Doing my fourth BIAB on my new single kettle set up. First three brew days were pretty much uneventful but today I ran into a problem. I decided to do a 104F rest to check PH and adjust but my temps overshot to 111F before the grain went in. I had a lot of trouble getting the temps to drop, unplugged the element, tested to make sure it was not getting 120 or 240 to it when the temp was higher than set point and it wasn't. Eventually the temps came down but very slowly. When I got to mash out temps I noticed the wort volume in the kettle getting closer to the top which was unusual so I killed the power and pulled the bag away from the sides of the kettle. It seemed as if the wort was near boiling underneath the bag and a suction had been created. I recovered after a lot of extra work which I will spare you the details.
Any ideas what went on? I am recirculating the wort and that never slowed or stopped so it hadn't created any kind of stuck situation. It was 15 lbs of grain in a 15 gallon kettle with 10 gallons of water so it should have had the room. The crush was finer than I usually do which as far as I know is ok for BIAB.
Not sure if it's an element problem (doubt it) or just a technique issue. Sorry for the tough one!