Main Circuit Panel vs Sub Panel

James Braka

New Member
Joined
Feb 26, 2021
Messages
10
Hi, hope you don't mind the newbie question. I am trying to setup the AC portion of my solar All-in-One. I did some search on setup of AC breaker box for use with solar, in particular, an All-in-One like the MPP Solar. It seems to me, at this point, most people connect the AC Output of the All-in-One solar charger/inverter to a Sub Panel or, even, a Main Panel converted to a Sub Panel. Is this the correct understanding that most people use a Sub Panel?

If an AC Output is connected to a Sub Panel, the charger/inverter AC wire is connected to an AC Circuit breaker and done through **back feeding** and the main lug is not used. No grounding rod.

However, if an AC Output is connected to a Main Panel instead, the connection is to the Main Circuit Breaker and both Netural and Ground busbars are bonded and grounded to a grounding rod. Is this correct? Did I missed something here? It seems like either a Main Panel box and Sub Panel can be used. Correct? Thank you.

I am referring to the AC breaker box in which the AC Output from the All-in-One is connected to; and this breaker box then connect to the wall outlet. Thanks.
 

rjpear

New Member
Joined
Jul 18, 2021
Messages
28
I like this use of the Sub Panel and intend to duplicate it...
DThames stated in this post ( https://diysolarforum.com/threads/s...d-using-battery-backup-for-grid-outage.15715/ ) :
Use my example. I put in a 60amp sub panel. I pulled 4 critical house circuits out of my main panel and moved them to the sub panel. The sub panel came with two 60 "main breakers", but only one can be on at a time. Actually they are not "main breakers" but the input feed. Under normal conditions the 60amp that is connected to the main panel is where the sub panel gets its power. If the power goes out, I switch that 60amp off and switch the second 60 amp on. That second 60amp is feed from a inlet plug (power goes in, not comes out) on the wall. I can plug my inverter in there or I can plug my generator in there. But again, both 60amps can not be on at the same time. There is a mechanical device always blocking one of them.
 

Boomtown

New Member
Joined
Jan 8, 2022
Messages
2
Hi, hope you don't mind the newbie question. I am trying to setup the AC portion of my solar All-in-One. I did some search on setup of AC breaker box for use with solar, in particular, an All-in-One like the MPP Solar. It seems to me, at this point, most people connect the AC Output of the All-in-One solar charger/inverter to a Sub Panel or, even, a Main Panel converted to a Sub Panel. Is this the correct understanding that most people use a Sub Panel?

If an AC Output is connected to a Sub Panel, the charger/inverter AC wire is connected to an AC Circuit breaker and done through **back feeding** and the main lug is not used. No grounding rod.

However, if an AC Output is connected to a Main Panel instead, the connection is to the Main Circuit Breaker and both Netural and Ground busbars are bonded and grounded to a grounding rod. Is this correct? Did I missed something here? It seems like either a Main Panel box and Sub Panel can be used. Correct? Thank you.

I am referring to the AC breaker box in which the AC Output from the All-in-One is connected to; and this breaker box then connect to the wall outlet. Thanks.
I am going to be connecting my AC output to my grid tied Main Panel. I am a bit confused in that it appears both AC Input and AC Output will both connect to the Main Panel. I will probably even use the same circuit - seems odd. Let me know how yours works out!
 

time2roll

Photon Sorcerer
Joined
Mar 20, 2021
Messages
2,458
I am going to be connecting my AC output to my grid tied Main Panel. I am a bit confused in that it appears both AC Input and AC Output will both connect to the Main Panel. I will probably even use the same circuit - seems odd. Let me know how yours works out!
Seems odd. Maybe the inverter is not intended to be used as expected.
 

Ampster

Renewable Energy Hobbyist
Joined
May 3, 2020
Messages
4,676
Location
Kenwood, California
Seems odd.
I agree. The purpose of using a subpanel is to take advantage of the transfer switch in the AIO inverter. Another purpose is to put essential loads on a subpanel so they can be powered when the grid is down. If the AC out connection is connected to the main panel there is no protection upstream for linemen from backfeeding the grid.
 

OffGridInTheCity

Solar Addict
Joined
May 23, 2021
Messages
556
Location
Southern Oregon
I do main panel w/ATS, subpanels with and without ATS, and stand-alone ATS....

