need advice on stir paddle for HLT

I have an electric HLT with a 4500W 220V heating element. The element is installed in the side of a keggle about 6" off the bottom. The first time I used it I was really surprised about how well the water separated into layers. Natural convection above the element kept everything really well mixed, but I was amazed that the bottom section of the water didn't get heated at all.

So I need to stir it somehow, and since I'm automating nearly everything else I figure I might as well automate this too. I have a old cordless drill and a 12V power supply that should do the trick, and I can add speed control if I want to get fancy. I've also been looking for a cheap ice cream maker.

However, what do you guys use as a paddle? I'd like to make something simple and cheap, but I'm not sure about the best place to start.

I used a domestic water pump. I think it is rated to 240 degrees. The pic is the bottom of the HLT. My output and inlet is all through one fitting on the bottom of the keg. The pump draws off the bottom and returns through a fitting on the top. I have a 90 fitting on the inside of the keg that sort of whirlpools the return. This works great for my HERMS coil.

That's a solid plan, but I'd rather not purchase another pump just to circulate my HLT. I have a 2-tier setup with gravity feeding from the HLT into my mash tun. That's why I'm leaning toward some sort of in-pot agitation.

I've read that people use a fish tank air pump to bubble and cause agitation. Does that really work well enough to keep a keggle mixed?

This is the only way I have ever stirred my HLT so I cannot say how other methods may work. I picked up the pump on e-bay for about $60. I can tell you that with this system, what I set my controller at is the temp I get out. It works great!

I started with a different pump that wasnt handling the temps very well. When I was planning this I posted a thread that someone had mentioned using an aquarium pump.

https://www.homebrewtalk.com/f51/hlt-stirring-159623/

Yah, I saw that. I was hoping that someone who commented about the aquarium pump stirring might also respond here.

I do have a pump sitting around that I bought for aeration but haven't used very much. I tend to just let it splash into my fermenter when it comes out of the CFC. Then I shake the living daylights out of it. I tried it both ways (air pump and shaking) and didn't see an appreciable difference, so I gave up on the pump. If it works, that would be a cheap solution to the stirring since I already have the hardware sitting around.

bblack7489 said:

However, what do you guys use as a paddle? I'd like to make something simple and cheap, but I'm not sure about the best place to start.

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mcmaster: 34935K66
and whatever motor you have to make it go round.

Well if you have the pump, It wouldnt take much to test it. I had a hard time believing that the little stream of bubbles that those pumps put out would do much but I may be wrong. Give it a try...I would be curious to find out how it works.

I may give it a test with the aquarium bubbler tonight or tomorrow night. I need to test my seals on the thermocouple mounting port that I made, and I might as well test the plumbing on my filter system while I'm at it. I'll let you know what I find.

Bjornbrewer said:

mcmaster: 34935K66

Click to expand...

Does the 2.5" paddle really have enough umph to get enough mixing to stir a keggle? I guess that if the stream of bubbles from an aquarium pump will stir it, then this will definitely do the trick.

A simple plastic paint stirrer works wonders and it's designed to work with a drill, cost about 4.00.http://image.ec21.com/image/terryngb/OF0009422936_3/Sell_stirrer.jpg

What's wrong with a couple pieces of 2" x 3" x 1/32" thick stainless shim stock screwed to a piece of stainless bar stock? Add a little gear motor and it works for me. No pumps or whistles needed.

The paint stirrer also does a great job of stirring the mash keeping the temps the same

Alright, so I ran a test tonight. It's far from definitive. I spent 6-ish years in academia doing research, so it pains me to say that I can't report and confirm a solid conclusion; however here it goes.

I filled up my keggle with 10 gallons of tap water at about 78F (testing my filtering system for leaks...none found...but I did find that barbed fittings work really well on half inch hose under tap pressure...so well that when I slipped them on for a simple test of the system, not only did they not leak, but they also didn't let me pull them off...I had to cut them off and waste ~3" of my 10' hose...but I digress...). I then plugged in my 4500W 220V element that is about 8" off the bottom. I used a bread tie to wire a 3/4" nut to the end of the air line from my aquarium pump, and I lowered that to the bottom of my pot to provide agitation. I put a kitchen meat thermometer in the pot, submerged about 2" and walked away for about 30 min.

When I came back the digital part of my thermometer had fallen into the pot, meaning that it was useless. Since I had recently installed a thermocouple near the bottom of my keggle, I decided it was time to test it. I hooked up my temperature control board to it (it's based on a PIC16Fxxxx and a MAX6674 thermocouple to SPI chip) and I got a reading of 138 at the bottom of the pot. In an attempt to test my thermocouple system as well, I used an analog thermometer to test the temperature at the top of the water column, and I read 180F.

I then stirred the pot vigorously using a mash paddle.

I took the temperature again at both places. The temperature at the thermocouple was bouncing back and forth between 140 and 142. The temperature at the analog thermometer was ~180.

I think I have learned two pretty important things here. The first is that either my thermocouple / MAX6674 / PIC system is completely screwed up or my analog thermometer is messed up. The second is that from what I can tell, a bubbler actually does provide enough turbulence to induce enough current to keep a HLT mixed. It's definitely not conclusive, but it's what my time, wife, alcohol consumption and 6-week old child will allow me to produce this evening. I would be really interested to hear of other accounts of using an aquarium pump to mix a large vessel to keep it at a homogeneous temperature.

bblack7489 said:

Does the 2.5" paddle really have enough umph to get enough mixing to stir a keggle? I guess that if the stream of bubbles from an aquarium pump will stir it, then this will definitely do the trick.

Click to expand...

I use one in my 10g cooler HLT and it works fine.