What do you mean by “Rated grid voltage: 208V/240V”?

dks1
dks1 Registered Users Posts: 20 ✭✭
Does the back slash (/) mean it either can work with a 208VAC OR 240VAC Incoming Voltage?

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Depends on what it is your device is (load or GT inverter/etc.)...

    For 240 VAC, typically the allowed range is from ~208 VAC to 264 VAC (85% to 110% of "nominal" voltage)
    For 208 VAC, typically would be 177 VAC to 229 VAC (85% to 110%)

    In North America, the nominal house voltage is 120/240 VAC "split phase".

    Commercial 3 phase power (lowest available voltage) is 208 VAC for Wye 3 phase power, and 240 VAC for Delta 3 phase power.

    The 110% max voltage is type typical max voltage one would accept from a power company--But a GT inverter may be set for ~260 VAC peak to allow for limits of GT inverter's accuracy.

    Interestingly enough--There does not seem to be an "official" line voltage range in the US... And the "nominal" 240 VAC used to be 220 VAC nominal many decades ago--And has been sneaking up higher.

    If I see a device rated for 208/240 VAC--My first assumption is that the device is programmable (or rewired for a motor) to operate at either of those voltages...

    Below ~204 VAC would be low voltage cutoff for a 240 VAC nominal utility connected GT inverter on a 240 VAC line... While 177 VAC would be low line for a 208 VAC line--And you would not mix the two up (get an unhappy utility engineer in brownout conditions?).

    At times, there have been issues with (for example) 260 VAC not being high enough voltage (false trips on GT inverter)--And the utility engineer may allow a higher limit voltage to be set (if you are at the end of a utility run in a rural area, the voltage regulation is not always ideal--Also, you have voltage "rise" from GT inverter to the pole transformer--And you could "allow" higher GT voltage set point (i.e., 264 VAC max line + 5 volt line rise from pole to GT inverter = 269 VAC) in some cases.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dks1
    dks1 Registered Users Posts: 20 ✭✭
    BB. said:
    Depends on what it is your device is (load or GT inverter/etc.)...

    For 240 VAC, typically the allowed range is from ~208 VAC to 264 VAC (85% to 110% of "nominal" voltage)
    For 208 VAC, typically would be 177 VAC to 229 VAC (85% to 110%)

    In North America, the nominal house voltage is 120/240 VAC "split phase".

    Commercial 3 phase power (lowest available voltage) is 208 VAC for Wye 3 phase power, and 240 VAC for Delta 3 phase power.

    The 110% max voltage is type typical max voltage one would accept from a power company--But a GT inverter may be set for ~260 VAC peak to allow for limits of GT inverter's accuracy.

    Interestingly enough--There does not seem to be an "official" line voltage range in the US... And the "nominal" 240 VAC used to be 220 VAC nominal many decades ago--And has been sneaking up higher.

    If I see a device rated for 208/240 VAC--My first assumption is that the device is programmable (or rewired for a motor) to operate at either of those voltages...

    Below ~204 VAC would be low voltage cutoff for a 240 VAC nominal utility connected GT inverter on a 240 VAC line... While 177 VAC would be low line for a 208 VAC line--And you would not mix the two up (get an unhappy utility engineer in brownout conditions?).

    At times, there have been issues with (for example) 260 VAC not being high enough voltage (false trips on GT inverter)--And the utility engineer may allow a higher limit voltage to be set (if you are at the end of a utility run in a rural area, the voltage regulation is not always ideal--Also, you have voltage "rise" from GT inverter to the pole transformer--And you could "allow" higher GT voltage set point (i.e., 264 VAC max line + 5 volt line rise from pole to GT inverter = 269 VAC) in some cases.

    -Bill
    Thank you bill!! 🙇🏻