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Totalizing Power using TagTot()

Question asked by vwitzel on Sep 1, 2016
Latest reply on Sep 2, 2016 by bbregenzer

Hi all,

 

I am trying to use the TagTot function to totalize power over a period of time. More specifically, I have a PI tag storing an instantaneous kW reading and am trying to calculate a monthly kWh from this tag. I understand that the TagTot function assumes the variable being totalized is expressed in units per day. If not, an adjustment has to be made to the output of the function to account for this. For example, the result produced by TagTot for a flow rate variable expressed in gallons/hour would have to be multiplied by 24 hours to calculate the gallons flowed over a day. What I am unsure of is how this works when dealing with a kW reading, since it has no time unit associated with it.

 

Let's assume the instantaneous kW reading is 10 kW for an entire month. TagTot over that month (assuming 31 days) equals 310 kW. In other words, PI thought 10 kW were generated per day, so 310 kW must have been generated that month. However, 10 kW were actually generated at any given time that month. So what is needed to adjust the TagTot result to be in kWh? Presumably it needs to multiplied by the number of hours per day (i.e., 310 kW * 24 hours = 7,440 kWh). Does that make sense? Appreciate any insights you can share!

 

Thanks

 

EDIT: Looking at this simple kWh calculator, 7,440 kWh would appear to be the correct result, but if somebody could confirm my approach, I'd appreciate it

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