Roof Air units performance puzzling. Do I have a possible problem?

[birdshill123]

 We normally do not travel much in super hot temps. We  leave Canada just before snowfall and return when snow is gone. A few times we have been in Phoenix in 85 to 90 degree heat. Dash air does lose freon but one can a year brings it back to life. This year I left Canada Sept.4. By South  Dakota I was using the dash air. In New Mexico I was using both the dah air and the front roof ac. No problem keeping up to  85 to 90 degree heat. But arixona called for the front 2 roof air and dash air while travelling. Left Tucson for Mexico on the 10th of September. By 1 pm it was 103 degreees and a super hot Mexican sun. I had all3 roof airs and the dash air running. By 4 pm it was getting hot in the MH. I checked the vents and the front one was  not super cold. The rear roof airs were blowing hot/. Is there some sort of thermal protector for the roof unit?. No shade  in the desert and no clouds.  Whe I started heading west it was later in the day and the sun was unreal. Windshield was hot. I tried the roof units the next day and although I was stationary all was good. Is all of this normal?? Thanks

[vito.a]

Do you still have the original Penguin roof top A/C units?  They may not be as good as when they were new.  

Regardless, the A/C units pull in air form the coach, cool it, and blow it out the roof vents.  They are designed for a 20-degree temperature drop and when it's very hot it may seem like they are not blowing very cold.  

[birdshill123]

I guess that the 20 degree drop may be what I was seeing. 

[Tom Cherry]

On 10/13/2024 at 2:47 PM, birdshill123 said:

 We normally do not travel much in super hot temps. We  leave Canada just before snowfall and return when snow is gone. A few times we have been in Phoenix in 85 to 90 degree heat. Dash air does lose freon but one can a year brings it back to life. This year I left Canada Sept.4. By South  Dakota I was using the dash air. In New Mexico I was using both the dah air and the front roof ac. No problem keeping up to  85 to 90 degree heat. But arixona called for the front 2 roof air and dash air while travelling. Left Tucson for Mexico on the 10th of September. By 1 pm it was 103 degreees and a super hot Mexican sun. I had all3 roof airs and the dash air running. By 4 pm it was getting hot in the MH. I checked the vents and the front one was  not super cold. The rear roof airs were blowing hot/. Is there some sort of thermal protector for the roof unit?. No shade  in the desert and no clouds.  Whe I started heading west it was later in the day and the sun was unreal. Windshield was hot. I tried the roof units the next day and although I was stationary all was good. Is all of this normal?? Thanks

The CORRECT way to determine what is going on..

Pull the Sponge Filters and CLEAN THEM (hand soap and water....rinse... Then roll up in a towel and squeeze out the excess....let them air dry for a while or GENTLY dry with a hair dryer). NOW....reinstall them.

System needs to be running and the MH is stable...as in the temp outside have stabilized....not increasing nor decreasing.  Use a thermometer....One with a probe.  If you have a OUTSIDE temp unit, use a bent paper clip and hang it.  Some will put the units in DUMP.  That way you get the REAL output of each unit.  Some will only RUN one unit....thus no INTERACTION with the others as one side is on a common duct....maybe 2, depending on your MH.

Measure the output of the unit....either the closest ceiling vent or the DUMP slider.  Record the OUTLET TEMP.  Then, if you used DUMP.  Close the DUMP and record the temperature at the INLET grill.  OR if you used a nearby outlet, record the temperature at the return or inlet.  The Delta T is supposed to be around 18 - 22 Deg.  The reason you have to have CLEAN FILTERS.  The dirty filters impeded or reduce the air flow.  THUS, you will get a higher Delta T.  Many members have done the test and said... MY HVAC is beating the range.  I must have a SUPER UNIT.  Wrong.  A HIGH Delta T means the Filter is clogged.  I was at Lazy Days and attended their HVAC seminar and that was discussed.  I went back.  Did the test.  YEA>>>  24 deg.  Then washed the filters.  Delta T was 20.  GREAT...

That's it.  Test your unit.  That is the ONLY way to determine if it is working OK. 

[RVerBob]

Delta-T ?

Dump ?

[b_faster]

45 minutes ago, RVerBob said:

Delta-T ? Temperature difference between inlet and outlet air temperature. 

Dump ? Some units have the ability to bypass the vent system, I.E. open the local vent on the cover and "dump" the outlet air directly under the A/C. 

 

[RVerBob]

Thank you, learn something every day

[Tom Cherry]

39 minutes ago, RVerBob said:

Thank you, learn something every day

If your unit doesn’t have a sliding tab on the filter grill….  Our cheaper units are simple.  If you don’t have a dump slider tab.  Then measure the temperature inside the center.  Then find the closest outlet (round one) to the unit you are testing.  Measure the temp difference.  Should be 18 - 22 degrees, THEN look.  If it is HIGHER, your filters are clogged….keep them clean.

Good Luck.