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Old 08-22-2012, 09:06 PM   #1
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Default HERMS vs. "Counterflow" HERMS

I am in the process of building a new brew rig, this time going with a two-tiered HERMS (Mash tun on top).

As I build and design the system, I am considering a few problems with HERMS and trying to see if there are some viable solutions.

The main problem I can see is temperature stratification in the HLT as it is heated from the bottom. Without adequate stirring, it will continue to be a problem. As a way to combat this, I thought perhaps it would be wise to recirculate my mash through a counter flow chiller, back into the mash tun, while recirculating the hot water from the HLT through the "cold water" side of the counter flow chiller.

The advantages of this, as far as I can tell:

  1. Eliminate the temperature stratification problem as the recirculation of the HLT water would provide constant stirring
  2. Would not need to drill as many holes in the HLT
  3. Would get more utility out of the copper needed in the chiller

However, some of the disadvantages I've considered are:
  1. Would need two pumps (at present I only have one)
  2. Possibly less energy efficient (would burn more propane)

Does anyone have any experience or advice on this? Are there any advantages and/or disadvantages I have not considered? Any input would be appreciated.
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Old 08-22-2012, 09:13 PM   #2
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I'm no engineer, so this may be "out there", but I don't think it will work that well. The reason for recirculating/stirring the HLT is to avoid stratification. But sending water through the CFC to work as the HERMS may mean it's not able to hold temperature. You may find the water cooling to the mash, instead of raising/holding the mash at the HLT temperature. I hope that makes sense.

If you take the hottest water out, for example, from the bottom, the HERMS may be too warm. If you take the cooler water out from the side or top, the HERMS may not be warm enough and then the mash will "suck out" the temperature.

You want to recirculate the water in the HLT, or stir, or otherwise agitate. But the water being recirculated may not be the correct temperature is what I"m trying to say.

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Old 08-22-2012, 09:18 PM   #3
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Originally Posted by Yooper View Post
I'm no engineer, so this may be "out there", but I don't think it will work that well. The reason for recirculating/stirring the HLT is to avoid stratification. But sending water through the CFC to work as the HERMS may mean it's not able to hold temperature. You may find the water cooling to the mash, instead of raising/holding the mash at the HLT temperature. I hope that makes sense.

If you take the hottest water out, for example, from the bottom, the HERMS may be too warm. If you take the cooler water out from the side or top, the HERMS may not be warm enough and then the mash will "suck out" the temperature.

You want to recirculate the water in the HLT, or stir, or otherwise agitate. But the water being recirculated may not be the correct temperature is what I"m trying to say.
I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).
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Old 08-22-2012, 09:24 PM   #4
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I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).
I have a little stirrer with a motor on my HLT. If you don't want to have another pump to just recirculate water, something like that could work.
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Old 08-22-2012, 09:44 PM   #5
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We have done HERMS brews. We do have 2 pumps and the system is simple. We used pump the Wort into one side of a counterflow Chinchiller. We pumped hot water on the outside tube. We were able to maintain a constant temp without a problem. We use about a 5 to 10 degree difference between the HLT and the MLT as a starting guide. We recently purchased a Stout Conical HLT with HERMS but I had a tangential inlet installed so that I could "stir" the HLT water. Again, that would use the second pump. You can use a lower temp pump for the Wort as it does not get above 170 (or shouldn't).

We actually have 4 pumps but only use three. We need only one with the HERMS we have, but more pumps make it easier. We normally only move the "pump out" hoses and do not mess with the supply side. We prime all the pumps with just plain water before we brew and have lost most of our cavitaion problems by using full 1/2 inch flow on all fittings and use the short 3/4 inch silicone for the supply

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Old 08-22-2012, 09:50 PM   #6
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I failed to mention that were just put the water back into the HLT. We just put it back with a hose and a copper spigot we made that could hang onto the lip of the HLT. We now use the tangential inlet and the HERMS coil sits in the HLT. The CFC worked as well as our new system and if I knew what I know now, I would keep doing it that way. We do use an inline trub filter from BrewersHardware in bot cases on the outlet side of the pump.

