Unbalanced voltage at main panel

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BJReacher

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Hi folks,

I'm a brand new member and am troubleshooting an interesting problem that would be great to get some opinions on. The residence has a small 6K solar hybrid inverter. The main utility feed connects through an ATS (for a generator) and then to the inverter. When the inverter is in 'grid mode' it essentially is a pass-through for the power back to the main panel. The loads on the panel are 240V pumps and some 120V outlets. In 'grid mode' the 120v legs are balanced and happy. When the inverter switches to create 240v from the batteries the 240V output in the panel is just fine but the 120v legs are unbalanced (eg. 185v and 24v). So the 240V pumps continue to work normally but the 120V outlets are unusable. The specs for the inverter specifically instruct that if you use 240V for your loads or a mix 240/120, you connect only the two hot wires for the output (i.e. no neutral). This doesn't seem to be a problem for the 'grid mode' pass through, but seems to be a problem for the inverted battery power. Thoughts?
 
Welcome to the forum.

It sounds like the inverter depends on the service neutral to act as a voltage divider.
 
LarryFine said:
Welcome to the forum.

It sounds like the inverter depends on the service neutral to act as a voltage divider.
Click to expand...
Yes, but the inverter accepts no neutral input (from the service) and allow no neutral output if you want to use 240V. If you want to use just 120V loads it instructs you to connect only one hot and provides a neutral. It's confusing that the pass-through service power has no issues even without its neutral propagating through the inverter.
 
Perhaps the inverter is made for other countries that don't have 120/240V split phase, and only have a two wire supply for single phase services. Apparently some have used an autotransformer in this case to get 120/240V.
 
230321-1743 EDT

If your inverter is connected in parallel with the utility transformer, and thus is essentially a parallel source to your home, then the utility transformer provides the balancing operation, and you won't see what you describe.

If there is a transfer switch that disconnects you from the utility transformer when your generator runs, then your voltage distribution will be established by the impedances of the various loads.

.

.
 
gar said:
230321-1743 EDT

If your inverter is connected in parallel with the utility transformer, and thus is essentially a parallel source to your home, then the utility transformer provides the balancing operation, and you won't see what you describe.

If there is a transfer switch that disconnects you from the utility transformer when your generator runs, then your voltage distribution will be established by the impedances of the various loads.

.

.
Click to expand...
When the generator runs, it triggers the ATS to isolate the grid and the generator power is a pass-through for the inverter the same way the actual grid power is. Interestingly, the 240V from the generator works just like the grid power and the 120 V legs are balanced in the panel.
 
synchro said:
Perhaps the inverter is made for other countries that don't have 120/240V split phase, and only have a two wire supply for single phase services. Apparently some have used an autotransformer in this case to get 120/240V.
Click to expand...
Hmmm. I don't know. It's sold on Amazon. I've called their support line but it's a Chinese manufacturer and not exactly responsive.
 
230321-2203 EDT

BJReacher:

Clearly, if you are isolated from the power grid, as has now been stated, and you simply have a 240V source with no neutral of its own, then your original neutral can float anywhere between the 240 V lines from the generator (source ). The relative loads on the two sides of what was a neutral wire will now define the voltage distribution on the two sides of the now floating neutral. This should be self evident.

.
 
BJReacher said:
When the generator runs, it triggers the ATS to isolate the grid and the generator power is a pass-through for the inverter the same way the actual grid power is. Interestingly, the 240V from the generator works just like the grid power and the 120 V legs are balanced in the panel.
Click to expand...

gar said:
230321-2203 EDT

BJReacher:

Clearly, if you are isolated from the power grid, as has now been stated, and you simply have a 240V source with no neutral of its own, then your original neutral can float anywhere between the 240 V lines from the generator (source ). The relative loads on the two sides of what was a neutral wire will now define the voltage distribution on the two sides of the now floating neutral. This should be self evident.

.
Click to expand...
Maybe I wasn't clear with the statement about the generator. When either the grid or the generator supplies power as a pass-through to the inverter and then on to the panel, all voltages are nominal i.e. both legs are balanced. It's only when the inverter supplies the power (sourced from batteries or solar) to the panel via the same two hot wires that we get the unbalanced voltages. I can buy your argument about supplying the two hot wires to the panel without a neutral as the cause, but why do those same two hot wires work just fine in the inverter's pass-through mode?
 
230324-0655 EDT

BJReachher:

When you power your load from any source that provides two voltage sources ( note I am saying voltage source, and you need to understand what this means ) referenced to a common neutral, then those voltages will remain relatively invariant in voltage relative to load current changes. If one voltage is 180 degrees shifted in phase from the other, then you will see double the voltage of one when measuring across the outer two poles.

If there is no neutral wire from the source, then two loads in series across that total source voltage will have voltage drops across each load that are a function of.the relative impedances. That is what you are seeing.

.
 
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