diff --git a/bundles/org.openhab.binding.iaqualink/src/main/java/org/openhab/binding/iaqualink/internal/handler/IAqualinkHandler.java b/bundles/org.openhab.binding.iaqualink/src/main/java/org/openhab/binding/iaqualink/internal/handler/IAqualinkHandler.java
index 791bf26b4..d2ae0dc51 100644
--- a/bundles/org.openhab.binding.iaqualink/src/main/java/org/openhab/binding/iaqualink/internal/handler/IAqualinkHandler.java
+++ b/bundles/org.openhab.binding.iaqualink/src/main/java/org/openhab/binding/iaqualink/internal/handler/IAqualinkHandler.java
@@ -296,7 +296,7 @@ public class IAqualinkHandler extends BaseThingHandler {
             }
 
             if (confSerialId != null && !confSerialId.isBlank()) {
-                serialNumber = confSerialId.replaceAll("[^a-zA-Z0-9]", "").toLowerCase();
+                serialNumber = confSerialId.replaceAll("[^a-zA-Z0-9]", "").toUpperCase();
                 if (!Arrays.stream(devices).anyMatch(device -> device.getSerialNumber().equals(serialNumber))) {
                     updateStatus(ThingStatus.OFFLINE, ThingStatusDetail.CONFIGURATION_ERROR,
                             "No Device for given serialId found");
@@ -306,6 +306,8 @@ public class IAqualinkHandler extends BaseThingHandler {
                 serialNumber = devices[0].getSerialNumber();
             }
 
+            logger.debug("Using serial number {}", serialNumber);
+
             initPolling(COMMAND_REFRESH_SECONDS);
         } catch (IOException e) {
             logger.debug("Could not connect to service {}", e.getMessage());