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Old 10-01-2011, 08:59 PM   #1
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Default Scorching on Heating Element

For some non-conformist reason I’m doing my best to get an eMLT to work without a recirculation pump. I’ve been playing with constant slow stirring. Worked pretty well when I was using a heat plate for the heat source. I never got any scorching on the bottom of the pot, but was worried that, even with the stirring, the grain would mostly be at the bottom at a higher temperature than the rest of the mash. My latest “upgrade” has a heating element mounted horizontally in the pot about three inches from the bottom. The trouble is that I get some scorching on the element. There’s a probe mounted about a half inch away from the element to regulate it, but it’s either an on or off control, so the element has the potential to get really hot when the probe calls for heat. Works fine for maintaining temperature, but can scorch when it stays on for prolonged temperature steps.

Somewhere on this board I read about using a router speed control to regulate temperature. The idea sounded good because this way I could adjust the temperature of the element manually to prevent scorching and let the probe control the temperature of the mash. It would slow the time for a step, but prevent excessive temperature at the element.

So, I’m running some tests on it to see how hot the element gets at different settings on the controls dial. The question is how high can that get before there’s scorching? Has anyone tried this idea to prevent excessive temperatures in their RIMS tube? Even with a PID turning your element on and off, when it’s on it can get the wort and enzymes in it to temperatures higher than you’d like.

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Old 10-13-2011, 12:29 PM   #2
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Here's what I've got so far.

The controller varies the voltage. The element I’m experimenting with is 120V, 1000W and 15.6 ohms. I used V=I*R to calculate the amperage at a given voltage and P=I*I*R to calculate the corresponding wattage.

For example, on a 1 to 10 scale the controller puts out 71 volts at a setting of 8. This would mean that the power output is 330 watts and draws 4.6 amps. Since the area of the element remains the same, what the controller does is change a high-density element to low or ultra low. This should be what I need to prevent scorching, but mash steps could be too slow. I’ve seen spread sheets that can calculate heating time for a given wattage and volume. Now I have to experiment to see at what density scorching begins and what the corresponding step times would be when staying below that.

(Thanks to Walker for the formulas. Hope I used them correctly.)

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Old 10-13-2011, 12:36 PM   #3
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You know that I have no idea what you said- but I thought something was worth mentioning.

Someone on this board mentioned they have a lower-watt ULWD heating element (I think in the HLT) and that even though it heats just fine, it doesn't get that hot and they can even touch it. I have a 5500 w ULWD heating element in my BK and it gets hot, so it could be they were full of it, or it could be true. What size element is in the MLT? 1000W? Does it get hot to the touch?

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Old 10-13-2011, 01:36 PM   #4
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Does it get hot to the touch?
Hmmmm. I'll have to try . . .


. . . but why am I thinking this is kind of like telling your buddy it's OK to pee on that electric fence?
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Old 10-13-2011, 02:37 PM   #5
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I can definitely touch my element when it's on full blast (submersed in water of course!), it's a low density even. Ultralow density would be even less hot. I now have mine on during my mash and just occasionally stir (it's only on 1/20th of the time though).

If your element is a "high" density element you're going to be creating more heat per square inch of element surface, so higher chance of scorching.

Swap it for a low density and problem solved?

edit: I should also clarify that mine is a 4500watt 240v element from the hardware store, higher wattage but otherwise nothing fancy. I can heat 8 gallons from tap to 155 in about 25 minutes.

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Old 10-13-2011, 03:18 PM   #6
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I guess I am trying to figure out how you are running an element in an eMLT?
Are you placing the element below the false bottom somehow? Is the grain coming into contact with the element?

You refer to a RIMS tube and probe, but are you using these without a pump? What's the probe connected to? A PID?

I am thinking that scorching is coming from the element resting against the grains--if that's the case?

It sounds like what you want is a PWM with a dial to manually controlly input?

I just can't get a good bead on what you have going on there...

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Old 10-13-2011, 03:25 PM   #7
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I get some 'buildup' on my element but it isn't black, it's like a tan caramelized sugar.

Is yours tan colored or actually black?

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Old 10-13-2011, 03:27 PM   #8
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A high density element in the mash WILL cause scorching and will tend to get burnt grain stuck to it. Real mess.



(They work fine in the BK, though)

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