HERMS design question

Perhaps this is a goofy question or answered elsewhere, but is there any reason why one couldn't install a HERMS coil in a vessel smaller than a keggle/boil kettle? Wouldn't it be easier for the heating element to maintain the desired temp if the HERMS coil was installed in a one gallon pot?

I was recently considering turning my old IC into a HERMS coil, and at first glance this seems like the cheapest/simplest way to do it.

Anyone try this?

Thanks for the input!

No reason not to. Folks have done it before. I have seen a few conry's used as the heat exchanger.

kinda like this?

see my post here...

Mine looks like Audger's only I use a 2gallon water cooler. Google 'Rubbermaid Victory' if you're unsure what I mean. The heater element is installed vertically in the bottom, and my herms coil is attached to the lid. It was cheap, easy, works great, and can ramp temps fairly quickly.

As long as the coil is covered, it can be in any size vessel. It's just easier for me to have it in my (bigger) HLT since I have hot water for the sparge anyway, heating up my HERMS coil at the same time.

Yooper said:

As long as the coil is covered, it can be in any size vessel. It's just easier for me to have it in my (bigger) HLT since I have hot water for the sparge anyway, heating up my HERMS coil at the same time.

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+1
Why have a separate vessel for the HEX coil when you can just drop it in your HLT? Fewer vessels and more efficient since you have to heat sparge water anyway. A smaller vessel would enable faster temp changes for step mashing or bringing to mash-out, but that's a double edged sword. The fact that my HLT is a little slow to change temp makes it much easier to hit and hold mash temps.

scottland said:

Mine looks like Audger's only I use a 2gallon water cooler. Google 'Rubbermaid Victory' if you're unsure what I mean. The heater element is installed vertically in the bottom, and my herms coil is attached to the lid. It was cheap, easy, works great, and can ramp temps fairly quickly.

Click to expand...

Sounds like we basically have the same design. You can see pics of mine from back when I was constructing it here.

Like the OP was saying, the smaller thermal mass allows the system to react quicker, so step mashes work better than with a combination HLT/HEX. That said, they still don't respond as quick as a direct fired MT. Cost-wise a separate HEX is slightly more expensive than a combination HLT/HEX because you'll have two vessels and you'll want to be able to control both of them at the same time (heating sparge water in your HLT while also maintaining or increasing mash temps in the HEX). Most people use some type of controller for this. That could mean two temp controllers versus one for a combo HLT/HEX.

microbusbrewery said:

Sounds like we basically have the same design. You can see pics of mine from back when I was constructing it here.

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Ya, mine looks just like that, only I jammed twice as much copper in mine (20'). Those are compression fittings on the copper that seal against the tee and the elbow, the lid just sits freely in between. My temp probe threads into the tee.

JuanMoore said:

+1
Why have a separate vessel for the HEX coil when you can just drop it in your HLT?

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because when you are heating the wort running thru the HEX coil, you *should* be taking the temp reading at the exit of the coil to make sure you arent scorching it. reading it from this point means your controller is ignoring the temperature of your HLT itself and only concentrating on the wort temperature. that, coupled with the greather themal mass of the HLT, means that it is probably going to overshoot the HLT temp quite a bit.

so if your cold-side of the HEX is set to 169*-170* for mashout, the hot-side of the HEX is probably closer to 190* or 200* because of the temp delta and the logical distance between the controlling temperature probe and the heat source (the way to avoid the shorfalls of having such a distance between temp probe and heat source is to use a much longer piece of copper pipe to minimize the temp delta, which adds considerable costs of materials).
if your HLT is acting as the hot-side of the exchanger, you arent going to be able to sparge with 200* water. you would either need to pump cold water into it, or you wouldnt be able to mashout before sparging.

also for fly sparging- you can have the HLT water set at mashout temp, and use the HEX to preheat the runoff to reach a boil faster. my HEX, depending on flow rate, will heat the wort by 5-10 degrees in one pass thru it. that shaves 25+% off the time to reach a boil, and uses less propane. you cant do that with one vessel.

I always figured that if you want the benefits of a dedicated Herms vessel that you may as well go with a RIMS tube. Of course there are people worried about scorching and like the water buffer. If that's the case, I guess you could even jam a HEX coil into a 4" piece of pipe.

Bobby_M said:

I always figured that if you want the benefits of a dedicated Herms vessel that you may as well go with a RIMS tube.

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After scorching a mash with my RIMS tube, I was always paranoid it would happen again. It cost about $45 to build this, and the piece of mind has been well worth the $45.

audger said:

because when you are heating the wort running thru the HEX coil, you *should* be taking the temp reading at the exit of the coil to make sure you arent scorching it. reading it from this point means your controller is ignoring the temperature of your HLT itself and only concentrating on the wort temperature. that, coupled with the greather themal mass of the HLT, means that it is probably going to overshoot the HLT temp quite a bit.

Click to expand...

I see what you're saying, and can see why you would prefer a separate vessel for your set-up. A lot of the pros/cons depend on how the system is set up and how it's used. The way I set-up and run my HERMS it's actually much easier to prevent temp overshoots with a single vessel and larger thermal mass than my previous set-up which was closer to what you're describing. The only advantage a separate vessel would give me is faster step changes and reaching mash-out faster. Since I rarely do step mashes, and often skip doing a mash-out, it doesn't make any sense for me. My burner puts out so much heat that the time difference would be minimal anyway.

FWIW the controller for my HLT burner reads the water temp inside the HLT. I have a second controller measuring the HEX output and controlling the recirc pump. I'm able to easily hit and hold any desired temp with virtually no effort. It works great for me and my process, but I realize it wouldn't work well for everyone.

yea, the "which is better" question really depends on how you built your system and how you use it. with what i had on hand, it didnt cost me hardly anything to add an extra heating vessel. i wanted to do step mashing and be able to control the entire mash temperature as fast as possible (and i like building stuff), so i settled on this design. if you were going for simpler or cheaper, or tailored to a different process, i agree there are probably better methods.

I have a second controller measuring the HEX output and controlling the recirc pump.

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im interested in how this is setup... is it a 'variable rate' type of control somehow, or simple on/off ?

audger said:

With what i had on hand, it didnt cost me hardly anything to add an extra heating vessel

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This is the reason I built a seperate HEX. As I said, I started off with a RIMS tube, decided I wanted to do HERMS instead. 1500w element, 20' of copper, $8 2 gallon cooler, and a couple compression fittings came to about $45. I don't have a dedicated HLT, so this was definitely the cheapest route for me.

audger said:

im interested in how this is setup... is it a 'variable rate' type of control somehow, or simple on/off ?

Click to expand...

Just a simple on/off using cheap aquarium temp controllers, the flow is controlled manually with a ball valve. I have thermowells that can read the center of the mash, the MLT exit, the HEX output, and the center of the HLT, so depending on where I put each of the controller probes I have a lot of options for configuration and control. I mainly started using the system this way because I couldn't yet afford to automate the burner, and this acted as a safeguard against overshooting temps. Now that my system and process is pretty much dialed in, the pump usually comes on once the HLT gets up to temp and stays on throughout the mash. It's still nice to know that it will shut down if there's a malfunction that causes temps to get out of range.

Here's what my ghetto control panel looks like-