Contact the manufacturer by calling customer service department at 1-877-891-7333. Make sure you have your warranty, your sales receipt, the location of purchase and the model/serial number of your product..
I have this heater in my office and it puts out amazing comfortable heat! It's also suuuuuper quiet. I have had other space heaters that circulate the air with an internal fan, but this one takes the cake! It's the quietest space heater I have ever had.