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Old 07-27-2021, 07:45 PM   #1
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2015 25' FB Flying Cloud
Redmond , Washington
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Dometic Air Conditioner / Heat Pump replacement - 3rd unit in ~5 years.

Our 2015 FCFB25 trailer came with an ac unit that had an overly loud thud sound on startup. I attributed it to the compressor and ignored it for a few months. When the summer of 2016 rolled around the ac would not cool. I took it in to our local dealership and they replaced it with an identical unit (Dometic 651816C751C0) under warranty. The flow of air through the vents in the trailer seemed weak.This is something I had brought up with the service tech at the dealership and was told that the airflow was normal.

Last summer (2020) I noticed the ac wasn't cooling very much. We weren't venturing out much so we so I chose to ignore it. Fast forward to late June 2021 and we had a heat wave in the Pacific North West (100 - 110F over 3 or 4 days) and I wished I hadn't ignored the problem with the ac.

I tried remote troubleshooting it with the help of Darren at Myrvworks.com. The compressor's current draw was nowhere near what it ought to be - Normal should be around 11-14amps after running for 20 minutes but this was pulling ~7.2 amps. Darren told me I needed a new ac as the coolant had likely leaked.

I tried getting in touch with our local dealership and they seemed swamped. I did not get a response to a voicemail left with the service department. After waiting two days, I decided to order an ac directly from PantherRv.com and see if I could replace it myself. And I am so glad I did because I found all kinds of things that should have been addressed at the factory or at the time of the replacement of the first ac.

Our trailer has ac ducts(2015 was the first model year). The return air area between the inside and outside skin (it's a cavity of 3-4 inches where the duct-work runs) had no solid blocking of any kind, thus pulling in air from the cabin as well as the inner area between the outer and inner skin. There is a solid cross-member each to the front and back in this area but the sides were not sealed well at all. I had some aluminum foil tape and rigid foam lying around from another project so I made good use of them.
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After uninstalling the old ac I looked underneath and saw that other than the rectangular foam gasket there was no foam separating the conditioned air from the return air. You can see what I mean in a Youtube video titled 'Airstream Travel trailers: Quietstream.' Pause at the 38-40sec mark and you can clearly see a piece of foam gasket that separates the incoming air from the outgoing air. This is in addition to the rectangular gasket that is stuck on the new unit. I reused a length of gasket material from the old ac and applied it to the new one.
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Here's what the middle foam gasket looks like now from inside the return air cavity, just past the drain tube. No more mixing of conditioned and return air.
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Another air leakage point was the opening on top of the trailer where the conditioned air enters the trailer. There is a black plastic transition box/plenum that the two branches of duct connect to. There are gaps between the skin of the trailer and plenum itself.
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I was able to seal this with aluminum tape and thus make the air flow that much more efficient. The aluminum tape would not bond with the slick plastic, so I used some sandpaper to scour the surface. Make sure to clean the plastic shavings with a moist rag if you do this.

Having done just this much of sealing has considerably improved the airflow from the vents.

The new ac had a Molex connector on the 120v power cable. I could have cut the connector and used a junction box but decided to order a Molex connector from mouser.com. It will make the connection process that much easier for the next person replacing/servicing the ac.
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I also installed Microair's Easy Start 364 on the new unit. Roger at Microair was helpful with some questions I had regarding placement of the unit. A soft copper tube had to be bent. They do not send out any connectors with the Easy Start, so if you think you will need them make sure to order a kit as well. I have a 30amp service outside our home but this was an add-on in case we need to use the ac with a Honda 2200 on our travels.
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The ac is bolted down from the roof and I used some leftover Tempro 635 to seal the spaces under the foam blocks where the 4 bolts go in. The hardest part of the install was lifting the new ac on to the trailer roof.

I hope this helps the next person who is considering an ac replacement or has issues with airflow.
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Old 07-27-2021, 11:01 PM   #2
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This is helpful thank you. Now Iím gonna go inspect my 2017 for leaks at the air intake!
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Old 07-28-2021, 05:25 AM   #3
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Well documented.

I don't have this system but looks like you addressed a hidden problem. Have you measured the current draw with the new system and any temp readings showing return vs cooled air?

I wonder if Darren would have made this into a video if he had to tackle this one.

Airflow, yup you gotta keep it going in the right direction.

Gary
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Old 07-28-2021, 11:00 AM   #4
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Compressor base reading

Quote:
Originally Posted by GCinSC2 View Post
Well documented.

I don't have this system but looks like you addressed a hidden problem. Have you measured the current draw with the new system and any temp readings showing return vs cooled air?

I wonder if Darren would have made this into a video if he had to tackle this one.

Airflow, yup you gotta keep it going in the right direction.

Gary

The first thing I did after getting the ac working was get a base reading for the compressor.

Compressor was pulling 13.6 amps after 20 minutes of running at 81F. This reading was taken from the roof. The cover was removed from the unit to take the reading.

The remote display on our Surge Protector (Progressive Industries EMS HW30C) was showing around 11 amps of usage on the old unit. It showed around 16-17 amps with the new unit running. I didn't have any other major system working in the trailer when these readings were taken on the remote display.

