HERMS Build Advice

I am Building a HERMS with a 3500W 240V element. My vessel is a 2 gal igloo cooler. I went to HD today to buy the copper tubing for the HEX and wasn't sure what to get. I was looking to get Type L tubing. They have 1/2 OD which takes a 3/8 copper plumbing fitting or they have 5/8 OD which takes the regular 1/2 copper plumbing fitting.

I would like to use the 5/8 OD tubing but maybe the size is overkill. My concern would be flow rate but not having used a HERMS system before I don't know if the difference between the 1/2 and 5/8 really means anything.

Also my cooler is 8" diameter at the top but it has these ribs on the inside. The best I could measure is that the diameter at the bottom is about 6.75" between the ribs. Would the 5/8 tubing be able to bend in that tight of radius? Below is picture of my cooler.

In heat exchangers, surface area matters. So go for the biggest OD you can (manage to bend).

uhg, surface are is not all that matters.

It is the surface area to volume ratio. Let me illustrate, a piece of tubing with a 2 inch diameter 6" long will not cool the liquid as well as a 3/8" pipe 6" long. To put it simply, the heat does not have enough time to penetrate into the fluid in the center of the pipe and therefor is not cooled.

I use a RIMS but, I would use 3/8" tubing. If you need more flow make 2 or more circuits and plumb them in parallel. You will be very happy with the results and it will be cheaper.

FWIW...

My old HERMS used 25' of 1/2" OD copper coil...

IT WAS PLENTY

Look, you arent trying to win a race when you recirculate, your flow isnt THAT fast. You have plenty of length and surface area with the coil specified above to meet your requirements. Trust me.

The Pol said:

FWIW...

My old HERMS used 25' of 1/2" OD copper coil...

IT WAS PLENTY

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Meh, real men use RIMS.......

CodeRage said:

Meh, real men use RIMS.......

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Which is why the new rig will be

Thanks for the advice guys. I installed the heater element last night. I put a bead of silicone on the bottom and let sit overnight. I leak tested when I got home today and no looks so I'm stoked about that.

I went with 20' 3/8 because I didn't think I could get the 1/2 inch bent in tight enough radius to fit in the cooler. I got a 5.5" vent pipe at Lowes to bend the tubing around and it worked out to be perfect. My coils just fit inside the ribs inside my cooler. I got most of the fittings sweated on now I am just waiting for my thermowells before I sweat the last few fittings. I just need to cut some holes in the lid or make wood lid out of some scrap plywood I got laying around.

Looks nice! The real leak test will be at operating temp, that is when the inner liner starts to expand... a lot, and can create leaks.

Glad to see someone else is going with a seperate Herms Hex! I am in the middle of building my stand/rig. I have the basic rig built and used it last weekend, will try to get some pics up of it later this week. I am planning the same thing with a hex. I currently have a 5 gallon cooler, now im wondering if its too big, but i think it should be ok. I am pretty much following This build as a guilde. But i plan to build the controller onto the cooler as i believe The Pol did. At least i think it was him, i have looked at so many dam rigs lately. I am also planning on incorporating a stirring motor to prevent stratification of the water.

Proetus said:

Glad to see someone else is going with a seperate Herms Hex! I am in the middle of building my stand/rig. I have the basic rig built and used it last weekend, will try to get some pics up of it later this week. I am planning the same thing with a hex. I currently have a 5 gallon cooler, now im wondering if its too big, but i think it should be ok. I am pretty much following This build as a guilde. But i plan to build the controller onto the cooler as i believe The Pol did. At least i think it was him, i have looked at so many dam rigs lately. I am also planning on incorporating a stirring motor to prevent stratification of the water.

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Yeah I had the A419 mounted to the HLT HERMS HEX... now Yooper has it

I chose the smaller cooler becuase I was limited on the size of my element (3500W). I only have a spare 20 A 240V breaker for my garage. So I thought if I could fit the 3500W element in the smallest volume It would be easier to heat 2 gal than 5 or 6 gal with the same 3500W element. Your should be ok with the 5 gal. Many guys have them and they work fine. I plan on initially using a aquarium pump to aerate the HERMS tank. I may go to agitator but we will see how aerator does. I will update this once I get it up and running and let you know who it works.

I am going to use a 1500 watt 120v element. Might take a little more time to heat up, but it can be done while heating my sparge water and all setting up. The water isn't going anywhere once its in there so once its heating its all set for the most part. Good luck with your build look forward to more pics.

Excellent write up regarding heat exchange theory can be found here

http://www.google.se/url?sa=t&source=web&ct=res&cd=1&ved=0CA0QFjAA&url=https%3A%2F%2Fwww.u-cursos.cl%2Fingenieria%2F2004%2F1%2FME43B%2F1%2Fmaterial_docente%2Fobjeto%2F27858&ei=YfFSS7C_Fs_D-Qb8qLHUCA&usg=AFQjCNGe3KMQQLxBRkIjrreUt0kwwbhITA&sig2=r3RGDDaoMDGnFE9wSOhRhA

rockytoptim said:

I plan on initially using a aquarium pump to aerate the HERMS tank. I may go to agitator but we will see how aerator does. I will update this once I get it up and running and let you know who it works.

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I'm using an aquarium pump in my heat exchanger and it works just fine. It's pretty much the same as yours: 2 gallon cooler, 20' of 3/8" copper and a 1500W/120V heater element.

Flow rate isn't an issue at all with the 3/8" tubing, I seem to be more limited by my grain bed than anything else.

Proetus said:

Glad to see someone else is going with a seperate Herms Hex! I am in the middle of building my stand/rig. I have the basic rig built and used it last weekend, will try to get some pics up of it later this week. I am planning the same thing with a hex. I currently have a 5 gallon cooler, now im wondering if its too big, but i think it should be ok. I am pretty much following This build as a guilde. But i plan to build the controller onto the cooler as i believe The Pol did. At least i think it was him, i have looked at so many dam rigs lately. I am also planning on incorporating a stirring motor to prevent stratification of the water.

Click to expand...

Currently I have a HLT HEX but am also looking to do a separate HEX. For the chamber though I was looking to cut a 5 gal sanke in half (or so). I'd like to have the coil enter and exit through the sides though and not out of the top. I'm not sure if I can coil 1/2" stainless to a diameter of 7" though.