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Motor Efficiency is not recognized

asked 2016-02-03 10:03:12 -0600

updated 2020-01-27 18:43:52 -0600

I am using the OpenStudio with EnergyPlus for energy simulation.

It seems to me "Motor Efficiency" is not being accounted in the calculations for Fans.

I'm setting the field "Motor Efficiency" in OpenStudio, but when I open the EquipmentSummary report: Fans, the field "Total Efficiency" shows only the setted value for Fan Efficiency field in OpenStudio.

According to my calculations, the power calculated reported in "Rated Electric Power [W]" also does not account for the "Motor Efficiency".

I have already exported the file to .idf and efficiencies are all there in inputs, but even direct running on EnergyPlus, the problem remains.

This is a bug or am I'm failing at something.

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2 Answers

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answered 2016-02-03 11:33:09 -0600

updated 2016-02-03 11:35:43 -0600

The 'Fan Efficiency' input represents the product of motor efficiency and fan efficiency. The 'Motor Efficiency' input will not impact the amount of fan power directly but it will impact the amount of heat added to the airstream when the 'Motor In Airstream Fraction' is greater than 0.

See my preview answer to this post for more detail: Fan Motor Efficiency

EnergyPlus Input Output Reference

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@Chris Jones and @Lyle K Thank you very much. I understood perfectly.

In my opinio, the term "Fan Efficiency" leads to error and could be replaced by "Total Efficiency", because it leads us to think this is only the efficiency of the fan, and not, this value is already the product of the fan efficiency with motor efficiency.

Geraldo Pithon gravatar image Geraldo Pithon  ( 2016-02-03 12:43:57 -0600 )edit

Agreed, this OS field should be changed to follow the corresponding EP field name.

MatthewSteen gravatar image MatthewSteen  ( 2016-02-03 12:50:35 -0600 )edit

I agree as well. The OS team typically sticks with the E+ field names but they deviated in this case. It would be really user friendly to have a field description somewhere in the OS App that highlights nuances like this or pulls language directly from the E+ input/output reference.

Lyle K gravatar image Lyle K  ( 2016-02-03 13:16:37 -0600 )edit

answered 2016-02-03 10:54:04 -0600

Chris Jones gravatar image

EnergyPlus has an input for total fan efficiency and fan motor efficiency. If you change just the fan motor efficiency, there is no change in fan energy. You have to change the total fan efficiency if you want to examine the benefits of more efficient motors.

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Asked: 2016-02-03 10:03:12 -0600

Seen: 125 times

Last updated: Feb 03 '16