AC Input/Output setup

James Braka

New Member
Joined
Feb 26, 2021
Messages
10
I have done some searching on YouTube, but still not clear. Do we use a main AC panel or AC sub panel to house the AC output for an MPP Solar that has ground, two hot, and one neutral AC output line? Connect to a two poles breaker switch? For example the MPP Solar LV 5048. Anybody has photo of their AC Output box to share? Thanks in advance.

As for the AC Input, I guess we just connect the GLLN (four wires) AC Input on the MPP Solar to one of the house circuit breaker (two poles breaker) on the house sub panel, correct?

Thanks in advance.
 

elewis33

Solar Enthusiast
Joined
Feb 13, 2020
Messages
92
I've not done this myself but I've seen a couple people on YT just cut the plug end off a 3 wire power strip and wire that directly to the AC out on the MPP all-in-one. Looks like a clean simple solution, but of course a little limiting in how you can run power out from the power strip.

Seems like this is a good portable option for a small cabin/emergency power system but not ideal for a more permanent install.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
1,484
How you wire it depends on whether or not you also have grid power coming into the house? If you do, the two must be kept totally separate.

For my own cabin, I have no grid, so I wired my inverter directly to the main panel. L1 on the inverter to L1 on the panel. L2 from the inverter to L2 in the panel. And so on and so on.

If however there is the presence of grid power you must have either a transfer switch, or an either/or toggle breaker so the two power streams can never meet. Life threatening!!!

If you look at the internal connections of the main panel, directly above where all the breakers are, there should be two threaded terminals. One will be L1, and the second L2. If you take an ohm meter, and touch one probe to the L1 screw, what you will see is as you go down the left hand row of breaker terminals each alternating terminal will have zero resistance, and the second alternative will be ∞. Then, when you move the meter probe to L2, the breakers that were zero are now ∞, and the ones previously ∞ are now zero.
 

boondox

Chief Engineer, RedNeckTech Industries
Joined
Mar 1, 2020
Messages
672
Under no circumstances wire the output of your solar power system to a breaker in your existing mains systems. This is illegal and for good reason as it is dangerous. Best case scenario if you forget to turn off the main is that you destroy your inverter. worst case is you back feed to the grid, energize a pole transformer and create 12-15kV that can kill a lineman. As noted above a transfer switch is required. And don't try to use some cheap multi-pole switch you see on Amazon. Get a real UL approved transfer switch and have that properly installed.
I've not done this myself but I've seen a couple people on YT just cut the plug end off a 3 wire power strip and wire that directly to the AC out on the MPP all-in-one. Looks like a clean simple solution, but of course a little limiting in how you can run power out from the power strip.

Seems like this is a good portable option for a small cabin/emergency power system but not ideal for a more permanent install.

Using stranded wire in a set screw type of connector is not a good idea. They are intended for solid wire. Stranded wire will deform and strands will break off.

So tell us a bit more about your project. Do you want to energize the existing house wiring? Do you intend to have a separate system? Is your inverter a true 2 phase inverter? There is always a safe way to do what you need.
 

boondox

Chief Engineer, RedNeckTech Industries
Joined
Mar 1, 2020
Messages
672
Lookin at your diagram, the generator is connected directly to the mains. You have to have a transfer switch. It shows that only the inverter output runs to its own outlets and in no way connects to the mains. That is fine.

However, with some of the questions you have, make sure you really know what you are doing before starting to connect things up.
 

Joe BoyKey

Watts, Watts, more Watts
Joined
Sep 11, 2020
Messages
523
Location
Austin Texas
Generator feeds sub-panel with either or lock-out breakers, (manual switch over) , diagram is for reference to op, not for dissection - as it has been running perfectly since 9-2020, thanks.
 

James Braka

New Member
Joined
Feb 26, 2021
Messages
10
Thank all of you for your great comments. I am building an off-grid solar system. The MPP Solar company recommended having one circuit breaker between the utility and the All-in-One and another separate circuit breaker between the All-in-One and the load. I do not intend to send any power to the utility; hence, keeping the AC input and output separate. So, this is what I am considering.

  1. All-In-One AC Input: Either option A, connect the AC Input with a four wires power cord (G-L1-L2-N) to a 50 amp or 30 amp utility outlet. This require building out the 30/50 amp outlet. Or option B, connect the AC input directly to one of the utility circuit breaker on the sub panel. Please see diagram. I do not intent to send power to the utility. Only get power from utility when solar is insufficient.
  2. As for the All-in-One AC output: I am thinking of connecting the All-in-One AC output via a four conductor wires to a circuit breaker on a dedicated AC panel. Do you recommend a main or sub panel? Please see diagram. Then from this dedicated circuit panel, I will have separate solar powered outlet.

