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how to control DOAS supply fan and damper?

asked 2019-03-15 03:57:39 -0500

xzb86 gravatar image

updated 2019-03-17 11:12:00 -0500

Hi everyone, I'm simulating FCU + DOAS system in energyplus, when I get the result, I checked with the variables, I tried to change controller: outdoor air and air terminal: singleductVAV: Noreheat, but I still can't control DOAS supply fan as scheduled, it always constant. can anybody tell me how to control DOAS supply fan (fan: variable volume) as schedule?

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answered 2019-03-19 11:42:05 -0500

The fan does not control the flow, it reacts to flow. Other objects control flow such as the air terminals as you describe or the outdoor air controller. The outdoor air controller can adjust the OA flow rate as specified in the inputs for that object. See example file DOAToFanCoil.idf as a start. Alternately, and since you mentioned schedule, you can use the Minimum Outdoor Air Schedule Name, Minimum Fraction of Outdoor Air Schedule Name and/or Maximum Fraction of Outdoor Air Schedule Name to control the flow. Also see the Controller:MechanicalVentilation object for demand controlled ventilation. See the InputOutputReference document for more information.

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answered 2019-03-17 16:16:58 -0500

In the Fan:VariableVolume object there is a field called Availability Schedule Name. You can create an On/Off or fraction schedule and specify it in this field to turn off the fan whenever the schedule value is 0.

Alternatively, the fan may not be turning off if your minimum flow fraction or fixed minimum air flow rate is greater than zero in the AirTerminal:SingleDuct:VAV:NoReheat object. Setting this field to zero on all the terminal units should turn off the fan when the building is unoccupied and has no heating/cooling load, even if your fan availability schedule is always 1.

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As I know, availability schedule can only realize on/off, what if I want to simulate the 0~1 fraction schedule?

xzb86 gravatar imagexzb86 ( 2019-03-19 08:52:23 -0500 )edit

Yes the availability schedule would only control when the fan is allowed to operate, it would not vary the fan speed. If the fan is operating at constant speed, perhaps this is because there is a constant ventilation requirement that the DOAS is providing, or some other continuous load. If you share your model I could take a look.

ericmartinpe gravatar imageericmartinpe ( 2019-03-19 11:32:04 -0500 )edit

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Asked: 2019-03-15 03:57:39 -0500

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