Neutral shifting on split phase service?

[SunFish]

Having some issues with a couple inverters on a residential site. We've had two inverters fail now, both with the same issue.

Referencing the manual for the error code says "For all 3-phase inverters, especially in new installations, (but also in existing installations, depending on the grid quality on site) the error often appears in connection with a shifted neutral point / star point. This can be caused by larger consumers on the grid, for example air conditioners, pumps, large motors and lifts or by a faulty installation."

Everything I'm reading on neutral shifting indicates this is an issue with three phase sites, but we are 240 split phase. Anyone know if neutral shifting can occur on split phase services? Or is this problem only seen on three phase services?

The customer does have several heat pumps wired up without neutrals, as well as a welder that doesn't use a neutral. Also, we have another customer with the same inverters that is across the street, and they haven't had any issues with their system.

 

[electrofelon]

So by "fail" you mean they threw an error code? But they work again after a Time?

Are you sure you have the country standard or grid type set correctly?

Jumping ahead a little bit, if nothing else works, can you just set them for a 240 Delta grid, no neutral reference (I know you can do that on sunny boys).

You could indeed have a neutral shift from voltage drop on one leg, but would need to be a helluva load or undersized wire I would think.

 

[LarryFine]

I take "neutral shift" to mean unbalanced voltages, which is almost always due to a compromised neutral current pathway.

Line-to-line loads can cause line-to-neutral voltages to sag, but only a bad neutral can cause one line's voltage to rise.

 

[kwired]

Line-to-line loads can cause line-to-neutral voltages to sag, but only a bad neutral can cause one line's voltage to rise.

Excessively long runs without increasing conductor size for voltage drop can fool you into thinking you have open neutral problems. The more unbalanced you are with line to neutral loads the more it will actually look like an open neutral condition as voltage drop on the neutral will contribute to the effects. The line with the heavier current draw will have a voltage sag while the other line with light loading will show higher than nominal volts to neutral.

 

[pv_n00b]

I would look for a problem with an open neutral. Once a neutral is open the current can find all kinds of alternate paths that cause problems. I've seen it burn up cable TV ground conductors when the neutral current used it to get back to the service. The other problem might be a seriously unbalanced 120V loading on the two sides. The 240V loads should not be a problem.

 

[tortuga]

Having some issues with a couple inverters on a residential site. We've had two inverters fail now, both with the same issue.

Referencing the manual for the error code says "For all 3-phase inverters, especially in new installations, (but also in existing installations, depending on the grid quality on site) the error often appears in connection with a shifted neutral point / star point. This can be caused by larger consumers on the grid, for example air conditioners, pumps, large motors and lifts or by a faulty installation."

Same here, are you getting error code 7702?

 

[SunFish]

Same here, are you getting error code 7702?

Yup, 7702

 

[SunFish]

So by "fail" you mean they threw an error code? But they work again after a Time?

Are you sure you have the country standard or grid type set correctly?

Jumping ahead a little bit, if nothing else works, can you just set them for a 240 Delta grid, no neutral reference (I know you can do that on sunny boys).

You could indeed have a neutral shift from voltage drop on one leg, but would need to be a helluva load or undersized wire I would think.

No, had to RMA them