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rcrabb22
Joined: 23 Dec 2010
Posts: 462
Location: Illinois
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 Link Posted: Sat Dec 24, 2016 3:22 pm Post subject: Temperature Pb offset |
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I used to think I had a heat loss issue and needed to set my HLT PID 2 or 3 degrees F above the desired mash temperature to maintain exact mash temperature. Using a Thermapen I discovered I really needed to adjust the Pb offset to get the HLT PID to match the Thermapen reading. I got into the habit of checking it every brew session and found it needed to be adjusted each session. Generally it needs to be adjusted somewhere between the range -1 to +1 degrees. I found the same offset issues for the MLT readings as well. I have wiggled the connections at the 3 points (probe connector, panel mount male connector and at the PID) and I do not see any temperature swings on the PID display.
I brew in the basement so the ambient environment in the brew room is fairly stable.
I do not think I should need to adjust the Pb offset every brew session to get accurate PID temp readings. Given it is 2 different PIDs and 2 different RTD probes I do not think they are defective.
Has anyone else experienced this?
I have a cheap multi meter but not sure I really know how to use it other than to "buzz" wires to verify current flow. If anyone has some ideas how I could trouble shoot I would appreciate it.
Merry Christmas!
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11122
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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| Link Posted: Sat Dec 24, 2016 3:36 pm Post subject: Re: Temperature Pb offset |
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| rcrabb22 wrote: | | I do not think I should need to adjust the Pb offset every brew session to get accurate PID temp readings. |
Correct. Set it once using the instructions here: http://www.theelectricbrewery.com/control-panel-setup
How exactly are you measuring to determine that it needs to be adjusted somewhere between the range -1 to +1 degrees? Unless your thermapen is inline with the probe that's connected to the PID, you don't know if what you're seeing in normal. For example, if you put the thermapen in the top of the mash to measure, that's not necessarily always going to be at the same temp as what the PID is measuring at the HLT output. This is especially true if the mash is still heating up as the top will heat up before the bottom. It'll take time to stabilize. If you're using a good performing false bottom/kettle/pump setup (as per the recommendations in the build instructions) and are pumping at 100% then it should stabilize all over to the same temp (I did a bunch of tests during my trial runs). If you have a poor performing false bottom or have flow issues (pump running slow, too fine of a crush, etc) you may have channeling or other issues causing some parts of the mash to be colder than others.
To ignore all these variables I recommend properly calibrating the PID temp probe by putting it in a glass of warm water at around mash temp (150-160F) together with a known accurate NIST traceable thermometer like the ThermaPen. This way you ignore all the other system variables.
You also need to measure at the same temperature every time. For example, the PID probe may be a degree too high at 70F but a degree too low at 150F mash temp. This is because the PID temp probe may not accurate over a wide range. I recommend calibrating the probes at mash temp of around 150-160F. Ignore any errors at room temp. In other words, don't turn on the panel and notice that a probe reads a degree too high and adjust the Pb setting, as then at mash temp it may read a degree too low.
Good luck!
Kal
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rcrabb22
Joined: 23 Dec 2010
Posts: 462
Location: Illinois
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| Link Posted: Sun Dec 25, 2016 4:14 pm Post subject: |
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| Quote: | To ignore all these variables I recommend properly calibrating the PID temp probe by putting it in a glass of warm water at around mash temp (150-160F) together with a known accurate NIST traceable thermometer like the ThermaPen. This way you ignore all the other system variables.
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Thanks Kal. I will remove the 2 probes from the tee fittings and calibrate each in a smaller glass of warm water.
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rcrabb22
Joined: 23 Dec 2010
Posts: 462
Location: Illinois
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| Link Posted: Sun Dec 25, 2016 7:45 pm Post subject: |
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Both probes were spot on compared with a Thermapen in a glass of 155F water without any further adjustments.
I am not sure why the difference between the MLT and HLT readings I see. The outflow of the MLT is consistently 1F less than the HLT outflow.
I am using Blichmann G1's with the Blichmann false bottom in the MLT and the pump running wide open. Knowing the calibration is correctly set I will adjust the HLT temperature accordingly.
Thanks and once again Merry Christmas
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11122
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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jphussey
Joined: 17 Oct 2012
Posts: 171
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| Link Posted: Wed Dec 28, 2016 12:04 am Post subject: |
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If we have already assembled the brewery before calibrating in a glass of water I guess the recommendation would be to unscrew the probe from the tee valve and calibrate?
I just did the calibration today but did it with the thermapen in the HLT vs. in a glass of water. I figured since it was recirculating it'd all be equalized?
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kal
Forum Administrator
Joined: 12 Dec 2010
Posts: 11122
Location: Ottawa, Canada
Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter
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| Link Posted: Wed Dec 28, 2016 12:19 am Post subject: |
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| jphussey wrote: | | If we have already assembled the brewery before calibrating in a glass of water I guess the recommendation would be to unscrew the probe from the tee valve and calibrate? |
Correct. Unless you use something inline like described here: http://www.theelectricbrewery.com/forum/viewtopic.php?t=30555
| Quote: | | I just did the calibration today but did it with the thermapen in the HLT vs. in a glass of water. I figured since it was recirculating it'd all be equalized? |
Should be close, as long as you set the temp and let it equalize for a while to make sure it's all well recirculated/stirred up.
Kal
_________________
Our new shop with over 150 new products: shop.TheElectricBrewery.com
We ship worldwide and support our products and customers for life.
Purchasing through our affiliate links helps support our site at no extra cost to you. We thank you!
My basement/bar/brewery build 2.0
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