RTD Temp Probe - Off by >15 deg.???

Finally made it. Built my electric brewery and fired it up today for the first time. Did a 5 gal initial batch (s.m.a.s.h. recipe). Set my water temp to 175 (using the PID with a Pt100RTD temp probe from Auburn Inst.) and put 2 gal. into mash tun to warm it. Drained it, added 15 qts. of 175 water and then put in 10# of 2 Row. And as my next step - checked the mash temp.

Holy Cow! Using a liquid thermometer and a another smaller thermometer, both agreed - 130 degrees in the mash tun!!! What happened?? Checked the HLT with the liquid thermometer, a pretty good model that seems reasonably accurate, and found the 175 water shown on the PID was actually less than 160.

So is it possible an RTD temp probe could be that far off? I guess I can adjust the PID to compensate, but would have expected a few degrees off. Not over 15 degrees different!

Or is it just me.

Here is a link to the probe: http://www.auberins.com/index.php?main_page=product_info&cPath=20_15&products_id=107

One thing that happened to me on the first time I used my electric setup is that I didn't stir or recirculate the water in the HLT. The water under the element didn't heat up and I noticed the first bit of water I pumped was basically cold. I'm not sure if that's what happened to you, but if you didn't keep the water moving in the HLT it's a possibility.

my hlt rtd is sometimes off 10 degrees. I traced this to a weak connection in my xlr plug. If i wiggle it, it stops working, sometimes it is 10 degrees off, sometimes it is dead on. I would check your wiring.

Thanks jsguitar and milldoggy. Both suggestions give me ideas to look into. I'll do some more testing since I am so ready to brew some more.

One other question, I set the PID to 175 and watched the temp overshoot to 190 and keep going. That's when I manually stopped it and let the water cool back down. Did I miss something in setting up the PID that it wouldn't stop at the preset (SV) value?

KEG99 said:

Thanks jsguitar and milldoggy. Both suggestions give me ideas to look into. I'll do some more testing since I am so ready to brew some more.

One other question, I set the PID to 175 and watched the temp overshoot to 190 and keep going. That's when I manually stopped it and let the water cool back down. Did I miss something in setting up the PID that it wouldn't stop at the preset (SV) value?

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Have you tuned or autotuned it yet? It might overshoot a bit, but 15 degrees is excessive.

Actually, no. I read through the directions that came with it and not being familiar with controls of this type (or of any type), I tried my best to understand it. Didn't see anything about tuning or autotuning the PID, though.

Is there supplemental reading material available to help me understand this complex little gizmo?

KEG99 said:

Actually, no. I read through the directions that came with it and not being familiar with controls of this type (or of any type), I tried my best to understand it. Didn't see anything about tuning or autotuning the PID, though.

Is there supplemental reading material available to help me understand this complex little gizmo?

Click to expand...

What PID do you have? SYL-2352 ??

Yep. The SYL-2352.

You might want to download the Instruction Manual for the PID.
Check out page 8 (Quick Guide) for basic setup info.
You do need to do an auto tune as well.
When you do this, make sure your water temp is at least 10 degrees less than your intended set temperature.

Hope this helps.

Also, you will want to read 4.5 on page 4.

Sorry to threadjack, but if I am auto tuning my hlt with a herms coil in it. Should I be running my pumps and water through my mash and herms coil?

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