Here is my question, When i lite the pilot and then turn the k**b to light the flame it stays on about 15 min?

Question

then when its ready to go back to pilot it goes out and i have had three techs come look at it and they can not figure it out help me some one please im at my wits end.

Answer 1

The thermocouple or the control is bad, call the people who made the heater and they will explain what is wrong!

Answer 2

Sounds like a bad heat/flame sensor.  That's a safety device to tell the control that the pilot is lit.