MLT flow rate through 50' 1/2" ID HERMS coil

larrysand · Joined: 13 May 2016 Posts: 25

I'm testing my build with water and am interested to know if anyone has measurements of re-circulation through a 1/2" ID 50 foot coil with the thick 1/2" ID silicone tubing and full bore camlocks and ball valves? I measured an average of 1.2 gallons per minute with a head of 1.5 feet.

The reason I'm asking is that i have to have the HLT about 3 degrees F higher than the MLT to maintain the mash temp. HLT flow rate is about 6 GPM.

Thanks.

**kal** · Posted: Mon Apr 01, 2019 4:07 pm Post subject:

Hi!

Having a HLT to MLT temperature lag is a very common issue. Using parts that are different from the ones I recommend in our build instructions can cause this. To minimize the difference, make sure to:

- Calibrate both the MLT and HLT temp probes per the instructions here: http://www.theelectricbrewery.com/control-panel-setup
Unless both are calibrated with a known accurate thermometer at the mash temp, you don’t know if what you are seeing is accurate.
- Make sure to set up the PIDs per the instructions here: http://www.theelectricbrewery.com/control-panel-setup
- Use the thicker walled hoses I recommend here: http://www.theelectricbrewery.com/hoses
Thicker hoses will lose less heat. Try to minimize distances as well.
- Set your mill gap crush per the recommendations here (0.045 to 0.050"): http://www.theelectricbrewery.com/grain-mill
You want to mill looser for good flow, not tighter.
- Use the pumps I recommend here to ensure adequate flow: http://www.theelectricbrewery.com/pumps
- Run both pumps at 100% open when mashing. To get good flow without any channeling use the kettles I recommend here: http://www.theelectricbrewery.com/kettles-overview

For example, users have reported on our forum and by email how they were seeing a temperature differential between the MLT and HLT and were able to make it go away by swapped out their hoses and pumps for what's recommended in the build instructions. A quote from one of them:

"I had originally tested the HERMS with the thinner 1/2 ID silicon and had my pumps setup with the inline heads (long story). I was landing about 1-2 degrees cooler in the mash kettle. I swapped out the pump heads for the front inlet and swapped out the silicon with what you recommend and I now hit the same temp!" - Todd W.

Other things that are sometimes done differently that can cause a differential:

- Make sure the heating elements are wired correctly and being fed 240V and not 120V. Running heating elements at 120V will result in 1/4 the power you expect. You can check this by looking at the amp meter. A 4500W element will draw 18.8 amps while a 5500W element will draw 22.9 amps.
- Brewing in a very cold location may cause the MLT temp to drop slightly by the time it reaches the MLT temp probe.

This question gets asked a lot on the forum too. These threads may provide further hints:

http://www.theelectricbrewery.com/forum/viewtopic.php?t=25474
http://www.theelectricbrewery.com/forum/viewtopic.php?t=26722
http://www.theelectricbrewery.com/forum/viewtopic.php?t=30387
http://www.theelectricbrewery.com/forum/viewtopic.php?t=28283

Good luck!

Kal

larrysand · Joined: 13 May 2016 Posts: 25

Thanks Kal,

I've done everything on the list.

I have not tried to mash yet. Just testing with water and everything stabilizes. So I was wondering about flow rates. I don't use your quick disconnects but big C camlock should have less restriction.

It's not a big deal because i can measure it and compensate the process.

Thanks again,
Larry

larrysand · Joined: 13 May 2016 Posts: 25

I use thermapens. I love those things and give them as gifts all the time.

**kal** · Posted: Mon Apr 01, 2019 10:03 pm Post subject:

dp Brewing Company · Posted: Tue Apr 02, 2019 12:04 pm Post subject:

Big C camlocks have a larger bore. I think that is what he meant about less restriction

**kal** · Posted: Tue Apr 02, 2019 12:14 pm Post subject:

Thanks - that's what I figured he meant. For what it's worth my QDs are not full bore and I've never had issues with flow rate. Having full bore certainly won't hurt anything however.

Kal

dp Brewing Company · Posted: Tue Apr 02, 2019 12:25 pm Post subject:

larrysand · Joined: 13 May 2016 Posts: 25

Yes, DP is correct. I was just looking for a cause. I will let you know what I find out.

Larry

dp Brewing Company · Posted: Tue Apr 02, 2019 7:50 pm Post subject:

This is a long shot but see what your PID values are at. Kal gave me a baseline to start from and then do the auto tune. Worked wonders for mine being off by about 2 degrees and the HLT overshooting set temps.

P 40
I 350
D 2

**kal** · Posted: Tue Apr 02, 2019 8:04 pm Post subject:

Correct. See the control panel setup instructions here: http://www.theelectricbrewery.com/control-panel-setup

Cheers!

Kal

larrysand · Joined: 13 May 2016 Posts: 25

DP,

The PID is set to those default values and the HLT does not have any trouble maintaining it's temperature. I calibrated the RTD with my thermapen.

Thanks,
Larry

dp Brewing Company · Posted: Wed Apr 03, 2019 12:12 pm Post subject:

larrysand · Joined: 13 May 2016 Posts: 25

The temp probe is exactly as in Kal's build, Kettle, Valve, close nipple, T.

Anyway the problem was several things. My space is on the cool side, about 65F. I had the kettles sitting on a terry towel on a stainless table and the towel was wet. I upgraded that to something better and replaced the thrust washer and impeller in the pump. That took care of the problem.

Thanks,
Larry