AC Efficiency?

[KeninAZ]

I just picked up an older 2000 Fleetwood Bounder Class A. It's very clean.
But today, when I brought it home I plugged the unit into AC and tried the single roof AC unit out. The lowest vent temperature I can get is about 66° and the lowest temperature in the unit is about 84° with an outside temperature of 91° and very low humidity.
The dash air on the Ford chassis performs just fine but I find that the roof AC unit is a little lacking.
This MH is a 31' unit and I have no idea what the AC is on the roof size wise. The thermostat on the wall that controls it is a Coleman.
Maybe it's low on coolant and needs service?
Or are these temps I have provided about what it's capable of?

[wa8yxm]

To tell if it's working properly you need 4 Temp readings and two or 3 humidity readings

1 OUtside air temp (intake for condenser)
2: Condenser outlet temp
3: Evaporator intake
4: Evaporator outlet
and Inside and outside humidity

Also if not done recently CLEAN the condenser coils.. and in fact everything else you can clean.

But at first glance. that might not be working properly

IF low on coolant it will ice up on you.

[Chris_Bryant]

Retired JSO wrote:
20 degrees difference from ambient is great.

This is not exactly correct- the 20 degree difference is between the air going in to the air conditioner (return) and the colder air coming out (supply), it has little to do with the outside temp. A well sized air can easily keep it at 70 degrees in 100 degree ambient (outside). The problem with most RVs is the lack of insulation, plus now they paint them black (!) That's why most higher end rigs come with 3, 4, or even 5 rooftop units.

[Retired_JSO]

20 degrees difference from ambient is great.

[LadyRVer]

Are you by any chance prewired for a 2nd a c?

[Chris_Bryant]

Keep in mind, efficiency and sizing are different issues- if, after running for at least a half hour, the difference between the return air and supply air is in the 20 degree range, the air is doing what is is supposed to- it is just too small.
A 31 foot rig with a big windshield along with Arizona sun, a single 13.5 *or* 15 k btu/hr is most likely too small.

That said, it is nearly always possible to tune it up a bit for better performance- cleaning coils and sealing any ductwork.

[RedRocket204]

Watch these videos and then address your AC unit. Your RV is older and chances are just needs a little attention, an easy fix. All the movement over the years results in AC unit seals that are no longer doing their job as good as should be.

Coleman or Dometic roof AC not cooling properly. Check, test and fix

All Seasons Mobile RV Repair. RV AC not cooling properly

[prichardson]

Agree with Mr Wizard. By the numbers you posted the A/C is working properly. At that outside temp. it will some time for it to catch up; especially if you are not in the shade.

[MrWizard]

what was the time period involved
the whole RV every piece of framing siding, interior
was heat soaked

it takes time to remove that heat
your A/C output was 25* cooler than outside ambient air
18* than the return air, i bet if you turn it on in the morning
it will cool down real nice

[tpi]

Also operate it from a cool start- before the day warms up and see how it holds the interior temperature. Cooling a big hot RV can take many hours in the sun.

How you orient that big windshield could also be important. If the engine had been recently run, drivetrain heat will be seeping into the RV.

[Tyler0215]

Clean the fins and fan before you call a service man. That can make a big difference in cooling.

[phillyg]

A properly sized AC unit should be able to cool 20 degrees below the ambient temperature. I suggest you get it serviced. A single AC unit should adequately cool a 31' RV in low humidity conditions.

[LadyRVer]

I have gotten roughly about the same figures, on about 4 different units.
Motor homes or fifth wheels in the 31'range with 1 ac. Called ac man, said that was normal.