michael, thanks for answering so fast. I have 120v on both hot wires for L1/2 connections. I have been stepping up my loads (lights, drill, saws, pump) to see how system handles it. I actually mis-spoke in the description. I had my clear water transfer pump on when it tripped the breaker. The pump is getting old(25 yrs), the numbers were less the last couple of weeks of use than I quote on next sentence. The pump startup wattage was 2.2kw to 2.3kw and would drop back to .8kw while running. While watching the LCD screen on the AC outputs; only AC1 would show power, AC2 never energized. Why won't inverter energize AC2? I thought I had 12kw surge for startups. I specifically got this model to run my well pump, freezer and frig when we lose power for ice in winter and hurricanes in summer (NC).

I have 6 panels total, 2 parallels of 3 each. Inverter won't recognize over 120vdc per PV connection. When I was doing the initial install when I connected the 4th panel, the inverter no longer showed the PV connection. I thought it was a bad wire/panel, but after lots of trial and error, found that all panels were functioning the same and that it was the system that would not recognize more that 3. I am getting about 112 volts/550 watts per array. The panels are mounted in a parallel line so all the same sun.

I really do appreciate any and all help or advice. I know enough to not electrocute myself and my retired electrician friend did all the panel/connection work freely admits he's never done "solar", so I am on my own for the sun side of things. He's more than willing to help trouble shoot the panel side of things.
 
Your response raises concerns at serveral points. First, does L2 support regular 120VAC loads on it's own? What's the biggest thing that L2 has actually run without a hiccup?

How are you measuring the startup wattage of 2.3 kW for the pump? Is it the display on the unit, or a clamp meter? 0.8kW vs 2.3kw sounds about right for a pump motor (~4X).

Is the pump being fed 240VAC via a standard dual-pole breaker? With the pump disconnected, do you see 240 voltage on both sides of the breaker? I wonder if one pole in your breaker might be bad?

I don't understand your statement above that the "Inverter won't recognize over 120vdc per PV connection". Is the spec table I posted above correct for your unit? It appears that 120VDC is the minimum voltage needed, but you say that you can't go above 120VDC? That suggests to me that something might be wrong with the unit? Have you contacted MPP yet?
 
I can't isolate L2 on it's own in the 240v configuration. L1/L2 are on 40 amp bipole breaker back feeding my distribution panel. So it hasn't run anything solo. I have 120VAC at the wire connections on the inverter and at the actual circuit breaker on the panel. I read the startup wattage on the inverter display, when my wife turned the pump on for me. The pump is just plugged in to a regular 120VAC outlet in an equipment shed. I will recheck breaker tomorrow, but was check by my electrician when he stated installation was complete. I guess it could have gone bad in last 6 weeks.

This is from my owner's manual:
PV INPUT / SOLAR CHARGING Max PV Input Power 8000W (4000W each input)
Max PV Array Open Circuit Voltage @145Vdc
PV Range 60 - 110VDC
Number of PV Input 2
Max Charging Current 160A (80A X 2)

My panels are 33VDC so when I connected 4 of them totaling 132VDC, that exceeded the 110VDC for the array. I would lose the icon showing the connection on the LCD screen of unit. It would only show the icon for a max of 3 panels, so I just got another set of wires and created the 2nd PV array.

I emailed MPP right before opening this thread.
 
Just skimming here... so forgive me if I missed an important detail :)

You may have to rig up a temporary panel that splits out L1 & L2 so that you can test loads on L2 individually.. Just watched a David Poz video on the previous model to this MPP and that's what he did for testing...
 
OK, some things here are now clearer, and some are now murkier? Let's divide up your statements from the last post.
Max PV Array Open Circuit Voltage @145Vdc
OK, it appears that I was looking at the specifications of another inverter if yours has a Voc of 145VDC. So, that makes sense now that only three panels can be wired in series. Here are the specs for your panel (I think). With a Voc of 136V, three in series barely is under the 145V cutoff. I would be very concerned about cold weather. As the temperature goes down, the voltage goes up, so in winter, just as you get to freezing, the Voc will >150Voc. Use this string calculator to determine what your winter lows will be like. https://www.midnitesolar.com/sizingTool/index.php You are so close to the Voc limit that you might have to drop down to just two panels in series, depending on your weather.
1638633394955.png

I read the startup wattage on the inverter display, when my wife turned the pump on for me.
No, this might be inadequate. The inverter display, or even a regular clamp meter is not fast enough to read the inrush current of a starting motor. You need a clamp meter designed to read "inrush current". The one I'm using right now is a Uni-T 216C. But, since your measured readings of 0.8 kW and 2.3 kW jibe with my inrush readings, maybe your display is fast enough.

L1/L2 are on 40 amp bipole breaker back feeding my distribution panel
This sounds like you have a standard split-phase electrical distribution panel if you are using a dual-pole breaker to get 240VAC. For all the single-pole breakers on L1, does there appear to be an empty space right next to them, or are they snuggled against each other in the panel? If it is a split-phase panel as I think it might be, then all the empty spaces are L2 circuits. Pics here would help! All this could be verified in seconds with a voltmeter set to read AC volts.

