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Piggy Bank · 09-17-2019, 07:29 PM

We recently traded into a 27 Flying Cloud FB Twin with the 50 amp service and 2 AC units.

It seems that the rear area with the kitchen and table area gets a lot more cooling than the front area with the beds.

Anyone else experience this? Do we need to find out why?

ghaynes755 · 09-17-2019, 07:42 PM

Check to see where the temperature sensors are located. Front bedroom units seem to get much warmer than the rest of the trailer since they typically have wrap around windows and the narrow aisle opening. And with only a couple of vents don't get the same airflow as the rest of the trailer. I have a Dyson fan that I use to help move air into the front bedroom of my Classic for exactly the reason you describe.

brick1 · 09-17-2019, 07:58 PM

We just turn the temp down in whichever area is hotter. Send to work.

mikeinca · 09-17-2019, 08:04 PM

You should also check the vents in the ceiling. The more powerful 15,000 BTU unit is probably over the living area but in practice since the ceilings are ducted, airflow from both AC units feeds all of the vents. If vents in the rear are opened wider than the ones in the front you will get more cooling in the rear. Adjusting the vents to more evenly distribute air throughout the coach can be as effective, if not more so, than adjusting the thermostats front and rear.

twbucksr · 09-18-2019, 06:12 AM

We live in our 27FBQ FC. The 15k AC is over the kitchen and the 13k AC is over the bedroom. The temperature sensor for the 15k is behind the tv and the heat from it while watching tv will influence it and it will get much cooler in the space than the set point. The bedroom unit is looking at the thermostat for its temperature sensing.

turk123 · 09-18-2019, 06:30 AM

My 2019 Classic 30 also has an imbalance in cooling. Part of the problem in mine is the rear two return vents for the rear AC are open when the front AC runs and a lot of cool air is coming out of them. We can turn up the temp in the rear, but the front AC still pumps cold air to the rear through those two return vents.

I would be interested to see if other Classic owners and others have a similar problem. It seems like the rear AC should pull the return air not from the ceiling duct, but from a separate duct isolated from the ceiling duct. It appears as if it gets part of its air from the ceiling duct. A bit counter-intuitive. I guess I can pull the covers and take a look inside. I have a snake camera just for this kind of purpose.

johnparris · 09-18-2019, 06:53 AM

My 2019 Classic is also cooler in the rear like yours, turk123.

turk123 · 09-18-2019, 08:16 AM

Quote:

Originally Posted by johnparris

My 2019 Classic is also cooler in the rear like yours, turk123.

Are you getting air coming out of the rear return when rear AC is off and front AC is running?

dmslawson · 09-18-2019, 09:32 AM

We’v found that our 2016 Classic has always been cooler in the rear bedroom area whether the rear A/C is on or off (when we use the A/Cs in hot weather).
We simply minimize the 4 vent openings in the bedroom when necessary. That way it stayed in the 70’s inside throughout the trailer when we camped in 105 degree weather. Comfortable inside!
Glad to hear that the 27’ FC now has two vented A/Cs. One of the main reasons for trading in our previous 2011 27’ FC was the single A/C with 20+ higher temperature readings at the front and back of the trailer (away from the “polar vortex” immediately under the A/C vents).
Recommend previous comments about checking placement of front and rear temperature sensors and return air ducts, etc.
Good luck!

uncle_bob · 09-18-2019, 09:55 AM

Hi

A lot depends on what you mean by "more cooling".

If you mean that one end gets more cooling air than the other then sure, that's always going to be the case. The trailer layouts are pretty much all asymmetrical. (= one end is more open than the other).

If you mean that it actually gets noticeably colder, then no, that is not an given. Sensor calibration and the location of the sensors play a part in it. ( mounting them over the TV and having that running .....). Depending on exactly what you have for thermostats there might be a calibration adjustment ( most do not have one ...).

Bob

emelaich01 · 09-18-2019, 10:34 AM

The biggest culprit in our 2017 25' FCFB wasn't the television, vents or proximity to the stove but where AS in its wisdom mounts the remote temperature sensor in our model--right on the exterior panel for the 'fridge.

This compartment generates a LOT of heat despite the roof vent and the fans we installed in the 'chimney' to pull some of it out in warmer weather. But not all. Add to it the hole that the wire to the sensor passes through helps warm the sensor as well!

Solution: remove the cover and you'll see a little thermistor soldered to the wire. If you'd rather not unsolder the device, pull out some of the excess wire--should be at least 6 - 8"--and cut the wire a couple of inches from the thermistor. Strip the insulation of each end and add a couple of feet of speaker wire, lamp cord, whatever you have handy, and connect the wires with small wire nuts; polarity isn't important. If neatness counts, slip some heat-shrink tubing over the wires, solder the ends and shrink the tubing over your completed extension.

You can strap the thermistor and any excess wire to the power cord of the TV or wherever you like with a nylon tie but position the thermistor between the set and the wall and you're done.

After moving our sensor, the temperature differential between the two units will now be about 2 - 3 degrees providing of course, that the sun isn't cooking one end of the coach! And the sensor cover? We put it in the 'AS parts' box with the original sink sprayer hose, shower door threshhold sweep and dead taillight.

dznf0g · 09-18-2019, 10:47 AM

I found the same issue with just a plain old ccc1 mounted on the fridge wall. If you have the fridge out for any reason, staple prodex or other foil bubble insulation on all the surfaces on the interior fridge compartment. Fixed the thermostat inaccuracy and helps a bit with heat load to the interior.

jnm30327 · 09-18-2019, 10:59 AM

I have to adjust the rear temperature setting all the time because of the location of the temperature sensor. It is not set and forget.

