Originally Posted by onthekeg
2. Your autotune function will indeed be different due to the gravity of the fluid going through it at the time. I would tune it for wort, and use that tune for heating the water as well. It won't be as big a deal to run the other tune on the water as it doesn't have to be as precise.
If that makes sense.
I don't think the difference is S.G. will make nearly as much difference as the speed of the liquid. In a HERMS or normal heating operation, there is this huge thermal mass, meaning the measured temperature doesn't change that fast. I image the tune for that is way different.
But in the RIMs tube, I'm speculating that when the liquid temperature needs to be changed:
1. A fast flow will show a big differential between target and actual.
2. A slow flow(sparge, for example) will have a much smaller differential, thus more time may be spent pulsing the heating element since the measured temp is almost "there". Will that cause overshoot, slow heating or some funny stuff if I leave the pump valve during HLT operation wide open?
For it to work right for mashing, supposedly I should auto-tune for the flow rate and amount thermal mass (liquid, mash tun & grain) I'd be using most offten, and that's probably what I'll do. Just wondering what that means for the HLT. I'd like to set and forget on the HLT twice, without overshoot:
1. Once to get to strike temp, and
2. Raise what's left to sparge temp.
I'm using a cooler for the HLT, so holding the HLT temp once I move to MLT recirc is no problem.
I suppose I could just solve this by keeping the outlet valve on the pump pretty much the same as on the MLT during sparge, that is, partially open.
Originally Posted by mendesm
2. The way I understand you is that you're going to "share" the rims between HLT and M/T, is that correct? If so, I believe you want to auto tune it for M/T recirc and run it in manual to heat up the HLT, since you want to heat that up fast as possible.
3. Not a problem. Scorching has been debunked in a lot of other threads.
2. I was looking for set and forget on the HLT without overshoot. I'd like to do other stuff(grind grains, measure water salts, etc) while it's heating. If that means I'll need another PID or use a software programmable PID like Arduino (and change profiles), so be it. Just kinda hard to buy the right size box or do panel design if I don't know what I"m doing,
Maybe I need to just get one and do a breadboard trial run....