A/C unit cycles excessively

[Denny and Angie Miller]

Originally Posted by unclesam

I used expanding foam in all holes under sinks etc. I also cut cardboard to plug all furnace vents in the floor and furnace return ducts under the steps. I did everything I could think of to prevent cold air from escaping, I'll remove cardboard in furnace vents and return air when A/C is no longer required.

I also used expanding foam. I changed out my furnace floor vents with the closeable type, and I'm looking for a good way to close off my furnace return vents at the steps that still looks good, but doesnt require removing them to return them to use....any ideas?

[Denny and Angie Miller]

btw, my local hardware store doesn't carry the right size closeable vents for the stairs...not even close where I could maybe trim them down or something

[waynemoore]

I just put black poster board and closed them up. There is more than enough make up air in the furnace area.

[unclesam]

Originally Posted by Denny and Angie Miller

As an update, I found my return air ducts were both collapsed down to about 1" opening. I cut 1 1/4" pvc pipe into 6" sections and stuck those in there to hold the return duct open. I used aluminum tape to seal the duct/vent transition on the supply side. While doing that I used my phone as a video camera to inspect all the supply ducts, and didnt find any other issues. I did find 2 holes about 6" diameter each in the lower corners of the garage where cold air was pouring out, so I bought some black "great stuff" foam sealant and filled those. While I was there I went ahead and sealed the garage from the 2 propane compartments to prevent mud dobbers/wasps from getting in. I guess I'll surrender the propane compartments to them....Anyone use window screen to cover the large lower opening on the propane compartments?

More on A/c cycle issue, I found this past week end that when the temperature in my RV is within 1 or 2 degrees of the outside temperature, my A/C will cycle 5 or 6 times before it "figures out" what to do: kick compressor on and cool or shut off. If I change the thermostat setting to a lower setting by 3-4 degrees, the unit comes on, operates normally and cools the RV. The trick is to off set the "set temperature" on the thermostat to fool the A/c unit. When the inside temperature is lowered and is different than the outside temperature, everything works as advertised. I haven't had time to get with my dealer and discuss this "magic" with him. Will get back with you when I get an answer.

[jameswbarton]

The floor heat vents are standard residential size. You can replace them with closeable ones. Some day I will also change out all heater duct hoses with insulated ones. I am also isolating the basement from the living areas and using electric bilge heaters to heat it in cold weather so I have removed the furnace feed into the basement.

[PeteandJoan]

Originally Posted by jameswbarton

The floor heat vents are standard residential size. You can replace them with closeable ones. Some day I will also change out all heater duct hoses with insulated ones. I am also isolating the basement from the living areas and using electric bilge heaters to heat it in cold weather so I have removed the furnace feed into the basement.

If I close off the vents under the stairs to improve the AC during the summer do I really need to open up those vents during the winter when using the furnace ?
If I am in very cold areas I can always run an electric heater in basement to avoid frozen lines. Just want to be safe.

[jameswbarton]

Closing off the heater air return vents under the stairs is a band aid to a bigger issue. The area under the stairs in the front of the unit is very open to the outside air and also has large openings into the living areas through the wall and cabinetry and the main electrical panel. If you want to find drafts leave your baggage compartment door open in a high wind and feel the drafts. In my unit there is more air leakage into the hutch between the kitchen and front living room than the vents under the stairs. The easiest way to get good heating and cooling is to make everything above the floor living area and everything below the floor basement area. This requires a lot of insulation and sealing. If done right it will make the AC and Heating better by allowing a much higher percentage of air to recirculate requiring much less btu's to heat or cool the recirculated air.

[kdeiss]

Originally Posted by unclesam

More on A/c cycle issue, I found this past week end that when the temperature in my RV is within 1 or 2 degrees of the outside temperature, my A/C will cycle 5 or 6 times before it "figures out" what to do: kick compressor on and cool or shut off. If I change the thermostat setting to a lower setting by 3-4 degrees, the unit comes on, operates normally and cools the RV. The trick is to off set the "set temperature" on the thermostat to fool the A/c unit. When the inside temperature is lowered and is different than the outside temperature, everything works as advertised. I haven't had time to get with my dealer and discuss this "magic" with him. Will get back with you when I get an answer.

What is happening when in Auto is the Fan shifting from High to Lo or Low to High depending on set temp and room temp I discribe this in more detail in a previous post on this thread. You will not get the cycling in High low or medium Just Auto.I have two Dometic thermostats both are 5 degrees of I set at 77 actually it is 72

[unclesam]

I may have finally resolved my cycling issue, not sure and I hate to make blanket statements. I've found these campers are like kids and make a liar out of you at the drop of a hat! My service department at the dealership, told me to cut 2 inch pvc pipe and put it in the supply ducting to increase the height to 2 inches, seems the ducting tends to collapse and prevent the air from completely escaping after shut down. I cut my 2 inch pipe into 2 1/2 inch sections, and installed them up thru the vent holes on each side of the ducting all the way to the outer edges. Seems their is a problem with back pressure from air being trapped in the supply ducting after the A/C shuts down. I haven't had any problems since installing the the pvc pipe, knock on wood!