250/125v With Solar?

[Andy D]

I noticed when my inverters are running my house voltage is 250v/125v. I killed the grid tie switch and the line voltage went back to 239/240v.

I assume this is normal as the inverter output must be high than the base line voltage to work?

125v is however on the edge of some equipment including incandescent light bulbs.

[Naptown]

Do you have a very large system?
And a small service?
I have seen this happen when the impedance is high with the above circumstances.

[Andy D]

Do you have a very large system?
And a small service?
I have seen this happen when the impedance is high with the above circumstances.

11kw panel capacity
9.3kw inverters (1) 6kw and (1) 3.3kw)

Service is 200a with a 60a solar tap breaker.

Note that feeders are 2/0awg aluminum and are about 50 feet to pad transformer.

[solarix]

Does the voltage go up for the whole house or just the inverters? Could be the wire going from the inverter to the panels should be larger.
On the other hand 2/0 AL is only good for 150A max. Sometimes they will double it to get the ampacity though.

[Andy D]

Does the voltage go up for the whole house or just the inverters? Could be the wire going from the inverter to the panels should be larger.
On the other hand 2/0 AL is only good for 150A max. Sometimes they will double it to get the ampacity though.

Whole house, measured about 6 wire feet from the panel.

Many utilities seem to under size the feeders based on what they assume an average household needs. Remember they are above the NEC and local codes in most places.

It's not causing me any problems (yet), I'm just curious if this is normal.

[Sunking]

In the early days the USA residential electric system was 220/110 and this was due to the Edison Bulb of the era. Higher would burn the filament out, and lower would be too dim. As lighting technology improved the US topology went to 250/125. Today the utility tolerance is +/- 10% 250/125 or as low as 225/112 and as high as 275/137What you are seeing is likely just voltage drop between the utility transformer and your Disconnect. When you have solar producing the voltage is always going to be higher than utility. Well unless you are using more than you are producing.

[JFinch57]

My utility tells me that their tariff allows +/- 5%, or 240V * 1.05 = 252V max. Because of the resistance in your undersized aluminum wire the inverter has to raise the voltage higher than if it was properly sized, but the voltage is still within the limit. You should have 4/0 AL or 2/0 CU minimum for 200A service.

[Jerry Liebler]

11kw panel capacity
9.3kw inverters (1) 6kw and (1) 3.3kw)

Service is 200a with a 60a solar tap breaker.

Note that feeders are 2/0awg aluminum and are about 50 feet to pad transformer.

With 9.3KW @ 250V =37 amps you move the line voltage 10 volts! You have a serious problem with the undersized wires & possibly a bad connection or more. Drawing a full 200 amps from the 240 volt line would drop your incoming voltage by 54 volts and 10.8 KW would be dissipated in the conductors & terminations. Contact your utility post haste, before it burns!!!