Voltage Climb

[GRickard]

I recently helped my uncle install a 13.57kw system with a SolarEdge SE11400 inverter. The inverter is kicking out with an error code 33 (high AC voltage). I noticed that at 1720 watt output, I am showing 252 VAC but as the wattage goes up to 8659, the voltage also goes up to 260.5. As the wattage continues to go up, is when it will start to trip.

Being in a rural area, the utility coop normally runs the voltage between 245 and 250 so the people at the end of the line don't have low voltage problems. The inverter is connected to a panel in the barn that is fed with #2 copper about 150' away from the meter/main combo panel. I have installed three other systems in this area (on the same line) that haven't had any problems.

I've seen this problem mentioned here before. What have you seen to be the solution?

Thanks,
Greg

[Mike90250]

Wire resistance is causing voltage to rise. Are you at the end of the utility feed, or at the transformer ?
How long is the cable from inverter to main panel? What gauge wire is that cable
It comes down to , is the utility power too high, or your cable resistance too high for the length of your run. What if you turn on large loads, will that pull the line voltage down some ?

[GRickard]

Are you at the end of the utility feed, or at the transformer ?

The transformer is on the utilities pole and feeds overhead to the meter/main on the house. Then the #2cu feeds from the meter/main to the barn (150').

How long is the cable from inverter to main panel? What gauge wire is that cable

There is a #6cu from the inverter to the panel in the barn that is about 10' long.

[GRickard]

One other thing I noticed today. The 2 pole 100A breaker that is used as the main in the barn panel is heating up and needs to be replaced. Looked like a bad connection to the bus bars. Would this added resistance cause the increased voltage?

Greg

[inetdog]

I recently helped my uncle install a 13.57kw system with a SolarEdge SE11400 inverter. The inverter is kicking out with an error code 33 (high AC voltage). I noticed that at 1720 watt output, I am showing 252 VAC but as the wattage goes up to 8659, the voltage also goes up to 260.5. As the wattage continues to go up, is when it will start to trip.

Being in a rural area, the utility coop normally runs the voltage between 245 and 250 so the people at the end of the line don't have low voltage problems. The inverter is connected to a panel in the barn that is fed with #2 copper about 150' away from the meter/main combo panel. I have installed three other systems in this area (on the same line) that haven't had any problems.

I've seen this problem mentioned here before. What have you seen to be the solution?

Thanks,
Greg

A difference of 6900 watts at about 255V corresponds to a change in current of about 27 amps.
A corresponding voltage difference of 8.5 V gives an effective resistance of a little over .3 ohms.

Please measure the voltage at the main panel end of the 150 foot run to see whether most of the voltage drop is happening there.
A quick calculation with an online voltage drop (rise) calculator suggests that with #2 wire properly terminated you should get less than 1/4 of the voltage drop over that 150' run of wire.
If the majority of the voltage rise is seen at the main panel, then the resistance is in the POCO transformer secondary and the service wiring to the main panel.
Possibly the service wiring is undersized for its length or there may be some bad connections.

If the service wire is OK and POCO is not able to lower their delivery voltage (possibly with a tap change on their pot) and it is not possible to increase the upper voltage limit through software on the SolarEdge inverter, then your only other recourse would be to add a buck transformer to reduce the voltage seen at the AC input terminals of the inverter.
You would have to use a buck configuration with symmetrical windings on each leg of the 240 to maintain the neutral balance that the inverter also looks for.

[sensij]

One other thing I noticed today. The 2 pole 100A breaker that is used as the main in the barn panel is heating up and needs to be replaced. Looked like a bad connection to the bus bars. Would this added resistance cause the increased voltage?

Greg

Yes. Heat = Voltage drop (or rise, in this case)

[inetdog]

Yes. Heat = Voltage drop (or rise, in this case)

But the whole 8V drop at near 30A would be 240 watts and the breaker would be glowing like small heating element.
Getting rid of the voltage drop at the breaker will help but it may not be enough all by itself.
If you want to know how much voltage you are dropping at the breaker measure from the incoming line terminals to the breaker output terminals. (Carefully, of course, if you are working with the dead front of the panel removed.)

[bcroe]

Your breaker should not heat up, its already in trouble. It will just get worse until something literally smokes,
don't wait till that happens. Bruce Roe

[GRickard]

Inetdog & bcroe,
I definitely understand the safety side of this. I spent the first 21 years of my career as an industrial construction electrician doing everything from fiber optic to 369kv switchyards and the last six as an electrical designer designing control systems for coal burning power plants. I will be replacing the breaker this weekend and I may replace the whole panel if needed. The breaker is not glowing hot, but it is definitely a lot warmer than it should be. If I can lose 3 to 4 volts of rise it will take care of the problem.

I am however new to the solar issues. I'm used to dealing with voltage drop only. But I feel like I still learn something new every day. One thing I've learned over the years is when to ask the engineer.

Thanks for the help,
Greg

[NEOH]

Did you add the sub-panel in the barn?
Are there any other loads in that sub-panel.
Is the Sub-Panel bus rated at 100 amps?
You connected a 56 Amp GTI to that panel?

[max2k]

Inetdog & bcroe,
I definitely understand the safety side of this. I spent the first 21 years of my career as an industrial construction electrician doing everything from fiber optic to 369kv switchyards and the last six as an electrical designer designing control systems for coal burning power plants. I will be replacing the breaker this weekend and I may replace the whole panel if needed. The breaker is not glowing hot, but it is definitely a lot warmer than it should be. If I can lose 3 to 4 volts of rise it will take care of the problem.

I am however new to the solar issues. I'm used to dealing with voltage drop only. But I feel like I still learn something new every day. One thing I've learned over the years is when to ask the engineer.

Thanks for the help,
Greg

fix the most obvious thing first, breaker in your case then worry about problem analysis if it will still be there.