Case #2: Enclosure humidity is too high
Excessive humidity can be a problem when external temperatures are low and/or when your cave is "well stocked" with cheese.
The tests below were done in our test cave in an un-heated garage. We used a wet towel to generate excess humidiy, and logged data using (1a) no control, (2a) commercial desiccant, and (3a) our Desiccant Pillow with the HCS.
(click on charts to enlarge)
2a: No control
Without the compressor cycling and/or another means to remove excess humidity the %RH will continue to climb. As the graph below shows, when %RH approaches 100% the dew point temperature will match the actual temperature indicating the water vapor is at the saturation point. In these cases the vapor can condense on the coolest surfaces including the cheese.
2b: Commercial De-humidifier
There are compact electronic de-humidifiers on the market that use a solid-state thermoelectric module (TEM) to condense water vapor. They work well, but they aren't "controllers" and the TEM will heat the enclosure causing the compressor to run more, very likely causing a "low humidity" problem.
A better option are passive devices that have some type of vapor-adsorbing material like silica gel. Eva-dry is one brand that is popular, relatively low cost (<$30), and is sold as a means of de-humidifying in closets, bathrooms, etc. Thinking it could be effective in a refrigerated enclosure we purchased the E-500 and placed it in our test cave.
As the results below show the Eva-dry was not effective. This test was done during a cold snap here in SC and my garage temperature dropped to 50 for a couple of days which made matters worse. But even before that the %RH was approaching 100%. This was a surprising result given that silica gel is a good desiccant. The sidebar discusses some theories about why the test results were poor.
2c: Desiccant Pillow with HCS
In this case we placed one of our silica-gel filled pillows on top of the Cave Cube fan and set the CC-RH controller to de-humidification mode and again used a wet towel to provide excess humidity. Humidity control was very good and stayed at or near target %RH for 24 hr. Depending on humidity generation rate in the cave, the pillow's adsorption rate will eventually start to drop. The following chart illustrates this over a longer time period.
2d: Desiccant Pillow with HCS (3 days)
This was the same test extended a couple of days longer. The pillow was effective for 2 days and then %RH started to slowly increase. Note that we were using a wet towel to generate a lot of excess humidity. At the end of the test the Pillow had adsorbed .25 lb. water (1/4 of it's dry weight)
Also note that during this test the external temperature was quite cool, more than 10 deg. below the target 55, so we used our prototype two-stage controller with a small (60W) incandescent light bulb for the heating cycle. We plan to add the two-stage controller (Control Cube T2) in mid February 2014.