Ranco controller readout incorrect, tank much colder than controller

[CSBC]

We have 7 fermenters of various sizes 3-10bbl. On our 2 7 bbl tanks coincidentally, the temperature of the fermenting beer is much lower (10F) than what the controller is reading. Controller on 1 is set for 66, but after dumping 2 full pint samples, the third sample is measuring 57F and the fermentation is slow. We are using Ranco ETC digital temp controllers. Purchased 5 new controllers at 1 time. The others are great.

We have been around for 4 years now and upgraded glycol chillers this summer. We have thermowells into the FVs about 16" in. This has never really posed a problem before. Here in Hotlanta, the temperature just finally dropped outside, which causes our brewery space to be in the low 60s at night. I don't see this to be an issue. My only thought here is that the new chiller is much colder than before and when the sensor is much deeper in the liquid towards the center, it will take more btu to chiller the beer, which can cause an overchill. However, this still doesn't solve the fact that the controller readout is incorrect.

Has anyone had issues with Ranco controllers? Do the sensors go bad? I am wondering if we had 2 sensors go bad...at the same time.

Cheers and thanks.

[TIPA0303]

What's the brix on your glycol?

Generally when we have (cold crashed) tanks freeze beer it's because our glycol mix is too concentrated especially when ambient temps begin to drop.

Might be the source of the problem if it's affecting multiple tanks.

Sent from my SM-N910V using Tapatalk

[mmussen]

I've been using Ranco's for years and never had any problems with them at any of the breweries I've used them at.

A thought for you
Do you have any thermal grease on the temp probes? - you might be having problems with the ranco reading the actual temp of the beer - also you'll want to make sure that the probe itself is pushed all the way into the opening. The thermal grease will make sure that the probe is actually feeling the temp of the beer around the thermowell.
Also, did you add wire or move the temperature probes at all? I know that you need a special low resistance wire to get an RTD sensor to read correctly without needing specific calibration.

I can think of another few reasons why the beer temp would be off, but I would think that it would still indicate the correct temperature.

[NatchezBrew]

In the last 6 months I have had to replace 4 ranco temp probes. One was 3+ years old the others were a little over a year. They all started showing the wrong temperature.

[katfish59]

7 in 11 months

I have replace 7 of them in the 1st 11 months of operation. I think that it must be a bad run of the thermo couples.

[gitchegumee]

Check your solenoid valves....

Most times in this situation I find that it's not the temperature controller, but the solenoid pilot stuck open. Is the Ranco actually sending signal at lower than setpoint? That's first step. If not, then your glycol is chilling the tank when it's not supposed to. Likely teflon tape or pipe cutting crumbs stuck in the solenoid pilot. Good reason to install a strainer in your glycol loop post-pump. Good luck!

[TGTimm]

First, what Philip wrote above, and what mmunsen wrote.

Second, are you getting stratification in your ferms? Poorly placed cooling jackets, particularly ones that are too low on the ferm, can easily result in fermenters with warm beer sitting on top of cold. How high are your thermowells?

Do the Rancos use 3- or-4 wire RTDs, or just 2-wire thermocouples? The RTDs are much more accurate, and self-compensate for length of wire and the effects of ambient temperature on the resistance of the wires.

Just some thoughts....

[TiminOz]

I also think the solenoid could be the culprit. Often in a new glycol system particles get stuck in the diaphragm. Rinse in a bowl with water and you may actually see the bits that are causing problems. The RTD does not have many moving parts and I know the Reotemp RTD that if there is a problem it would a wiring issue. Have you taken a meter to the connection from the RTD to the temp controller?

[lhall]

Take the thermocouple out and put it in an ice bath, and see if it reads 32 F. If not, there may be a programmable offset in the Ranco that you can use to set the temperature to 32 F.

Make sure the TC is inserted all the way into the thermowell too.

I can't remember exactly but I think thermocouples shouldn't be run more than about 100'. You should use thermocouple extension wire of the same type as your thermocouples.

If accuracy of about +/- 2 F is ok, you can get by with making your own thermocouples out of thermocouple extension wire. Just skin the two wires and twist them together, and solder the tip. A whole lot cheaper than thermocouples.

[TGTimm]

For any application where fine temperature control is essential, like, for instance, fermenting, we use Fuji PXR controllers with 3-wire, platinum RTDs and PID logic.

We use Johnson A419 controllers for less critical situations, like our HLT. The 419 is equivalent to the Ranco controller.

For calibrating thermometers, a certified Mercury-In-Glass thermometer is essential. Don't trust any thermometer--or any meter of any kind--that has not been calibrated against a known standard. Ice water is one standard, but thermos should be calibrated for the range in which they are used. Boiling water is not a good standard, as the temperature is dependent on elevation,and, to a lesser degree, air pressure and water chemistry.