diff --git a/Thermo.Active.NC/NcAdapter.cs b/Thermo.Active.NC/NcAdapter.cs
index 5b8e665f..382e98ae 100644
--- a/Thermo.Active.NC/NcAdapter.cs
+++ b/Thermo.Active.NC/NcAdapter.cs
@@ -32,7 +32,7 @@ namespace Thermo.Active.NC
 
         public void Dispose()
         {
-            if (NcConfig.NcVendor != NC_VENDOR.SIEMENS)
+            if (NcConfig.NcVendor != NC_VENDOR.S7NET)
                 numericalControl.NC_Disconnect();
         }
 
@@ -47,7 +47,7 @@ namespace Thermo.Active.NC
             if (!numericalControl.NC_IsConnected())
                 return numericalControl.NC_Connect();
 
-            return null;
+            return NO_ERROR;
         }
 
         public NcThermo SetNumericalControl()