Issues with high temp in tun vs RIMS readings

[brundl3fly]

Hello, first post here.

I've been dialing in my new system (RIMS-based, 2 keg system using BCS) and wanted to get some outside help for a temperature problem I'm having. I'll give you the data I have and see if you have any suggestions.

I use constant circulation from my RIMS tube. I heat the water up to my strike temp and add grain to the tun which shoudl allow the RIMS to maintin temp.

I have checked my 2 probes by putting in the correct BH coeffecients and chekced them both with another thermometer in low, medium, and higher temp settings. They are fairly accurate, within a degree of each other.

What I ran into this last time was that the mash tun temp was higher, using the same independent thermometer, than what was coming out of the RIMS tube (I have my probe on the output) by a good 12 degrees. I have had other issues with stuck mash previously but adjusting my grain crush has solved this problem so I'm moving on to my temp issues.

One would think that the temp from the RIMS out would be higher than the mash at least until evnerything circulated a few times and yet I had to dial down my mash temp on the RIMS to maintain the ~152 I was shooting for. Keep in mind that using these same thermometer and probes they were fairly accurate on standing liquid temps.

I admit I've only had the one experience since my other temp fluctuations could have come directly from the stuck mashes and the lack of liquid flow in previous batches so I'm only using this one as data.

Anyone have any ideas? I mean I could test again and find the temp variable and always set my mash lower, I just don't understand what this difference is coming from, it seems counterintuitive...

[JonW]

You talk about trying to maintain 152 on the recirculation, but you leave out a lot of details about your temps, settings, etc.

What was the temperature of your strike water?
What was the mash temperature right after mashing in? (before applying any additional heat)
What is the heat/temp method you are using? (e.g output setup with PID, hysteresis, duty cycle, directly on )???
What are the set points you're using?

[brundl3fly]

Hi, thanks for the reply.

What was the temperature of your strike water?

I was using both Beersmith and Brew 365 to calculate strike temps and volumes. I think I used 167 that time, based on grain temp and water volume.

What was the mash temperature right after mashing in? (before applying any additional heat)

I was close, within a few degrees but the problem is that the temp probes are simply off on temps by checking with 2 different thermometers. I made an ESB today and I had to set the temp of the RIMS probe to about 138 to keep it at around 152 according to the thermometer. As I said I used the coeffecients from the manufacturer to program them in BCS.

What is the heat/temp method you are using? (e.g output setup with PID, hysteresis, duty cycle, directly on )???

PID.

What are the set points you're using?

I'm not sure exactly what you are asking me. Temp set points?

I wish I could simply adjust the readings in BCS in some way if I determined the temp was simply inaccurate based on placement. For example if the RIMS tube probe is actually shorter than it should be and this makes the temperature reading off 10 degrees that I could simply do an offset. Is this possible?

[brundl3fly]

In interest of helping others out that may have similar issues in a situation like this (2 keg setup) here's what I've found to help:

1. Stratification of heat from the RIMS tub coming into the mash tun gave me a different reading from the external thermometer and the tun's probe. Solution is to heat water to strike temp based on the mash tun's probe while stirring water to try to homogenize the temperature. I will do this and stop circulation, add grains and wait until the temp is all the same in the tun before turning the pump and RIMS tube on set for my mash temp. A friend with a similar setup also suggested a lid for the keg to help hold a steadier temp.

2. My RIMS tube temp still reads low by around 5-6 degrees with a static water temp reading on bot mash tun probe and external thermometer. I am now assuming one of my hunches is correct, that the temp probe is not sitting far enough in the flow of wort/water. I have ordered a new bushing for the top of the RIMS tube so that I am not reducing from 1 1/2" to 1/2" and then again to 1/4". This will gain me at least an inch more probe and I should likely see more accurate readings. I'll find out shortly.