# How can I measure 3 phase power consumption for an equipment?



## giyad (Jun 7, 2007)

I have a piece of equipment thats 3 phase. I want to use something like a Kill A Watt to measure how much power I'm using so that I can have a good idea of what my electric bill is going ot be like. How can I go about doing this? Is there a device I can use to measure like a kill a watt?

Thanks!


----------



## Drabdr (Nov 26, 2007)

giyad said:


> I have a piece of equipment thats 3 phase. I want to use something like a Kill A Watt to measure how much power I'm using so that I can have a good idea of what my electric bill is going ot be like. How can I go about doing this? Is there a device I can use to measure like a kill a watt?
> 
> Thanks!


If the entire load on the equipment is 3 phase, then measure one leg with an amp meter.

Or, turn the equipment on and measure amperage across all three phases; take the highest load reading.

Easiest thing is to accept the name plate amperage use rating.


----------



## Koot (Nov 25, 2007)

giyad said:


> I have a piece of equipment thats 3 phase. I want to use something like a Kill A Watt to measure how much power I'm using so that I can have a good idea of what my electric bill is going ot be like. How can I go about doing this? Is there a device I can use to measure like a kill a watt?
> 
> Thanks!


Your best method is to use a clamp-on ammeter to measure the amperage load. If your equipment is only a 3-phase load, then all three [of the] phase legs will be equal in the load being pulled. However, if your loads are comprised of some single phase loads (e.g. 2-pole that uses only two of the phases or phase-to-phase, or 1-pole that uses only one of the phases or phase-to-neutral), then each of the three phases (A-B-C) will vary in the amount of load being pulled.

If you do not have access to a clamp-on ammeter, you may be able to borrow (or rent) one briefly from an electrician or local electrical contractor.

Once you obtain your amperage, you can easily calculate the wattage by using one or both of the following formulas depending on whether your load is only 3-phase or comprised of some single phase loads:

For Single Phase: Wattage = Amperage x Voltage 
For 3-Phase: Wattage = Amperage x Voltage x 1.73

Note: Just so you'll know - calculating 3-phase requires multiplying by the square root of 3 [as in 3-phase], which is the figure 1.73


----------



## giyad (Jun 7, 2007)

Koot said:


> Your best method is to use a clamp-on ammeter to measure the amperage load. If your equipment is only a 3-phase load, then all three [of the] phase legs will be equal in the load being pulled. However, if your loads are comprised of some single phase loads (e.g. 2-pole that uses only two of the phases or phase-to-phase, or 1-pole that uses only one of the phases or phase-to-neutral), then each of the three phases (A-B-C) will vary in the amount of load being pulled.
> 
> If you do not have access to a clamp-on ammeter, you may be able to borrow (or rent) one briefly from an electrician or local electrical contractor.
> 
> ...


Awesome thanks! So I purchased a clamp on ammeter, first time I ever use it though so I don't know what I'm doing just yet, but the instructions say to clamp on only one of the hot leads... I don't have access to the wires everything is insulated obviously as anything should be, is there anyway I can just clamp on the whole thing? I didn't test it yet because it didn't come with batteries haha... Am I misunderstanding or do they want me to do this in the breaker box?


----------



## Koot (Nov 25, 2007)

The meter's clamp mechanism goes (fits) around only one (at a time) of the three insulated hot wires - known as the Phase A, Phase B & Phase C wire. You'll need to have access to these wires from inside a panel, disconnect switch, enclosed C/B or motor starter enclosure that feeds and/or protects your 3-phase load. Your load must be energized when using the clamp-on ammeter for it to work. If your only load is 3-phase then you will find that all three hot wires will have the same amperage being pulled through them.

Be careful!


----------