I guess I only need a transfer switch only if I intend to (1) sent power to the AC house sub panel or (2) connect both the All-in-One AC output and AC Input to the SAME House AC panel. Correct? But since, I don’t intent to send power to the house Utility AC panel, I don’t need a transfer switch. Correct?

Thank in advance.
 

Attachments

  • switch.jpg
    switch.jpg
    142.1 KB · Views: 12

James Braka

New Member
Joined
Feb 26, 2021
Messages
10
Under no circumstances wire the output of your solar power system to a breaker in your existing mains systems. This is illegal and for good reason as it is dangerous. Best case scenario if you forget to turn off the main is that you destroy your inverter. worst case is you back feed to the grid, energize a pole transformer and create 12-15kV that can kill a lineman. As noted above a transfer switch is required. And don't try to use some cheap multi-pole switch you see on Amazon. Get a real UL approved transfer switch and have that properly installed.


Using stranded wire in a set screw type of connector is not a good idea. They are intended for solid wire. Stranded wire will deform and strands will break off.

So tell us a bit more about your project. Do you want to energize the existing house wiring? Do you intend to have a separate system? Is your inverter a true 2 phase inverter? There is always a safe way to do what you need.
Hi boondox, thanks for the comment. This is what I am looking to do. You think this will work (see diagram)? Would you do it differently? At the moment, mainly just want a separate off-grid, but with the utility as backup power to the MPP in case solar is insufficient. I have posted the details in other part of this thread, but let me duplicate it here for convenience. Hoping you and others can comment and give me your thoughts.

The MPP Solar company recommended having one circuit breaker between the utility and the All-in-One and another separate circuit breaker between the All-in-One and the load. I do not intend to send any power to the utility; hence, keeping the AC input and output separate. So, this is what I am considering.

  1. All-In-One AC Input: Either option A, connect the AC Input with a four wires power cord (G-L1-L2-N) to a 50 amp or 30 amp utility outlet. This require building out the 30/50 amp outlet. Or option B, connect the AC input directly to one of the utility circuit breaker on the sub panel. Please see diagram. I do not intent to send power to the utility. Only get power from utility when solar is insufficient.
  2. As for the All-in-One AC output: I am thinking of connecting the All-in-One AC output via a four conductor wires to a circuit breaker on a dedicated AC panel. Do you recommend a main or sub panel? Please see diagram. Then from this dedicated circuit panel, I will have separate solar powered outlet.

I guess I only need a transfer switch only if I intend to (1) sent power to the AC house sub panel or (2) connect both the All-in-One AC output and AC Input to the SAME House AC panel. Correct? But since, I don’t intent to send power to the house Utility AC panel, I don’t need a transfer switch. Correct? Is the setup in this diagram correct? Thanks.

1623463142997.png
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
How you wire it depends on whether or not you also have grid power coming into the house? If you do, the two must be kept totally separate.

For my own cabin, I have no grid, so I wired my inverter directly to the main panel. L1 on the inverter to L1 on the panel. L2 from the inverter to L2 in the panel. And so on and so on.

If however there is the presence of grid power you must have either a transfer switch, or an either/or toggle breaker so the two power streams can never meet. Life threatening!!!

If you look at the internal connections of the main panel, directly above where all the breakers are, there should be two threaded terminals. One will be L1, and the second L2. If you take an ohm meter, and touch one probe to the L1 screw, what you will see is as you go down the left hand row of breaker terminals each alternating terminal will have zero resistance, and the second alternative will be ∞. Then, when you move the meter probe to L2, the breakers that were zero are now ∞, and the ones previously ∞ are now zero.
Thanks,
Is it possible to energize a totally off grid double phase panel with L1 only? And would that create every other breaker available to protect circuits?
It would seem nice to send my inverter single phase to one side of a panel to localize and protect a few circuits.
So,From my inverter to one side of a ( service) panels hot leg and common will
circuit breakers operate safely?
And, how would you ground that panel?
Also, with a second inverter is thier a shared common to energize the second hot leg in that panel?
Thanks
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
1,484
Thanks,
Is it possible to energize a totally off grid double phase panel with L1 only? And would that create every other breaker available to protect circuits?
It would seem nice to send my inverter single phase to one side of a panel to localize and protect a few circuits.
So,From my inverter to one side of a ( service) panels hot leg and common will
circuit breakers operate safely?
And, how would you ground that panel?
Also, with a second inverter is thier a shared common to energize the second hot leg in that panel?
Thanks
I'm not big on non-standard juryrigs. The reason is that I've had to come to the aid of neighbors when their systems have failed, and repairing someone's else's concept of acceptable ain't fun! That being said, take a look at the pic below at my own hypocrisy. Well, it was for test purposes only.

