First timer with questions on wire gauges

[Mikep4485]

Need to brush up on the difference between power and energy. Maybe the inverter manual will explain this but not the appliance.

Watt = power. Instantaneous draw
Watt-hour = energy

Watt meter (incorrectly named) is more of an energy meter. If it has a peak reading then maybe you can use it. Please research it on your own. I don't trust it but I could be wrong from being an elitist -- I would use clamp meter with surge or a energy meter that collects 1 minute data in a graph. Summing over 24 hours doesn't help with amps.

1000W for 1 hour = 1kWh
41.6W for 24 hours = 1kWh

First case: 1000W / 120V = ~8A
Second case: 41.6W / 120V = ~0.34A

Thanks. I took advice from before and I’m looking up clamp meters

 

[zanydroid]

Ok cool. It would give you the most accurate answer. The surge on a kill-a-watt is probably more for convenience.

Do you already have the inverter?

 

[zanydroid]

Ah I just checked, you have a pretty common inverter/battery combo for this forum, and it is 48V, so I doubt the surge from a fridge or freezer will cause a problem. You can probably also ask people.

 

[glandpuck]

Most appliances will have a label or include a manual with the wattage. Some may also have amps too. But it's simple Ohm's law: volts x amps divided by ohms = watts (power).

So if an appliance uses 1200 watts of power plugged into a 120 volt outlet, ignore the ohms and simply divide the 1200 by 120 and that's your amps, in this case 12 amps of current flow.

In the case of say a dryer, it may use 7200 watts of power (240 volts x 30 amps) on high heat. After it reaches temperature, the thermostat will turn on and off to maintain temperature as well as some models may use a variable amount of wattage to maintain temperature rather than an all or nothing heating. A room fan with 3 speeds is likewise, three fixed amounts of power used.

 

[Mikep4485]

Most appliances will have a label or include a manual with the wattage. Some may also have amps too. But it's simple Ohm's law: volts x amps divided by ohms = watts (power).

So if an appliance uses 1200 watts of power plugged into a 120 volt outlet, ignore the ohms and simply divide the 1200 by 120 and that's your amps, in this case 12 amps of current flow.

In the case of say a dryer, it may use 7200 watts of power (240 volts x 30 amps) on high heat. After it reaches temperature, the thermostat will turn on and off to maintain temperature as well as some models may use a variable amount of wattage to maintain temperature rather than an all or nothing heating. A room fan with 3 speeds is likewise, three fixed amounts of power used.

Thanks for the info. I was using that formula but the numbers on the freezer didn’t seem right. It was coming out to lest then .5 amps. But after doing some googling that seems right.

 

[zanydroid]

Thanks for the info. I was using that formula but the numbers on the freezer didn’t seem right. It was coming out to lest then .5 amps. But after doing some googling that seems right.

The surge can be crazy so keep that in mind if you every try to drive freezer with like a smaller inverter in an emergency.

I tried using a 300W modified sine wave inverter on my modest size chest freezer. First of all, ugly waveform = not good for the motor, it probably wouldn't have kept working. Plus the surge of the motor instantly reset the inverter.

 

[glandpuck]

Thanks for the info. I was using that formula but the numbers on the freezer didn’t seem right. It was coming out to lest then .5 amps. But after doing some googling that seems right.

Remember, a modern fridge/freezer is just a fancier Igloo box with a small compressor, fan to circulate the air, a thermostat and a programmed defroster element with a drain for the melted frost. They don't take much energy now days to keep cold.