After my last test on the effects of a recirculating fan on kegerator temperatures (See: Kegerator Beer Line Temperatures & Reducing Foam with a Recirculating Fan), I decided to test the effects of kegerator temperature probe placement. I went with three configurations: Immersed vs Ambient Non-Immersed vs… Zip Tied to a Beer Can. Those tests yielded some interesting findings.
Test 1 Zip Tied to a Beer Can:
For this test, the probe was zip-tied to a 14.9 Ounce Can of Beamish Irish Stout. This is the technique I’ve used for years. At the time, I wanted something with some mass to help regulate temperature and I didn’t want to have to mess with submerging the probe and the required container of liquid. For this test, the can was placed close to the wall of my keezer on the compressor hump. The second probe was immersed in 500 mL of water in a Lab Container. See the picture in test 2 for more info on placement.
I also placed a ChefAlarm Thermometer & Timer in my keezer – Hands on Review – as another point of reference, giving me an ambient temperature reading. The ChefAlarm has some great features, including high and low temperature logging. Those highs and lows are what I used as a reference.
Here are the temperature results for test 1 – zip tied to a can. The top shows the temperature probe zip tied to a beer can. The bottom, for comparison, shows an immersed temperature probe. This method produces and nice clean and reliable reading.
- High Temp: High temperature in deg F as measured by the primary/controlling probe.
- Low Temp: Low temperature in deg F as measured by the primary/controlling probe.
- Variance High to Low: The variance in deg F between general high and low readings from the primary probe.
- Cycle Length: Overall length of one typical cooling cycle, measured from high point to high point.
- ChefAlarm High: Ambient temperature high in deg F as recorded by my ChefAlarm
- ChefAlarm Low: Ambient temperature low in deg F as recorded by my ChefAlarm
- ChefAlarm Variance: Variance in deg F between high and low ChefAlarm readings
- Estimated Freezer Cycle Time: Estimated time that the freezer is running as measured from one high to the following low.
- Estimated Freezer Time: Hours Per Day: Estimation of how long my freezer would run in 24 hours based on frequency of cycles and freezer cycle time.
Results Test 1:
- High Temp: 40.03
- Low Temp: 37.64
- Variance High to Low: 2.39
- Cycle Length: 1 Hour 2 Minutes
- ChefAlarm High: 42
- ChefAlarm Low: 34
- ChefAlarm Variance: 8 degrees
- Estimated Freezer Cycle Time: 12 Minutes
- Estimated Freezer Time: Hours Per Day: 4.6
Test 2 Submerged Probe:
Setup: I placed the probe immersed in about 500 mL of water one of my Bel-Art Scienceware 500 mL Polypropylene Lab Containers. I covered the top with aluminum foil. I have used these containers since 2011 for a bunch of things including yeast rehydration water (see tips page, tip #1), sample storage and more. That container was placed in about the same spot as the can used it test 1. Also Pictured: Eva Dry E-500 – Hands on Review – to handle kegerator condensation.
Here are the temperature results for test 2 – immersed. The top shows the immersed temperature probe. The bottom, for comparison, shows the probe zip tied to a beer can. Notice the stuttered temperature changes toward the bottom of this cycle. It doesn’t happen every cycle, but periodically, it also comes close to flat lining. That period of flat lining can last up to 18 minutes. The mass of the water makes temperature readings inefficient. That’s what we want to some degree. We want some sort of a buffer to give a good representation of temperature without quick swings. However the stuttering temperature changes along with flat lining, make me think that this method has it’s drawbacks.
Results Test 2:
- High Temp: 40.19
- Low Temp: 36.76
- Variance High to Low: 3.46
- Cycle Length: 1 Hour 59 Minutes
- ChefAlarm High: 43
- ChefAlarm Low: 30
- ChefAlarm Variance: 13 degrees
- Estimated Freezer Cycle Time: 25 Minutes
- Estimated Freezer Time: Hours Per Day: 5
Test 3 Ambient Non-Submerged Probe:
Here are the temperature results for test 3 – ambient, non-submerged. The top of this graph shows the ambient probe, the bottom, for comparison, shows a probe zip tied to a beer can. The left most portion of the graph is part of a previous test, disregard that. The middle portion shows the ambient non-submersed probe with a recirculating fan. By the way… all previous tests were completed with a fan. The right portion shows the same test, without the fan. I’m not reporting those results here. That test was much as you would expect it to be. Similar to the fan test, with larger swings and slower cycles. Thoughts… I was actually impressed with the consistency of the ambient air results. When I first looked at the graph, I noticed the semi-wild start of the test and I thought… here we go… this one is going to be all over the place. However, when it settled in, it was very reliable. It also has good accuracy. The difference between the zip tied readings and the ambient readings are small. The downside of this method is how often the freezer kicks on. This method had the shortest cycle length, by far, at just 27 minutes. It also had the highest estimated freezer utilization at 5.3 hours per day.
Results Test 3:
- High Temp: 40.01
- Low Temp: 36.39
- Variance High to Low: 3.62
- Cycle Length: 27 Minutes
- ChefAlarm High: 39
- ChefAlarm Low: 35
- ChefAlarm Variance: 4 degrees
- Estimated Freezer Cycle Time: 6 Minutes
- Estimated Freezer Time: Hours Per Day: 5.3
Here side by side comparisons of key metrics…
The submerged test produced the longest cycle length, by far. Nearly twice as long as the zip tie test and four times the length of the ambient test. It had middle of the road temp variances (compared to zip tied) but it’s ChefAlarm (ambient air) test showed a whopping 13 degrees difference. Those swings are the result of how much time the freezer has to stay on to overcome the mass of the water used in the immersed test. That mass also causes inconsistent temperature readings and periods of flat lining.
The ambient test produced good accuracy (second best variance and best ChefAlarm ambient air varience) but the short cycle length of 27 minutes means your freezer is kicking on a lot. That shows up in the estimated freezer hours per day… 5.3 hours, the highest of any method.
I think the zip-tied can approach provides a good middle of the road solution. It provides the best accuracy, based on it’s 2.39 degree temp variance, has a middle of the road overall cycle length, middle of the road freezer run time and uses the least amount of energy with an estimated 4.6 hours of freezer run time per day. The can also offers the benefit of not having to mess with containers of water or other liquids. It’s also easy to move and reposition when cleaning or reconfiguring your kegerator.
Tips and Gear for Your Kegerator:
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Some Additional Notes: These tests are with my equipment. Your results will vary based on a lot of factors including freezer/refrigerator, temp controller, amount of liquid used, probe placement, etc. In spite of those variances, I think these tests give you a good general idea about probe placement. I used a BrewBit Model T, sourced via Kickstarter, to log temperature. Look for a review of the BrewBit Model T here, if and (hopefully) when it becomes readily available to purchase.