How fast will a RIMS system change temps?

Is it better to have a gas fired burner for large temperature changes in a step mash or will a RIMS system do good on its own?

If I want a faster step, I'll supplement my electric with an infusion of near boiling water. But really it depends on your system. A longer RIMS tube and a long element that's ULWD will give you faster steps without scorching.

Thanks for responding. So that I am clear on this. When you have a large temp change the PID doesn't just turn the element on all the time, but cycles the element to prevent scorching.

jbb77 said:

Thanks for responding. So that I am clear on this. When you have a large temp change the PID doesn't just turn the element on all the time, but cycles the element to prevent scorching.

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Not quite. The PID cycles on and off very frequently to effectively heat at less than 100%, but it does so as a function of maintaining temperature. There is no guarantee that it will not stay on at 100% for a while if that is what its programming tells it to do as part of maintaining temperature. Using a lower watt density element is what makes scorching less likely. So a ULWD element is best. Another approach is to run a 240v element at 120v, which reduces the watt density to 1/4 of what it would be at 240v.

jbb77 said:

Is it better to have a gas fired burner for large temperature changes in a step mash or will a RIMS system do good on its own?

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I use my RIMS tube to change temperatures and it works fine.

Even the big guys don't change their mash temperature instantly.

On my RIMS - a 4500W 240V element running on 120V (IIRC) and running in a RIMS tube slightly longer than the element by maybe 4", it will raise a mash consisting of 22 - 27 pounds of grain mixed with water at 1.25 qt/pound ratio a little slower than a degree per minute.

To raise mash temps from 150f to 168f usually takes 20-30 minutes - about the time it takes to get my sparge water to 170f...

atoughram said:

On my RIMS - a 4500W 240V element running on 120V (IIRC) and running in a RIMS tube slightly longer than the element by maybe 4", it will raise a mash consisting of 22 - 27 pounds of grain mixed with water at 1.25 qt/pound ratio a little slower than a degree per minute.

To raise mash temps from 150f to 168f usually takes 20-30 minutes - about the time it takes to get my sparge water to 170f...

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Your long rise time is because you are only getting 1125 watts out of your 4500 watt element. Run at full 4500 watts of power and your rise time from 150F to 168F should be 5 - 7 minutes. One degree every 1/2 minute would be pretty good.

My only caution in using a larger wattage element to step quickly is in regard to the local temp of the wort going past the element. I have a 5500W element that I can switch between 120VAC/240VAC so that I can quickly heat up water to strike temps but then step and maintain temps at 120V/1375W. If I try to step or maintain wort at mash temperatures using the higher power setting I will locally boil the wort around the element since the temp rise at the element is huge. The case may not be the same at 4500W, I'd have to dig out my heat transfer books again but my guess is that it is.

My step time from 140F to 150F mash temps with mash thickness of 1.5qt/lb and about 8 gallons of water takes less than 10 minutes and I've never had a problem, just make sure you're looking at the mash temp and not the outlet temp of the RIMS tube.

Smelson said:

My only caution in using a larger wattage element to step quickly is in regard to the local temp of the wort going past the element. I have a 5500W element that I can switch between 120VAC/240VAC so that I can quickly heat up water to strike temps but then step and maintain temps at 120V/1375W. If I try to step or maintain wort at mash temperatures using the higher power setting I will locally boil the wort around the element since the temp rise at the element is huge. The case may not be the same at 4500W, I'd have to dig out my heat transfer books again but my guess is that it is.

My step time from 140F to 150F mash temps with mash thickness of 1.5qt/lb and about 8 gallons of water takes less than 10 minutes and I've never had a problem, just make sure you're looking at the mash temp and not the outlet temp of the RIMS tube.

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I use a 5500 watt element in my RIMS tube with no problem. The trick is to move water through the RIMS fast enough to pull heat away from the element fast and to monitor the output temperature.

I have a long RIMS tube with a ULWD 4.5kW element at 240V. The temp sensor is at the exit port of the RIMS tube, which is pretty standard. I set my PID to have the exit temp of RIMs a couple of degrees higher than my desired mash temp and let it go. I try to open up the flow as fast as I think I can without compacting the grain bed (no clue if it is compacted or not).

I think the keys are the flow rate and PID settings (the P, I, and D values). If I'm trying to step from 150F to 168F, I can change the PID set point to 170F and the tube heats quickly. i don't think the PID hits 100% duty cycle, but if it does, it is only for a few seconds. After the RIMS is at the new set point, I open up the valve on the exit of my pump to increase the flow rate. Then I just have to wait for 170F wort from the RIMS to raise the MLT temp to 168F, and then I change the PID to 168F.

kenh said:

Your long rise time is because you are only getting 1125 watts out of your 4500 watt element. Run at full 4500 watts of power and your rise time from 150F to 168F should be 5 - 7 minutes. One degree every 1/2 minute would be pretty good.

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I'm ok with the rise time - it won’t denature the enzymes that way. Now if I were going to do a protein rest before the saccharification rest the long rise time might be a bit annoying, but I don’t typically use a lot of adjuncts and use highly modified malt.

Interesting thought though, if I moved my temperature probe to the outlet of the RIMS tube (Planned) and stepped up to 240VAC, I could quicken the rise times without scorching. Hmm... I've answered my own question in a different thread...

I have a 2000 LWD 120 volt element and I can rise the temp 1 degree every 45 seconds for a 10 gallon batch. My mash tun is insulated, this does make a difference.

cfrazier77 said:

I have a 2000 LWD 120 volt element and I can rise the temp 1 degree every 45 seconds for a 10 gallon batch. My mash tun is insulated, this does make a difference.

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I also have an insulated MT - it's a hot water tank blanket.

atoughram said:

I also have an insulated MT - it's a hot water tank blanket.

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I am using a keggle and at first I was not able to raise temps very quickly and had a hard time holding a temp without a lot of fluctuations. I wrapped it with reflex insulation, bubble wrap with an aluminum type covering, put it in the bottom, and put a 2" foam board on top as a cover. Big change.

Me happy now.:fro:

cfrazier77 said:

I am using a keggle and at first I was not able to raise temps very quickly and had a hard time holding a temp without a lot of fluctuations. I wrapped it with reflex insulation, bubble wrap with an aluminum type covering, put it in the bottom, and put a 2" foam board on top as a cover. Big change.

Me happy now.:fro:

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The foam board on top probably helped more than the insulation on the sides and Here a link to an article that helps explain why.
http://goo.gl/nqWQDi

If I read the article right the biggest heat loss is from running uncovered and that makes since. I mash in a 10 gallon GOTT cooler and use a RIMS tube to maintain temperature.

Very interesting, I did notice a difference with the side and bottom wrap when the top had not been made yet. This was just a water test. But, your data explains why the cover made such a difference.

Thank you fellow brewer, have a cold homebrew on me!