New To Dual A/C on 2015 Montana

[RKassl]

We were in South Dakota a couple of weeks ago and it was 95+ with extremely low humidity. Turned both air conditioners on full blast and they did a pretty good job of keeping it around 72 to 75 degrees. Now we are in our home area, the humidity has been absolutely terrible and in the 80's. Last night I wanted to put the small bedroom AC on auto it would run but never cycle off. Checked it this morning and the same thing. I called Dometic and they first wanted to see if it would shut off, yep no problem. The room registered about 74 on our thermometer but the Dometic panel indicated 67 or so. The tech thought that it may have been frozen up. They had me shut off the main AC in the living room then turn the small AC up to 65 with high fan. The little thing actually kept the coach nice and cool for a while. The sensor then indicated the proper temperature in the bedroom. I then shut off the small one and now the large Quiet cool is doing its job. Do you think that the small AC froze up? Is there a trick to running both the big AC and the small AC so that they play good together? I didn't have two air conditioners on our first Montana so this is a new to me. And suggestions from your experiences how I should run the two together?

Thanks!

[bigskyjimmy]

When I run 2 A/C's ,I put both on low fan and temp at 55 and I close the down chute vent in the bedroom and leave the door open and the cool air from the bedroom flows into the living area ALSO make sure your return air filters are nice and clean..Works for me in 100 degree heat Also block off your stair vents and another thing I found out was I always ran my ceiling fan with the A/c on but when I turned it OFF one time it made a difference and could feel the cold air come down on me

[jcurtis934]

We always set the bedroom ac a degree or two higher than the living room and keep doors closed.to bed/bath. Also keep the living room ac set to 75 for most cases. Fan is auto for both and we are comfortable inside. How well the ac's work in every montana model and year could well be luck of the draw. I believe the normal ducted ac's are probably close in performance...but each montana may well be different. John

[Virginia Young]

We are in central FL and keep the a/c fans on High. We have been told that low fans will allow the a/c to freeze up.

[LDFieglein]

We have a 2015 Montana 3711fl, that is the front living room style. The front a/c unit seems to really struggle in hot weather. Temperature setting 74* on t-stat actual room temps would be 80 up to 85 even after being gone 2 hrs. & never would catch up. Rear unit seems excellant to the extent we looked forward to retiring to bedroom. After checking with Holiday world we were told maybe try a dehumidifier in living room as unit appeared to be in full specs as return air and discharge air had adequate change in temperature. Read about blocking stair vents, will try as I could feel warm muggy air from floor in that area. Anyone have any thoughts

[rohrmann]

I'm not an HVAC person, but I am confused about all these problems with freeze issues in these units. If these units were installed properly, there is a freeze sensor probe that is supposed to be installed into the evaporator coil, that should prevent a freeze issue in these units. I have checked ours, and both units have the freeze sensor, and we have never had a problem with the coils freezing up. Maybe some installations are missing these sensors, or the sensors came loose from the coils. The information is in the Dometic installation manual for these units, which can be obtained on the Dometic site.

[jfaberna]

I have the Dual A/C units with the Dometic thermostat. I leave both Z1 and Z2 on AC with auto fan. Works good considering the heat lost of RVs. During the heat of the day, both units run all the time. As the sun sets, I set the Bedroom zone 2 to 2 degrees higher than zone 1. This keeps the bedroom A/C off during sleeping and by setting the dump valve in the bedroom to the duct setting, both A/C units cool the whole RV when they are running. So zone 1 will cool the whole RV at night without Zone 2 running.