220V single phase amps to watts

[MikeRuth]

I know this isn't exactly related to us in our vans but...

I know how to measure a 120V single phase line for current draw and convert to watts. But what happens when our source is 220 Volt? 

You now have two hot lines that are both pulling current. Do we measure both and add? or do we just go with the measurement off of one>? 

It would be my guess that we read both and add them together, then convert to watts. 

Thank you.

 

[tx2sturgis]

Are you using an amp-clamp to directly measure current into a motor or compressor or heating element or what?

Or are you measuring the current into an appliance, taking the reading at the wall socket or plug?

Some appliances split the 110/120 volt loads, one per leg, and others directly feed both legs across a load...so we need more information about what you intend to measure.

One more wrinkle: 220v USA stuff is different from European 220v stuff. So again, we need more 'input'...

 

[speedhighway46]

The formula is:

P (watts) = I (current in amps) x E (electromotive force in volts)

 

[skyl4rk]

Example: 5 amps on each leg:

120V x 5 amps = 600W
PLUS
120V x 5 amps = 600W

Total: 1200W

 

[B and C]

If you have a clamp-on meter, the easy way is to make a loop out of one hot wire and put the loop part along with the other strand through the clamp. Only two wires and not three if you put the overlap part of the loop through. This will get both legs in phase so they can be directly read.

 

[tx2sturgis]

Example: 5 amps on each leg:

120V x 5 amps = 600W
PLUS
120V x 5 amps = 600W

Total: 1200W

This would be correct if the load is split, using neutral return, but would NOT be correct if the load is across the 220v, as in a dryer element. Some 220v electric ranges and ovens have seperate feeds on 110, or 220, to various elements.

But most european 220v (or 230v) appliances are native 220 (or 230), meaning that you dont measure seperate legs...there is only one loop or leg (counting hot and neutral) plus a ground...

So thats why we really need more input about what is being measured or tested.

 

[MikeRuth]

Well to clarify a bit, this is an AC unit in the US. Feed to the house is 220V single phase.
It is wired with three wires, 2 hot and a neutral.
There is not enough wire to do a loop. I can only measure the current through each leg with a clamp on meter at the service panel.

I would simply get the name plate data but they mounted the unit up against a wall and I would have to tear off a few panels to get to that. Don't wanna do that.

As an aside, the 220 breaker is rated to 40 amps, dbl pole.

 

[Low277]

You mention that the fed to the house is 220V single phase with 2 hot and a neutral wire.  What is the AC unit fed with? The important part is whether it has a bare or green equipment grounding conductor?  If so it is a 220 volt appliance, the bare or green equipment grounding conductor is not allowed to be used in a 115/230 volt split circuit as a current carrying conductor.   Also attached is a really handy tool.  E is voltage, I is amperage, R is resistance and P is watts.

[img=474x468]https://cdn11.bigcommerce.com/s-h9he6/product_images/uploaded_images/ohmslaw.png[/img]

 

[DannyB1954]

Watts is Voltage times the amperage. Watts is also called Power because to get anything done electrically it is a combination of the voltage and amperage. A 1,200 Watt device will use twice as many amps at 120 volts than it will at 240 volts. You do need some sort of device to convert the voltage if you want to use the exact same device with a different voltage. If you double the voltage, the amps will be half to get the same watts.
10 amps at 120 volts has the same wattage or power as 5 amps at 240 volts.
If you are thinking about international travel another thing that can complicate things is called Cycles.

 

[highdesertranger]

bi-cycles or motor-cycles. LOL, just kidding for some reason I couldn't resist. highdesertranger

 

[MikeRuth]

Just an FYI. I learned about and how to use Ohm's law when I was about 12, 50 years ago and I could state it verbatim today with out looking at a chart LOL. I love electronics etc. But this question was because I didn't really understnad how I am being charged by the utility company on a 220V AC appliance that is 2 wire and ground. 

You mention that the fed to the house is 220V single phase with 2 hot and a neutral wire.  What is the AC unit fed with? The important part is whether it has a bare or green equipment grounding conductor?  If so it is a 220 volt appliance, the bare or green equipment grounding conductor is not allowed to be used in a 115/230 volt split circuit as a current carrying conductor.   Also attached is a really handy tool.  E is voltage, I is amperage, R is resistance and P is watts.

[img=474x468]https://cdn11.bigcommerce.com/s-h9he6/product_images/uploaded_images/ohmslaw.png[/img]

 

[DannyB1954]

bi-cycles or motor-cycles.  LOL, just kidding for some reason I couldn't resist.  highdesertranger

Is a bi- cycle something that anyone can jump on?

 

[DannyB1954]

Two 120 volt wires and a neutral wire come to your house. The 120 lines are out of phase with each other so that the voltage difference between them is 240 volts. Your fuse or circuit breaker box has two separate bars that feed the breaker or fuse. Half the things will be run off of each leg, but large items like stoves clothes dryers, water heaters will get fed off of both . They are designed to run off of the higher voltage. The 50 amp RV plug is really the same thing. so in effect you can use three times the energy than you can off of a 30 amp outlet. You can use 50 amps off of both legs or 100 amps of 120 volts. The 30 amp plug has only one 120 volt and a neutral line line going to it, so you can use only 30 amps of 120 volt.

How you are charged for this is if energy flows through either line, your meter will keep track of this. I think that you are actually charged less for 240 volt appliances as the currant flow will be the same on both legs and the amperage will be half of what it would be if the device was running on 120 volts.

 

[DannyB1954]

Two 120 volt wires and a ground come to your house. The 120 lines are out of phase with each other so that the voltage differenmce between them is 240 volts. Your fuse or circuit breaker box has two separate bars that feed the breaker or fuse. Half the things will be run off of each leg, but large items like stoves clothes dryers, water heaters will get fed off of both . they are designed to run off of the higher voltage.

How you are charged for this is if energy flows through either line, your meter will keep track of this. I think that you are actually charged less for 240 volt appliances as the currant flow will be the same on both legs and the amperage will be half of what it would be if the device was running on 120 volts.

 

[tx2sturgis]

How you are charged for this is if energy flows through either line, your meter will keep track of this. I think that you are actually charged less for 240 volt appliances as the currant flow will be the same on both legs and the amperage will be half of what it would be if the device was running on 120 volts.

Actually no. 

Although this myth prevails....

For normal on-grid power, the utility company charges you by the kwh. Kilowatt-hour.

Kilowatt hours are consistent, no matter the voltage.