retrofitting a manual control non-ducted to a Cycled Digital Thermostat

[rodsterinfl]

Greetings. I am about to take on a project that I know very little about. I read an article form RV Forum where a guy had retrofitted his manual Dometic AC to a Digital Wall Thermostat. The REASON for doing such a thing is to add the cycling of the fan (on/off) to quiet the running noise down- like a stick home unit. Dometic was good to provide the correct controller unit and thermostat for my AC unit but now I will have to figure out what comes out of the old one and what goes in and where. Is anyone well-versed in these things to offer a bit of advice for the project?

[HowieE]

Unfortunately you can not afford to cycle the fan off in an RV. The fan is needed to move the air around lest you will have very hot areas of the trailer before the unit call for cooling.

You might get away with that if you had other quieter fans place to circulate the air.

Another approach would be to make ducks that would deliver air to the back and front of the trailer leaving the return at the unit. This could lessen the fan noise and allow you to leave it running for the needed circulation. This would require some creative duct work since the delivered air is at the rear of the unit and the return air is at the front. But one duct straight out the back and 2 ducts out of the side of the unit going forward.

Give it some thought because I doubt you are going to like the results of cycling the fan in Fl. when the sun is out.

[rodsterinfl]

Understood. My thoughts on this are more related to load. I have noted that once the interior cools down and the humidity is drawn out, the cycling of the compressor begins. At this point, the AC is maintaining the cooler dryer air. The fan running continuously is not of benefit. Unlike some who have posted about having hot air on one side of their trailer and cool air on the other, I do not have that issue with the 5-way ADB replacement. I just flip a knob and it balances nicely.

If the fan shuts off during the warmer time of day, great. At night, it may shut off more. I believe the new Airstreams all have cycling air now don't they- the wall control?

[HowieE]

What is 5-way ADB?

If you have found a way to off set hot spots in the absence of circulation you have defied some of the basic law of physics.

[voxmaestro]

Since Airstream went to or has used heat pumps for non-ducted cooling, they all cycle off when not calling for cooling. They have for years.

[voxmaestro]

Rodster, I am also interested in this very modification.

[Al and Missy]

The CCC and CCC2 wall mounted thermostats let you choose between low, high and auto for the fan. On low or high the fan runs all the time. On auto it runs with the compressor, and at the speed required by the temperature differential requested.

I actually like to run mine full time on low at night. We camp with pets and close the doors between the living area and bath area and bedroom. Very little air gets to the bedroom area unless the fan is running. I also like having the background noise.

ADB = Air Distribution Box, the lower part of the non-ducted AC unit.

Al

[vintagemotor]

The controller goes up on the roof unit, remove cover and the controller is on the street side of the AC unit, remove and replace with one from Dometic. The thermostat is another thing, you have to run the com wire from the overhead down to where you want to mount the thermostat, going through walls and such, remember that this is the actual thermostat now so place it in a smart location.
There are small "DIP" switches on the controller that have to be in the correct position for everything to work.
I suggest opening everything up (cover on the roof and cover inside) and call Dometic for assistance, they will walk you through the install or any troubleshooting that may come up.
Good luck and be safe!

[rodsterinfl]

Thank you. I am in the middle of it this morning. It appears my trailer has the com wiring and all there already but I have no idea where it ends. Where were the AC thermostats in 2006? My furnace only one is on the wall beside the fridge.

[rodsterinfl]

Originally Posted by rodsterinfl

thank you. I am in the middle of it this morning. It appears my trailer has the com wiring and all there already but i have no idea where it ends. Where were the ac thermostats in 2006? My furnace only one is on the wall beside the fridge.

[rodsterinfl]

Anyone who can help on this?

[rodsterinfl]

Ok, I have a suspicion that the ac wiring that is in the photo going to the left, does so as to hook to the furnace, then make its way around to the refrigerator area. I am still hunting for the other end of those wires for the thermostat. I DID find out that the thermostats in '06 models were almost always located on the panel wall (never outer walls) usually next to the fridge and, that means the most probable location is that they are in that area now. Perhaps even in the wall just the furnace wires coming out for the current furnace-only thermostat.

In the photo, you can see the yellow electrical wire going to the manual controller box still installed on the air distribution box. The only other thing that gets plugged into it is the one white component plug shown also. The other wires I am holding includes a com wire (phone-type) so, I am assuming that these wires end up beside the fridge. The reason is that Airstream shows them ending on the road side 141" forward of the last outrigger per se. Which is where the current furnace-only thermostat is. Thermostats have to be placed on panel walls. I have no other panel walls except the bedroom.

