Airxcel seems to take forever to cool park model

[woodland_park]

I have an Airxcel model 46413-812, that's mounted under my park model, that's always seemed to take a long time to cool our 500 sq ft park model. It's a 13,500 BTU unit, so it's plenty big..The park model has skirting all the way around the unit and the skirting is vented with 3 - 2' x 3' screens to allow airflow under the unit.There is no debris in the coil and the inside air return is clean. The airflow out the 4 vents seems very weak to me. It's 7 years old. I don't believe there's a high or low speed fan connection by looking at the diagram. The other day it was 91 degrees here and the A/C unit ran for 5+ hours before it turned off at 77 degrees.
Thanks for any comments

[MEXICOWANDERER]

Yup. Stand and watch a thermometer NOT go down for a long time when high temp wet and dry bulb readings are close. Water takes A LOT of energy to change temperature. And UNTIL it changes temperatures - loses heat and precipitates in the form of condensation the mercury ain't moving...

The action of a dehumidifier is to "overly chill" the air. Forcing vapor coalescence and then drops which fall. Drier air exiting the evaporator is mixed with air heated by the condenser exchange but it does not exhaust outside the room. The net process increases temperature slightly.

The object is to get that freakin' relatively humidity down out of the high sixties. Look at it objectively: Say there is a Delta T of thirty degrees between indoors and out. That's a lot. High Delta T means higher loss through structure walls, roof and glass. OK? Reducing the Delta T to twenty degrees means an enormous reduction in active thermal transmission. If I remember the lesson right the BTU loss reduction is logarithmic. How to be comfortable with a higher c or F. Maintain R/H from 25% to 40% (optimum).

I have seen incidence of ridiculous over cooling. Freezing movie theater temperatures in the sixties on a 105F day. My hygrometer fits in my pocket. Humidity was still in the upper sixties - talk about "unclear on the subject".

Eighty degree air cannot hold anywhere near as much moisture as 100F air. When I used to suffer nose bleeds, with 2% R/H winter air the figure was quoted for outside air temp of say 10F. At 70F inside temp the humidity was a flat zero and pennies.

If you are comfortable fine. That is the goal. If comfort seems hard to achieve and especially if discomfort comes with a high utility bill, it may be time to get a decent hygrometer and treat the cause not the symptoms.

[smthbros]

Chris Bryant wrote:
Of course, if you are in Minnesota you should not need as much cooling capacity as we do in Sarasota, Fl. 🙂

Some thing to keep in mind when comparing cooling design conditions between FL and MN, is that while dry bulb summer design temps may be as close as 5 degrees, the grains of moisture difference at 50% rh indoor in MN can be as low as 15 while FL can be as high as 66. What this means is that the latent load on a cooling system in FL can be significantly greater than a cooling system in MN at the same dry bulb temps. While some are content to ignore latent loads on cooling systems when diagnosing a cooling problem, that will not make the load go away.

[MEXICOWANDERER]

Really RUDE summer weather is found in the southern 50% of Florida state. There are times in August, when I hobnob Miami weather and emit a low whistle. And I am afeared Lone Star mosquitoes would flee in utter terror if they would ever happen upon a Minnesota insect drill rig. Just sayin'

[dougrainer]

Chris Bryant wrote:
Of course, if you are in Minnesota you should not need as much cooling capacity as we do in Sarasota, Fl. 🙂

Chris, As someone who has lived in Northern Indiana(Elkhart) Kansas and Oklahoma/California and Texas, I HOPE you are joking. One thing I have learned living in Texas for 37 years is, a LOT of Texans and people in the south are Ignorant of the weather North of Texas. They think it snows in the summer and never gets warm. FYI, Minnesota mean summer temps are 92 to 98 in June July and August. With highs hitting 104 to 106. Right now, YOU are at 86 degrees. Minneapolis is 81 degrees. NOT real different:B So, the AC capacity will be the same required for southern temps. Just not as long a heat problem. Doug

[MEXICOWANDERER]

"Finally .. it is getting hotter out there no matter what some politicians say"


I remember moving from fog and overcast in 1955, because my mother suffered chronic sinus infections. We moved to Concord, California. There, as an eight-year-old until age 26 I experienced five or six SEVERE UNLABELLED El Ninos, and never EVER EVER did we have a summer where June, July, August and September did not reach 100F at least 20-30 times in that four month period. We had neighbors that included 5th generation Italian families whose memories went back to the 1880s. Listening to conversations (I had a genuine double box NWS weather station) the oldsters would laugh and say "Yes it is 108F! It is normal. Open your windows for the night and close them in the morning".

Insulation is the key. Shading from the sun is key. Proper air circulation and dehumidification is key. Adding more A/C without thinking is counter-productive.

[bobsallyh]

The AC is small for the square footage involved. A ceiling fan will help somewhat.

[Chris_Bryant]

Of course, if you are in Minnesota you should not need as much cooling capacity as we do in Sarasota, Fl. 🙂

[woodland_park]

Thanks, I'll do that today as it's supposed to get toasty here again after a nice 75 degree low humidity day yesterday

[Dave_H_M]

Why don't you check the input air and the output air and see if the differential looks OK?

[wa8yxm]

Multiple comments 13,500 BTU's may not be enough to cool it swiftly I live in a 38' Class A,, I have 30,000 BTU's and well. some days it's not enough.

What color is the Park Model? Light colors reflect sun heat better and are easier to cool

How long since you cleaned the A/C... On my rooftop units if I park near cottonwoods 4 weeks ago (I DID) the condensers quickly need cleaning (I Cleaned). NOTE Air-Xcel are easier to clean than others (Good news) and easier to inspect as well. But take a look.

Finally .. it is getting hotter out there no matter what some politicians say so you may wish to UPGRADE that unit, or add a 2nd one.

[MEXICOWANDERER]

Why?

[woodland_park]

WOW! I feel so small! Thanks for all the replies. At least I have the comfort of knowing that it's not an issue with the unit. It's just too small. Wonder why Woodland Park would install an undersized unit especially since this model has a loft? Oh well, thank you all again!

[MEXICOWANDERER]

A rig's roof broiling in direct sunlight will absorb "x" BTUs of direct solar radiation. If you can figure out a way to shade it while allowing airflow between the shade and roof top, it definitely will make a significant difference in the balance of heat extraction versus input.

And remember it takes lots of energy to dehumidify air. My A/Cs spend the first half hour of operation reducing humidity. The water condensation of the evaporator coils contains all of the "cooling ability" of the unit. How much energy does it take to precipitate water from air? A lot. It is felt in the form of reduced cooling. It may pay to investigate the practicality of using a LARGE capacity dehumidifier if your inside humidity is 60% or above at ANY temperature. Changing the temperature of water (vapor) takes a lot of energy.

[ScottG]

Too small of AC. You could use a free standing residential unit or get a second AC installed.
Or even a ductless heat pump.