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Subpanel is 99% 120V except by Dryer that is 240V. Is it still okay to connect the Inverter AC-OUT 120V into both L1/L2 ?

usphisics

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Austin, TX
First of all, I'm super new on this solar/inverter world. So, please, easy....
Here is my scenario that Im pretty sure that a lot of people may have something similar.
  • Main panel receives 240V split phase from grip.
  • Everything in the main panel has a 2 pole breaker (240v split phase)
    • Generator 30amps breaker (it has an Interlock)
    • AC heat pump breaker
    • Furnace heater breaker
    • Sub-panel breaker
  • At the sub-panel 99% of all breakers are 120V (15amp or 20amp) EXCEPT by the Dryer that is 240V that I DONT USE AT ALL as I have a gas dryer, but the breaker/outlet everything is there just in case I (my wife) need it.
When I started to study about this solar/inverter world I came with the idea to not touch in the main panel (at least for now) and just connect the sub-panel into the solar system. So still using the grid/generator for the AC/Furnace and using another Interlock in the sub-panel to be able to totally disconnect it from the main panel and at the same time safely allowed connect it into the solar system. Or even in case of a main failure in the solar system be able go back and reconnect the sub-panel into main panel 100%.
So far so good until I start to think which would be the a good inverter to my design. First thing that came to my mind is that I would need to have a 240v split phase inverter. In my mind it is simple. 240V split phase comes from the main panel, so in order to replace it I also need a 240v split phase. So I started to research by reliable 240V inverters, like the ones from Schneider as they look to be bullet proof beasts. But then I red in this forum someone talking about have 240v split phase VS really have 240v split phase loads and as I said before, on my sub-panel 99% of the breakers/loads are single 120V phase EXECEPT by a 2 pole breaker for the dryer THAT I DONT USE AT ALL (at least now).
So we go back to the title of this post. It looks like that I could use a nice 120V single phase interver to connect into my sub-panel and have both L1 and L2 legs connected. So this way I will have 120v single phase (not 240v split phase) into both legs.
  • IS IT RIGHT ? 120v connect into both L1/L2 legs of my subpanel
  • If so how I would do with that dryer breaker ? Is it okay to leave it there ?
  • If I lease it there what happens if in the future someone goes and connect a dryer into it while the solar system is the one that is providing power to the sub-panel ? Is it safe or even legal ?
Sorry my long post but as I said... Im totally newbie and just trying to learn as much it is possible.....

Thank you everyone......
 
You are correct with regard to connecting 120V from the inverter to both bus bars in the subpanel and the subpanel is then derated to 120V only, no split phase.
My suggestion would be to remove the 240V breaker or lock it out. Unplug the dryer and clearly label the subpanel as 120V only service.
 
Please, correct me if Im wrong, but in my case, having 2 x 120V that are single and not split phase that also come from the same source will basically make a dryer, if for some reason in the future someone connect it into that 240v outlet, not work as it will understand that I only have 120v, right ? Is my understanding right or Im totally wrong ? My worry is to not burn anything or put someone in danger or even not be legal accord with some law/regulation.

Btw, thanks @timselectric ....
 
Please, correct me if Im wrong, but in my case, having 2 x 120V that are single and not split phase that also come from the same source will basically make a dryer, if for some reason in the future someone connect it into that 240v outlet, not work as it will understand that I only have 120v, right ? Is my understanding right or Im totally wrong ? My worry is to not burn anything or put someone in danger or even not be legal accord with some law/regulation.

Btw, thanks @timselectric ....
No Hazzard.
It just won't work on 120v.
 
