10,500 A/C Test Results, Part One

[magnusjansen]

I was interested in the cooling capabilities of a single, small A/C unit when my wife and I were purchasing a new camper. We've since purchased the camper and have been testing the A/C extensively in various conditions, and we wanted to share (some of) the results with you to help others decide whether a unit of this size is sufficient for their needs.

For the tests, I am measuring how quickly and efficiently the A/C unit will get the camper to a "comfortable" temperature - which for us is between 68 and 73 degrees - in two different, outside climates. The first climate is where the outside temperature is less than 10 degrees warmer than what we consider comfortable for the inside temperature (i.e. less than 83 degrees outside). The second climate is where the outside temperature is between 10 and 20 degrees warmer (i.e., between 83 and 93 degrees outside). Today's test results are focused on the latter scenario.

We ended up purchasing a small 18' trailer with a vented Dometic COOL CAT 10,500 BTU air conditioner and heat pump. The trailer is a 2018 NuCamp T@B 400 with a 30 amp connector.

Test conditions:
The outside temperature was 90 degrees and 52% humidity. The inside temperature of the camper was 95.9 degrees Fahrenheit at 48.3% humidity. The temperature sensor inside the camper was initially located on a table in the sunlight, but was moved just prior to recording to a shaded area on a kitchen table and away from any vents. All of the shades/blinds were in the "open" position, and all outside windows and doors were closed. All lights and electronic devices were off during the test, and the temperature was monitored remotely without anyone inside the camper.
The camper was (incidentally) half in the shade and half in the sun at the time of testing.
The camper and A/C was powered by a Westinghouse iGen 2500 generator. A 30 to 15 amp adapter was used to connect the 30 amp male socket to a 15 amp female socket on the generator. The generator is capable of producing 2,200 watts of continuous power for approximately 3 hours (which time is determined by fuel).
I tested in this condition for a couple of reasons: The first was that I wanted to get a baseline for the A/C without any interference and avoiding un-reproducible results (such as if someone were present and giving off body heat, or if a certain number of appliances were left on). The second was just that the goal was to provide a relatively realistic real-world scenario, where one would be running the A/C while leaving the blinds open to enjoy the outside views.

Test equipment:
Raspberry Pi connected to a DH22 temperature and humidity sensor. The DH22 sensor was placed on a kitchen countertop in the shade and away from A/C vents.
A quick program was run on the Raspberry Pi to get readings from the sensor every one minute, and which wrote the results to a file including the precise date and time, temperature, and humidity readings.
The DH22 sensor was calibrated with two other sensors (i.e., the Alde temperature system installed in the camper and a Klein Tools clamp multimeter with temperature) and was within ~2 degrees Fahrenheit of accuracy.

Test results (interpreted):
I'll provide the raw results at the bottom. Using these results, the readings inside the camper were 95.9 degrees Farhenheit at the start of the test.
After 53 minutes, the temperature finally reached a 'comfortable' 73 F at an average temperature reduction of .43 degrees per minute.

The A/C was able to reduce the cabin temperature by 23 degrees in less than an hour. The A/C can (and did) run off of a portable generator, which I believe is noteworthy since the A/C can be run while boondocked.

Future tests will or may include running from 85+ outside temperature to 65- inside temperature, as well as performing the same test above but with one or two people inside with a couple of laptops or appliances (since people and electronics produce a lot of heat; as much as 400 watts). I'll also perform tests on energy consumption if anyone is interested. Overall, I am impressed with the results and am reasonably confident the COOL CAT can provide comfort even in hot climates.

