Just ran my new PID-controlled RIMS HEX for the first time in production... and had a startling problem. I heated my strike and sparge water in a conventional manner (fire) to 167F. I doughed in, mixed well.. gave it a minute to settle, and then started recirculating very slowly (wild guess - about 1/4 gallon a minute). I visually confirmed the flow before firing the element. according to my PID, I was 20 degrees F low (!!!!). So at 100% power I let it ramp up. After 15 minutes, only gaining about 10 degrees F, I suspected a problem. I eased up on the output valve to increase flow just a little bit... and all hell broke loose. The PID started reading 150...155..160...165...168 (!!!!) in a matter of seconds. I immediately snapped the element cutoff switch off. The PID leveled out around 169, and then over the next 20 minutes or so cooled down to my original target of 153. The PID easily held that once I put the power to the element back on.
During my pre-production beta testing of the tube, I had run into issues with overheat, due to air getting into the system... that I fixed... and resultantly became VERY aware of the symptoms of having an exposed element / probe causing problems with boiling the liquid / steam producing / false readings. I had that resolved with reorientation and proper "burping" of the system (a gentle rocking of the tube back and forth to dislodge any air bubbles).
I have no idea how a system, with NO air in it, running at a low flow rate, can heat the wort a full 20 degrees greater than the probe (3 inches away) reads. It is not physically possible for it to have cooled that much from the element to the probe, even if the pump was completely off and I wrapped the tube in frozen towels.
I intend to install an 'economy' plastic flow meter at my RIMs outlet and determine my minimum allowable flow for this system to be accurate... but I still am baffled as to what happened... Opinions would be very helpful.
During my pre-production beta testing of the tube, I had run into issues with overheat, due to air getting into the system... that I fixed... and resultantly became VERY aware of the symptoms of having an exposed element / probe causing problems with boiling the liquid / steam producing / false readings. I had that resolved with reorientation and proper "burping" of the system (a gentle rocking of the tube back and forth to dislodge any air bubbles).
I have no idea how a system, with NO air in it, running at a low flow rate, can heat the wort a full 20 degrees greater than the probe (3 inches away) reads. It is not physically possible for it to have cooled that much from the element to the probe, even if the pump was completely off and I wrapped the tube in frozen towels.
I intend to install an 'economy' plastic flow meter at my RIMs outlet and determine my minimum allowable flow for this system to be accurate... but I still am baffled as to what happened... Opinions would be very helpful.
