Anyone ever have this problem?

[kydan47]

I'm almost done w/ v2.0 of my e-brewery and am having an issue with primarily the Auberins PT100-L50M14 rtd probe.

I drilled a hole in the side of my BK for the body & probe itself, but the PID shows an incorrect temperature. At the beginning, the displayed temp is close, but as the temperature rises, the error is worse & worse.

That said, the same probe hung over the side/top with the probe in the water shows the correct temp - it is only incorrect when I use the RTD connected to the body/probe mounted into the side.

I've replaced PID's, probes, probe bodies, hooked up both direct to the PID's & with an rtd extension, I've grounded out the BK using jumper cables to a much larger ground. I've measured the BK for any stray electricity, etc. I've measured the probe(s) for the correct wire hookup AND for correct resistance.

I've switched out the hookup from the side probe to a 2nd probe from the top and the PID begins to read correctly.

Any thoughts or suggestions?

Thnx in advance,
KY Dan
LAGERS/FOSSILS

 

[BadNewsBrewery]

My only suggestion is to give Auber a call / email. I'd ask if you have the PID programmed for the correct style of probe, but it sounds like you probably do. Have you tried different probes in the same hole, and different wires with different mixes of probes, and the problem always shows itself in the same way regardless of which probe/wiring setup you use? If so, it's pretty clear that the kettle is the issue - but no idea what that issue would be.

 

[kydan47]

Thnx Bad,

I appreciate the thoughts. Yep, at first I thought I had it nailed down to a bad probe body (and previously to the probe extension), so bought another one. Soon as it arrived, replaced it but the problem was still there.

Talked to a tech for an hour yesterday, but no luck yet. A friend of mine who is an Electrical Engineer is also supposed to stop by today, but he seemed as stumped as well. All 3 PID's are set to 21 & 0 for the Pb.

The tech is also going to check with his supervisor and I'm going to set up a couple more scenario's to rule out. I'm sure there is a simple explanation.

Cheers,
KY Dan
LAGERS/FOSSILS

 

[P-J]

Quick question: How low in the kettle is the temp probe placed - near the bottom?
If you are heating the water with a built in electric element, you might have stratification within the BK. A layer of cooler water will remain at the bottom of the kettle.

Try it again but during this trial stir the water or keep it moving by recirculating it with a pump. I think the probe will show spot on.

 

[jeffmeh]

Quick question: How low in the kettle is the temp probe placed - near the bottom?
If you are heating the water with a built in electric element, you might have stratification within the BK. A layer of cooler water will remain at the bottom of the kettle.

Try it again but during this trial stir the water or keep it moving by recirculating it with a pump. I think the probe will show spot on.

Occam's Razor dictates good odds that you are correct.

 

[BadNewsBrewery]

That was going to be my next proposal - if we've eliminated the probe, wiring, and PID from being an issue, then we know the issue lies with the kettle. The only thing you really change is the location of the probe, so it's very likely that as the temperature heats up you get increased thermal layering. I know in one of my kettles my probe will measure 10-30* low if I don't have the pump running to recirculate the liquid.

 

[kydan47]

Correct!! - stratification!

I added the pump and the temps matched almost perfectly! The probe is about 2 inches from the bottom = even with the ballvalve. Have never noticed that much difference before in the HLT. Possibly the unusually cold water we are having?

Also Suyi called and indicated that a longer probe would be needed.

I just wanted the alarm to prevent boil overs, so I can handle a little off w/o circulation. I'll just circulate a little prior to taking temps.

Thanks for everyone's help! V2.0 should be complete shortly.

KY Dan
LAGERS/FOSSILS

 

[BadNewsBrewery]

Once you hit boil, it'll mix itself just fine - problem is, you'll have boiled over and who cares what the temperature is, so... a longer probe that reaches to a less stratified layer, or a different probe location, look to be your only non-pump / stir options.

Glad it's figured out though! Happy brewing!
-Kevin