Farm Camp wrote:
Measure the temperature of the air getting sucked into the intake, then measure the temp of the supply/output air and look for about a 20 degree difference. If that's what you see then the unit is most likely working OK. It may not have the capacity you need to keep the space at the temperature you want.
I'm assuming this rule of thumb still holds true. Maybe the new refrigerant and compressors have changed though. I was taught this little trick in 1983 LOL.
Right there is the key the A/C has little to do with what the outside temp is and this 20 deg delta often mentioned is across the Evap. How cold you can get the inside of the trailer is mostly dependent on the overall insulation and duct losses vs. outside conditions including sun and ambient temperature. You can get close to measuring the intake temp, but measuring the outlet at anywhere but right at the main air plenum will be somewhat higher due to ducting heat losses. This is why when it really gets hot outside those units with the factory registers off the main air plenum or those of us who have modified their ducting to add registers at or close to the main air plenum, can get increased cooling. Also a couple of small fans to circulate the air inside a trailer can also help cool the entire trailer some. A lot of folks think closing some registers to try and redistribute the air sounds like a good idea, but in fact can be counter productive since A/Cs need a designed minimum of free air register outlet to provide maximum cooling and most factory systems do not provide a lot of extra registers above the minimum required.
Finally our A/C units only come in basically two sizes, 13.5 and 15K BTU and generally only have one unit for the common 30A TT configuration and once above about 25' a 13.5K BTU single unit has two strikes against it from the get go and is always running to catch up in warmer weather.
Larry