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-   -   RIMS heater boiling wort? (http://www.homebrewtalk.com/f170/rims-heater-boiling-wort-238521/)

Dimerizer 04-08-2011 10:36 PM

RIMS heater boiling wort?
 
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?

trigger 04-09-2011 04:57 AM

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.

Dimerizer 04-09-2011 03:05 PM

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?

trigger 04-09-2011 06:51 PM

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
http://i1003.photobucket.com/albums/...r/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.

Dimerizer 04-11-2011 02:39 PM

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?

Walker 04-13-2011 07:57 PM

Quote:

Originally Posted by Dimerizer (Post 2826819)
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).

trigger 04-13-2011 10:50 PM

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.

Dimerizer 04-14-2011 06:41 PM

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!

Walker 04-14-2011 07:11 PM

Quote:

Originally Posted by Dimerizer (Post 2837809)
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.

Ohio-Ed 04-15-2011 02:03 AM

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.

http://www.homebrewtalk.com/gallery/...MS_Heater1.JPG


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