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  • Inverter ac output volt setting

    I have a Go Power GP ISW 3000. Currently (no pun) set for 120 V output. Go Power states this uses more power to generate. What do you suggest 100, 110, 115 or 120 V?
    2021 Imagine 22MLE

  • #2
    I can’t see any reason to operate at any setting but 120V in North America.
    John & Kathy
    2014 Reflection 303RLS
    2014 F250 SC SB 6.2

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    • #3
      Well, certainly. Higher voltage will push more current through a given load. Hence, higher load demand. Will you be satisfied with appliaces under-performing?

      I'd stick with 120v.
      Ted
      2021 Reflection 310RLS
      2020 F350 PS,CC,LB,SRW

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      • #4
        Actually, when voltage drops for a given load (resistance) of a device, current will increase. It's Ohm's law. A great example of this is when you're trying to run an air conditioner on an RV park's shore power during peak summer demand. As the voltage drops, the current goes up and when it hits around 104 volts, the breaker will trip due to excessive current demand.

        The National Electrical code specifies 120 volts as the U.S. standard. That is where I'd set it.

        Jim
        Jim and Ginnie
        2024 Solitude 310GK
        GDRV Technical Forum Moderator
        GDRV Rally Support Coordinator

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        • #5
          Originally posted by TucsonJim View Post
          Actually, when voltage drops for a given load (resistance) of a device, current will increase. It's Ohm's law. A great example of this is when you're trying to run an air conditioner on an RV park's shore power during peak summer demand. As the voltage drops, the current goes up and when it hits around 104 volts, the breaker will trip due to excessive current demand.

          The National Electrical code specifies 120 volts as the U.S. standard. That is where I'd set it.

          Jim
          I will disagree. Current will not increase as voltage drops. E = I x R Ohm's law. E and I are directly proportional.
          If you assume power demand is constant, then W = I^2 x R, then current and resistance vary inversely. But, power demand does not remain constant, except for maybe an ac motor with frequency trying to maintain rpm while voltage drops. Resistive loads are not constant power loads.
          Ted
          2021 Reflection 310RLS
          2020 F350 PS,CC,LB,SRW

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          • #6
            Originally posted by TedS View Post

            I will disagree. Current will not increase as voltage drops. E = I x R Ohm's law. E and I are directly proportional.
            If you assume power demand is constant, then W = I^2 x R, then current and resistance vary inversely. But, power demand does not remain constant, except for maybe an ac motor with frequency trying to maintain rpm while voltage drops. Resistive loads are not constant power loads.
            Ah, electrical theory. What fun! Based on your other posts, TedS, I'm sure you know what I'm going to write below so don't be offended. I'm sure there are individuals here that don't understand and they are the true audience for this response.

            Jim can certainly speak for himself, but I'll guess he is assuming the wattage demanded by the powered item remains constant. In that case the only possible result is higher current when voltage drops. The apparent resistance, or better term impedance, will change. Impedance is another leap beyond a simple resistive circuit where Ohm's Law is so easy to understand. ( Rudy , you should be able to speak to this now!)

            A simple example from a purely resistive circuit: Put a 12v battery across a 12 ohm resistor and the amperage is 12 v / 12 ohms = 1 amp. If the voltage drops (say to 10v), the current drops. 10 v / 12 ohms = .83 amps. There are many examples of this we've witnessed in the "real world", like a flashlight. The bulb is going dim because the voltage is dropping, which pulls less amperage, so less overage wattage from the lamp.

            Now let's calculate the wattage using the 12v and 12 ohm example. 12v (squared) / 12 ohms = 12 watts, or 12v * 1 amp = 12 watts. Doesn't matter how you slice it, the result is 12 watts.

            So what happens if voltage drops but the device still pulls 12 watts to operate????

            Current must go up when voltage goes down to keep the wattage constant.

            Using the earlier example of a drop to 10v (from 12v) and a constant 12 watt demand, that means the amperage is now 12 W / 10 v = 1.2 amps. To accomplish this the impedance of the appliance has to less than it was when the voltage was 12. Otherwise the math doesn't work.

            Howard

            P.S. Sure hope that math is right...

            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

            2017 Ford F-350 DRW, '19 315RLTSPlus

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            • #7
              That's the key assumption howson . Fixed power. If a device has a fixed power requirement of say 1000 watts. 1000 watts/120 volts = 8.3 amps. 1000 watts/100 volts = 10 amps.

              In the real world we were in an RV park and running our AC. When the park voltage dropped to 103 Volts, the breaker kicked due to high voltage.

              But of course the type of load comes into play.

              Jim
              Jim and Ginnie
              2024 Solitude 310GK
              GDRV Technical Forum Moderator
              GDRV Rally Support Coordinator

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              • #8
                Ah, the mystery of electricity. Devices like heaters are resistive loads. So lower voltage results in lower current and less heat. Even though they are called 1500 watt devices, they are not constant, fixed power devices. 100 watt light bulbs will dim with lower voltage; not as much current going through to heat the filament. The resistance or impedance of the heat element will generally increase with temperature tending to limit current.

                Air conditioner motors are a different animal. It draws high startup current at zero speed. The running speed is frquency dependent, voltage and current adjust to keep that speed. So lower voltage is accompanied by increased current trying to keep the frequency controlled speed.