[voxmaestro]

Originally Posted by rodsterinfl

Attachment 290672

I have a friend who has a 2006 Classic CB 25 and his thermostat is located on the panel wall facing the living area right where the refrigerator is with microwave above it.

I have the same floor plan in a 1990 Excella, but mine is a narrow body. Mine has wires for the furnace thermostat run in the refrigerator plenum which is on the interior side of that panel wall. Yours could have terminal wires coming from the roof air unit but I'm guessing they would run between the microwave and the wall above the refrigerator. Either that or through that plenum area coming down through the ceiling

Hope this helps...

[rodsterinfl]

Thank you so much for replying. Not being an electrical person I am in over my head on this seemingly simple retrofit. My father, Mr electric, has not taken interest and keeps saying just look around. I just wish I knew where the wires hanging out of the ceiling ended without tearing out the couch and the fridge.

[rodsterinfl]

you have to run the com wire from the overhead down to where you want to mount the thermostat, going through walls and such, remember that this is the actual thermostat now so place it in a smart location.
There are small "DIP" switches on the controller that have to be in the correct position for everything to work.
I suggest opening everything up (cover on the roof and cover inside) and call Dometic for assistance, they will walk you through the install or any troubleshooting that may come up.

I wish. Dometic would not help me. They said they could not offer assistance in a modification. My biggest hurdle is not the control box. They DID SEND me the installation directions and it is located inside the adb; however, I do not know where the Airstream pre-wiring terminates. The wires are right there, I have removed the fridge and see only the furnace blue and blue-white wires. I DO see a telephone COMM cable in a wire group but do not know if it is tank COMM or what. I need a wiring diagram. I am surprised that Airstream could not tell me when I called.

[rodsterinfl]

Well, tonight I completed and tested the upgraded AC system. It works! I am ecstatic! First, let me share that my goal was achieved; however, there was an added bonus too. The AC and Furnace both run off the thermostat- no surprise. In the original Safari, the AC is controlled from the AC unit and the furnace has a wall thermostat.

The fan now cycles on and off. Initially the fan comes on with the Hi setting. Blowing loudly. In the past it would do this continuously until I would choose to reach up and set it to low. Today it was 93 degrees in the trailer with 90% humidity. I turned on the AC and it started up like always. After about 40 minutes or so, it lowered the fan speed on its own and here was the surprise- a low fan speed. I, for the first time, could faintly hear the compressor inside the trailer. Prior to this, I never heard the compressor, only fan sound whether on high or low. So, the fan speed is lower than the manual low speed. The noise level was amazingly decreased. I got up and walked under the unit. I could hear faint compressor sound and soft blowing. WONDERFUL! I waited another hour or so to see if the unit ever cycled off. It did! Note too that the unit has a built-in freeze sensor to increase the cycled air if needed. In the past, I would have to turn off the unit if it froze or run it on high continuously if conditions required it. With the ability to direct air with the newer ADB (already had) and the fan cycling, it is a major improvement my opinion. I expected the cycling of the fan but the quieter operation was an unexpected bonus. I took sound readings to compare to my other readings I took with the old manual controls.

The work: The job was sorta intense considering the task was only to replace a thermostat and a control unit. I was retrofitting per se so I had to be creative. I ended up having to run new wire from the AC cutout between the walls down to the refrigerator area and the thermostat location. There are five wires needed to be run- the two furnace connections at the wall currently had to be extended and rerun to the AC cutout (2 wires) and there was a three-wire cord to be connected to the new control box and the thermostat. The other connections were straightforward. I located the control box where the original manual box was but it was tightly wedged in so I just decided to leave it just wedged as it is very tight. The freeze sensor was also easy to plug into the box and then stick it between two evaporator coil fins. I purchased two 7/8" metal plugs for the ADB previous manual knob location. Yes, I removed the ADB and the fridge to do the work.

[rodsterinfl]

Very little air gets to the bedroom area unless the fan is running. I also like having the background noise.

Do you have the newer ADB? The sorta oval one? If not, get it! There is a HUGE difference in trailer airflow as you can control the flow better with 5 directions. Also, if you note the two knobs, they are the ones I removed and plugged the holes with the 7/8" silver plugs. I had to remove my heat coil when I got this ADB but I never used it anyway. I have an Dyson electric heater/fan.