Fermenter over-cooling

[Sean W.]

I could really use some help figuring this out:

We have 5, 7 bbl fermenters all tied in on the same glycol system. All are double-jacketed. We have one fermenter that we have to turn the glycol on/off manually by opening and closing the ball valves, because it over-cools the beers. I think the problem is electrical, but I don't know that for sure. Here is what I've seen/done:

-Replaced the solenoid. I think we had 1 good brew after this, where it fermented at 67, but then the next 2 batches, it over cooled. For instance when we set the temp controller to 64, and come in the next day and it's at 51.
-Switched the temp controller with one from another tank. The same tank was still over-cooling, so there went that theory (none of the other tanks have issues).
-I've been feeling the glycol lines manually to see if we are getting glycol flow into the tank even when it's not calling. I haven't been able to catch it doing that.
-The thermocouple that goes into the probe is just 2 wires wrapped together. The manufacturer assures me that is what it's supposed to be. I cut off about an inch of wire, re-stripped and re-wrapped it just in case the tip of the wire was bad.

At this point I'm stumped...thoughts? Maybe something else electrical? I don't see how it could be glycol bypassing the solenoid when it's closed, since it's brand new.

[poltz]

Not sure this is it...someone will chime in to help/poo-poo this.... I think the solenoids come in two versions. One is open when it is triggered, one is closed when it is triggered. I think. Or...is it possible to be wired backwards to have the same effect. So depending on the temp when you set it and the cut off point...if "upside down" it keeps running away from the cut off and never triggers a shut down.... Or something like that.... Help....

[panadero]

There is likely something stuck in the solenoid keeping it from closing completely. Pretty easy to take it apart and see, ours all got stuck a number of times before the mechanics realized they forgot to put in a screen, and also never flushed the system before putting it into operation. A small fleck of pvc kept ours open.
Hope this helps,
David

[RobW]

I had a very similar thing happen with one of my 20bbl fermentation tanks. It was the last one in line, my glycol lines were at about waist level, and the jackets were plumbed in parallel. I tried 2 solenoids, then a motorized ball valve, still failed. Finally I hooked the jackets up in series and the problem vanished. My only guess was that with the jackets in parallel and no valve on the return line, that it was creating a thermosiphon and actually creating a flow through the jackets only utilizing the return as an input.. I have no clue, but I know it fixed my problem.

Good luck,
Rob

[515Dave]

There is likely something stuck in the solenoid keeping it from closing completely. Pretty easy to take it apart and see, ours all got stuck a number of times before the mechanics realized they forgot to put in a screen, and also never flushed the system before putting it into operation. A small fleck of pvc kept ours open.
Hope this helps,
David

I'd say this is the most likely answer. I'd double check all the plumbing, but if everything is done properly, (i.e. the returns go to the top port, and supplies to the bottoms, and you don't have a return mixed up with a supply or something crazy like that), it almost has to be the solenoid not fully closing. If you had a NO solenoid by accident, it would be cooling your beer WAY past 51. A slow leak (i.e. not fully closing) would explain why it's only dropping ~10 degrees and you aren't noticing a flow difference (the glycol will warm up to fermenter temperature on the return side, and will only be a little bit below ambient on it's way into the fermenter). It doesn't take a whole lot of 28 degree glycol flow to drop 7 bbls of beer from 64 to 51 or so over the course of 12 hours.

[Natrat]

After you swapped controllers, did you check the thermistor/thermocouple probe for calibration? I received a lot of 12 identical probes, once, and just one read about 6 deg out at the low part of the range, but registered correctly above 60. Manufacturer told me that happens occasionally from improper fusing of the sensor and probe.

Hope you find the problem. Frustrating!

[Sean W.]

Thanks for all the input. I am leaning towards checking for something stuck in the solenoid next. It's an old system and I don't know when or if it's ever been flushed. The glycol is plumbed in correctly, at least going in the bottom and out the top on both jackets (and both going through the solenoid).

