Cooling expectations in small 23' class C

[jagert59]

Just had a new Furrion 15.5K AC unit installed in my 2006 23' Class C and with it running constantly with the thermostat set at 75 the temperature in the RV won't get below 83-85, of course the outside temp here in TN is 97 with a pretty healthy amount of humidity. This is a non ducted AC and the RV is in my driveway in direct sunlight not much shade. Is this a normal situation? Should I expect it to be lower than 83?

Thanks

[Old-Biscuit]

No not normal
Should be able to pull temps down into the low 70's

Sounds like installation was not done right
Return air needs to be completely sealed from the discharge plenum


Discharge Air temp S/B roughly 18*F - 20*F lower than the Return air Temp

[DavidEM]

First measure air out vs air in temp with an IR gun. Should be at least 15 deg F after it stabilizes.

But 97 deg outside air temp plus full sun is a huge heat load to deal with. Definitely check the plenum inside the discharge grill for any bypassing. BTW bypassing should make the temperature differential even more than 15 deg but will reduce overall cooling effectiveness.

You can put separators/deflectors inside to minimize bypassing.

David

[wopachop]

Turn the thermostat down to the lowest setting and see what happens.
It could be the settings and difference between auto/low/high.
Easy test is to lower the thermostat. Figure out the settings later.

[twinboat]

My AC has a tough time cooling down the 25 ft MH unless I have it on when it just starts warming up.
If I turn it on after the inside temps are above 80 degrees, it's not going to bring it down.

I also close off the drivers seats and close the bathroom door if in the upper 90s.

[jagert59]

Ran it for 4 hours starting temp inside coach 94 degrees outside temp 93, after 1 hour inside temp 84, outside temp 93, after 2 hours inside temp 83, outside temp 80 and raining, after 3 hours inside temp 83 outside temp 80 and still raining, after 4 hours inside temp 83 outside temp 78.

Checked temps with IR thermometer return air ~82 discharge air 73.

Suggestions?

Thanks

[SJ-Chris]

Probably not this, but worth mentioning I guess...


On my rooftop AC, on the ceiling inside the RV is where the controls are. There is a knob for On/Off and Fan or AC (hi or low). But there is also a knob that is the thermostat. To someone who isn't familiar with the unit, they might not understand the diagram/coloring on the thermostat knob. If that knob isn't set very low, then the AC could turn on and run (and cool the coach a little) and then it would continue running but just not provide more cooling (...the thermostat knob thinks this is what the user wants). Is it possible your AC has a similar knob that acts as the thermostat? It is conceivable that you have a wall thermostat AND a knob thermostat (on the actual AC unit).


Just thought I'd throw that out there.


-Chris

[twinboat]

Pull down the ceiling cover and see if they screwed up the intake connection. It may be blowing the cold air right back to the evaporator.

My new MarkIV, on my boat, has a cloth boot that keeps the intake and discharge separate. It's held in place with tape

[jagert59]

SJ-Chris, thanks for that advise, but there are no knobs on the Furrion unit, just a thermostat, no knobs.

After sitting in there while it's running, it seems that the compressor cycles on & off quite a bit, runs for 2-3 minutes, shuts off for 2-3 minutes almost more off than on and the air coming from the unit doesn't stay real cold unless the compressor is running. Is it normal for it to cycle that much? Shouldn't the compressor continue to run until the air in the coach has reached the set temperature of the thermostat?

[Soppy]

Could the unit have possible iced up . It may happen in humid conditions with not enough air flow. Also check to make sure the condensed coil is not dirty.

[computerguy]

I have a 36' class A. I put Reflectix in the front window and west facing side front window. I have window awnings on all the other windows. I pull the day shades down on them. I have a 15k and 13.5k btu ACs. In summer in sun the AC kicks on at around 8:30 AM and doesn't shut off until 9:30 PM. In the mid 90's I am lucky to maintain 80 inside. Near the walls it is considerably higher. The little bit of insulation just can't fight the heat of the day.
So, it may be normal it may be not. I'd check the output air temp out of the registers. I've seen high 50's when it is in the 70's inside. It goes up throughout the day as the heat from outside builds and it cannot keep up. I do have the AC Silencer from Wacko products on my Coleman Mach units and it did help as it helps to seal the airflow much better than stock.

[jaydee325]

Something is not right. That sized AC in a 23' coach should be able to make snow.

Had the same size AC in a 32' class A circa 1995 and it did an excellent job.

Find an RV HVAC tech that knows what they are doing.

[jagert59]

Originally Posted by twinboat

Pull down the ceiling cover and see if they screwed up the intake connection. It may be blowing the cold air right back to the evaporator.

My new MarkIV, on my boat, has a cloth boot that keeps the intake and discharge separate. It's held in place with tape

This ^^^^ appears to be a part of the issue, I removed the distribution box and the foam gasket wasn't sealing to the distribution box allowing cold air to be pulled into the return air path, I added some foam material to seal it up, the other issue is that the room air temp sensor is inside of the distribution box and NOT in the thermostat as I thought, it was tucked up in the air stream of where the cold air was leaking past the gasket, causing the compressor to continually cycle on and off, making the unit think that the RV had reached the set temp. I moved it down and into the return air stream.

I'm seeing temps in the 70's now and the humidity is being removed from the RV also.

Thanks for all of the advice/ideas.