                DC motors are resistve devices, no frequency involved. Lower voltage results in lower speed, lower current. Also not a fixed, constant load device. If its load increases and voltage remains constant, the slide jams or drags, the current increases so that the increased torque tends to increase the speed back to where the voltage says it should be. DC motors have a stalled rotor current rating due to its resistive load characteristic.

                It's a curse being interested in this stuff. I'll sit down.
                Ted
                2021 Reflection 310RLS
                2020 F350 PS,CC,LB,SRW

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                • #9
                  TedS . Then you have guys like me who worked in 5v TTL devices and Cmos. Totally different world... kinda.
                  Jim and Ginnie
                  2024 Solitude 310GK
                  GDRV Technical Forum Moderator
                  GDRV Rally Support Coordinator

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                  • #10
                    Cmos sounds to me like stuff that washes up on the beach.
                    Ted
                    2021 Reflection 310RLS
                    2020 F350 PS,CC,LB,SRW

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                    • #11
                      Interesting discussion! This mechanical engineer now has a better understanding of things I thought I already understood .

                      Rob
                      Cate & Rob
                      (with Border Collies Molly & Angel + Kitties Hazel & Elsie)
                      2015 Reflection 303RLS
                      2022 F350 Diesel CC SB SRW Lariat
                      Bayham, Ontario, Canada

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                      • #12
                        ..and this software developer has no idea what anybody in this thread was talking about. Well, except for the first couple of posts...
                        Brian & Kellie
                        2020 Grand Design Solitude 310GK-R, FBP, MORryde IS, 1,460w solar and 540ah BBGC3
                        2020 Ford F-350 Platinum SRW PSD Tremor, 60g TF fuel tank, Hensley BD3-F air bag hitch

                        Previous setups:
                        2019 Grand Design Solitude 373FB-R, 2019 Ford F-350 Platinum DRW Powerstroke, Hensley BD5 air bag hitch
                        2016 Grand Design Reflection 318RST, 2016 GMC 3500 Denali SRW Duramax, Hensley BD3 air bag hitch

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                        • #13
                          Originally posted by bertschb View Post
                          ..and this software developer has no idea what anybody in this thread was talking about. Well, except for the first couple of posts...
                          X2 along with you Brian and Dallas d2reid - yikes spinning my head this early in the morning is painful !

                          Dan
                          Dan & Carol
                          2014 303RLS Reflection #185 (10/2013 build)
                          2012 Silverado LTZ Crew Duramax 2500HD - 2700/16K Pullrite Superglide

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                          • #14
                            The good old days of an IBM 360/370 main frame running off punch cards, Fortran, Watt5. Cmos, others, and machine code. I had to learn machine code on my own to finish my senior project. Nothing like going through 500 to 1000 pages of dump trying to find the one line of messed up code the someone else put in year earlier.

                            As for electricity - well lets say I know its working when I get bit or fry something. Transistors were new when I took electronics in High School. Funny I was a wiz at identifying resister color coding.

                            Speaking of punch cards and hanging chads , The punch card machines in College did not type what you punched as you typed. You had to go over to a compiling unit to do that, then go back through the cards and check for typing and spelling which I am great at..........NOT And heaven help you if you dropped your card box before you numbered your cards

                            It is great having the experts here - I have learned a lot and you folks have helped me not mess things up.......well yet

                            Keith
                            2018 Reflection 150 Series 220RK 5th whee, Star White 2022 F350 King Ranch CC Long bed (HAL) (CCC 4062lbs), B&W 25K OEM Companion,. SteadyFast system, Trailer reverse lights, rear receiver spare tire holder, storage tube, sumo springs, Victron MultiPlus 12/120/3000, Solar, Custom 6K axles upgrade, and other modifications.

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                            • #15
                              Originally posted by Yoda View Post
                              Speaking of punch cards and hanging chads , Keith
                              Ahhhh! Memory lane. TTY and paper tape. Or you could spend hours on the midnight shift manually typing hex into the registers saving each line to specific address. Atari was the best computer. Wordperfect was the best word processing software. I hated it when GUI replaced CLUI, it was sooo slow. But it did eliminate having to memorize hundreds of shortcut keys.

                              Where has all the time gone.

                              What I get a kick out of is when something is renamed and sold as the latest greatest idea, like the "Cloud". Ok Cloud sounds better than server.

                              How electrically challenged am I?

                              When I buy a new multi-meter I have to take a marker, look at the manual, and mark one side AC and the other DC.

                              I always set my multi-meter to the biggest number so it doesn't blow up in my hand. You don't know, could happen.

                              It took me about 4 times getting shocked before I figured out you could turn the power off before replacing an electrical outlet.

                              If you get zapped by a charge from the coil on the car it will knock you on your butt.

                              If you take a car battery, jumper cables and two rods, connect the rods/cables to the battery and shove the rods into the ground about 10 feet apart the worms come out of the ground real fast, particularly if it has rained recently.

                              If you are having trouble finding a short in an auto lighting system just start the engine and turn everything on, then watch for smoke.

                              See, I really do know a lot about electricity....

                              2017 Momentum 376, 2019 Ford F450
                              2022 Triumph Scrambler Motorcycle
                              E-bikes, Hobi Pedal Kayaks
                              Kota the dog and KC the Kitty Cat

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