Will like to know the size of your tank? It should not be any bigger then a 2ft, as any bigger will be pushing it's limit and increasing the time taken to chill the tank.
It takes too long to cool down 1 deg, normally will take 20 to 45mins. Did u check the flow rate of your pump output to the chiller flow rate. If your pump flow is too slow then it will take a long time to chill your water. From hailea website, it state that it needs a flow rate of 200~1000L/H. If you meet the requirement, then u might need to check your chiller to see if it is faulty.
Might be that the internal thermostat is faulty and register a wrong temperature reading, thus contributing to the long chilling duration. Try getting a thermometer and see if the temperature is the same as the one register on your chiller. If a faulty thermostat, then u might want to get a external thermostat as it will register accurate reading of your tank temp and will minimise the number of time the chiller needs to kick in. It help to save on your electric bills and also make your chiller last longer.
Happy Reefing!