2 Vessel temp/output question

[Bayoujeeper]

My setup is basically a brutus 20 no sparge system. The mash tun has a temp probe (Temp1) that is located about mid mash during a 5G batch, and the boil kettle has a temp probe(temp0) as well as heating element(Output0). It does not have a herms etc, but I do recirculate through the tun/kettle to maintain temps (basically like the original counter top brutus).
On my old controller I just had a temp probe in the boil kettle and adjusted that temp about 2-4 degrees higher to keep my desired mash temp. I know you cannot associate multiple temps with a single output.. Could I use ladder Logic to basically utilize both temp probes to manage the one output? Would it be better to regulate temps based off of the center of the mash rather than overshooting temps in the boil kettle to compensate for heat losses? I know some recommend to place the probes on the HE out, but like I said, no herms, etc and I don't want to reconfig my plumbing.

I was thinking something like this for the ladder logic:
assert Output0 when Output1 is on. Associate my mash temp probe(Temp1) with output 1. Then in my Process heat strike with boil kettle temp(Temp0) and output 0. During the mash maintain temp and mash out with Temp1 and Output1. In doing this, would the PID still function correctly since output1 would be being used, but output0 is really wired to the SSR?

Thoughts? Any reason not to use the temp probe in the mash tun to maintain mash temps? I do understand that temps on top of the mash are a bit higher than the bottom/middle.

[clearwaterbrewer]

If you try to measure at the middle of the mash, you will overshoot every time... you stand a good chance of scorching or denaturing enzymes, and at the least, you will never have a repeatable brew day...

it is hard to read what you have, we are not all up on every version of brutus... It sounds like you are pumping wort to the boil kettle, heating it with the element, and returning it to the mash tun? that is basically RIMS with a large, open RIMS tube... in any case, you want your control temperature sensor as close to the liquid being heated as you can....

If you place the sensor in the BK(volume may be issue I assume) or in the return line and set it for your mash temp, it will get to that temp... it may get to the last few tenths of a degree fairly slowly, but if you flow 154 wort through the mash continually, the mash will get to 154 for all practical purposes..

more importantly, your results will be repeatable!

[JonW]

I agree with clearwaterbrewer - if you're going to heat in the BK, measure in the BK (or at least the output of the BK). Use the probe in the MT to verify that your grain bed is getting to the required temp, but it won't be the one controlling the element. I understand what you're looking at doing, but like clearwaterbrewer said, you'll overshoot if you use the probe in the MT to drive the BK temp.

Part of the issue with using two vessel heating arrangements is that you need to use some empirical evidence to fine tune your setpoints based on your exact configuration. Kettle types, hose lengths, rate of flow, lid on/off, outside temperature, etc. all play a part into the heat loss that you may see when moving wort from the BK to the MT. This may mean that if you want a mash temp of 152, that you need the BK at 153/154. If you have very little losses, you may be able to run the BK at 152 and still see 152 in the MT, it really just depends on your setup.

Another option is that you could use the MT probe (set at your actual desired mash temp) to trigger the pump on/off as needed and have the BK set to a degree or two above the MT setpoint. This is basically how most herms users do it.

[oakbarn]

In a way I have a simalar but different set up.

I have a MLT that I pump from.

I do have a modified HERMS where I use a CHINZILLA as the HERMS.

There is a 9 GAL HLT with an Element that heats the outer tube HERMS water. This also requires a pump.

By using this setup, I cannot scald the WORT and it is easy albeit somewhat slow to adjust (which is really a good thing in my case)

I have lots of probes

0 = MLT Tee In
1= MLT Tee Out
2= MLT Body
3 = sHLT in the sHLT Body

Out 3 = sHLTe is my 1500 watt element in my small HLT.

I have tried various configuartions and the one that works the best is exactly what Clearwater recommends. I have the #3 sHLT Temp Probe controlling the sHLTe Element in the small HLT. I constantly cycle the WORT. ( I can turn off the pump if needed).


I normally run the sHLT about 3 to 4 degees F above my desired "MLT In" Temp.

I tried to run the sHLT Element using the other probes but the one closest to the Element absoulutely worked the best.

If I got my Strike close, I have my MASH Temp stable on ALL 3 Mash Tun Probes after about 25 minutes.

And as Jon said, my heat loss is about 2 to 3 degrees from my #3 Probe sHLT to the # 0 MLT Tee in Probe. I had to do a few runs before I confirmed that. I normally start at 4 degrees F high and coast it down.

Since I got it down with the BCS and an element, I just sit back and watch the MASH and am no longer running around like a chicken minus a head. I use the Temp Setpoint to make the small changes.


BTW, the #2 MLT Body Probe can be misleading and I am thinking of doing away with mine. It get low and takes time to recover as it is on the outside of the MLT. When I did use that probefor control, It was a chase up and down and not at all good for my WORT. The MLT Tee in and MLT Tee Out agree much quicker. I do "spread" the returning WORT on top of the grain bed. I in the process of making a MASH Rake that might make that probe more useful, but right now I would say it is the least "true" of all my probes as to the total MASH situation.

[Bayoujeeper]

Thanks for the input guys! I will keep it the same and continue to adjust my brew kettle temp a few degrees higher.

I may toy around with that pump suggestion Jon, thanks!

[Bayoujeeper]

Jon,
If I were to associate temp1 with the pump output like in your example, and set that to mash temp, would I use direct on for the pump, or PID, Hysterisis?
Could I have the BK set to hold at say 154 and the mash temp set at 152 and tied to the pump to maintain temps in the same state?

Dustin

[JonW]

Yes, you can do it exactly as you stated. You would use hysteresis with the pump. If you have your BK set at 154 and the MT at 152, the MT probe will kick on the pump and keep recirculating the wort from the BK until the MT hits 152, at which point it will stop recirculating until it drops and needs to kick the pump on again.

FYI - Direct on means always on. e.g. the state is directly forcing the output on and it is not under temperature control. It is the same as the non-temperature controlled outputs. PID should only be used with electric heating.

[Bayoujeeper]

I assume it would be hysterisis in heat mode, how much swing should I allow?

[JonW]

Yes, heat mode. I do 1 degree swing with my gas fired system. As slow as yours would be, 1 degree would probably be fine.