First of all, I'm super new on this solar/inverter world. So, please, easy....
Here is my scenario that Im pretty sure that a lot of people may have something similar.
  • Main panel receives 240V split phase from grip.
  • Everything in the main panel has a 2 pole breaker (240v split phase)
    • Generator 30amps breaker (it has an Interlock)
    • AC heat pump breaker
    • Furnace heater breaker
    • Sub-panel breaker
  • At the sub-panel 99% of all breakers are 120V (15amp or 20amp) EXCEPT by the Dryer that is 240V that I DONT USE AT ALL as I have a gas dryer, but the breaker/outlet everything is there just in case I (my wife) need it.
When I started to study about this solar/inverter world I came with the idea to not touch in the main panel (at least for now) and just connect the sub-panel into the solar system. So still using the grid/generator for the AC/Furnace and using another Interlock in the sub-panel to be able to totally disconnect it from the main panel and at the same time safely allowed connect it into the solar system. Or even in case of a main failure in the solar system be able go back and reconnect the sub-panel into main panel 100%.
So far so good until I start to think which would be the a good inverter to my design. First thing that came to my mind is that I would need to have a 240v split phase inverter. In my mind it is simple. 240V split phase comes from the main panel, so in order to replace it I also need a 240v split phase. So I started to research by reliable 240V inverters, like the ones from Schneider as they look to be bullet proof beasts. But then I red in this forum someone talking about have 240v split phase VS really have 240v split phase loads and as I said before, on my sub-panel 99% of the breakers/loads are single 120V phase EXECEPT by a 2 pole breaker for the dryer THAT I DONT USE AT ALL (at least now).
So we go back to the title of this post. It looks like that I could use a nice 120V single phase interver to connect into my sub-panel and have both L1 and L2 legs connected. So this way I will have 120v single phase (not 240v split phase) into both legs.
  • IS IT RIGHT ? 120v connect into both L1/L2 legs of my subpanel
  • If so how I would do with that dryer breaker ? Is it okay to leave it there ?
  • If I lease it there what happens if in the future someone goes and connect a dryer into it while the solar system is the one that is providing power to the sub-panel ? Is it safe or even legal ?
Sorry my long post but as I said... Im totally newbie and just trying to learn as much it is possible.....

Thank you everyone......
Do you have an interlock device between main panel breaker and your generator/inverter breaker? If powering L1 & L2 on single phase you can't have 220VAC breakers on. Also there needs to be consideration on how much current the neutral will be carrying...will it be shared between L1 & L2.....hence double?
 
That's a good point.
Make sure that none of the breakers in your sub panel feed multi-wire branch circuits. (One neutral shared for two circuits)
 
Is there room to move the 240v breaker to the main panel?

If not, I’d unwise the dryer from the breaker and leave a note.
 
Do you have an interlock device between main panel breaker and your generator/inverter breaker? If powering L1 & L2 on single phase you can't have 220VAC breakers on. Also there needs to be consideration on how much current the neutral will be carrying...will it be shared between L1 & L2.....hence double?Hi
Hi @Hank Waconda , not if I understood what you said. But here is what I have today in my main panel.
PXL_20230502_010020160.jpg
PXL_20230502_010040003.jpg
It is a 240V split phase for the generator breaker with the interlock. It is to be use by a Wen GN625i.
https://generatorbible.com/generators/wen/gn625i/

So it is a invert generator and I hook up it using its 240V 30A (L14-30R) receptacle into my main panel today and it is able to run everything, except the furnace, in my house. Even the AC heat pump with a easy started it can run.
But again, the idea is to isolate the sub-panel L1/L2 wires but as you guys said the neutral will be shared, is that okay or something else to take into consideration ?

Here is my sub-panel.
PXL_20230502_012217852.jpg
And you can see it doesnt have a Top Main breaker. The idea is (if possible) move the 2 top right breakers (kitchen GFCI outlets) to the botton and add a 240v breaker for the Solar system 120v AC output but connecting both L1/L2 as that was the idea. And of course the Solar system breaker and the Top Main one MUST have a Interlock.



Thank you....
 
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Hi @Hank Waconda , not if I understood what you said. But here is what I have today in my main panel.

View attachment 147436
View attachment 147437
It is a 240V split phase for the generator breaker with the interlock. It is to be use by a Wen GN625i.
https://generatorbible.com/generators/wen/gn625i/

So it is a invert generator and I hook up it using its 240V 30A (L14-30R) receptacle into my main panel today and it is able to run everything, except the furnace, in my house. Even the AC heat pump with a easy started it can run.
But again, the idea is to isolate the sub-panel L1/L2 wires but as you guys said the neutral will be shared, is that okay or something else to take into consideration ?

Thank you....
The shared neutral at the panel feed, shouldn't be a problem. I'm sure that the wires are rated for more than the output of the inverter.
What could be an issue is if you have multi-wire branch circuits.
 
Looking at the picture.
The only possible multi-wire branch circuit is the garage circuits.
Would have to look inside the panel to know for sure.
 
The shared neutral at the panel feed, shouldn't be a problem. I'm sure that the wires are rated for more than the output of the inverter.
What could be an issue is if you have multi-wire branch circuits.
Tomorrow I can check the AWG of the wires going from the main to the sub panel. But sub-panel breaker is 80A and the distance between both are less than 50ft, so probably it is at least 4AWG. But I will check. I need to open the sub-panel to install a Emporia VUE any way so I can also take a look on the wire AWG.