Test results (raw):
(Ignore the first line's temperature readings - the temperature sensor produces inaccurate readings when it is first "polled". I simply included it so you can note the time the test and A/C was started).
{"time":"2019-07-07 16:17:08", "temp":102.6, "humidity":42.5}
{"time":"2019-07-07 16:18:09", "temp":95.9, "humidity":48.3}
{"time":"2019-07-07 16:19:10", "temp":95.2, "humidity":49.0}
{"time":"2019-07-07 16:20:10", "temp":94.3, "humidity":50.8}
{"time":"2019-07-07 16:21:11", "temp":93.4, "humidity":51.1}
{"time":"2019-07-07 16:22:11", "temp":92.8, "humidity":50.0}
{"time":"2019-07-07 16:23:17", "temp":90.9, "humidity":47.6}
{"time":"2019-07-07 16:24:18", "temp":90.9, "humidity":47.5}
{"time":"2019-07-07 16:25:21", "temp":89.8, "humidity":46.3}
{"time":"2019-07-07 16:26:21", "temp":89.6, "humidity":46.2}
{"time":"2019-07-07 16:27:22", "temp":89.1, "humidity":45.5}
{"time":"2019-07-07 16:28:22", "temp":88.5, "humidity":47.1}
{"time":"2019-07-07 16:29:23", "temp":87.4, "humidity":44.0}
{"time":"2019-07-07 16:30:24", "temp":86.7, "humidity":42.4}
{"time":"2019-07-07 16:31:27", "temp":85.6, "humidity":46.3}
{"time":"2019-07-07 16:32:27", "temp":85.6, "humidity":46.2}
{"time":"2019-07-07 16:33:30", "temp":84.6, "humidity":42.7}
{"time":"2019-07-07 16:34:31", "temp":84.4, "humidity":42.6}
{"time":"2019-07-07 16:35:31", "temp":83.8, "humidity":42.0}
{"time":"2019-07-07 16:36:32", "temp":83.3, "humidity":41.6}
{"time":"2019-07-07 16:37:33", "temp":82.9, "humidity":41.6}
{"time":"2019-07-07 16:38:33", "temp":82.6, "humidity":40.8}
{"time":"2019-07-07 16:39:34", "temp":82.2, "humidity":40.3}
{"time":"2019-07-07 16:40:34", "temp":81.7, "humidity":40.2}
{"time":"2019-07-07 16:41:35", "temp":81.5, "humidity":40.4}
{"time":"2019-07-07 16:42:38", "temp":80.8, "humidity":40.4}
{"time":"2019-07-07 16:43:39", "temp":80.6, "humidity":40.3}
{"time":"2019-07-07 16:44:39", "temp":80.4, "humidity":40.0}
{"time":"2019-07-07 16:45:40", "temp":80.2, "humidity":40.1}
{"time":"2019-07-07 16:46:43", "temp":79.7, "humidity":39.4}
{"time":"2019-07-07 16:47:43", "temp":79.5, "humidity":39.4}
{"time":"2019-07-07 16:48:44", "temp":79.3, "humidity":39.4}
{"time":"2019-07-07 16:49:45", "temp":79.0, "humidity":39.4}
{"time":"2019-07-07 16:50:45", "temp":78.8, "humidity":39.6}
{"time":"2019-07-07 16:51:46", "temp":78.6, "humidity":39.7}
{"time":"2019-07-07 16:52:49", "temp":77.9, "humidity":39.7}
{"time":"2019-07-07 16:53:49", "temp":77.9, "humidity":39.7}
{"time":"2019-07-07 16:54:50", "temp":77.5, "humidity":39.5}
{"time":"2019-07-07 16:55:51", "temp":77.4, "humidity":39.6}
{"time":"2019-07-07 16:56:56", "temp":76.5, "humidity":40.2}
{"time":"2019-07-07 16:57:57", "temp":76.5, "humidity":40.2}
{"time":"2019-07-07 16:58:57", "temp":76.3, "humidity":39.9}
{"time":"2019-07-07 16:59:58", "temp":75.7, "humidity":39.7}
{"time":"2019-07-07 17:00:59", "temp":75.4, "humidity":39.9}
{"time":"2019-07-07 17:01:59", "temp":75.0, "humidity":40.1}
{"time":"2019-07-07 17:03:00", "temp":74.7, "humidity":40.5}
{"time":"2019-07-07 17:04:00", "temp":74.5, "humidity":40.5}
{"time":"2019-07-07 17:05:01", "temp":74.3, "humidity":41.0}
{"time":"2019-07-07 17:06:02", "temp":74.1, "humidity":41.1}
{"time":"2019-07-07 17:07:02", "temp":73.8, "humidity":40.7}
{"time":"2019-07-07 17:08:05", "temp":73.2, "humidity":41.2}
{"time":"2019-07-07 17:09:06", "temp":73.2, "humidity":41.2}
{"time":"2019-07-07 17:10:06", "temp":73.0, "humidity":41.3}

[Ray,IN]

There is a flaw IMO in the stats methodology. Air conditioning effectivness depends upon humidity levels as well as ambient temperature. When air conditioning was "invented" the original goal

chilled air, the inventor quickly realized the potential.
An air conditioner that is too large for the area to be cooled will not lower the humidity level enough to prevent a damp feeling in the air at thermostat set temperature. Quicker is not always better, humidity level must also be lowered at nearly the same rate as temperature.