A/C Cycling in our 2018 29RS

[surfintom]

I know this has been discussed a lot and I have read a ton already and not found my solution so I'll ask and hope someone has a fast answer.

Our 29RS has only one unit over the living room. I presume it's a Dometic, because that's the thermostat. We're in Austin right now. It's 90-95 all day. We put the A/C on set at 80 and fan on Auto. It runs for awhile and then starts cycling on and off fairly frequently. Sometimes when I turn it on, it starts cycling immediately. Because of some of my reading, I changed the fan to Low and the cycling has stopped. Why is this the solution? Why doesn't Auto work the way we would hope? Why does is cycle on and off incessantly? Is there a better solution? Is it a problem with the baffle between the in and out? I like to close the out vent on the unit so there's more air going thru the ductwork.

One other point. Before we left Colorado, we spent a day loading, etc. I had the A/C on and I don't think it was cycling. There it was plugged into the garage. Here we're plugged into 30 amp.

Right now it's set on 80, fan on low and it's running. It feels like it's cooler than 80. I don't think it's just the fan that's running. I think the compressor is running too.

Anyone have an answer? Thanks.

[TNFisher]

I prefer to set unit to on, fan speed on high, and set the temp wherever I want it. This keeps the air moving and allows the unit to fully cycle as needed. At low fan speed I have seen situations where the unit may freeze up due to lack of air flow across the coils.
Just my opinion.


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[livinthelife]

I know this has been discussed a lot and I have read a ton already and not found my solution so I'll ask and hope someone has a fast answer.

Our 29RS has only one unit over the living room. I presume it's a Dometic, because that's the thermostat. We're in Austin right now. It's 90-95 all day. We put the A/C on set at 80 and fan on Auto. It runs for awhile and then starts cycling on and off fairly frequently. Sometimes when I turn it on, it starts cycling immediately. Because of some of my reading, I changed the fan to Low and the cycling has stopped. Why is this the solution? Why doesn't Auto work the way we would hope? Why does is cycle on and off incessantly? Is there a better solution? Is it a problem with the baffle between the in and out? I like to close the out vent on the unit so there's more air going thru the ductwork.

One other point. Before we left Colorado, we spent a day loading, etc. I had the A/C on and I don't think it was cycling. There it was plugged into the garage. Here we're plugged into 30 amp.

Right now it's set on 80, fan on low and it's running. It feels like it's cooler than 80. I don't think it's just the fan that's running. I think the compressor is running too.

Anyone have an answer? Thanks.

Are you sure it's not cycling on and off to change fan speed? That's what ours does.

[surfintom]

By the way, when I say it cycles, I mean it runs for a period - sometimes several minutes, sometimes a minute - then it turns off for just a second to two and then turns back on. i can't really tell if the fan speed has changed. It just sounds like stop and go.

[livinthelife]

By the way, when I say it cycles, I mean it runs for a period - sometimes several minutes, sometimes a minute - then it turns off for just a second to two and then turns back on. i can't really tell if the fan speed has changed. It just sounds like stop and go.

That's what ours does. The speed difference doesn't sound a lot different, but I can hear it. My husband can't. It usually has a shorter "on" time when the temperature has reached the set one on the thermostat.

[Canyonlight]

X2 on what @livinthelife shared in post #3 . When ours cycles between low and high fan speeds when set to auto, it does pause as if it the unit turns off for a second or two. It can be hard to distinguish at times the difference between low and high fan speeds but it can be heard. Kind of annoying when the thermostat says the set temp is reached (I think W/I 3-5 degrees) thus the fan going to low since the set temp is close to being achieved. Take a look at your manual to learn more on this process.

When we have this condition occur, we set the temp lower to prevent the cycling (to usually low speed) so the fan will stay on high or simply set to high or low as suggested. Try setting to 70 and see what happens and report back.......the fan will probably stay on high longer before cycling (if it will cycle at all) trying to get the RV to close to 70 degrees.

Dan

[surfintom]

Kind of annoying when the thermostat says the set temp is reached (I think W/I 3-5 degrees) thus the fan going to low since the set temp is close to being achieved.

Try setting to 70 and see what happens and report back.......the fan will probably stay on high longer before cycling (if it will cycle at all) trying to get the RV to close to 70 degrees.
Dan

Tom A reporting back, Sir!
Yep - I set it to 70 with the fan on Auto and it just runs. Like 70 will never be achieved so just keep running. I must say - this is annoying. I don't like the this works. It's like "I'm getting close to desired temp so I'm going to scale back so I never reach it. I'll keep jumping back and forth just above your temp forever."
My preference would be that it behave like a home A/C. Cool it to a bit below desired temp and then turn off til it's a bit above desired temp. Back and forth - on and off - but give it a rest while it's in that range. Oh well. Things are different in RVs. Often sitting in the sun with nowhere near the insulation a home has.
By the way, how do you know what the actual temp is and whether it's close to the set temp? I only see the set temp and the system keeps running.

[livinthelife]

Tom A reporting back, Sir!
Yep - I set it to 70 with the fan on Auto and it just runs. Like 70 will never be achieved so just keep running. I must say - this is annoying. I don't like the this works. It's like "I'm getting close to desired temp so I'm going to scale back so I never reach it. I'll keep jumping back and forth just above your temp forever."
My preference would be that it behave like a home A/C. Cool it to a bit below desired temp and then turn off til it's a bit above desired temp. Back and forth - on and off - but give it a rest while it's in that range. Oh well. Things are different in RVs. Often sitting in the sun with nowhere near the insulation a home has.
By the way, how do you know what the actual temp is and whether it's close to the set temp? I only see the set temp and the system keeps running.

Not sure how your thermostat works, but on ours, we have to turn it off to see what the actual current temperature is. We also installed a thermometer that has 4 sensors (1 built in and 3 remote) on the end of the island in the middle of the living room. The 3 remote sensors are outside the rig, in the freezer, and in the refrigerator.

[Canyonlight]

Tom - with our rear 15K Atwood and front 13.5 BR Dometic Low Profile Penguin II, the documentation states that if the RV temp inside (at the thermostat location, of course) is within a few degrees (3 degrees as I recall) of the thermostat setting the fan will stay on low. If and when the temp spread is greater, then the fan will change to high as we have been sharing until such time as the previous spread is achieved at which time it will go back to low fan.

In other words, if your AC documentation states the same 3 degree spread and the AC starts cycling from high to low fan, you will know you are W/I 3 degrees at the thermostat location. Certainly different areas of the RV can and will be hotter or cooler depending on many factors affecting the temp both inside and outside.

When the RV interior is warm to hot, the AC fan(s) will run on high for sometime depending on thermostat set point when on the auto setting. It is all done to move more air to help cool the RV down more quickly.

Does this help ?......clear as mud ?

Dan

[Canyonlight]

Not sure how your thermostat works, but on ours, we have to turn it off to see what the actual current temperature is. We also installed a thermometer that has 4 sensors (1 built in and 3 remote) on the end of the island in the middle of the living room. The 3 remote sensors are outside the rig, in the freezer, and in the refrigerator.

X2 - we also have to turn off to see what the temp is at the thermostat location. Knowing what we know with where we set the temp and seeing/hearing the fan speed change to low, we have a good idea of what the actual temp is.

This said, when the temp spread is greater and the fan in running on high.......not so much except when sticking a wet finger in the air to find out.....yup, that works well !

Dan