Thank you btw @timselectric
 
Hi @Hank Waconda , not if I understood what you said. But here is what I have today in my main panel.

View attachment 147436
View attachment 147437
It is a 240V split phase for the generator breaker with the interlock. It is to be use by a Wen GN625i.
https://generatorbible.com/generators/wen/gn625i/

So it is a invert generator and I hook up it using its 240V 30A (L14-30R) receptacle into my main panel today and it is able to run everything, except the furnace, in my house. Even the AC heat pump with a easy started it can run.
But again, the idea is to isolate the sub-panel L1/L2 wires but as you guys said the neutral will be shared, is that okay or something else to take into consideration ?

Thank you....
Looks good.....is this generator split phase?
 
Last edited:
@timselectric
When you said multi-wire branch circuit is the garage circuits what exactly are you look for ? Sorry for my newbie question :(
Usually it's a 3 wire romex. Black, red,white, and bare.
Black and red are circuits on L1 and L2, white wire is the neutral for both. (Shared neutral)
Since you will be combining L1 and L2, a multi-wire branch circuit neutral would have to carry twice the current.
 
If it is split phase gen L1 & L2 would be 180 degree out anyway ....they would cancel each other out then there would not be an neutral current problem. I thought we were talking about single phase on L1 & L2...same phase.
 
If it is split phase gen L1 & L2 would be 180 degree out anyway
Not quite, but that's another conversation.
But this conversation is about the sub panel and combining L1 and L2 to be fed by a 120v inverter.
The generator feeds into the main panel. And is split-phase.
 
Please, correct me if Im wrong, but in my case, having 2 x 120V that are single and not split phase that also come from the same source will basically make a dryer, if for some reason in the future someone connect it into that 240v outlet, not work as it will understand that I only have 120v, right ? Is my understanding right or Im totally wrong ? My worry is to not burn anything or put someone in danger or even not be legal accord with some law/regulation.

Btw, thanks @timselectric ....
The outlet would actually be at 0V
 
Usually it's a 3 wire romex. Black, red,white, and bare.
Black and red are circuits on L1 and L2, white wire is the neutral for both. (Shared neutral)
Since you will be combining L1 and L2, a multi-wire branch circuit neutral would have to carry twice the current.
@timselectric Got it. Yes, it makes sense. Today as the sub-panel is fed by the main using a 240v split phase, the neutral wire in a give moment will carry current from just one of the hot wires, or L1 or L2. Does it make sense ? But once I combine L1/L2 it can have to carry current from both wires at the same moment. But in that case it will be limited to the max current that my inverter can delivery, right ? Make sense ?
So as long the inverter AC output is < than the neutral wire rate I will be good and what means that I must use a right breaker for the solar system AC output.
Am I at least going/thinking in the right direction or Am I totally lost ? :ROFLMAO:
 
@timselectric Got it. Yes, it makes sense. Today as the sub-panel is fed by the main using a 240v split phase, the neutral wire in a give moment will carry current from just one of the hot wires, or L1 or L2. Does it make sense ? But once I combine L1/L2 it can have to carry current from both wires at the same moment. But in that case it will be limited to the max current that my inverter can delivery, right ? Make sense ?
So as long the inverter AC output is < than the neutral wire rate I will be good and what means that I must use a right breaker for the solar system AC output.
Am I at least going/thinking in the right direction or Am I totally lost ? :ROFLMAO:
Yup
You've got it.
 
@timselectric
as promised, here is my sub-panel inside. It looks like the only wires coming from the main panel is the L1, L2, N and Ground. And again the breaker to disable the sub-panel is in the main panel but the original idea is to add one top main breaker (using the same 80amps that we have in the main panel) and add a 2 pole breaker on the top left + interlock, so that way I would be able to turn on/off (switch) the current coming from the main pain or inverter.
PXL_20230503_141653844.jpg

Btw, I installed an Emporia 2 Vue with 16 sensors. Tried to organize it the best way to leave wires not in from of any break, so it is +- okay.
But that thing is amazing. How now I can see all my usages in that sub-panel. I would love to install it as well for my heat pump and furnace but as both breakers are in the main panel I dont want to mess with it for now.

And on my researches/studies I saw that I will need permits in order to install a solar system in my house. So Im looking for some company that can help with the design and also have a signed engineering plans. Lets see.....
 
In addition to the good advice above - get a 120v dryer (heat-pump model) and wire a different plug and then you're 100% 120v both panel and operationally within you're home :)
 

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