RIMS heater boiling wort?

Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum

Help Support Homebrew Talk - Beer, Wine, Mead, & Cider Brewing Discussion Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Dimerizer

Member
Joined
Oct 8, 2007
Messages
15
Reaction score
0
Greetings all - long time reader, first time poster...

So I've set up an electric brewery using RIMS, with a 1" stainless tube containing a 1500W/120V, low density heating element under PID control with the thermocouple in the same tube on the output side.

The issue I'm having is that the heating element is boiling the wort when it's on (i.e. bubbles are coming off the heating element) and I'm having trouble maintaining temp in the RIMS tube. It will turn the heating element on, shoot up to ~165 deg. F, and then drop down as colder wort flows over the element.

I'm not sure if this is an issue others have since I've done research on this forum which indicated a low-watt density element would work OK, but I'm a little worried that boiling the wort during the mash will cause problems with efficiency. I've thought about putting a variac in line to adjust the heating element's output to avoid boiling, but I'm not sure it's necessary. Does anyone have any insight into this issue?
 
What you're running into could be caused by a couple different issues or a combination of them. First off, did you autotune your PID? If so, what are the values? Also, what kind of flow rate are you using?

I say this because I know exactly what you're talking about. Tuning the PID will help minimize those fluctuations. Also, you'll need a decent flow rate to ensure complete mixing of the heated fluid prior to contact with the thermocouple so your PID is getting an accurate temperature read.
 
I put this system together with a friend, and I wasn't the one doing the PID wiring, so I don't have an answer right now (I did email him to find out, though). Couple of comments on the setup:

The RIMS tube is a 12" stainless tube with threaded tees on each end - the inlet and outlet are 90 degrees to the tube, the heating element is about 10 inches long and threaded into one end, and the thermocouple is threaded into the other end. If you can imagine it, the heating element and the thermocouple are basically "facing" each other. I'll post pics later when I get a chance to take some.

One thing, though - even if the PID is tuned, won't the wort still boil? I say this because the heating element seems to boil the wort pretty much instantly any time the PID turns on the element. Maybe it's not as big a deal as I think, but I'm worried about deactivating amylases that are in contact with the element.

The indications are noise coming from the RIMS tube and bubbles coming up the outlet tube (we can see them through clear 3/8" tube). Is this normal?
 
If I have the flow too low then I will get boiling as you described. Try recirculating faster and see if it stil happens.

I have basically the same thing you are describing
PC150201.jpg


What I'm pretty sure is happening is that you have a pocket of hot wart enveloping your element, while the cooler wort flows around it. The cooler wort is passing your temp sensor and causing your PID to fire the element. When it turns on it is boiling that already very hot fluid around the element. For me, like I said before, the solution was to run the wort through faster so that I get better mixing of the fluid.
 
Yeah, that picture is exactly what we have going on for our setup. We don't have a march pump, but we do have a centrifugal pump with a variable flow rate from 0-16 gpm. Is it OK to let it go full bore when mashing? I was a little worried about disturbing the grain bed, but we do have a showerhead-type plastic end on the outlet tube to help spray the water/wort on the grain.

Our electronics guy is going to come over to take another look at the PID, too - he did mention that we hadn't tuned it at all and he thought he could adjust it to help out.

What wattage/density is that heating element you've got there?
 
Yeah, that picture is exactly what we have going on for our setup. We don't have a march pump, but we do have a centrifugal pump with a variable flow rate from 0-16 gpm. Is it OK to let it go full bore when mashing? I was a little worried about disturbing the grain bed, but we do have a showerhead-type plastic end on the outlet tube to help spray the water/wort on the grain.

I don't think you want to let it run wide open... at least not right at first. My pump is only 12.5 gpm max, and I've had issues with the suction it creates compacting the grainbed onto my false bottom and getting my mash stuck if I start recirculating with a high flow rate.

I start slow, and then increase it after a while (after the grain bed settles a little).
 
I agree with what walker is saying, bring the speed up as the filter sets. Don't start all out or you'll just be making a brick.
 
Don't you end up boiling during that period of slow flow rate? About how long do you think it takes you to form a stable grain bed so you're able to ramp up the flow rate? Lastly, what average flow rates do you think you recirculate at?

Thanks guys - very informative!
 
Don't you end up boiling during that period of slow flow rate? About how long do you think it takes you to form a stable grain bed so you're able to ramp up the flow rate? Lastly, what average flow rates do you think you recirculate at?

Thanks guys - very informative!

I am a HERMS brewer, so I don't have to worry about the boiling problem. I was just giving advice about running the pump wide open at first. That part is not specific to HERMS or RIMS since it's just related to the pump and MLT.

I've never paid a lot of attention to times on things. But I would say that I don't touch the valve for the first 10 minutes of the mash, and then I start opening it up a little more at a time until I get it maybe 2/3 open. I never run it completely open. There's no need for me to do it.
 
Here is a graph of the temp inside my RIMs tube when I shut off the flow completely (several times). This was an experiment to see how quickly the system would stop an over shoot in case of a stuck mash.

I'm using a BCS in PID mode, but you can see the wort never came close to boiling temps.

RIMS_Heater1.JPG
 
I don't use a RIMS system, but it would appear to me that you should leave your heater off until you get enough flow. Maybe wait 5 minutes and gradually get flow through the mash before you turn it on?
 
Here is a graph of the temp inside my RIMs tube when I shut off the flow completely (several times). This was an experiment to see how quickly the system would stop an over shoot in case of a stuck mash.

I'm using a BCS in PID mode, but you can see the wort never came close to boiling temps.

If I may, what kind of heating element are you using? We're using a 1500W, 120V, low density element.

