Temperature Variations - PID / Thermo / RIMS

[jayareo]

I use a RIMS set-up for mashing / all gain recipes, and I recently tried (failed) to heat up the sparge water using the same system ... which is where my question comes in.

But first, a couple details. My system for mashing is a large insulated cooler with a spigot, mesh filter (false bottom) and a thermowell. I am measuring temps at two locations. Once at the OUT end of the RIMS tube (the heating element is mounted on the IN end), and another temp probe in the mash using the thermowell.

I have calibrated both my PID and the digital thermometer I use in the thermowell to the most reliable thermometer I have - its' solid, I have no concerns with the temp probes - normally.

When mashing, I use water that I have heated using my boil kettle. Its MUCH faster. I am really using the PID to manage small steps in the mash, and to generally maintain my target temps. Works great, BUT:

My question(s):

When the heating element is running, I assume its relatively normal for the temp probe in the RIMS tubs can read hotter than the mash temp. I can see differences up to +25 at the RIMS though - which seems ridiculous to me. Eventually the temp comes down to match the mash temp, but takes too long to be useful during a brew day ... like 45+ minutes.

If this is normal, then do you simply manage to the mash temp and adjust the SV accordingly?

If its not normal, then thoughts on issues? Heater element too close to the probe? Hot spots in the RIMS tube??

 

[Vale71]

How did you tune the PID parameters?

 

[augiedoggy]

I use a RIMS set-up for mashing / all gain recipes, and I recently tried (failed) to heat up the sparge water using the same system ... which is where my question comes in.

But first, a couple details. My system for mashing is a large insulated cooler with a spigot, mesh filter (false bottom) and a thermowell. I am measuring temps at two locations. Once at the OUT end of the RIMS tube (the heating element is mounted on the IN end), and another temp probe in the mash using the thermowell.

I have calibrated both my PID and the digital thermometer I use in the thermowell to the most reliable thermometer I have - its' solid, I have no concerns with the temp probes - normally.

When mashing, I use water that I have heated using my boil kettle. Its MUCH faster. I am really using the PID to manage small steps in the mash, and to generally maintain my target temps. Works great, BUT:

My question(s):

When the heating element is running, I assume its relatively normal for the temp probe in the RIMS tubs can read hotter than the mash temp. I can see differences up to +25 at the RIMS though - which seems ridiculous to me. Eventually the temp comes down to match the mash temp, but takes too long to be useful during a brew day ... like 45+ minutes.

If this is normal, then do you simply manage to the mash temp and adjust the SV accordingly?

If its not normal, then thoughts on issues? Heater element too close to the probe? Hot spots in the RIMS tube??

When do you see this 25 degree difference? Hopefully not when recircing mash? Wort leaving rims should be the desired set point or a degree higher.. conversion takes place in the wort not necessarily the mash tun so you would be denaturing the enzymes at 25 degrees too high. there should be a several minute lag between what the output temp and the mash tun temp probe read... it takes time for the wort exiting the rims to completely saturate and equalize so the grain bed matches (or in most cases is a degree or two less)

The important questions here is what does you rims look like? what element are you using in it? how close is the rims temp probe to the end of the element and what is the flow rate your pumping liquid through it? all these things have important influences on performance and accuracy.

 

[mabrungard]

You definitely don't want the temperature of the wort leaving the RIMS tube to be higher than your targeted mashing temperature. The temperature of the actual mash bed does not matter as much as the temperature of the wort exiting the RIMS. If the exiting wort temp is actually 25F over your intended mash temp, you are prematurely denaturing your enzymes and you'll end up with underattenuating, worty beers. (I've been there).

Set up your PID to precisely control your exiting wort temp and your mash temp will eventually get to that temperature.

 

[muhteeus]

Also, may be helpful to see your P-I-D settings for each controller.

 

[augiedoggy]

Also, may be helpful to see your P-I-D settings for each controller.

pid setting really should have no effect on mash taking 45 mins to catch up with the rims output.

OP what is your strike temp? When you mash in and stir in the grain you should be close to your desired mash temp. Theres no reason for your rims output to be any higher than the desired mash temp let alone 25+ degrees (there may be a few degree difference between the two depending on hose length and room temps).
Lets say your rims output is set to 153 and your mash is 148... If your flow rate is restricted down to 2gpm and this is a 5 gallon mash with say 4 gallons of strike water mixed with the grain. The liquid deposited on top of the grain bed at 152 degrees should only take 2 minutes to get to the temp probe at or near the mash tun exit port... Now it might take a few extra mins for everything to stabilize but we should be talking like a total of 5-10 mins not 45.
If I had to guess which I do since we have little info, Id say your pump is running at a fast speed and the wort leaving the rims tube is not equally heated which would cause unven temps and whats worse is it would cause serious channeling in the grainbed which means the wort surrounding the temp probe in the mash tun might not be seeing the flow and it might be taking much longer for the temps to rise in that location and match up with other areas if it ever does.. This would also likely cause poor efficiency.

 

[muhteeus]

pid setting really should have no effect on mash taking 45 mins to catch up with the rims output.

OP what is your strike temp? When you mash in and stir in the grain you should be close to your desired mash temp. Theres no reason for your rims output to be any higher than the desired mash temp let alone 25+ degrees (there may be a few degree difference between the two depending on hose length and room temps).
Lets say your rims output is set to 153 and your mash is 148... If your flow rate is restricted down to 2gpm and this is a 5 gallon mash with say 4 gallons of strike water mixed with the grain. The liquid deposited on top of the grain bed at 152 degrees should only take 2 minutes to get to the temp probe at or near the mash tun exit port... Now it might take a few extra mins for everything to stabilize but we should be talking like a total of 5-10 mins not 45.
If I had to guess which I do since we have little info, Id say your pump is running at a fast speed and the wort leaving the rims tube is not equally heated which would cause unven temps and whats worse is it would cause serious channeling in the grainbed which means the wort surrounding the temp probe in the mash tun might not be seeing the flow and it might be taking much longer for the temps to rise in that location and match up with other areas if it ever does.. This would also likely cause poor efficiency.

Need more coffee. Sounds like a flow issue.

 

[Vale71]

pid setting really should have no effect on mash taking 45 mins to catch up with the rims output.

He said it takes 45 minutes for the wort temperature at the RIMS output to come down to the set value, not for the whole mash to reach the set value. Sounds like his PID settings are seriously off in addition possibly to a low flow situation, but it's hard to tell if he doesn't give us more information.

 

[Bobby_M]

You say you measure temps at the RIMS output and the Mash tun but you are not clearly describing where your PID's temp probe is installed. It should be on the output of the RIMS so that the controller tells the element how hot to heat it. Do not fire your RIMS element based on what the controller senses in the mash.

 

[augiedoggy]

He said it takes 45 minutes for the wort temperature at the RIMS output to come down to the set value, not for the whole mash to reach the set value. Sounds like his PID settings are seriously off in addition possibly to a low flow situation, but it's hard to tell if he doesn't give us more information.

understood. I misunderstood his issue. if his mash temp isnt climbing and the rims eventually comes down to match the mash something else may be wrong... if the pid is firing the rims the mash temp should also be rising at least somewhat.