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Old 12-17-2010, 06:13 PM   #1
LordUlrich
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Default Portable electric AG system

I am attempting to build an electric rims system for my mash. My design goals are:
• Use as much of my existing equipment as possible (I like my mash tun , rectangular Colman cooler)
• Be as compact and portable as possible (so I can take it with me and brew off site, I drive a Malibu)
• Use 120v – I will most likely be moving in less than a year, but for now I have two 20A GFI circuits I can dedicate while mashing (they are in the same box, so no need to run extension cords) I also have another 20A circuit with basically noting in it
I would prefer to be able to heat my hot water “on-demand” and therefore eliminating my HLT (both space and more equipment.
Here are my designs thus far:
My original design:
The long horizontal tube contains 2 heater elements (one from each end), I plan to have one on a controller, and the 2nd is on a switch (it is an auxiliary to make steps faster and for heating sparge water)

http://picasaweb.google.com/lh/photo...eat=directlink

My preferred design:
I think the pump will run better, and I won’t need to have as much fluid in the mash tun to keep head on the pump, but it will make step mashing harder as I cannot use the “Auxiliary” element for heating the mash

http://picasaweb.google.com/lh/photo...eat=directlink

Based on my calculations (using a spreadsheet I found in this forum) I should be able to get sparge water at just less than 1qt per minute up to 170 F (.87 qt/min using 2 2000w element, or .75 qt/min using a 2000w and a 1500w).
This is too close for my likeing (perhaps the engineer in me) I would like to be able to find a way to improve the heating power just a little bit. Any ideas?

On the other side of design, I am considering using either a Love TS2 temperature controller or an Auber PID (the little one). I vaguely understand the difference, but is there a real difference from a practical standpoint. What I see as differences is
Love:
• Simple concept (if temp is low, turn on heat, when it gets to set point, turn off)
• Built in relay (no SSR as long as I use a 1500 w element)
• Probe/thermowell is cheaper(almost half the price)
Auber:
• Contains logic to prevent overshooting the set temp (is this really a big difference when dealing with the thermal masses involved?)
• Output is just a control, and a SSR with heat sink will be needed

Am I missing something here? Or are they essentaly the same except the need for a SSR (for this situation).

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Old 12-26-2010, 07:03 PM   #2
jmer1234
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With the masses we are talking about, combined with the flow rate, I feel that a pid is necessary. With a simple love, probe placement will be critical. If the element is simply on, and dumping hot water onto the top of the grain bed, it may take a while for the wort coming out of the bottom of the grain bed to begin to reflect the difference in temperature. By the time the system detects that the mash has reached the desired temperature, there is a good chance that there will be an excess of hot water that has been pumped to the top of the grain bed and is still working its way through the mash, heating it up more. This is the same concept as "carry over heat" in BBQ-ing or roasting, where you want to remove the meat from the oven when it is still 5 - 10 degrees below your target temperature, cover it with aluminum foil and allow the heat at the surface of the meat to continue to penetrate into the meat.

A pid overcomes this by easing into the target temperature, so that the chances of dramatically overshooting are reduced, and fine-tunable.

Edit: A love controller is probably fine for the hlt and boil kettle, since there is no grain bed thermal mass, and flow is unrestricted.

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Old 12-26-2010, 07:27 PM   #3
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As I look at your design more, I am liking your idea for the heat on demand water supply. I would suggest, though, that you independently switch both heater elements. You can use both when adding water to the system, but I predict that during recirculation, the first rims tube will form a "backwater" for lack of a better description, and begin to boil and produce steam if you can not turn it off independently, forcing all of the water out of the tube, and potentially causing scorching and a dry element situation. I know that I initially had my rims tube mounted vertically with the element at the top, and had scorching around the first 2 inches of the element since there was nowhere for steam to escape. I now run horizontally with no problems.

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Old 12-27-2010, 03:39 PM   #4
LordUlrich
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I guess forgot to include this, my plan was to either:
Switch the first element manually (it runs full power while spargeing) or
A switch that lets me select between controlling just the second or both elements.
Another question

On another forum somebody brought up a concern about the ability to over pressure the pump housing if the valve out of the pump is not closed. To prevent this i could put a check valve after the pump. I guess my question is how will a march pump respond to flow in reverse of the direction it is intended. as i have it IF the pump will allow flow in reverse the water will just flow into bottom of the mash tun (which could be used in an emergency to fix a stuck sparge). So can i run water in reverse though a march pump?

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Old 12-28-2010, 12:06 PM   #5
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Have a look at my small system, the first post in the thread in my signature. The whole rig is 20"x12" on the ground and can be run on 120V circuits.

I would use the kettle as a pseudo-RIMS and save yourself the extra complexity.

Joshua

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Old 12-29-2010, 03:54 AM   #6
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Interesting. I have never thought about trying to run fluid in reverse through a march pump. I have not disassembled the head, but since it is a magnetically impelled pump mechanism, I would not expect to do any damage to the motor. Not sure about the actual pump head mechanism. I am not a mechanical engineer by any stretch of the imagination, but the pump head is cheap enough to warrant an experiment, in my opinion.

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