I have a Bunn Model NHBX-B that has a heating element that won't turn off.

SOURCE: the water is not heated when I put my Bunn coffee maker on

If you plugged it in before water started coming out of the sprayhead (about 2 pots full of water poured in) you might have burnt out your element, But lets start with a simpler answer. Did you check the main burner switch on the side of the tank?
If so, then I would suspect your main heating element

SOURCE: bunn commercial coffee maker plug overheats, no hot water

Most likely this is your heating element, but it could also be your main thermostat

SOURCE: Can't find my BUNN NHBX-B manual...can I find it

I work for BUNN. Here's a link to the manual for your NHBX-B
http://www.bunn.com/pdfs/retail/usecare/41756.0000_STX_NBX_U_C_English.pdf

SOURCE: No manual with Bunn NHBX coffee maker.

Leave the unit unplugged and add a carafe of water to the top reservoir.
Close the lid.
Wait a bit to make sure the water has drained into the tank.
Add another carafe of water to the top reservoir.
Place carafe on warmer plate.
Close the lid.
When water stops going into the carafe, you may plug the machine in and make sure the "travel switch" is in the ON position. ON = |, OFF = O.
Wait at least 15 minutes for the water in the tank to heat up, and brew as you normally would for other BUNN coffee makers.

SOURCE: I have a bunn coffee maker the NHBX is the # it is

Please give Customer Service a call with the model and date code. If the machine is 3 years old or less, it will be replaced with a new machine. If it is older than 3 years, it can be exchanged for a reduced price.