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-   -   Anybody else scorch wort with a RIMS element? (http://www.homebrewtalk.com/f170/anybody-else-scorch-wort-rims-element-247009/)

wardenwheat 05-22-2011 02:41 AM

Anybody else scorch wort with a RIMS element?
 
In 5 batches with my 120 volt - 1500 watt element, I've scorched two batches of Hefe. I don't know why that is. Seems to work with all the other beers, but I do an acid rest at 110 then run it up to sacc rest temps. I'm going to quit using it to step my temps and just hold from now on. Any suggestions???

samc 05-22-2011 03:00 AM

Lower flow due to the wheat? Use rice hulls.

trigger 05-22-2011 04:26 AM

There's been some discussion recently on this topic. I've tried protein rests, adding water salts to "salt out" the protein that builds up on the element, and not heating for the first 10-15 mins of recirculation. All of them failed. My solution has been to increase wort velocity across the element so that it is pulling heat away before the element can create those little pockets of steam that allow the buildup to burn. Rice hulls will help with keeping the mash from sticking when recirculating fast. Other than that I haven't been able to prevent the buildup that's causing the problem in the first place.

wardenwheat 05-22-2011 01:47 PM

I've been using a thin mash - 5 gallons to 10 lbs of grain. I do an acid rest for 15 mins. Start the pump, (which is running about 1.5 to 2 gallons a minute) and let it run for another 15 mins and then start the heat. Even then it seems to want to scorch. I'm just going to use my element for keeping the sacc rest temp and for warming my strike water. Very dissapointed......

ScubaSteve 05-22-2011 04:29 PM

When you say scorch, what do you mean? Does the wort have a burnt taste? You WILL get some buildup on the element, and that's normal. Just wipe it off with a sponge after each brew.

Maybe you should get a low density element....it'll be folded over and have more surface area....so the heat at the element will be less intense but still transfer just as much energy.

trigger 05-22-2011 09:49 PM

Quote:

Originally Posted by ScubaSteve (Post 2944395)
When you say scorch, what do you mean? Does the wort have a burnt taste? You WILL get some buildup on the element, and that's normal. Just wipe it off with a sponge after each brew.

Maybe you should get a low density element....it'll be folded over and have more surface area....so the heat at the element will be less intense but still transfer just as much energy.

Yea, I get the buildup with all barley beers, but when I use more than 30%ish wheat or rye the buildup is so thick that it insulates the element. If the flow isn't fast enough the buildup literally burns on the element, like the inside of a dirty oven. I've probably had this happen in about 8 batches of beer, a couple were so bad I ended up dumping them. The bad batches literally tasted like burnt bacon. The not so bad batches had a smokey flavor. The really bad part is that if I didn't get every last little bit of burnt stuff off it would catalyze the same thing in all barley batches. I tainted a batch of american pils by not cleaning the element completely.

wardenwheat 05-22-2011 10:12 PM

I have a low density element. I have to soak my element in oxyclean every time to remove any residue between brews.

shushikiary 05-23-2011 06:55 AM

I have had this exact same problem. It's definitely scorching, a nice burnt grain smell and then POP goes the element if you let it go long enough, and by pop I mean it blows my GFCI sense its resistance to ground got below 3 mega ohm (I measured it) which at 240v (what I run at) is enough to cause enough leakage current to pop to the GFCI.

I tracked the problem down to 2 issues. One is too low a flow rate, the other is flow in the RIMS tube.

Originally I had a flow switch on the output of the RIMS tube and a flow control valve. First time I scorched it would happen any time I tried to restrict the flow so I wouldnt get a stuck mash. After some thought on it I realized that if I was restricting the output of the RIMS tube you could cause some very interesting circular flow issues inside the RIMS tube which can cause scorching even at high flow rates.

So I moved the valve to the input side of the RIMS tube and made sure there was enough tubing to balance out the restricted flow into a nice constant rate after the valve before it entered the RIMS tube. This solved the first time it poped.

The second time was the same issue, but due to the restriction of my flow switch. I removed the flow switch and didnt change the flow rate, problem solved.

So the lesson here is two fold. NEVER restrict the output side of the RIMS tube, only the input side, making sure that the flow is consistent and in one direction through the entire tube (aka let there be some tubing after your flow restriction valve to even out the flow before it enters the RIMS tube). Second, try to keep your flow rate around 1 GPM or higher if you can, go as fast as you can without compacting your grain bed.

A good way to measure the flow is to put a vacuum gauge on the input of your pump, and then always make sure to have very little to no vacuum there when restricting your flow rate, this will keep you from compacting your grain.

Next, get the largest area false bottom that you can, and use rice hulls. They help, A LOT. Use 2% of grain bill weight of rice hulls, aka 10lbs grain bill, add 0.2 lbs of rice hulls. This will help you keep your recirc rate up without getting vacuum.

The combiniation of all of the above is what solved the problem for me... it also upped my efficiency by 17% (due to no longer compacting the grain bed during mash).

As a final solution to the problem I'm going to switch to a true HEX, were wort gets its heat from RIMS heated water through a wood furnace hot water HEX, that way you CANT scorch the wort even at stupid low flow rates as the flow rate through the RIMS will be held at max the pump can do and so the output temp of the RIMS will be held at what you want it to, and so any wort that goes into the HEX cannot exceed that temp. You loose a little bit of energy efficiency due to lower heat transfer, but I think it's worth it.

Walker 05-23-2011 05:11 PM

Quote:

Originally Posted by shushikiary (Post 2945908)
POP goes the element if you let it go long enough, and by pop I it blows my GFCI sense its resistance to ground got below 3 mega ohm (I measured it) which at 240v (what I run at) is enough to cause enough leakage current to pop to the GFCI.

You've lost me here shushikiary.

Resistance of "what" relative to ground?

And what leakage current are you talking about?

shushikiary 05-23-2011 05:33 PM

So both legs of the 240v element, when they are brand new, have a VERY large resistance to the metal part of the element that has the threads on it. Usually in a house because the hot water heater is tied into the copper house pipe and the copper house pipe is used for earth ground, the threaded part of the element is tried to earth ground.

My rig is setup the same way, the entire thing is grounded, and so thus in my RIMS tube when the element is threaded in the threaded part is tied to ground as well. That's the ground I was referring to, earth ground.

So after scorching has happened I re-measured the resistance of both screws on the heating element and they both (duh it's a resistor) read under 2 megaohm of resistance to the metal thread part of the element, aka earth ground.

Thus due to this reduced resistance at 240v RMS we have 1 - 2 mA RMS of current that is leaking from the hot to earth ground. Where before it was well over 200 megaohm.

Sense the GFCI operates based on measuring the current difference between current leaving and returning on both hot wires (red and black) the return current will now be off by 1 - 2 mA because that much current is going to ground now through the 1 - 2 megaohm resistance. And that's enough to pop most GFCI's.


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