Still a bit curious though, anything that I have read, including Darren's own warning in the manual would suggest if you really did evacuate most of the wort from under the false bottom to the point where you had a "dry" element, the element would self destruct. Although after thinking about it a bit more, if you are just maintaining mash temps it probably is at a lower power level so this point may not be valid.
The first brew I did on my system was an Imperial Rye PA, which had about 1 1/2 lbs rye malt and a pound of flaked rye. I was using a Wilser bag which as noted
is much finer than the stock BB bag and I did use 1/2 lb of rice hulls. I was careful to throttle the output of the pump and never lost flow through the sparge arm. As the mash progressed I started getting very strange and varying temp readings, up, down, all over the place. Noticed that we didn't have as much excess bag over the rim of the kettle as when we started. Grabbed the bag on one side and with a bit of effort pulled it up with a huge sucking sound from both the bag and me :cross:
Once the brew was finished and I started cleaning up I found that the the bottom of the false bottom supports were bowed up a bit, the silicone feet, although intact were torn and I had four dents in the bottom of the kettle where the feet contacted it. Although there was some major "suck" taking place, I never lost flow and no scorching on the element.
I guess my point in all this is, at least in my experience it seems that it would be pretty hard to suck all the wort from under the false bottom with this system and end up with scorched wort on the element without destroying it. And possibly more to the point, if you did pump it dry, your pump would be screamin' like a banshee...
FWIW, the beer turned out great
I guess one question would be, At what power level would a dry element "pop"? If the controller is maintaining mash temps with occasional bursts of <20% would those levels be low enough to preserve a dry element, but high enough to scorch wort?