temps drop below set temperatures

[beerguy1]

Having trouble on my fermentors. I set the temp to 66 come in the next morning and its at 55. I have even had it as low as 42.There are ASCO valves on the tanks my repair guy checked the ohm reading all normal,he did find glycol on both sides of the rubber gasket that separates the valve. He changed it and it has happened again. My brite tanks are just fine. Of course they go to 34 and stay there.

They are valves have stopped the flow by the time I come in the next morning so they do work but they just dont shut off at the right temp. Just to be more confusing this does not happen all the time

Cheers

[jwalts]

Is your glycol piping made of plastic? If so, it could be depositing debris into your solenoid valve. I'm told this is common with new PVC piping (it happened with my FVs), and it takes very little to open a pathway for glycol to pass through a closed solenoid valve - think grains of sand. In addition to a large strainer on the glycol chiller outlet, which we've always had, we now have small strainers immediately upstream of all FV solenoid valves. I don't know if the strainers solved the problem or the piping was simply "broken in" by then. Having to babysit fermentations 24/7 was very frustrating.

To test whether or not the solenoid is trying to shut off at the correct temperature, all you need to do is cycle your controller a couple degrees above and below the actual FV temperature a few times and listen for the solenoid to click. Having a pressure gauge on your glycol loop can be informative as well (the pressure will drop when a valve opens).

Joe

[lhall]

Some ASCO valves require a minimum pressure differential to close. I had a lot of trouble like this when we first started, and were using ASCO valves with a 5 psi pressure difference. I bought the ones that had a zero minimum pressure difference and no more problems.

[TGTimm]

Depending on the type of ASCO diaphragm valve, glycol on both sides of the seal may be normal. The piloted valves do have liquid on both sides of the seal.

Have you insured that the problem is not in your temperature controller? Too high a differential, incorrect P (for a PID controller), etc? Is your temperature sensor bedded in heat-transfer paste in the well--this can easily cause the problem you're seeing. If the sensor is not properly bedded, ambient air can enter the temp. well, influencing the reading.

[gitchegumee]

I'm with Joe on this one...

Very typical for pilot operated solenoid valves to be stuck open with a tiny piece of debris. Especially on new systems. Especially if plastic has been cut with a saw as opposed to knife. Especially if you've used teflon tape as thread sealant. Take a closer look at how pilot operated solenoids work and you'll see the need for clean fluid. Pilot to operate is a small orifice. A fine mesh strainer on glycol supply outside the chiller is essential. To solve problem at hand, isolate your solenoid, disassemble, clean and reassemble. Should work fine. Best of luck!