I suppose it will work to connect just L1, but leave a big disclaimer pasted on the panel to document what you did. I suppose you can also attach a second inverter to L2, but I would be very confused by that, and mistakes could be made.

Both inverters could safely share neutral. There should be a neutral bussbar like the one you see in my pic.

The panel ground should be considered to be an above-ground earthing element. All your electrical sockets, light switches, ect. are all considered above-ground earthing elements that can be connected together.

All ground-rods, water-pipes, concrete rebar, are considered to be below-ground earthing elements, and can be connected together.

The critical rule is that all the above-ground elements are connected to all the below-ground elements at one and only one location. That could be your main electrical panel, your power center, or your inverter, depending on what your particular manufacturer recommends. With mine, it's the power center which is the routing box for all my DC/AC wiring.
 

Attachments

  • 003.JPG
    003.JPG
    633.3 KB · Views: 9

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
I'm not big on non-standard juryrigs. The reason is that I've had to come to the aid of neighbors when their systems have failed, and repairing someone's else's concept of acceptable ain't fun! That being said, take a look at the pic below at my own hypocrisy. Well, it was for test purposes only.

I suppose it will work to connect just L1, but leave a big disclaimer pasted on the panel to document what you did. I suppose you can also attach a second inverter to L2, but I would be very confused by that, and mistakes could be made.

Both inverters could safely share neutral. There should be a neutral bussbar like the one you see in my pic.

The panel ground should be considered to be an above-ground earthing element. All your electrical sockets, light switches, ect. are all considered above-ground earthing elements that can be connected together.

All ground-rods, water-pipes, concrete rebar, are considered to be below-ground earthing elements, and can be connected together.

The critical rule is that all the above-ground elements are connected to all the below-ground elements at one and only one location. That could be your main electrical panel, your power center, or your inverter, depending on what your particular manufacturer recommends. With mine, it's the power center which is the routing box for all my DC/AC wiring.
Lol, impressive; not sure what you have there.
I was just starting to work with output for the allinone mpp so I might use the power strip method; however, I have seen those explode into flames.
Ideally, I am under the impression that I could use every other breaker on a old panel by sending ground, hot and neutral to L1 and ground the box to a water pipe; or, to a grounding rod.
I don't quite understand the difference between the above and below ground methods; other than, lighting strikes would affect it differently.
Mostly, I will probably ground to a waterline. I really dont want to go near the 200 amp service though.
For now its power strips because my ac load is very minimal.
Thanks and good luck.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
1,484
I don't quite understand the difference between the above and below ground methods; other than, lighting strikes would affect it differently.
Mostly, I will probably ground to a waterline. I really dont want to go near the 200 amp service though.
For now its power strips because my ac load is very minimal.
Thanks and good luck.
I am sorry I was not more clear.

There is NO such thing as "above and below ground methods". All grounds lead go the earth.

What I was talking about is that part of the entire earthing system that are those components of the system that aren't physically touching the earth. The green earth wire stretching from an wall electrical socket to the main electrical panel and ends at the grounding bussbar. That's an example of a "above-ground" element. All the above-ground elements should join up at the same grounding bussbar.

After the grounding bussbar, you'll have a heavy 6-4 gauge copper wire that stretches from the bussbar to whatever metal object is buried in the earth that serves as the end of the path of the electricity from the short-circuit in the house to the earth. This might be a copper clad ground-rod pounded 8' into the earth. In your case, it might be a metal water pipe that is physically buried in the earth. The very important point to remember here is that the grounding bussbar is in no way connected to a SECOND below-ground earthing element that is NOT connected to the first below-ground element. Is that clear now?
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
Thanks, MichaelK;
Your explanation is logical ; again, thank you.
If I decide to run the MPP out put to a breaker panel I would ground to a waterline.
However, sharing a neutral of a this L1 out put with a second MPP out put to create a L2 in this panel is still questionable do to my ignorance.
Clearly, I will have to research thos further because it most definitely does not sound like " code" .
Incidentally, I installed my 200 amp service and went out and drove that copper grounding rod.
However, for what ever reason I now remember I also ran an additional ground out to a water line! Is this second ground unsafe?
Furthermore, I explored adding a sub panel ; but, I decided not to for now; anyway, I was confused on the isolated panel concepts.
I think my understanding of a sub panel was that the isolated sub panel screw must be removed and that sub panel must go directly back to the main service. Is this understanding correct?
I realize I have gone off topic so I don't mean to take up your time ; and , I appreciate you info on the MPP output.
Thanks.
 

