blockCoupled
Sequence of defining cooling tower fan speed when the plant is close coupled
Information
Block that outputs cooling tower fan speed ySpeSet based on the control
of condenser water return temperature for the plant that is close coupled.
This is implemented according to ASHRAE Guideline 36-2021, section 5.20.12.2, item a.6-7.
-
When any condenser water pump is proven on (
uConWatPumSpe > 0),
condenser water return temperature TConWatRet shall be maintained at
setpoint TConWatRetSet by a direct acting PID loop. The loop output
shall be mapped to the variable tower speed. Map the tower speed from the minimum tower
speed fanSpeMin at 0% loop output to 100% speed at 100% loop output.
-
The output tower speed
ySpeSet shall be the lowest value of tower speed
from loop mapping, maximum cooling tower speed setpoint from each chiller head
pressure control loop uMaxSpeSet (if the plant requires the chiller
head pressure being controlled), and tower maximum speed that resets
based on plant partial load ratio plrTowMaxSpe. All operating fans shall
receive the same speed signal.
Parameters
| Type | Name | Default | Description |
|---|
| Boolean | need_heaPreCon | true | True: the plant requires chiller head pressure being controlled |
| Integer | nChi | 2 | Total number of chillers |
| Integer | nConWatPum | 2 | Total number of condenser water pumps |
| Real | fanSpeMin | 0.1 | Minimum cooling tower fan speed |
| Controller |
| Buildings.Controls.OBC.CDL.Types.SimpleController | controllerType | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | k | 1 | Gain of controller |
| Real | Ti | 0.5 | Time constant of integrator block |
| Real | Td | 0.1 | Time constant of derivative block |
| Real | yMax | 1 | Upper limit of output |
| Real | yMin | 0 | Lower limit of output |
Revisions
-
August 9, 2019, by Jianjun Hu:
First implementation.
