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PID/RTD temperature changes during brew

 
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LarMoeCur




Joined: 14 Feb 2015
Posts: 18



PostLink    Posted: Tue Jan 10, 2023 6:29 pm    Post subject: PID/RTD temperature changes during brew Reply with quote


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I've got a weird one for y'all.

My temperature readings changes as the water heats up. I fill my kettles and check the temperature with a Thermapen. Which because I've made changes from my last brew so it doesn't match what the PID read out shows. I make the Pb change to match the temperatures. Well as the water and kettles heat up the temperature readings compared to the Thermapen start to separate. I continue to make Pb changes to keep them matched. At some point around 120F the temperature indications stay aligned for the rest of the brew day. Only happens with my boil and MLT kettles.

What I have done to trouble shoot them. I've checked and rechecked all connections from PID to XLR. I've checked all my cables and even tried different cables. I've run numerous auto-tune sequences. I've pulled and cleaned both RTDs to make sure no beer stone was insulating the probe.

The only thing I haven't tried is replacing the RTDs. Next brew I'll swap the MLT and HLT RTDs and see if I can duplicate the issue now with the HLT.

Or am just missing something in my settings?
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue Jan 10, 2023 7:03 pm    Post subject: Reply with quote

What sort of PID 'Pb' offset differences are you seeing at different temps? Can you give some examples?

Some error may be normal as the RTD probes may not track as accurately as (say) the NIST traceable ThermaPen that has comes with multi-point correction. This is why in the control panel setup instructions for setting Pb I mention "The critical range brewers care about is typically the 140-160F mash temperature range so if possible, it's best to calibrate to a sample in this range."

See: http://www.theelectricbrewery.com/control-panel-setup

Cheers!

Kal

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LarMoeCur




Joined: 14 Feb 2015
Posts: 18



PostLink    Posted: Tue Jan 10, 2023 7:35 pm    Post subject: Reply with quote

I forgot to add this just started about 5 brews ago. Or maybe I didn't notice it for the first 5 years.

I'm seeing large differences at the start up temperatures. Boil kettle is Pb at -3.8 and MLT is -3.5. As the temperature rises the Pb closes to around -1.5 for both kettles. The HLT holds at -1.2 for the entire process.

Sounds like I shouldn't worry about it. I'll just set my Pb to match at 140-160 ranges. This will not pair well with my Brewer's OCD but I'll have a homebrew and get over it.

Kal as always thanks for the help.
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kal
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Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Tue Jan 10, 2023 10:16 pm    Post subject: Reply with quote

If by "start up" temperature you mean room temperature (70F) and "as the temperature rises" you mean mash temp (140-160F or so) then a difference of 2 isn't unreasonable. It's the mash temp we care about usually so calibrate for that.

How long are your temp probe cables? Did you build these yourself?
What control panel are you using? Did you build it yourself?

You may have a poor or slightly loose connection in a cable or connector somewhere. I mention this as a few years back you had issues with temps jumping around that you found out was a bad connection: http://www.theelectricbrewery.com/forum/viewtopic.php?p=324980#324980

Kal

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We ship worldwide and support our products and customers for life.
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LarMoeCur




Joined: 14 Feb 2015
Posts: 18



PostLink    Posted: Thu Jan 12, 2023 3:27 am    Post subject: Reply with quote

8ft cables. I have ones that I built myself and some of the newer braided ones from Auber. I thought cables at first but the HLT is spot on. All my cables work perfectly with the HLT.

Control panel is the 50A version built by me. I've went back through it and checked every connection, every solder, I even check all the crimp on spade connectors. Everything appears to be tight and in place.
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kal
Forum Administrator



Joined: 12 Dec 2010
Posts: 11116
Location: Ottawa, Canada

Drinking: Pub Ale, Electric Creamsicle, Mild, Pliny the Younger, Belgian Dark Strong, Weizen, Russian Imperial Stout, Black Butte Porter


PostLink    Posted: Thu Jan 12, 2023 1:50 pm    Post subject: Reply with quote

You have x3 temperature displays so if you want to find out what's causing the offsets and/or where there may be a bad connection, you can swap the following around to find out what the problem "follows":

Temp probe tip
Temp probe cable
XLR receptacle and wiring in the panel
PID

Cheers!

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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