diff --git a/src/EnergyPlus/GeneralRoutines.cc b/src/EnergyPlus/GeneralRoutines.cc
index 010d8fbba26..d0eebdb3f56 100644
--- a/src/EnergyPlus/GeneralRoutines.cc
+++ b/src/EnergyPlus/GeneralRoutines.cc
@@ -1043,9 +1043,14 @@ CalcPassiveExteriorBaffleGap(
 			ICSULossbottom = 0.40;
 			ICSWaterTemp = 20.0;
 		} else {
-			ICSULossbottom = Collector( CollectorNum ).UbLoss;
-			ICSWaterTemp = Collector( CollectorNum ).TempOfWater;
-			MyICSEnvrnFlag = false;
+			if ( ! Collector.allocated() ) {
+				ICSULossbottom = 0.40;
+				ICSWaterTemp = 20.0;
+			} else {
+				ICSULossbottom = Collector( CollectorNum ).UbLoss;
+				ICSWaterTemp = Collector( CollectorNum ).TempOfWater;
+				MyICSEnvrnFlag = false;
+			}
 		}
 	}
 	if ( ! BeginEnvrnFlag ) {
diff --git a/tst/EnergyPlus/unit/CMakeLists.txt b/tst/EnergyPlus/unit/CMakeLists.txt
index a28be5326e1..d28748975eb 100644
--- a/tst/EnergyPlus/unit/CMakeLists.txt
+++ b/tst/EnergyPlus/unit/CMakeLists.txt
@@ -16,6 +16,7 @@ set( test_src
   HeatBalanceManager.unit.cc
   Humidifiers.unit.cc
   HVACStandaloneERV.unit.cc
+  ICSCollector.unit.cc
   ManageElectricPower.unit.cc
   MixedAir.unit.cc
   PurchasedAirManager.unit.cc
diff --git a/tst/EnergyPlus/unit/ICSCollector.unit.cc b/tst/EnergyPlus/unit/ICSCollector.unit.cc
new file mode 100644
index 00000000000..e2c99595d49
--- /dev/null
+++ b/tst/EnergyPlus/unit/ICSCollector.unit.cc
@@ -0,0 +1,111 @@
+// EnergyPlus::ICS collector un-allocated collector data bug fix test
+
+// Google Test Headers
+#include <gtest/gtest.h>
+
+// ObjexxFCL Headers
+#include <ObjexxFCL/FArray1D.hh>
+
+// EnergyPlus Headers
+#include <EnergyPlus/ConvectionCoefficients.hh>
+#include <EnergyPlus/DataSurfaces.hh>
+#include <EnergyPlus/DataHeatBalance.hh>
+#include <EnergyPlus/DataHeatBalSurface.hh>
+#include <EnergyPlus/GeneralRoutines.hh>
+
+using namespace ObjexxFCL;
+using namespace EnergyPlus;
+using namespace EnergyPlus::ConvectionCoefficients;
+using namespace EnergyPlus::DataSurfaces;
+using namespace EnergyPlus::DataHeatBalance;
+using namespace EnergyPlus::DataHeatBalSurface;
+
+TEST( ISCSolarCollectorTest, BugTest ) {
+
+	// ICS collector un-allocated collector data bug fix test.  This unit test 
+	// does not test ICS collector performance but it does test a bug fix for 
+	// issue #4723 (crash) occured due to unallocated ICS collector data. 
