Merge pull request #7702 from NREL/170845444_Issue7464

Addressed CoolingTower:VariableSpeed control problems
NREL · Mar 6, 2020 · 22b5d44 · 22b5d44 · nrel-bot-3 · Mar 7, 2020
2 parents 3eccb7f + 3d848e7
commit 22b5d44
Show file tree

Hide file tree

Showing 3 changed files with 499 additions and 1 deletion.
diff --git a/doc/input-output-reference/src/overview/group-plant-condenser-control.tex b/doc/input-output-reference/src/overview/group-plant-condenser-control.tex
@@ -299,6 +299,10 @@ \subsection{PlantEquipmentOperation:ComponentSetpoint}\label{plantequipmentopera
 
 In addition to load range based control on the plant loop, sequencing the plant components based on the outlet temperature of individual equipment is allowed. This scheme is common to many present-day Energy Management Systems sequencing. In this scheme, the sequencing is done based on the order specified in the control object described below.
 
+However, when sequencing a boiler and a cooling tower to control the heating and cooling set point temperatures of a condenser loop, it is recommended that the boiler and the cooling tower be placed in a parallel configuration. The series configuration of these two equipment, though possible to model them, may result in simultaneous heating and cooling operation when the boiler is ON and the cooling tower operates in free cooling mode, i.e., 
+the cooling tower may provide free cooling that could over cool the water below the boiler heating setpoint temperature.  
+
+
 \subsubsection{Inputs}\label{inputs-12-011}
 
 \paragraph{Field: Name}\label{field-name-6-014}

diff --git a/src/EnergyPlus/CondenserLoopTowers.cc b/src/EnergyPlus/CondenserLoopTowers.cc
@@ -5291,6 +5291,7 @@ namespace CondenserLoopTowers {
         // SUBROUTINE LOCAL VARIABLE DECLARATIONS:
         int SolFla;             // Flag of solver
         Array1D<Real64> Par(4); // Parameter array for regula falsi solver
+        Real64 const VSTowerMaxRangeTemp(22.2222); // set VS cooling tower range maximum value used for solver 
 
         //   determine tower outlet water temperature
         Par(1) = this->thisTowerNum; // Index to cooling tower
@@ -5299,7 +5300,7 @@ namespace CondenserLoopTowers {
         Par(4) = Twb;                // inlet air wet-bulb temperature [C]
         Real64 Tr;                   // range temperature which results in an energy balance
         auto f = std::bind(&CoolingTower::residualTr, this, std::placeholders::_1, std::placeholders::_2);
-        General::SolveRoot(Acc, MaxIte, SolFla, Tr, f, 0.001, towers(this->VSTower).MaxRangeTemp, Par);
+        General::SolveRoot(Acc, MaxIte, SolFla, Tr, f, 0.001, VSTowerMaxRangeTemp, Par);
 
         Real64 _OutletWaterTemp = this->WaterTemp - Tr;