MichaelK

Photon Sorcerer
Joined
Mar 21, 2020
Messages
1,484
If I decide to run the MPP out put to a breaker panel I would ground to a waterline.
However, sharing a neutral of a this L1 out put with a second MPP out put to create a L2 in this panel is still questionable do to my ignorance.
Clearly, I will have to research thos further because it most definitely does not sound like " code" .
Incidentally, I installed my 200 amp service and went out and drove that copper grounding rod.
However, for what ever reason I now remember I also ran an additional ground out to a water line! Is this second ground unsafe?
It is OK to have two or more below-ground earthing elements, in fact, it is preferred. In some locations, two ground rods are a requirement, pounded in at least 6' apart from each other. That thick 6-4 gauge wire that goes out from the main bussbar to waterline (what is it made of?) may also go to the ground-rod. Code states that the below-ground element connection needs to be made with a single unbroken wire that is not spliced in any way.

Let's say your waterline is 7 feet away from the bussbar, and you pounded the ground rod 8 feet away from the waterline. You would take a 15 foot 4 gauge wire that runs from the bussbar, is clamped to the waterline, and continues on to be clamped at the ground rod. BTW, 6gauge is for service up to 100A, and 4 gauge is for service up to 200A.

Furthermore, I explored adding a sub panel ; but, I decided not to for now; anyway, I was confused on the isolated panel concepts.
I think my understanding of a sub panel was that the isolated sub panel screw must be removed and that sub panel must go directly back to the main service. Is this understanding correct?
I realize I have gone off topic so I don't mean to take up your time ; and , I appreciate you info on the MPP output.
Thanks.
I have no experience with a sub-panel. I don't want to give any advice that might be contrary to code. You'd better ask an electrician this question.

Are you asking this because you also want a grid connection? If you also want to connect to the grid, you MUST have either a transfer switch, or an either/or breaker panel. If the grid is down, and a lineman is working on the line, your solar system could energize the line and kill a lineman. Do NOT try to rig something up! Pay an electrician to do this.

In the end, maybe it will be for straightforward for you to just get a split-phase 120/240V inverter. There are lots of models to chose from.
 

cisumma

New Member
Joined
Apr 2, 2021
Messages
112
It is OK to have two or more below-ground earthing elements, in fact, it is preferred. In some locations, two ground rods are a requirement, pounded in at least 6' apart from each other. That thick 6-4 gauge wire that goes out from the main bussbar to waterline (what is it made of?) may also go to the ground-rod. Code states that the below-ground element connection needs to be made with a single unbroken wire that is not spliced in any way.

Let's say your waterline is 7 feet away from the bussbar, and you pounded the ground rod 8 feet away from the waterline. You would take a 15 foot 4 gauge wire that runs from the bussbar, is clamped to the waterline, and continues on to be clamped at the ground rod. BTW, 6gauge is for service up to 100A, and 4 gauge is for service up to 200A.


I have no experience with a sub-panel. I don't want to give any advice that might be contrary to code. You'd better ask an electrician this question.

Are you asking this because you also want a grid connection? If you also want to connect to the grid, you MUST have either a transfer switch, or an either/or breaker panel. If the grid is down, and a lineman is working on the line, your solar system could energize the line and kill a lineman. Do NOT try to rig something up! Pay an electrician to do this.

In the end, maybe it will be for straightforward for you to just get a split-phase 120/240V inverter. There are lots of models to chose from.
Right, I don't need to mess with the service ; not yet anyway and, when and if that time comes I will have to get an electrician because grid tie and subpanel issues are unforgiving if not totally sound.
Correct, a split phase 120 /240 inverter is most likely code ; and, that is probably how to come up with a " shared " neutral that won't become energized. Thanks again.
Good luck with your system.
Although, these all in one MPP's are pretty badass! I will have to research; because, It might be possible to " plug and play" two each MPP's together and get split phase.
Off grid split phase is the goal; but, I am only half way there. ;)
Right now, my goal is to run a deep freeze on a thermostat for 3 to 4 hours a day and accomplish basic refrigeration with a couple bags of ice to hold thru the night.
Good luck and thanks.
 
Last edited:
Top