blockHeadControl
Sequences for enabling or disabling head pressure control for the chiller being enabled or disabled
Information
Block that generates chiller head pressure control enabling status array when
there is a stage change command (chaPro=true). It also generates status
to indicate if the head pressure control status change process has finished.
This development is based on ASHRAE Guideline 36-2021.
In the stage-up process, section 5.20.4.16, item d:
-
After the condenser water pumps speed or number has been changed by
thrTimEnb, e.g. 10 seconds, enable head pressure control for the chiller being enabled. Wait 30 seconds (waiTim=30).
In the stage-up process when requires smaller chiller being shut off and larger chiller being enabled, section 5.20.4.16, item g.3:
-
When the controller of the smaller chiller being shut off indicates no request for
condenser water flow, disable the chiller's head pressure control loop,
(
thrTimEnb=0andwaiTim=0).
In the stage-down process, section 5.20.4.17, item d:
-
When the controller of the chiller being shut off indicates no request for condenser
water flow, disable the chiller's head pressure control loop,
(
thrTimEnb=0andwaiTim=0).
In the stage-down process when requires smaller chiller to be enabled and larger chiller to be disabled, section 5.20.4.17, item a.3:
-
After the minimum flow bypass has been changed, enable head pressure control for
the chiller being enabled. Wait 30 seconds.
(
thrTimEnb=0andwaiTim=30).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nChi | 2 | Total number of chiller |
| Real | thrTimEnb | 10 | Threshold time to enable head pressure control after condenser water pump being reset |
| Real | waiTim | 30 | Waiting time after enabling next head pressure control |
| Boolean | heaStaCha | true | Flag to indicate if head pressure control of next chiller should be ON or OFF: true = in stage-up process so it should be ON |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uEnaPla | True: plant is just enabled | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerInput | nexChaChi | Index of next enabling or disabling chiller | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uUpsDevSta | Status of resetting status of device before enabling or disabling head pressure control | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput[nChi] | uChiHeaCon | Chillers head pressure control status | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uStaPro | Indicate if there is stage change | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput[nChi] | yChiHeaCon | Chiller head pressure control enabling status | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yEnaHeaCon | Status of head pressure control: true=enabled head pressure control |
Revisions
-
February 4, 2019, by Jianjun Hu:
First implementation.