Bright Tank Temp issues

[Squintymcguinty]

Hi There,
We are in the process of kitting out our 30HL brewery. We have a 3600L 316 Stainless tank we are using as a BBT. It is Ex-Pharma boil tank with 2 Dimple jackets (1 on the dished end and 1 covering bottom 2/3 of the cylinder). The tank has some scorching on the the inside so we are planning on pickling it and washing with 401. This will remove all traces of scorch. It will then be pasivated. Our glycol is coming from a 280 glycol tank(Cooled by 2kw compressor) into a maniford to solenoid and then piped to the BBT and FV(15mm Insulated Flow/Return lagged beer line). We have just had the BBT and Glycol unit installed so we isolated the BBT on the manifold and pumped the Glycol around the 2 jackets. I filled the tank with water(No beer yet) and set the Solenoids on the BBT to 1deg C to see what it comes down too. It was pulling up and down on the Glycol tank for approx 15hrs but when I came in this morning the BBT was down to 2.8 - 3 deg C.It seems to be struggling to get below this. The Glycol tank was sitting at approx -5deg C which was the setpoint. I checked the tank with a 2nd Therm and it was correctly reading 3. There was no traces of ice in the water. I also flushed jackets before hooking up the glycol. They are getting plenty of flow thru them. The flow from the pump on the Glycol units are good(More than once I got a face full of Glycol from a loose connection). Is there any reason it will not pull below 3 deg. Im worried we will not get to -1 with the beer. Any input is greatly appreciated.

Thanks
Steve

[jebzter]

Its possible you are freezing water over the the surface of the tank and that is effectively insulating the remaining liquid.

[TGTimm]

Well, your jackets are not ideally located, and water isn't the best test material.

Most of us set our glycol chiller around 27F, which is above the freezing point of beer, but well below that of water. If a layer of ice forms on the inside of the tank, it will effectively insulate the water from the jackets.

With a jacket in the dished top of the tank, you'll have headspace gasses between the beer and the cooling jacket--not a very efficient set up for heat transfer. The lower jacket, at the bottom of the tank, could lead to stratification within the tank--but you just might get just enough transfer from that top jacket to prevent this.

We have several fermenters with jackets in the cones. We almost never use the cone jackets, as the bottom of the beer chills, settles, and just sits there with the warm beer floating on top. A higher jacket, say mid-tank, tends to establish a thermal siphon within the tank, with the cooled beer settling along the walls while warmer beer rises in the center. We always try to use the highest jacket that is covered with beer.