See my pet peeves of a few days ago on this forum.

johnparris · 09-18-2019, 11:38 AM

Quote:

Originally Posted by turk123

Are you getting air coming out of the rear return when rear AC is off and front AC is running?

Not 100% sure about the return but seems like I remember feeling that before. I’ll check next time I fire it up.

pianolaw · 09-18-2019, 12:05 PM

Quote:

Originally Posted by emelaich01

The biggest culprit in our 2017 25' FCFB wasn't the television, vents or proximity to the stove but where AS in its wisdom mounts the remote temperature sensor in our model--right on the exterior panel for the 'fridge.

This compartment generates a LOT of heat despite the roof vent and the fans we installed in the 'chimney' to pull some of it out in warmer weather. But not all. Add to it the hole that the wire to the sensor passes through helps warm the sensor as well!

Solution: remove the cover and you'll see a little thermistor soldered to the wire. If you'd rather not unsolder the device, pull out some of the excess wire--should be at least 6 - 8"--and cut the wire a couple of inches from the thermistor. Strip the insulation of each end and add a couple of feet of speaker wire, lamp cord, whatever you have handy, and connect the wires with small wire nuts; polarity isn't important. If neatness counts, slip some heat-shrink tubing over the wires, solder the ends and shrink the tubing over your completed extension.

You can strap the thermistor and any excess wire to the power cord of the TV or wherever you like with a nylon tie but position the thermistor between the set and the wall and you're done.

After moving our sensor, the temperature differential between the two units will now be about 2 - 3 degrees providing of course, that the sun isn't cooking one end of the coach! And the sensor cover? We put it in the 'AS parts' box with the original sink sprayer hose, shower door threshhold sweep and dead taillight.

I had same problem with my 2015 27FB International. The heat from the fridge wall caused the AC to run longer and colder so I just took the cover off pulled out the wire a bit and let it hang in the air. Not as neat as you did but it worked. Can't see it because covered by TV.

NY24 · 09-18-2019, 07:15 PM

Yes

Piggy Bank · 09-18-2019, 08:03 PM

Wow lots of answers.

Basically, here is what we are experiencing.

We have both AC units on with thermostat set to same temperature. Like to 68º.

Seems to cool of really nicely by the table and kitchen area. When you walk through the trailer it is just hotter in the bedroom area.

I am assuming that whether you run 1 AC unit or 2 AC units, that all of the ductwork is connected and that both units are feeding the entire trailer. I have not uploaded the parts breakdown and studied this.

If we want to get it to feel cooler in the front of the trailer where the beds are, what is the best way to do that? Have the AC over that zone set colder, close vents in the other end of the trailer, or something else?

Thanks for any advice. We are going out again next weekend so I can fiddle around with things then.

Jmhandel · 09-19-2019, 05:24 AM

I had the same problem. The thermostat sensor is mounted on the wall were the tv is mounted. Look behind tv and you will see a small white object, that is the sensor for thermostat. If the tv is on the temperature near the sensor gets very warm. The solution that I found that works is to install a tv mount like the one in bedroom that allows it to be extended away from wall.
The root cause of problem is a design flaw. If Airstream had tested the AC with the tv on they would have found this problem and corrected it.

They wanted to move the sensor away from tv. But lowering or raising the sensor is not the answer removing the heat source from the sensor is a better solution.

turk123 · 09-19-2019, 05:57 AM

I went to my trailer and opened up the two rear air return vents (Classic30). It was located between two struts that run from side to side and about 12-13 inches wide. The AC is located right above. Blocking the main duct was a large electrical box with several large wires (Romex) running into it. It was actually hitting the AC fins. I pulled it down (it is not attached to anything) and positioned it between the two vents. I also cleared many wires away from the opening to the AC.

This is exactly the same thing that I found on my 27' international signature a few years ago. It had the same electrical box blocking the vent and a large piece of insulation. It probably has nothing to do with one area being colder than another, but certainly will make the airflow better. I will later look at the front vents to the front AC.

I suggest everyone take a look inside your vents to free up the rat's nest that Airstream puts up there blocking the flow of air.

Now, as for the cold air that comes down the vent. I put a snake camera up there to try to see where the cold air could be coming from. It was a bit inconclusive as my camera magnifies a bit too much and is hard to identify things. I did feel a 3" x 3" opening that may be the culprit. Since my Airstream is in storage I could not run the AC to tell, but I will the next time I bring it back home for our trip starting in October in a few weeks. If it is coming out of there, I will add a foam block to block the air and see what happens.

I can't imagine that there is a good reason to mixed the air from the front AC to the rear one, but maybe that is what it is for? Maybe some thoughts here?

lzhome · 09-19-2019, 08:59 AM

Question: my 2020 FC 27FB has two AC units, are they both 15,000 models? They both appear to be identical from outside view. Didn't get any documentation and looking for links to user manual.

Also, we have fewer AC outlets in the bedroom then the living area, this proably is why the temps are not atabe front to back.