+	// ! Collector.allocated() 
+
+	int const NumOfSurf( 1 );
+	int SurfNum;
+	int ZoneNum;
+	int ConstrNum;
+	int MatNum;
+
+	MatNum = 1;
+	ZoneNum = 1;
+	SurfNum = 1;
+	ConstrNum = 1;
+	// allocate surface variable data
+	Surface.allocate( NumOfSurf );
+	Surface( SurfNum ).Area = 10.0;
+	Surface( SurfNum ).OutDryBulbTemp = 20.0;
+	Surface( SurfNum ).OutWetBulbTemp = 15.0;
+	Surface( SurfNum ).WindSpeed = 3.0;
+	Surface( SurfNum ).Construction = ConstrNum;
+	Surface( SurfNum ).BaseSurf = SurfNum;
+	Surface( SurfNum ).Zone = ZoneNum;
+	Surface( SurfNum ).IsICS = true;
+	// allocate construction variable data
+	Construct.allocate( ConstrNum );
+	Construct( ConstrNum ).LayerPoint.allocate( MatNum );
+	Construct( ConstrNum ).LayerPoint( MatNum ) = 1;
+	Material.allocate( MatNum );
+	Material( MatNum ).AbsorpThermal = 0.8;
+	// allocate exterior vented cavaity variable data
+	ExtVentedCavity.allocate( 1 );
+	ExtVentedCavity( NumOfSurf ).SurfPtrs.allocate( NumOfSurf );
+	ExtVentedCavity( NumOfSurf ).SurfPtrs( NumOfSurf ) = 1;
+	// allocate zone variable data
+	Zone.allocate( ZoneNum );
+	Zone( ZoneNum ).OutsideConvectionAlgo = ASHRAESimple;
+	// allocate surface temperature variable data
+	TH.allocate( NumOfSurf, 1, 2 );
+	TH( SurfNum, 1, 1 ) = 22;
+	// allocate solar incident radiation variable data
+	QRadSWOutIncident.allocate( 1 );
+	QRadSWOutIncident( 1 ) = 0.0;
+	// set user defined conv. coeff. calculation to false
+	GetUserSuppliedConvectionCoeffs = false;
+
+	// SurfPtr( 1 ); // Array of indexes pointing to Surface structure in DataSurfaces
+	Real64 const VentArea( 0.1 ); // Area available for venting the gap [m2]
+	Real64 const Cv( 0.1 ); // Oriface coefficient for volume-based discharge, wind-driven [--]
+	Real64 const Cd( 0.5 ); // oriface coefficient for discharge,  bouyancy-driven [--]
+	Real64 const HdeltaNPL( 3.0 ); // Height difference from neutral pressure level [m]
+	Real64 const SolAbs( 0.75 ); // solar absorptivity of baffle [--]
+	Real64 const AbsExt( 0.8 ); // thermal absorptance/emittance of baffle material [--]
+	Real64 const Tilt( 0.283 ); // Tilt of gap [Degrees]
+	Real64 const AspRat( 0.9 ); // aspect ratio of gap  Height/gap [--]
+	Real64 const GapThick( 0.05 ); // Thickness of air space between baffle and underlying heat transfer surface
+	int Roughness( 1 ); // Roughness index (1-6), see DataHeatBalance parameters
+	Real64 QdotSource( 0 ); // Source/sink term, e.g. electricity exported from solar cell [W]
+	Real64 TsBaffle( 20.0 ); // Temperature of baffle (both sides) use lagged value on input [C]
+	Real64 TaGap( 22.0 ); // Temperature of air gap (assumed mixed) use lagged value on input [C]
+	Real64 HcGapRpt; // gap convection coefficient [W/m2C]
+	Real64 HrGapRpt; // gap radiation coefficient [W/m2C]
+	Real64 IscRpt; //  
+	Real64 MdotVentRpt; // gap air mass flow rate [kg/s]
+	Real64 VdotWindRpt; // gap wind driven air volume flow rate [m3/s]
+	Real64 VdotBouyRpt; // gap bouyancy driven volume flow rate [m3/s]
+
+	// call to test fix to resolve crash
+	CalcPassiveExteriorBaffleGap( ExtVentedCavity( 1 ).SurfPtrs, VentArea, Cv, Cd, HdeltaNPL, SolAbs, AbsExt, Tilt, AspRat, GapThick, Roughness, QdotSource, TsBaffle, TaGap, HcGapRpt, HrGapRpt, IscRpt, MdotVentRpt, VdotWindRpt, VdotBouyRpt );
+
+	EXPECT_NEAR( 21.862, TsBaffle, 0.001 );
+	EXPECT_NEAR( 1.692, HcGapRpt, 0.001 );
+	EXPECT_NEAR( 3.694, HrGapRpt, 0.001 );
+	EXPECT_NEAR( 0.036, MdotVentRpt, 0.001 );
+
+	// delete allocated variables
+	Surface.deallocate();
+	Construct( ConstrNum ).LayerPoint.deallocate();
+	Construct.deallocate();
+	Material.deallocate();
+	ExtVentedCavity( NumOfSurf ).SurfPtrs.deallocate();
+	ExtVentedCavity.deallocate();
+	Zone.deallocate();
+	TH.deallocate();
+	QRadSWOutIncident.deallocate();
+}