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Energy Plus Control Fan Pressure

asked 2016-09-20 13:40:29 -0500

greengoomba's avatar

updated 2016-09-20 14:23:03 -0500


I am trying to simulate an HVAC system in a building on which the the discharge air temperature and the end static pressure are the primary control setpoints. I started with the HVACTemplate:System:VAV object and have been working with the expanded idf. I have figured out how to control the discharge air temperature by using an EMS actuator on the AHU SUPPLY FAN OUTLET:System Node Setpoint:Temperature Setpoint and have been able to verify tracking of the setpoint with the Energy+ outputs.

However, for the pressure setpoint I have tried to use an EMS actuator on AHU SUPPLY FAN:Fan:Fan Pressure Rise. I know there is the AHU SUPPLY FAN OUTLET:System Node Setpoint:Mass Flow Rate Setpoint, but I am not interested in controlling the mass flow rate. I wish to control the end static pressure of the AHU. I'm writing an external value to this actuator, but when viewing the results in the .csv file, I see no difference in pressures from the AHU MIXED AIR OUTLET:System Node Pressure to the AHU COOLING COIL OUTLET:System Node Pressure to the AHU SUPPLY FAN OUTLET:System Node Pressure. The values across all 3 are equal. I would like to verify that the fan pressure rise I am specifying is actually occurring. Are there other values I should be looking at? Is there another way to control the end static pressure of an AHU in Energy+?

Thank you for your help!

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answered 2016-09-20 15:57:14 -0500

Archmage's avatar

Those output variables for System Node Pressure are not actually very useful, they are sort of a placeholder for future more detailed pressure modeling. At present they are just going to show barometric pressure.

The only impact of the EMS actuator Fan Pressure Rise will be to change the resulting Fan Electric Power and temperature rise.

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Thank you Archmage for the info. In that case, if changing the Fan Pressure Rise only changes the Fan Electric Power and Temperature Rise in the system, is there some other way to actually control or change the end static pressure, or pressure rise across the fan? Or some way to specify what the current fan speed should be? Or any method that will allow control of the fan in some fashion?

greengoomba's avatar greengoomba  ( 2016-09-20 18:37:08 -0500 )edit

It isn't clear what you want to happen. The VAV dampers in the air terminal units will control the supply air flow to meet the zone loads and that information is used to control the VAV fan. In the real building fan is using pressure control, but in the simulation it can just sum up what the air terminal units are requesting for flow and pressure is not simulated.

Archmage's avatar Archmage  ( 2016-09-21 10:20:31 -0500 )edit

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Asked: 2016-09-20 13:38:54 -0500

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Last updated: Sep 20 '16