The Danby Air Conditioner in a Tab320s

grassgd

I use the AC in my trailer quite a bit and really didn’t have a problem other than a crack in the plastic drip pan until I improved the venting on the unit to ensure it will perform the best it can in very hot weather. 

The modification was very successful and the unit performs very good in 100 plus temps and direct sun. The problem that I see now is the humidity becomes excessive when the temps are moderate outside and the compressor only runs a short time before cycling off.  Once this happens the humidity climbs as the water remaining on the condenser is put back into the trailer since the fan runs continuously on the Danby AC along with the water vapor from us inside the trailer.

 

This is the classic example of an air conditioner which is over capacity, which the Danby is when outside temps are only moderate.  My modification to improve the cooling air circulation on the Danby condenser has actually made this problem show up more than ever.

Since the Danby AC only runs with the fan on all the time, I plan to modify the AC to only turn the fan on when the compressor is running.  I pull the AC out to determine how to accomplish the wiring change and determined a DPDT relay can be installed and controlled by the compressor to turn the fan on.  If I was replacing the AC, I would make sure the new unit could run with the fan in auto to cycle it on and off with the compressor.

While I had the unit out I began looking at the auxiliary fan NuCamp installed in the trailer to aid in the AC air flow.  To my surprise I found the fan as installed by the factory is pulling air out of the AC compartment and not into the AC compartment which is on the cool side of the condenser.  I don’t know if mine was just installed backwards or that’s how they intended it to be.

 I removed the auxiliary fan to reverse it and found the roof top vent was installed by cutting through one of the roof aluminum structural members.

 

 Also I noticed the roof top vent is essentially about an inch and a half diameter with a bug screen which was about 40% plugged. 

 

The vent is way too small for the size of fan used.  I judged the amount of air the fan blows with the roof vent restriction is likely cut in half after cleaning the bug screen compared to the fan with no inlet restriction.

It may be a couple weeks before I get the relay, complete the modification and test to confirm if this helps as much as I hope it does.  In the meantime, I hope this sheds some light for others experiencing high humidity in their trailers.  You have to understand basic AC issues which I’m learning the hard way.

Tabaz

Thank you for this post.  Very interesting information.  My Aux fan draws air from the ceiling vent into the A/C cabinet.  Also, the last time I looked into the vent opening, I didn't notice any aluminum bracing.  This would have really concerned me.  I'll definitely be checking that screen for obstructions.

Mickerly

We tested the Danby output temperature with the AC fan on and OFF. there was no difference, just more noise.. Didn't think about checking the screens for bugs. 

MuttonChops

A]   My fan was installed to pull air in (correct direction).

B]    My 1.5 inch Vent tube/cab also was placed to Cut the Roof Framing.

C]    I replaced the 1.5 inch vent pipe { 1.77 sq inch max air flow without bug screens } with a

       4 inch pipe and Radon Hood/Cap should provides  14 sq inch max air flow.

grassgd

Installed a relay to modify the wiring on Danby AC so the fan cycles on and off with the compressor.  Tested it out in my driveway and found it works extremely well at controlling the humidity.  Outside temps were not very high so the load on the AC was not high which is when the humidity problem is the worst.

The fan will not run fan only is selected by I never ran the fan only before anyway.

The relay coil is energized with the power from the thermostat that controls the compressor.  The fan high and low wires are run to the normally open contacts of the relay contacts so when the compressor is not running the fan is off.

grassgd

Here is a graph of temperature and humidity this past weekend showing the improvement in humidity control with the fan modification to only run when compressor is running.  

pthomas745

Would the newer inverter AC's currently available be better at handling this sort of issue?  A 2017 air conditioner is ancient tech these days, it would seem.

grassgd

If the inverter AC would run longer at a slower compressor speed when the heat load is lower, it should work better for controlling humidity since it would continue removing moisture while it is running and have less or shorter "off" time. I assume the inverter AC fan would shut off when the compressor stops also, otherwise the humidity would increase after the compressor stops while the water on the condenser is re-evaporated by the fan and put back in the trailer.

With the modification I made to have the fan turn off with the compressor, I have demonstrated it does an acceptable job at controlling humidity during low heat loads since the moisture left on the condenser is not re-evaporated and put back into the trailer. 

 Would the inverter AC do a better job?  Seems like it may but for under $20 dollars for the relay and a little work, I am happy with the modification.

When I need to replace the Danby AC, I'll only replace with a unit that can have the fan turn off when the compressor stops too. 

pthomas745

It is a "cool" mod...and, what device were you using for the Temp/Humidity measurements?

grassgd

pthomas745 said:

It is a "cool" mod...and, what device were you using for the Temp/Humidity measurements?

A bluetooth device made by Govee - bought it on Amazon.

Mickerly

We replaced the Danby with the Frigidaire 5000Btu unit. It's the same size as the Danby. It has a thermostat, a lower low fan speed and you can select to run on low or be off between compressor operations. The air is a lot colder.

MuttonChops

I so miss the 'window' style AC.
The current 320S (360S?) Air8 + a cassette toilet (a capacity & lost single dumping process {with gray tank} issue)

nüCamp 'enhancements' have really changed the original EU Design concepts.

rcarlson1957

3 years ago I replace the Danby with a Emerson Quiet Cool 5000 BTU unit. When I had the A/C unit out, I did some mods as far as insulation and venting. Here's the link to mods. https://tab-rv.vanillacommunity.com/discussion/14595/a-c-mod#latest

Here's the link to the Emerson Quiet Cool. Functions better. Has digital thermostat, remote, dehumidifier function, split vents, eco mode, auto restart if power failure and some other useful features. 

https://www.amazon.com/gp/product/B096ST86R4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

Been happy with it. 

Personally, I think the biggest problem with window A/C units in older T@Bs is lack of side venting in that confined space. Window A/C units are designed to hang out from window and make use of their side venting. I tried to address some of that by separating the intake and exhaust routing a little (only so much you can do in that space). 

Mickerly

I agree with this completely. The upper vent is too small with too much restriction and the side opening is too small to allow enough air to enter. More air entering the unit would make it quieter and cooler at the same time.

I like having the fan run constantly; then again, I have the Frigidaire unit. It has a lower low fan speed and a thermostat.

grassgd

Mickerly said:

I agree with this completely. The upper vent is too small with too much restriction and the side opening is too small to allow enough air to enter. More air entering the unit would make it quieter and cooler at the same time.

I like having the fan run constantly; then again, I have the Frigidaire unit. It has a lower low fan speed and a thermostat.

Just keep in mind, if the humidity level inside the trailer is high while running the AC with the fan on constantly, you should try turning the fan to run only when the compressor is running.  This helped reduce the humidity significantly inside the trailer.

I agree the vents are small, especially the roof top vent.  My roof top vent fan was installed pulling air out of the AC space which is the wrong way.  Should have been pushing outside air into the AC compartment but the roof vent is so small, it doesn't move much air.

I made a modification to ensure the AC pulls outside air in without mixing with the hot air being discharged.  This has worked extremely well and the unit performs good even when temps are above 100, therefor the wall vent size being small seems not to be a problem.

Mickerly

I checked my AC fan when I traded AC units. It was installed correctly, pulling air in. I'm replacing the vent assembly for a slightly larger one later this summer. I expect that will reduce noise and increase cooling.

If we have to park in the sun, we would put a 13x13 canopy over the trailer. It reduces the AC load significantly. Shade is important. When the aluminum ceiling is heated by the sun, the cabin is much warmer (or the AC works much harder).