Coleman Mach 15 AC Unit

I know what some will say---The salesman mouth was moving and he was lying. Well, sorry to say this is true, he may not be lying, but he has NO IDEA what he is talking about. The 20 degree "rule" is just an operational check for non technical people to verify if the AC is running and cooling to spec. That means the OUTPUT cold air will be 20 to 22 degrees LESS than the input air. HAS NOTHING TO DO WITH OUTSIDE AIR TEMP. It just means as the RV (or house) cools down the OUTPUT air will be 20 to 22 degrees colder than input---ie-- the inside of the RV is 90 degrees and the AC is started. After about 15 minutes the OUTPUT will be around 65 to 70 degrees and will get colder--after running the input air is now 80 degrees and the output is 60 or a little lower. The output will gradually get colder and colder as the RV cools down. The MAX output cold air will usually peak at about 40 to 48 degrees depending on humidity and the insulation of the RV and how hot the outside temps are. Home units operate about the same differential. The NEW Tiffins use the Mach 8 which is a brand new smaller physical size RVP (Coleman). Still has the same BTU's but is quieter and more efficient than the previous model RV models. Doug

Actually Tiffins, Winnebagos, and Berkshires are among the more poorly insulated units out there so it will take a heck of an A/C unit to cool them.

I think the unit you are referring to is the one that Entegra is now using.

The temperature of the air coming off the coil should be about 35 -40 degrees. If it get any colder, and sometimes it does, it will freeze up form ice on the coil, I stick a dial thermometer in the duct where it comes into the motor home and I get about 40 -43 degrees.

A lot of people get confused over the "20 degree rule". They think that means it will only lower the temp in the rig that much. What it really means is the air that passes through the AC unit should cool about 20 degrees. But the same air passes through many times so it's plausible it could cool it much more than that amount - depending on heat load and humidity.
Mine has pulled the temp down almost 30 degrees.

I depends on the size of the RV, how well its insulated, how tight its built and what outdoor temp. its dealing with. A "sales guy" will tell you anything to make a sale. If its 75 degrees out side and and a unit can drop 30 degrees, that same unit would not do it at 95 0r 100 degrees ambiant.

Better add another qualifier: humidity.

It takes a lot of BTU's to condense moisture.

So, temperature delta in the desert WILL be different than along the coast.

Are you in a dry or humid area?