diff --git a/src/Backends/REFPROP/REFPROPMixtureBackend.cpp b/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
index 99f8f4ce..5ee4d66e 100644
--- a/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
+++ b/src/Backends/REFPROP/REFPROPMixtureBackend.cpp
@@ -426,7 +426,7 @@ void REFPROPMixtureBackend::set_REFPROP_fluids(const std::vector<std::string> &f
                      errormessagelength // Length of error message
                      );
 
-            if (ierr <= 0) // Success (or a warning, which is silently squelched for now)
+            if (static_cast<int>(ierr) <= 0) // Success (or a warning, which is silently squelched for now)
             {
                 this->Ncomp = N;
                 mole_fractions.resize(N);
@@ -438,11 +438,12 @@ void REFPROPMixtureBackend::set_REFPROP_fluids(const std::vector<std::string> &f
                 return;
             }
             else if (k < number_of_endings-1){ // Keep going
-                if (CoolProp::get_debug_level() > 5){std::cout << "REFPROP error/warning:" << herr << std::endl;}
+                if (CoolProp::get_debug_level() > 5){std::cout << format("REFPROP error/warning [ierr: %d]: %s",ierr, herr) << std::endl;}
                 continue;
             }
             else
             {
+                if (CoolProp::get_debug_level() > 5){std::cout << format("k: %d #endings: %d", k, number_of_endings) << std::endl;}
                 throw ValueError(format("Could not load these fluids: %s", components_joined_raw.c_str()));
             }
         }
@@ -517,21 +518,21 @@ long double REFPROPMixtureBackend::calc_T_critical(){
     char herr[255];
     double Tcrit, pcrit_kPa, dcrit_mol_L;
     CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255);
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     return static_cast<long double>(Tcrit);
 };
 long double REFPROPMixtureBackend::calc_p_critical(){
     long ierr = 0;
     char herr[255];
     double Tcrit, pcrit_kPa, dcrit_mol_L;
-    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     return static_cast<long double>(pcrit_kPa*1000);
 };
 long double REFPROPMixtureBackend::calc_rhomolar_critical(){
     long ierr = 0;
     char herr[255];
     double Tcrit, pcrit_kPa, dcrit_mol_L;
-    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+    CRITPdll(&(mole_fractions[0]),&Tcrit,&pcrit_kPa,&dcrit_mol_L,&ierr,herr,255); if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     return static_cast<long double>(dcrit_mol_L*1000);
 };
 long double REFPROPMixtureBackend::calc_T_reducing(){
@@ -575,7 +576,7 @@ double REFPROPMixtureBackend::calc_melt_Tmax()
     MELTPdll(&pmax_kPa, &(mole_fractions[0]),
              &Tmax_melt,
              &ierr,herr,errormessagelength);      // Error message
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
     //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     return Tmax_melt;
 }
@@ -589,7 +590,7 @@ long double REFPROPMixtureBackend::calc_melting_line(int param, int given, long
         MELTTdll(&_T, &(mole_fractions[0]),
              &p_kPa,
              &ierr,herr,errormessagelength);      // Error message
-        if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+        if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
         return p_kPa*1000;
     }
     else if (param == iT && given == iP){
@@ -597,7 +598,7 @@ long double REFPROPMixtureBackend::calc_melting_line(int param, int given, long
         MELTPdll(&p_kPa, &(mole_fractions[0]),
              &_T,
              &ierr,herr,errormessagelength);      // Error message
-        if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+        if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); } //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
         return p_kPa*1000;
     }
     else{
@@ -619,7 +620,7 @@ long double REFPROPMixtureBackend::calc_viscosity(void)
     TRNPRPdll(&_T,&rhomol_L,&(mole_fractions[0]),  // Inputs
               &eta,&tcx,                           // Outputs
               &ierr,herr,errormessagelength);      // Error message
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
     //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     _viscosity = 1e-6*eta;
     _conductivity = tcx;
@@ -639,7 +640,7 @@ long double REFPROPMixtureBackend::calc_surface_tension(void)
     SURFTdll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
              &sigma,                                 // Outputs
              &ierr, herr, errormessagelength);       // Error message
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
     //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     _surface_tension = sigma;
     return static_cast<double>(_surface_tension);
@@ -654,7 +655,7 @@ long double REFPROPMixtureBackend::calc_fugacity_coefficient(int i)
     FUGCOFdll(&_T, &rho_mol_L, &(mole_fractions[0]),  // Inputs
              &(fug_cof[0]),                   // Outputs
              &ierr, herr, errormessagelength);       // Error message
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
     //else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
     return static_cast<long double>(fug_cof[i]);
 }
@@ -665,7 +666,7 @@ void REFPROPMixtureBackend::calc_phase_envelope(const std::string &type)
     char herr[255];
     SATSPLNdll(&(mole_fractions[0]),  // Inputs
                &ierr, herr, errormessagelength);       // Error message
-    if (ierr > 0) { throw ValueError(format("%s",herr).c_str()); }
