blockHeatExchangerPump
Information
It implements the control of the waterside economizer valves when the chilled water flow through the economizer is controlled by the variable speed heat exchanger pump. It is implemented according to ASHRAE Guideline 36-2021, section 5.20.3.7-10.
When economizer is enabled (uWSE=true), start next condenser water
pump and (or) adjust the pump speed
(see
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.CondenserWater.Controller),
open the condenser water isolation valve to the heat exchanger (yConWatIsoVal=true),
and enable the chilled water heat exchanger pump.
The economizer heat exchanger pump speed reset requests shall be generated based on the difference between the chilled water return temperature upstream of the economizer and the economizer heat exchanger entering chilled water temperature.
- If the temperature difference exceeds 2 °F (1.11 °K), send 2 requests until the difference is less than 1.2 °F (0.67 °F).
- Else if the temperature difference exceeds 1 °F (0.56 °K), send 1 request until the difference is less than 0.2 °F (0.11 °K).
- Else send 0 requests.
When the heat exchanger pump is proven on, the pump speed shall be reset using Trim and Respond logic with the following parameters:
| Variable | Value | Definition |
|---|---|---|
| Device | Economizer heat exchanger pump proven on | Associated device |
| SP0 | Pump design speed (desSpe) | Initial setpoint |
| SPmin | Pump minimum speed (minSpe) | Minimum setpoint |
| SPmax | Pump design speed (desSpe) | Maximum setpoint |
| Td | 15 minutes | Delay timer |
| T | 2 minutes | Time step |
| I | 0 | Number of ignored requests |
| R | Pump speed reset requests | Number of requests |
| SPtrim | 2% | Trim amount |
| SPres | -3% | Respond amount |
| SPres_max | -6% | Maximum response per time interval |
When the economizer is disabled (uWSE=false), the chilled water heat
exchanger pump shall be disabled, the heat exchanger condenser water isolation
valve fully closed (yConWatIsoVal=0), and the last lag condenser water pump disabled
and (or) change the pump speed
see
Buildings.Controls.OBC.ASHRAE.G36.Plants.Chillers.Pumps.CondenserWater.Controller).
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | minSpe | 0.1 | Minimum pump speed |
| Real | desSpe | 0.9 | Design pump speed |
| Advanced | |||
| Real | dtHol | 900 | Minimum hold time during stage change |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uPla | Plant enable signal | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uWSE | True: waterside economizer is enabled | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uPum | True: heat exchanger pump is proven on | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanInput | uStaPro | True: in staging process | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TEntWSE | Chilled water return temperature upstream of the economizer | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TEntHex | Chilled water temperature entering heat exchanger | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yConWatIsoVal | Economizer condenser water isolation valve commanded status | |
| Buildings.Controls.OBC.CDL.Interfaces.BooleanOutput | yPumOn | Heat exchanger pump command on | |
| Buildings.Controls.OBC.CDL.Interfaces.RealOutput | yPumSpe | Heat exchanger pump speed setpoint |
Components
Revisions
-
July 14, 2022, by Jianjun Hu:
First implementation.