I think I'd see a similar graph during our mash if we took data from the thermocouple, but it's obvious upon visual inspection that boiling is taking place. The temp on our PID reads anywhere between 148 and 165, but if you watch the clear tubing on the outlet, you can see a lot of air escaping where none came in on the inlet. I think the wort gets mixed quickly enough to bring the temp down before it hits the thermocouple, but there is definitely boiling taking place directly on the heating element surface. I've seen the problem while testing with water, as well, at max flow rate (about 16 gpm).

Maybe I'm just overthinking this - it just seems that my efficiency would suffer if I was killing off enzymes that are in contact with the heating element when it fires, and I'd prefer not to (the last mash/first batch on this guy was messed up in other ways, so we didn't take an efficiency reading this time around).

What would you guys estimate is your max flow rate?
 
I have no idea what flow I'm getting, but I can tell you without a doubt that I can set the PID to 100% on manual with a 5500 W element and not boil pure water when I'm recirculating at full speed. I do this when I'm heating up my clean up water. On the other hand, if I recirculate too slowly during a mash I also get bubbles coming out the return tube while my PID reads 150ish. That's what's making me think that you're recirculating too slowly.

As far as flow rates, I would propose that there is a flaw in your overall design that is limiting your flow. At full speed you shouldn't be able to boil water with a 1500 W element if your PID is reading below 180 I wouldn't think. Look for obvious restrictionsin your connections, like places where teflon tape might have slipped out during assembly.
 
Just wanted to post an update to this thread:

We actually found out we were getting a slow flow rate due to some issues with our pump inlet. We increased the flow to the pump, and are actually getting a very smooth operation going now with no boiling whatsoever! The PID and RIMS tube are maintaining temperature very well throughout the mash, and it clears the wort very well.

The only issue I have (and it may be a non-issue) is that the flow rate is pretty fast, and the mash tends to foam with the spray from our diffuser/sprinkler-head type thing. I'm under the impression we should be more gentle with the grain bed, but I can't imagine disturbing the top is really affecting the bottom any, given that the whole grain bed is about 10-15" tall (13 lbs of grain in a 10gal cooler).
 
We actually found out we were getting a slow flow rate due to some issues with our pump inlet. We increased the flow to the pump

<snip>

The only issue I have (and it may be a non-issue) is that the flow rate is pretty fast, and the mash tends to foam with the spray from our diffuser/sprinkler-head type thing.

Maybe I am reading too much into this, but do you NOT have a ball valve on the output of your pump?

Your comments lead me to believe that you might have been trying to control flow by adjusting the ball valve on the MLT output and then just letting the pump go free.... and now you have changed things so that you are opening the MLT ball valve all the way.

You should have a valve on the output of the pump to control flow. This would allow you to have a more gently return of wort to the MLT during circulation.
 
We do have a ball valve on the output & we've been running it fast. I'm worried about slowing it down and getting the boil problem again. We'll test that soon, but the group I brew with and I are generally around 4-5 beers in by that time, so our focus is not great.

We always had the ball valve open on the MLT out, we just had the pump positioned too low and had too small an inlet hose for our setup. Raising the pump and putting a larger ID hose on the inlet helped a lot. One of the others is the pump expert, so I'm not super-clear on the details, but apparently the flow rate was severely depressed earlier because of the head pressure the pump was generating, based on its location and inlet.
 
As long as wort is moving at more than a trickle, it won't boil. I preheat to say 164, then adjust my set temp to 152, close the valve to stop flow and dough in. During this time the RIMS tube is still in the low 160's so it won't turn on. Once doughed in, I slowly open the valve. After 2 or 3 minutes I have the pump wide open but I don't think I am using a pump as powerful as yours. It takes about 6 or 7 minutes after dough in for the mash to settle at 152 and then the BCS starts to fire the element.

Linc
 
Yeah, I'll give it a try slowing it down next time. Though, other than disturbing the top of the grain bed, we haven't had any issues with stuck mashes at that flow rate or anything, so that's good.

I'll work on seeing how slow we can get it, but as of now I'm not really seeing any problems, so I'm happy. :mug:
 
...I've set up an electric brewery using RIMS, with a 1" stainless tube containing a 1500W/120V, low density heating element under PID control with the thermocouple in the same tube on the output side...

I am probably way off mark with this but; Most RIMS tubes I have seen are at least 1.5" if not 2", maybe there is something in the smaller pipe diameter that makes the boiling problem worse.
 
I am probably way off mark with this but; Most RIMS tubes I have seen are at least 1.5" if not 2", maybe there is something in the smaller pipe diameter that makes the boiling problem worse.

I think you are probably correct.
Below is an experiment I did with a 2" RIMs tube and a BCS control.
Where the temperature spikes in the graph, I closed the valve on the output of my pump to simulate a stuck mash. You can see that the temp spiked before it leveled back out to the setpoint temp (157f) but got no where near boiling. I did the same test several times as the input temp raised to see how it would respond.

A PID does not constantly monitor the temp. It measures the temp, calculates and executes a correction, then measures again. If there is not enough "buffer", the wort "could" boil during the "correction" before the next measurement.

In my experiment, I think the volume of the RIMs tube provided the buffer needed for the controller to respond before the temp got to far above set temp.

RIMS_Heater1.JPG
 
That makes sense to me, too. It'd be an easy test. With so little volume of wort in the heating chamber, I'm sure any lag in the power on/off cycle could pretty quickly heat everything.

I think we have some 1-1.5" adapters sitting around - I'll give it a try when I get a chance. A larger tube would actually be pretty nice, since I could use the ultra low density element I have (it's a 1" element, but it's bent 180 degrees, so it doesn't fit in a 1" tube).
 
Back
Top