humidity control example file

asked 2015-07-23 10:18:18 -0600

Rohini
683 ●2 ●11

updated 2015-07-23 10:20:49 -0600

10147 ●1 ●19 ●26 https://www.nrel.gov/b...

Hi All, Can some one please give me a step-by-step procedure to add humidity control (dehumidify to 50%) to a VAV system. Background - I have an existing idf files. I added humidistat object to few of the zones in the system. I have a setpoint manager:multizone:maximumHumidity:Average. I also have set the dehumidification control type to Coolreheat. What else do I need to do to get the coil to dehumidify? I can send the idf file, if someone is interested in looking at it. Appreciate any pointers. Thanks, -Rohini

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The VAV system also has a SetpointManager:Scheduled with temperature as control variable and a seasonal reset schedule. does this conflict with the humidity control? How does Eplus resolve the different control strategies?

Rohini ( 2015-07-23 11:57:41 -0600 )edit

DX or water coil?

rraustad ( 2015-07-23 12:35:46 -0600 )edit

DX coil. One is two-speed. The other (for second system) is TwoStageWithHumidityControlMode

Rohini ( 2015-07-23 13:09:01 -0600 )edit

Are both systems controlling humidity?

TwoStageWithHumidityControlMode will only switch between the two operating modes (Normal mode and Dehumidification Mode) and will control the coil to only meet the temperature set point (i.e., will certainly miss the humidity set point target). Change to a single speed DX cooling coil and get humidity control working. Once humidity control is working, switch to a two-speed coil and verify that humidity control still works.

rraustad ( 2015-07-23 13:40:40 -0600 )edit

I am trying the single zone system. I still cannot get the humidity control working. Re your answer below about using the outlet node of the cooling coil - SPM:HumidityMaximum, the node is the node after the cooling coil. But for SPM:SingleZone:reheat, the setpoint node is the node after the heating coil. If I change either one to match the other, I get severe error. Do I need any other setpoint managers? The only other SPM I have for this system (single speed DX coil) is mixed air - which I am assuming is not relevant for humidity control.

Rohini ( 2015-07-23 14:55:40 -0600 )edit

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answered 2015-07-23 13:00:44 -0600

rraustad

13834 ●79 ●12 http://www.fsec.ucf.edu/

The Set Point Managers place calculated values at a node stored in a node variable. Multiple SPM's can store information on the same node. Two SPM's setting the same storage value on the same node will cause a conflict.

The temperature SPM's set Node%TempSetPoint. The dual SP temperature SPM sets Node%TempSetPoint, Node%TempSetPointLo, and Node%TempSetPointHi.

The maximum humidity SPM's set Node%HumRatMax. The minimum humidity SPM's set Node%HumRatMin.

The return air bypass flow SPM sets Node%MassFlowRateSetPoint

Setting a Node%TempSetPoint AND Node%HumRatMax variable at the outlet node of the coil (and setting TemperatureAndHumidityRatio as the control variable in the Controller:WaterCoil object when using a water coil) and choosing CoolReheat as the control type in CoilSystem:Cooling:DX object should allow humidity control.