First of all i must warn you that this unit hasn't been designed to go beyond 200C and needing 30 minutes to reach this temperature is about right - make sure you are using the right temperature scale.
If you are indeed using the F scale then the temperature analogue controller (basically just a simple bimetal thermostat) is defective and it will have to be replaced - an extremely simple job, it just plugs in.
To order a replacement part you need to phone Masterbuild at 1.800.489.1581
You can get the user manual from here if you need it
http://www.masterbuilt.com/pdf/manuals/20070210%20ESQ3082%20Manual.pdf