I have an ATS + MTS combo on my main panel. Its limited to 240v@50a and the MTS can only 10 circuits - e.g. aprox 25% of the 200a service. For example, I can only do 1 high amp 240v circuit - currently wired to the dryer. I do the 120v side of the whole house heat-pump here - see below for the compressor side. The MTS let's me turn on/off individual solar circuits with a flip of a switch - for example I only turn the Dryer to "Gen" (e.g. Solar) in spring/summer when I have lots of power to burn off and the rest of the time it stays on "Line" (e.g. grid only) mode.
1641683594287.png1641684700589.png

I also subpanels with and without ATSs...
A subpanel is typically fed from a main panel and then used to branch off other circuits. For example, I have a 240v@50a circuit run from the main panel (above) to a subpanel at an opposite corner of the house. At that subpanel I have circuits branching off for the hot water heater, the rainharvest pump, the UV light for rainharvest, general lighting sockets. That subpanel also has a 240v@50a ATS on it fed on the grid side by the main panel and the generator side by one of my inverter distribution panels.

I also have stand-alone ATSs. This one is at the outdoor compressor part of the home heat-pump. Intercepted the main panel wiring for grid side of the ATS and ran a wire from the inverter distribution panel for the generator side and the output to the compressor on the other side of the wall. This let me intercept the main panel wiring and add an off-grid inverter power option without having rewire the existing house wiring or run new circuits from the main panel.
1641684216524.png
 
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Bvillebob

Solar Addict
Joined
Oct 21, 2021
Messages
148
My inverter has big letters in the manual that say "NEVER allow AC on the output of the inverter", it will fry the inverter if you hook the output to the grid line.a. You can't connect the output to the the main grid line, you need a transfer switch to change the circuits over from the grid to the inverter.
 

time2roll

Photon Sorcerer
Joined
Mar 20, 2021
Messages
2,458
Hi, hope you don't mind the newbie question. I am trying to setup the AC portion of my solar All-in-One. I did some search on setup of AC breaker box for use with solar, in particular, an All-in-One like the MPP Solar. It seems to me, at this point, most people connect the AC Output of the All-in-One solar charger/inverter to a Sub Panel or, even, a Main Panel converted to a Sub Panel. Is this the correct understanding that most people use a Sub Panel?

If an AC Output is connected to a Sub Panel, the charger/inverter AC wire is connected to an AC Circuit breaker and done through **back feeding** and the main lug is not used. No grounding rod.

However, if an AC Output is connected to a Main Panel instead, the connection is to the Main Circuit Breaker and both Netural and Ground busbars are bonded and grounded to a grounding rod. Is this correct? Did I missed something here? It seems like either a Main Panel box and Sub Panel can be used. Correct? Thank you.

I am referring to the AC breaker box in which the AC Output from the All-in-One is connected to; and this breaker box then connect to the wall outlet. Thanks.
Yes a pass through all-in-one inverter will generally output to a sub panel to feed critical loads during an outage. Many also use this in an RV to feed the main RV panel which is a sub panel. The utility cord would feed into the inverter.

Yes you can feed a breaker or connect to the main lug of the sub panel. The input of the inverter should be fed through a breaker and will be stated in the installation manual.

The sub panel fed by the inverter should not have any neutral-ground bond. The inverter may have a neutral ground bond while inverting. When passing power through from another source the neutral-ground bond will open and rely upon the other power source for the bond.

Would help to know what you are connecting the inverter to. Off grid home? on grid home back up? RV etc. I don't think this inverter is going to be a grid tie where you can push power back through the meter.
 

Boomtown

New Member
Joined
Jan 8, 2022
Messages
2
Seems odd. Maybe the inverter is not intended to be used as expected.
Yeah I think you and @Bvillebob and @Ampster are right - might be the wrong piece of equipment. I got the MPP Solar LV6548 but perhaps should get the LV6048. I think the LV6548 cannot feed PV watts into the main panel.

The LV6548 webpage says "Can offset your utility power by directly supplying loads from your solar panels (“net zero” effect) when running with or without batteries", but perhaps that doesn't mean -while the grid is connected-
 

time2roll

Photon Sorcerer
Joined
Mar 20, 2021
Messages
2,458
Yeah I think you and @Bvillebob and @Ampster are right - might be the wrong piece of equipment. I got the MPP Solar LV6548 but perhaps should get the LV6048. I think the LV6548 cannot feed PV watts into the main panel.

The LV6548 webpage says "Can offset your utility power by directly supplying loads from your solar panels (“net zero” effect) when running with or without batteries", but perhaps that doesn't mean -while the grid is connected-
By the description it would seem the inverter would not back-feed the utility but would supply power to a sub panel with priority of solar, battery, and lastly pass through power from the utility. This would be to use solar and avoid being a generator for the utility. This could be best if your feed in tariffs are at reduced rates and there is more value to use the solar power direct or store the solar in the battery for overnight use before drawing from the utility.

Best to start a new thread to discuss the options.
 
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