fix

pyheatpump/modbus.py

     )
 
     try:
-        casted_value = int(var_value.value) + (1 << 16)
+        casted_value = (int(var_value.value) + (1 << 16)
             if (var_value.value < 0)
-            else int(var_value.value)
+            else int(var_value.value))
 
         req_adu = rtu.write_single_register(
             slave_id=1,