+    if (static_cast<int>(ierr) > 0) { throw ValueError(format("%s",herr).c_str()); }
 }
 long double REFPROPMixtureBackend::calc_cpmolar_idealgas(void)
 {
@@ -704,7 +705,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                       &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions[0]), // Saturation terms
                       &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w,
                       &ierr,herr,errormessagelength); //
-            if (ierr > 0) { throw ValueError(format("PT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = value1;
@@ -726,7 +727,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                       &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                       &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w,
                       &ierr,herr,errormessagelength);
-            if (ierr > 0) { throw ValueError(format("DmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000;
@@ -755,7 +756,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                 &q,&emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength);  // Error terms
-            if (ierr > 0) { throw ValueError(format("DmolarP: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarP: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _rhomolar = value1;
@@ -785,7 +786,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                       &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                       &q,&emol,&smol,&cvmol,&cpmol,&w,
                       &ierr,herr,errormessagelength);
-            if (ierr > 0) { throw ValueError(format("DmolarHmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarHmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000;
@@ -815,7 +816,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                       &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                       &q,&emol,&hmol,&cvmol,&cpmol,&w,
                       &ierr,herr,errormessagelength);
-            if (ierr > 0) { throw ValueError(format("DmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000;
@@ -845,7 +846,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                       &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                       &q,&hmol,&hmol,&cvmol,&cpmol,&w,
                       &ierr,herr,errormessagelength);
-            if (ierr > 0) { throw ValueError(format("DmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("DmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000;
@@ -874,7 +875,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &rhoLmol_L,&rhoVmol_L,&(mole_fractions_liq[0]),&(mole_fractions_vap[0]), // Saturation terms
                 &q,&emol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
-            if (ierr > 0) { throw ValueError(format("HmolarPmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarPmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = value2;
@@ -904,7 +905,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&emol,&hmol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("PSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = value1;
@@ -935,7 +936,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("PUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = value1;
@@ -964,7 +965,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&emol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("HmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarSmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
@@ -995,7 +996,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("SmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("SmolarUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
@@ -1034,7 +1035,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&emol,&hmol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("SmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("SmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
@@ -1072,7 +1073,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&emol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("HmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("HmolarT: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
@@ -1110,7 +1111,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &q,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("TUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("TUmolar: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = p_kPa*1000; // 1000 for conversion from kPa to Pa
@@ -1148,7 +1149,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) { throw ValueError(format("PQ: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
+            if (static_cast<int>(ierr) > 0) { throw ValueError(format("PQ: %s",herr).c_str()); }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());}
 
             // Set all cache values that can be set with unit conversion to SI
             _p = value1;
@@ -1179,7 +1180,7 @@ void REFPROPMixtureBackend::update(CoolProp::input_pairs input_pair, double valu
                 &emol,&hmol,&smol,&cvmol,&cpmol,&w, // Other thermodynamic terms
                 &ierr,herr,errormessagelength); // Error terms
 
-            if (ierr > 0) {
+            if (static_cast<int>(ierr) > 0) {
                 throw ValueError(format("TQ(%s): %s",LoadedREFPROPRef.c_str(), herr).c_str());
                 }// TODO: else if (ierr < 0) {set_warning(format("%s",herr).c_str());