[wailingguitar]

With some solenoid designs, if the solenoid is installed upside down glycol can leak through even if there is no junk sticking it open. We had this issue recently

[TGTimm]

Bag the thermocouple, and get a temp controller that uses RTD input (yours may be capable of using an RTD, check the manual). Thermocouples are pretty much obsolete outside of pyrometers, which operate at temperatures in excess of 600C.

An RTD is a very finely calibrated and repeatable resistive device (your thermocouple is a generator--the hotter it is, the higher the voltage), with three wires connected to the temp controller. One of these wires compensates for differences in resistance due to wire length and wire temperature. I'm sure your thermocouple does not do this; is not repeatable or well calibrated. It's two wires twisted together--how much resistance is in that junction; how will it change as the two wires oxidize?

In addition, the RTD should be bedded in a thermo-conducting paste or grease inside the therwowell, to insure it's measuring the temp of your beer, and not that of the room.

As for the solenoid valve: someone already mentioned that these are easy to disassemble and clean. It takes a very small bit of anything to prevent the valve from fully closing. If you do find something clogging the valve, you'll need to either full flush your lines or install a filter screen or the problem will recur. If your valves are ASCO Redhats, there are relatively cheap rebuild kits available, and it's a matter of a few minutes to rebuild a valve in place (if you can get to it).

[Sean W.]

Problem Solved

Just to "resolve" this thread:

We tried a few things before we found out what was going on. It wasn't something stuck in the solenoid, and there wasn't any debris in our glycol. It was glycol back-flowing into the tank through the "out" line. I am having a hard time picturing the exact setup without looking right at it, but the solenoid only controls the "in" lines to the 2 jackets. The "out" lines are just open, and the lines to the top and bottom of the fermenter are kind of daisy-chaned together so it was possible for glycol to flow slowly into one "out" and out the other "out" (confused yet?). Anyway, we installed 2 check valves on the out lines, and, problem solved.

[BrewerBecky]

I too am having this issue. On my old 8/16 bbl tanks I could take the glycol hosing off and manually warm up the jackets. However I can't do so on my 60 bbl tanks. Anyone have an idea how to manually warm the beer up after the fermenter cooled it down well past it's fermentation range??

[barleyfreak]

I too am having this issue. On my old 8/16 bbl tanks I could take the glycol hosing off and manually warm up the jackets. However I can't do so on my 60 bbl tanks. Anyone have an idea how to manually warm the beer up after the fermenter cooled it down well past it's fermentation range??

If you have an empty FV, you can fill it with hot water, turn the jackets on for it and the FV you're trying to warm up while turning off the jackets of all the other FVs, and turning off your compressor on the Glycol unit (raise the set point to max, basically). That will effectively warm up the glycol solution and should warm up the FV. The only caveat is that I have done this on clearly a much smaller system than you have (I have 7/15 bbl FVs)

Another option might be if you have a glycol prechiller or glycol HX pass. You could again turn off the compressor on your chiller, close all non-affected FV jackets, and just run a bunch of hot water through the chiller which would also effectively heat up the glycol supply.

I think there might be a thread or two on probrewer about this.

[xFutballFanx]

I too am having this issue. On my old 8/16 bbl tanks I could take the glycol hosing off and manually warm up the jackets. However I can't do so on my 60 bbl tanks. Anyone have an idea how to manually warm the beer up after the fermenter cooled it down well past it's fermentation range??

If you have a PD pump, or an impellar pump with a VFD on it, you could create a sanitary loop coming out the side port of the tank and back into the racking arm with a length of hose coiled into a grant filled with hot water. Or, you could disconnect your glycol inlet from you tank and push hot water through the jackets until you feel hot water exiting the jackets (stop filling the jackets before you send hot water back into your glycol loop.) This is assuming your reservoir has the extra space to hold a tanks worth of glycol in it.