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Old 08-23-2012, 01:15 AM   #7
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Originally Posted by mightynintendo View Post
I think I see what you're saying. That basically my mash wort will cool my HLT water to the point that it won't be able to maintain its temperature. That would start a feedback loop that would result in unstable mash temps. Hmm.... so maybe i just need to buy the copper and the extra pump... I mean i don't really care to stand around and stir hot water for an hour (or more).
IMHO regardless of whether or not you use a CFC or a HERMS you are going to cool your HLT water with your mash. Both systems are heat exchangers and in order to heat your mash with HLT water, the HLT water loses energy to the wort and is cooled. The general idea is that you heat the mash slowly and consistently by varying the HLT temp. If you weren't heating the HLT for some reason then you would just dough in and recirculate through a heat exchanger to increase the thermal mass of the entire system thereby reducing heat loss over the mash duration.

Having said that I use a CFC with high temp tubing for the "cold side" as my mash heat exchanger. If you plan on using the mash heating water to sparge I wouldn't recommend using a CFC made with normal GH because of the potential to introduce GH flavor into your wort. I have had a lot of success using the CFC even without an automatic temperature controller for the HLT, I have to PWM it manually (which sucks) but it works for now.

If you want to do it on the cheap do what Yooper says and build a stirrer with an AC motor for the HLT, and install a HERMS coil. Then you can recirculate the mash with the pump and stir with the auto stirrer, leaving more time for drinking.

One other consideration with both HERMS and CFC heat exchangers is the possibility of grain husks getting through your false bottom. I use a SS washer hose braid and haven't had any problems with it. Just something to keep in mind.
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Old 08-23-2012, 01:44 AM   #8
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Quote:
Originally Posted by RTL

IMHO regardless of whether or not you use a CFC or a HERMS you are going to cool your HLT water with your mash. Both systems are heat exchangers and in order to heat your mash with HLT water, the HLT water loses energy to the wort and is cooled. The general idea is that you heat the mash slowly and consistently by varying the HLT temp. If you weren't heating the HLT for some reason then you would just dough in and recirculate through a heat exchanger to increase the thermal mass of the entire system thereby reducing heat loss over the mash duration.

Having said that I use a CFC with high temp tubing for the "cold side" as my mash heat exchanger. If you plan on using the mash heating water to sparge I wouldn't recommend using a CFC made with normal GH because of the potential to introduce GH flavor into your wort. I have had a lot of success using the CFC even without an automatic temperature controller for the HLT, I have to PWM it manually (which sucks) but it works for now.

If you want to do it on the cheap do what Yooper says and build a stirrer with an AC motor for the HLT, and install a HERMS coil. Then you can recirculate the mash with the pump and stir with the auto stirrer, leaving more time for drinking.

One other consideration with both HERMS and CFC heat exchangers is the possibility of grain husks getting through your false bottom. I use a SS washer hose braid and haven't had any problems with it. Just something to keep in mind.
I sort of thought that but I wasn't sure whether the efficiency of a CFC was that much greater than a HERMS coil. If I go this route, I would definitely use an all-copper CFC. Though when sparing I imagine I would probably re route the hlt water away from the coil anyway.

What do you mean by PWM the pump manually?
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Old 08-23-2012, 04:06 AM   #9
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Yooper, do you have a link for more info on your hlt stirrer?

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Old 08-23-2012, 03:26 PM   #10
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Yooper, do you have a link for more info on your hlt stirrer?
No- but here are some photos:

dscn0636.jpg

dscn0637.jpg

dscn0638.jpg

The fan is just to keep the motor cool for the stirrer. I didn't build it- it came with my system when I bought it. The "board" was added because it used to go through the top of the cooler lid that I used for an HLT back them and then I went with the keg HLT so I had to have a support for it.
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