A/C question

[dieselguy]

Is it just me or have any of you noticed the new A/C's with the 410A refrigerant work OK on "regular" days, but just don't cut it on really hot days compared to the old R-22 refrigerant units? It seems when you really push the 410A units, they don't seem to get the job done as well. I'm comparing 3 separate RV's here all with the new refrigerant.

[Trailer Trash 2]

Is that why my air conditioner is not working as good as my other older trailers, the refrigerant type.
I am at the point of pulling that Dometic off the roof and putting in a Coleman 1500 btu unit.
Another thing that I dont understand is the roof angle along with the air conditioner the same. why dont the make a roof jack that will bring it to a flat angle when the RV is level. most air conditioners do run with a slight angle for dranage, but the way they are mounted on RV's with a roof as ours it's a wonder.

[ole dude]

I would tend to believe, that if a manufacturer rated a unit at 15000 BTU it would have to produce that at the design temp no matter which refrigerant was in the unit. I have not looked at the design parameters of these new units, but it could be the big gotcha here is they will do 15000 BTU at 92 degrees ambient and 70 % RH as opposed to 15000 BTU @ 95 degrees ambient and 78% RH. Another thought could be these newer units are not as forgiving as the older units, in that a slightly dirty condenser coil or evaporater coil will deminish the capacity more. Just some thoughts on the subject. I have one of the newer units and have measured the Delta T across the evaporator a few times to see what is happening, and keep getting a 20-24 degree diff. What I haven't done is measured the humidity in the rig, which I suspect will be higher then usuall. This would tell you if the evaporator temp was cold enough to do a good job of removing humidity, so, that being the case the units do a pretty good job of sensible temp but not so good with latent temp, which would explain not feeling as cool. Well time for me to hushup.

[Clemson1881]

A lot of folks said the same thing about the conversion in cars in the 90s. I have never had any complaints about either, but that's just me.

[dieselguy]

Trailer Trash2 ... the freon police didn't change over to 410A until a year or two ago, so I think you'll still have a R22 unit. I know Carrier makes a wedge to level up the roof unit ... the fit should be universal. One thing I did to help the cooling was to temporarily block off all the wooden grills that allow air to the furnace. My storage under the front and belly pan always had cool air rolling out of them ... now not nearly as noticable. When you remove the grills you'll notice all kinds of water lines and electrical going down into the belly through 2" - 3" holes that are not sealed. Just a note on auto A/C's ... R134A is much more system pressure sensitive than the old R12 ... you have to get the low / high pressures just right for optimum cooling more so than the old R12. Optimum pressure is directly related to proper charge unfortunately for the "just put another can in the system" crowd .