AGH, to operate the boost function hold the green button in for approx. 3 secs, you should hear a loud click when a relay operates to start the heating. Hold it again for approx. 3 secs and it will click again to turn off. I just tried it and noticed that on the bottom row of the display, about 1/2 way in, is a capital L, when I turned on boost this started flashing then stopped when I turned off the boost. I'm guessing they're connected but, of course, don't know what the L stands for.Having sa ...