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EnergyPlus: enforcing user defined fan speed for air handler at each timestep [closed]

asked 2015-12-15 16:47:01 -0500

TN's avatar

updated 2017-05-17 12:31:24 -0500

Hello all:

Does anyone know of a way to either input a schedule for fan speed or a way to create a custom fan object that allows a user to specify fan speed at each time-step?

For my current study it would be nice to look closely at behavior of VFD control sequences. I have looked at the idf fields for Fan:VariableVolume, Fan:ComponentModel, Fan:ConstantVolume, and Fan:OnOff, and it does not appear that this is possible.

I believe one way this could work is if it were possible to enter a schedule value for certain relevant fan only it does not appear that this is yet possible as these fields expect a number only. Does anyone have an idea for a work around or another possible solution? Your help would be much appreciated.

Best regards, Tyler Noble

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Closed for the following reason the question is answered, right answer was accepted by TN
close date 2015-12-16 07:56:18.602938

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answered 2015-12-16 05:52:17 -0500

Archmage's avatar

For air systems that use AirLoopHVAC, the fan flow rates are determined by the flow requested by the air terminal unit(s) attached to the zone. The only way I know of to specify flow with a schedule is to override the flow requested by AirTerminal:SingleDuct:Uncontrolled using the EMS actuator to control Mass Flow Rate. Just put an EMS sensor on the schedule and set the EMS actuator with that value. The EMS program can literally be one line (for each zone).

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I could be wrong, but I don't think the process for UH here is to close the question, but rather for the original questioner to hit the little check mark next to the voting. Closure is for duplicates and questions that aren't likely to have value to others in the future.

Archmage's avatar Archmage  ( 2015-12-16 08:26:35 -0500 )edit

answered 2015-12-15 19:32:32 -0500

It looks like the Fan:ZoneExhaust object has an input field where you can specify a schedule to affect the max flow rate. This may not be the ideal situation, but that is a fan object where you can set a schedule to specify fan speed at each time step. For that process, it may be easier to create an external schedule file with flow speed values for each timestep, then use the Schedule:File object to have your E+ file read it in.

Looking over the Fan:ComponentModel object, there does seem to be input fields related to VFD. Namely, input fields for VFD Efficiency Type (calculate efficiency based on Power or Speed), Maximum Output Power of VFD Motor, VFD Motor Input Power Sizing Factor, and VFD Efficiency Curve (uses operational Power or Speed, depending upon value entered in "VFD Efficiency Type" input field). You may want to consider including some kind of analysis with these capabilities, since they are specifically for VFDs with fans. The E+ Engineering Reference doc makes two references to VFD data in the Air System Fans Section (search for the term "VFD" on that page) for justifying how these capabilities were incorporated into the tool.

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Thank you for your most helpful post Aaron. I have just looked again at these inputs related to VFD efficiency and such, and while this works to simulate VFD usage, I am truly hoping to command the the simulation in real time with a schedule type input to simulate varying the frequency and power over time.

TN's avatar TN  ( 2015-12-15 22:25:23 -0500 )edit

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Asked: 2015-12-15 16:47:01 -0500

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Last updated: Dec 16 '15