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diy solar

Trying to understand the sub panel and how 120/240v work

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khisanthax

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I have an off-the-grid DIY solar panel kit that has one 120 volt line leading into the subpanel in my garage. Before I install the solar panel there were two 120 volt lines coming in from the house I removed both lines and connected the line from the solar panel inverter to the subpanel box but then only one side of the circuit breaker subpanel would work so I had to connect One of the 120 volt lines coming in from the house in order to get the whole subpanel powered and for my mini split AC which runs at 240 volts to work as well.

Does this mean that the solar panel inverter is only providing power to half of the subpanel? and the other half is being powered from the house / utility?
 
You might want to start by thinking about voltages.
One 120v line from the solar panel inverter is a two wire system, Hot (L1) and Neutral (N) wires). 120v ac from wire to wire.
If you were running your minisplit on 240v ac before making the solar/inverter circuit change, the panel had a three wire system (L1, L2 and N (Neutral).
You need provide a three wire system to the panel.
Combining a two wire inverter 120v ac circuit with a 120v ac grid circuit may not work too well unless they are in sync.
 
In what way would they be in sync or not in sync? 50 vs 60 hz? If it's hz you're referring to I believe they are in sync.
 
They need to be 180 degrees out of phase to be "in sync". Need to be the same frequency to but that's not your problem here.

If it is wired as I read it, you have one side of your panel supplied with 120V from your inverter but the other side (leg) is supplied by the utility. That's a serious problem and will likely damage whatever 240Vac loads you are actively powering - damage as in destroy. If this is the case, I would undo what you have done and get some help.
 
If the above is correct, you should measure a voltage of anywhere between 0 and 240Vac between the two lugs of your panel. That voltage will vary slowly but sometimes eratically as the phase relationship between your inverter and the utility changes.

If your inverter has a utility AC input, it might sync with that and the phase relationship won't change and the system might work, but it will not be "right" as the single phase inverter will be supplying half of your 240V loads and the utility the other half. That is far from conventional.
 
You could power the sub panel from one of the following at a given time:

1) 120/240V from grid (wires from house)
2) 120V from your inverter together with an auto-transformer for 120/240V.

Auto-transformers are available from Victron, Midnight, and others.

Alternatively, can power sub panel from 120V only. It is possible to feed just half the panel, or both halves. Couple issues to address so you don't cause "brown out" low voltage damage feeding just one half, or excess current in neutral wires feeding both halves. (If your inverter is 2500W or less, won't be an over-current problem).
 
khisanthax said:
I have an off-the-grid DIY solar panel kit that has one 120 volt line leading into the subpanel in my garage. Before I install the solar panel there were two 120 volt lines coming in from the house I removed both lines and connected the line from the solar panel inverter to the subpanel box but then only one side of the circuit breaker subpanel would work so I had to connect One of the 120 volt lines coming in from the house in order to get the whole subpanel powered and for my mini split AC which runs at 240 volts to work as well.

Does this mean that the solar panel inverter is only providing power to half of the subpanel? and the other half is being powered from the house / utility?
Click to expand...
Yes and there could be big problems if you have any 240v circuits
 
The inverter does have a utility input and output but it sounds like I'm still running a risk?

Or I could get an auto-transformer so that the inverter can supply l1 and l2?
 
Wire in another sub panel for your 240v loads and run them off the utility, then jump your current 120v panel bus together to run off your current inverter; or buy a 120/240v inverter if yours can't be wired in parallel with another to create 240v.

How many watts is your current inverter, what's the model?
It may not even be worth the trouble of looking into an autotransformer.

Edit - wiring 120v to both busses of your current panel may not be safe. Continuing reading the next page for a technical explanation from @Hedges
 
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khisanthax said:
I have an off-the-grid DIY solar panel kit that has one 120 volt line leading into the subpanel in my garage. Before I install the solar panel there were two 120 volt lines coming in from the house I removed both lines and connected the line from the solar panel inverter to the subpanel box but then only one side of the circuit breaker subpanel would work so I had to connect One of the 120 volt lines coming in from the house in order to get the whole subpanel powered and for my mini split AC which runs at 240 volts to work as well.

Does this mean that the solar panel inverter is only providing power to half of the subpanel? and the other half is being powered from the house / utility?
Click to expand...
This is very bad...
How it is operating is beyond me.
Most likely, the inverter shuts down and the utility is feeding the loads through the inverter...

If you need 240, get a 240v inverter.
If you continue like you are you have unregulated neutral not bonded properly, out of synch phases, and potential for electrocution and fire...
 
Phases: AC peaks Positive and Negative. In 2 phase one Leg (L1) is positive while Leg2 (L2) is negative. They are 180 degree opposite throughout the 360 degree cycle. 2 Phase is rare for industrial use. 3 phase is a far more efficient use of hardware. They are 120 degrees apart. 120vac L1 to 120vac L2 is 208vac etc..
 
Pappion said:
Phases: AC peaks Positive and Negative. In 2 phase one Leg (L1) is positive while Leg2 (L2) is negative. They are 180 degree opposite throughout the 360 degree cycle. 2 Phase is rare for industrial use. 3 phase is a far more efficient use of hardware. They are 120 degrees apart. 120vac L1 to 120vac L2 is 208vac etc..
Click to expand...
Split-phase is single phase with a center tap for neutral. It's only one phase. Not 180deg apart.
One phase, one sinewave.
 
1201 said:
Semantics. It's 180 apart relative to neutral
Click to expand...
It's not.
When you stand at the riverside. You can look upriver or downriver. But the river only flows one way, no matter how you look at it.
 
timselectric said:
It's not.
When you stand at the riverside. You can look upriver or downriver. But the river only flows one way, no matter how you look at it.
Click to expand...
Not if that river had a neutral, then the flow would be 180 degrees apart relative to neutral, which is easier for EVERYONE to understand
 
1201 said:
Not if that river had a neutral, then the flow would be 180 degrees apart relative to neutral, which is easier for EVERYONE to understand
Click to expand...
You are the neutral in this scenario.
It's better to understand correctly, even if it's not easy.
 
timselectric said:
Split-phase is single phase with a center tap for neutral. It's only one phase. Not 180deg apart.
One phase, one sinewave.
Click to expand...
It is referred to as 2 Phase. Center Tap changes nothing, they are independent transformer windings . Either phase supplies 120v to neutral, They are 240v apart.
The language also accounts for 3 phase, 120 deg apart.
Phase 1 ,2 ,3
 
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