A/C thermostat adjustable?

[fallsrider]

Hi, I have a DuoTherm a/c in my Jayco. This evening is the first time I have really run the a/c in warmer weather (in camp backyard), and I kept adjusting it until I have the thermostat set as cold as it will go, and the temperature is just cool enough, but not as cool as I think we will want it for sleeping. The compressor is cycling on and off, so the thermostat is working.

My question is this...do the mechanical thermostats on these a/c units have an adjustment like mechanical house thermostats do? I would like to adjust it to run a few degrees colder if that's possible. It would be nice to find the comfort zone to be somewhere in the middle of coldest and warmest.

Thanks!

[chasd60]

I can tell you that an AC unit is working as designed if the output is 20 degrees cooler than the intake. Some may work better but those are more susceptible to a frozen evaporator.
 
If the popup is 90 and the output of the AC is 70, it is good. If the heat load is so much that the inside of the popup doesn't get any cooler than 90, the output will never get any cooler than 70 by design.
 
Some do get a little cooler and some don't.

[fallsrider]

I understand what you're saying, and if it was 95 degrees out, then that would make sense. But the temps at bedtime last night were in the upper 70's, maybe low 80's. The a/c has plenty of cooling capacity, but the thermostat is turning off the compressor long before it runs out of capacity. I was just wondering if the thermostat could be adjusted so that it would keep the compressor on longer to bring the interior temperature down lower.

[Safety_Chain]

I understand what you're saying, and if it was 95 degrees out, then that would make sense. But the temps at bedtime last night were in the upper 70's, maybe low 80's. The a/c has plenty of cooling capacity, but the thermostat is turning off the compressor long before it runs out of capacity. I was just wondering if the thermostat could be adjusted so that it would keep the compressor on longer to bring the interior temperature down lower.

Fallsrider, I spent 10+ years in the hvac industry but I dont have experience with RV air conditioners. I would suggest that you try and locate the sensing bulb tube that comes out of the thermostat and make sure that the sensing bulb is in the path of the return (intake) air flow and not touching the evaporator. You can test the thermostat by taking a hand warmer and cover as much of the sensing bulb as you can with it. The heat from the hand warmer should make the thermostat keep the compressor running. If the compressor continues to cycle on/off you may have another issue such as a low pressure switch cycling the compressor, this could be due to slightly low freon charge level or a dirty evaperator coil and or filter. Dirt is the biggest enemy of a/c equipment so make sure the whole thing is clean.
A 20 temperature drop across the a/c is not going to happen if humidity levels are high let the system run an hour or two with doors and windows sealed before checking temp drop. Remember low speed fan is going to give you a higher temp drop and better humidity removal.

good luck

[trumpet87]

Funny, we have just the opposite problem with our new 13,500 BTU duotherm. It is TOO cold at night, on the lowest settings, next lowest is fan only, GRR! So we're either freezing or sticky  :mad: And we're in hot humid S. Indiana. Maybe someone on here will have an answer for us both, fallsrider. Good luck!!

[James]

Could it be that the cold air is just hanging around the unit and not being pushed into the bunk ends.  Try using a fan to move the mix the air up a little bit.  I have found that the window unit in my pup tends to cycle off before the trailer is cool if I don't use fans.  Just an idea.  Good luck.

James

[wavery]

Could it be that the cold air is just hanging around the unit and not being pushed into the bunk ends.  Try using a fan to move the mix the air up a little bit.  I have found that the window unit in my pup tends to cycle off before the trailer is cool if I don't use fans.  Just an idea.  Good luck.

James

James is correct in that theory.
 
If your AC is simply cooling the main living space, the cool air may be cycling too quickly.

My Carrier AC unit has the cold air outlets pointing straight out at the bunks. It does a pretty good job that way. I have seen AC units that just shoot the air down. As the air goes down, it quickly warms and goes straight back up to the AC unit. It never gets the chance to circulate in the bunks and the AC unit tends to cycle before it really gets it's chance to do it's job. A small fan in each bunk will make a big difference.

[LimeJeeeep]

the tstat is almost certainly a bellows type.there very well may be a adjustment.but before i did that i would replace it,if your handy this should not be a big task....
there also has been very good advise previously in this thread....

[fallsrider]

I have a DuoTherm, and the ducts do point towards the bunk ends, so I don't think that is the problem. I still think the thermostat just doesn't go to a low enough setting. I will investigate it one weekend and see if it is adjustable. If not, I'll try another one.

Thanks for everyone's comments.

[LimeJeeeep]

i,m glad this came up ...if you want it really cool...go to your local trane dealer and pick up part #swt00842...install the cap tube in the evap fins from the top . wire it in series witn the compressor overload.then wire a switch across the terminals of the tstat.
when you want it very cold hit the switch and the compressor will cycle on the freeze stat.it will shut the compressor off at a coil temp of 25deg and turn it back on at 60 deg....its important that you wire it in the compressor line .so the fan will stay on and thaw the evap coil.....this is a last resort plan....replace tstat 1st :U