The pump is just plugged in to a regular 120VAC outlet in an equipment shed
OK, this is very confusing? Is this supposed to be a 240VAC pump or a 120VAC pump? Does the pump actually work at 120VAC? Does it run half as fast as it normally does? If it has a standard 120VAC plug wired to it, and you have it plugged into a 120VAC socket, why were you trying to run it at 240V? Does it have some kind of dual-voltage motor?
 
This is great, you are being so helpful. I will take pics tomorrow, but for now.

The pump is just a 120VAC, it's overloading L1 and I didn't understand why until you stated about the L1/L2 on the panel. The outlet is a regular(outdoor) 120VAC type on a 15amp single pole breaker. I didn't know the panel was separated that way. I have a bunch of single pole breakers clustered at top of panel, but everything is just lights and then 2 outlets for 120VAC tools. I am surmising then that since my well pump is on a dual pole breaker on my home's main panel it will access L1 & L2

The panel is a 20 circuit, 100amp sub panel from Home Depot. It is pole fed by a 100amp breaker on my house's main panel. My plan for bad weather power loss had been to turn "OFF" main house breaker; isolating the house from the grid; turn "ON" the 100amp breaker to link the barn solar power source to main house panel to power frig, freezer and well pump and maybe a couple of lights. Although I have many kerosene lamps if need be. My next step is installing a second pressure tank on well in series to limit how often it needs to run. I live in rural, central NC, it would be very easy to go "amish", except for food preservation.

Thanks for the heads-up on the VOC limit due to the cold, never expected to need to know that where I live.

I would be glad to share my cell phone #, if that isn't against forum protocol. I talk better that I type.
 
This spec sheet came with package. I have specifically model SN310M-10T. I just bought a clamp style multimeter.
 

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My plan for bad weather power loss had been to turn "OFF" main house breaker; isolating the house from the grid; turn "ON" the 100amp breaker to link the barn solar power source to main house panel to power frig, freezer and well pump and maybe a couple of lights.
This idea might be very illegal and physically dangerous to linemen trying to make electrical repairs during a blackout. To do this properly, you MUST incorporate a transfer switch or an "either/or" breaker that physically prevents breakers from being closed at the same time. The one thing that must be physically impossible if for your off-grid system to energize the grid while the grid is down.

Please have the electrician do this part.
 
My panel VOC is 40.1v, the midnight tool you included gives me green answers, so that means I am good right?
 
An electrician did do all the work. I spoke to several solar inverter companies with my idea and they were all good with it. My MPP LV6048 has a built-in transfer switch. It is a hybrid inverter, meaning it can be grid-tied or off -grid. It has settings that can be pole power as primary and then solar, then battery or combo of solar & battery.
 
I don't want to break the law, but I am the last house on road. How would me turning off only my house affect linemen doing work down the road. I would know when power is back on because my neighbor a half-mile away has a "sun" for a barn yard light that burns 24/7, you can still see it at high noon on a full sun day.
 
How would me turning off only my house affect linemen doing work down the road. I would know when power is back on because my neighbor a half-mile away has a "sun" for a barn yard light that burns 24/7, you can still see it at high noon on a full sun day.
Murphy's Law. If if can happen, it will happen. Sooner or later a mistake will get made, and someone will accidentally leave a breaker closed by mistake. That's what puts the lineman's life in danger.

But, since the transfer switch is already present, and it was set up by the electrician, I would say you are good to go.
My panel VOC is 40.1v, the midnight tool you included gives me green answers, so that means I am good right?
OK, the spec I found above was higher. Second time in a row now. Everyone should include links to what they talk about so mistakes don't get made by the uninformed like me. I would say yes, but what are your winter lows like? Did that number get included in the calculator? If yes, I'd trust what Midnight's calculator says.
 
Thanks for the info, I don't know what I don't know, otherwise I would quote links or attach spec sheets if needed as I have done as you asked your questions. I entered "0" as our lowest temp. We've only gone below zero once in the last 18 years and only for one night. The teens are generally as cold as we ever get.

I appreciate all of your help, the over-sight of decisions made and not being condescending as many are.
 
A lot of electric motors can be wired for 120 volt or 240 volt operation. The label on the water pump should state this if your pump is capable of this. There will be a junction box which contains several wires. Reconnecting the pump to 240 volts would be less of a load on the inverter as the pump would now use 1/2 the current required on 120 volts. This is a simple matter reconnecting to 240 volts. The label plate will list the voltages that the pump can be used with. This may well be the easiest fix, but does require a 240 volt service to the pump location. A second option would be to use a 240 volt to 120 volt transformer at the water pump. The wattage rating of the transformer needs to be greater than the start surge of the water pump. In either case the full output of the inverter would be suppling the pump power rather than powering it with only one half of the inverter.

On the issue of the transfer switch.....required under the code so in no way could backfeed the power network. This is not only a local law but is also a federal law as all power networks are connected together across state lines.
No way do you want the Federal power management agency (U.S. DOE) to charge you with shocking a lineman. They are really seriously about this issue. Backfeeding a power grid is very dangerous as the power transformers on the utility usually are converting 2kv to 8kv down to the 120/240 that you are using but work in reverse as well and can energize power lines to 8kv even though you are feeding only 120/240 to the grid.
 
The inverter has a built-in transfer switch. It shuts down instantly when pole power is turned on. This was a DIY kit, (needed an electrician to do panel install/inverter connections. Thanks. I think all my questions have been answered.
 
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