Johnson Control Analog Question

[Merlin-CO]

Does anyone know what the altitude calibration settings/adjustment #s are for an A19 analog temp controller? This comes into question since I live in the Denver area (at about 5000+ ft).

I recently picked up a new (not secondhand/used) analog A19 Johnson Controller for the second chest freezer. It works fine in terms of holding steady temps and such, its just that the temp on the controller dial doesn't match what the chest freezer is - like the controller would be set at 40F and the freezer would be 46-48F, or Controller at 32F and the freezer at 38-40F.

Would the higher altitude account for these differences in an analog/capillary bulb controller? It's not a huge issue for me to adjust myself to the difference in numbers, I was just curious to look for an explanation...

 

[Catt22]

The discrepancy is not due to your altitude. The solution is to adjust the controller downward until your freezer reaches the desired temperature and ignore what the dial on the controller actually indicates. What you are experiencing is due to the design of a chest freezer. We are using them differently than what they were designed for. The evaporator (cooling coils) are typically embedded in the walls of the freezer. The air in the freezer is primarily cooled as it comes into contact with the walls. Warmer air in the freezer will rise to the upper area and the colder air will fall to the bottom. This can often result in a temperature differential of something like 10-15 F between the top and the bottom areas. So the average temperature in the freezer will depend not only on the controller setting, but also on where you locate the controller bulb thingy. I mitigated this dilemma by installing a muffin fan in the freezer to circulate the air to help reduce the stratification. It made all the difference. The stratification issue can be troublesome as the beer lines and taps are typically located near the top of the freezer where they will be warmer than desired. This can contribute to foaming problems on the first pours and the kegs will be colder at the bottom than at the top. I like to adjust the controller based on the temperature of a poured beer. When making adjustments to the controller setting, it's best to do it gradually and allow time for everything to equalize. It takes a long time for the beer in the kegs to cool when you dial the controller down. Go too far too fast and you risk the beer freezing in the bottom of the kegs. The frozen beer can block the dip tube and you won't be able to pour anything until the ice block thaws. Trust me on this, I've been there. Get that air circulating and I think your problem will vanish.

 

[ClaudiusB]

Does anyone know what the altitude calibration settings/adjustment #s are for an A19 analog temp controller? This comes into question since I live in the Denver area (at about 5000+ ft).

could the higher altitude account for these differences in an analog/capillary bulb controller? .

No.
The liquid filled, enclosed sensing bulb is not effected by barometric pressure or altitude.
Not like precision scales which can be programmed with an offset based on your location.


Cheers,
ClaudiusB