Temp Probe Wiring

[BentTwigBrew]

This might be a pretty basic question, but I was wondering if I have the wiring correct on my temp probe. I seem to be having grounding issues where the temp will read correctly for a few days then all of a sudden go berserk and read orders of magnitude off. (for example, should read 65, but reads 250). I have a temp probe from Brewers Hardware and on their website the instruction for the BCS temp probes reads:

"Since these are thermistor-based temperature sensors, there is no polarity to the sensor itself. The black and orange wires are used, the red and brown wires are unconnected. The unshielded drain wire is in contact with the temperature probe end but is not electrically tied to ground."

On the sensor that I received from him there are black, red, white, and an unshielded wire. Not the colors indicated in the instructions. I was wondering which color I connect to Temp In and which I connect to Ground. Currently I have the black connected to Temp In and White to ground. It seems to work for a few days but then the temps just take off and read incorrectly as I stated above. Do I need to use the unshielded wire as ground? This is driving me nuts!!

A few other things to note...I have the BCS ground tied to earth ground. Also, when I take the temp probe out of the fermentor thermowell for a min or so and reinsert, the temps read normal again. I assume whatever interference is going on dissipates.

[Broph]

I have the white wire going to the BCS and the black going to ground on my brewers hardware probe.

[BentTwigBrew]

Alright I just switched the black and white to match yours. As soon as I take the temp prob out of the fermentor thermowell it reads normal again. I get the same reading no matter which wiring polarity I have using the black and white wires.

I ruled out the red wire. Whenever I connect that I get a reading of zero.

Will grounding the I shielded wire

[BentTwigBrew]

Oops. Hit submit by accident. I was going to ask if also grounding the unshielded wire will have any benefit?

[Broph]

I am using only the two wires from the temp probe. My system is using 3 probes from Brewers Hardware (Hot Liq.Tank (m8), Rims (tri-clover), and Mashtun(m8)). Derrin makes the best stuff.

I've had the BCS-460 for over 2 years, and have had weird things happen. All the weirdness disappeared after I added a grounding bar inside my control box. Not to say everything wasn't grounded before, but I haven't had the problems since.

[BentTwigBrew]

Thanks Broph, I have everything grounded together, even the control box, and the ground connections test out with a multimeter.

So last night during my brew session I hard wired the temp probe to the bcs, bypassing my control box to see if that solves the problem. That was an epic fail...less than 4 hours in the fermentor thermowell the temp reading exponentially increased. At 8am it was reading 456*. Pulled the probe out and went with the JC A419 until I figure this out. I'm ready to throw this thing out the window...

I can't figure out why the resistance changes so dramatically when in the thermowell. It seems to read fine everywhere else except in the thermowell. I ruled out wiring in my control box as I directly connected the probe to the BCS. That actually failed worse. I had tried grounding the sanke keg fermentor to the system but that seemed to also make it read worse. Could I have a bad probe?

[Broph]

That's too bad. Might be a bad probe. Is there anything nearby that could be causing any electrical interference?

[BentTwigBrew]

There is a refrigerator in the room which is about 10 ft away, plugged into the same wall outlet. Maybe I will try plugging that into a different outlet. The other electrical components that are used in the control system are the glycol pump and chiller for cooling and a ceramic heat bulb. The sanke fermentor is wrapped with a copper coil and sits inside a non functioning chest freezer. The glycol pump cycles on and off to circulate glycol around the fermentor to keep it cold. The ceramic heat bulb is inside the chest freezer in a light ballast which turns on if heating is needed. The pump and the heater are all grounded to the system.

[Broph]

I wonder if the pump is causing the interference... I've read in a few posts in this forum how how pumps can cause interference...

[BentTwigBrew]

Hmmm. I guess that is possible. If it was, what would a solution be? Does grounding that unshielded wire have any benefit. I might try that tonight anyway.