The difference between the cool air and return air was around 25F.
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Old 07-28-2021, 11:05 AM   #5
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Well done.
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Old 07-28-2021, 11:16 AM   #6
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2013 27' Flying Cloud
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Just had our AC unit die a few weeks ago on a 2013 (non ducted single AC unit). I agree the hardest part was safely lifting the thing onto the roof. We rigged a ramp to slide the old one off and new one on.



Also double check the dip-switch settings so it properly integrates with your furnace. Forgot that step and had to go back up on the roof to change them.



-Peter
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Old 07-28-2021, 11:24 AM   #7
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Quote:
Originally Posted by Peter C View Post
Just had our AC unit die a few weeks ago on a 2013 (non ducted single AC unit). I agree the hardest part was safely lifting the thing onto the roof. We rigged a ramp to slide the old one off and new one on.



Also double check the dip-switch settings so it properly integrates with your furnace. Forgot that step and had to go back up on the roof to change them.



-Peter
Yes, the dip switches have to be opened or closed according your rig setup.

I used an 'A' frame ladder, wrapped the original packaging with the unit inside with strong ties and then asked two neighbors to help lift it while I pulled it on to the roof. Thankfully there are no recorded photos of this manoeuver.
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Old 07-28-2021, 12:09 PM   #8
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Quote:
Originally Posted by wanderingduo View Post
Thankfully there are no recorded photos of this manoeuver.
Seen the satellite view yet?
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Old 07-28-2021, 12:31 PM   #9
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Quote:
Originally Posted by wanderingduo View Post
Our 2015 FCFB25 trailer came with an ac unit that had an overly loud thud sound on startup. I attributed it to the compressor and ignored it for a few months. When the summer of 2016 rolled around the ac would not cool. I took it in to our local dealership and they replaced it with an identical unit (Dometic 651816C751C0) under warranty. The flow of air through the vents in the trailer seemed weak.This is something I had brought up with the service tech at the dealership and was told that the airflow was normal.

Last summer (2020) I noticed the ac wasn't cooling very much. We weren't venturing out much so we so I chose to ignore it. Fast forward to late June 2021 and we had a heat wave in the Pacific North West (100 - 110F over 3 or 4 days) and I wished I hadn't ignored the problem with the ac.

I tried remote troubleshooting it with the help of Darren at Myrvworks.com. The compressor's current draw was nowhere near what it ought to be - Normal should be around 11-14amps after running for 20 minutes but this was pulling ~7.2 amps. Darren told me I needed a new ac as the coolant had likely leaked.

I tried getting in touch with our local dealership and they seemed swamped. I did not get a response to a voicemail left with the service department. After waiting two days, I decided to order an ac directly from PantherRv.com and see if I could replace it myself. And I am so glad I did because I found all kinds of things that should have been addressed at the factory or at the time of the replacement of the first ac.

Our trailer has ac ducts(2015 was the first model year). The return air area between the inside and outside skin (it's a cavity of 3-4 inches where the duct-work runs) had no solid blocking of any kind, thus pulling in air from the cabin as well as the inner area between the outer and inner skin. There is a solid cross-member each to the front and back in this area but the sides were not sealed well at all. I had some aluminum foil tape and rigid foam lying around from another project so I made good use of them.
Attachment 400539 Attachment 400537 Attachment 400538

After uninstalling the old ac I looked underneath and saw that other than the rectangular foam gasket there was no foam separating the conditioned air from the return air. You can see what I mean in a Youtube video titled 'Airstream Travel trailers: Quietstream.' Pause at the 38-40sec mark and you can clearly see a piece of foam gasket that separates the incoming air from the outgoing air. This is in addition to the rectangular gasket that is stuck on the new unit. I reused a length of gasket material from the old ac and applied it to the new one.
Attachment 400540

Here's what the middle foam gasket looks like now from inside the return air cavity, just past the drain tube. No more mixing of conditioned and return air.
Attachment 400544

Another air leakage point was the opening on top of the trailer where the conditioned air enters the trailer. There is a black plastic transition box/plenum that the two branches of duct connect to. There are gaps between the skin of the trailer and plenum itself.
Attachment 400541 Attachment 400542
I was able to seal this with aluminum tape and thus make the air flow that much more efficient. The aluminum tape would not bond with the slick plastic, so I used some sandpaper to scour the surface. Make sure to clean the plastic shavings with a moist rag if you do this.

Having done just this much of sealing has considerably improved the airflow from the vents.

The new ac had a Molex connector on the 120v power cable. I could have cut the connector and used a junction box but decided to order a Molex connector from mouser.com. It will make the connection process that much easier for the next person replacing/servicing the ac.
Attachment 400543

I also installed Microair's Easy Start 364 on the new unit. Roger at Microair was helpful with some questions I had regarding placement of the unit. A soft copper tube had to be bent. They do not send out any connectors with the Easy Start, so if you think you will need them make sure to order a kit as well. I have a 30amp service outside our home but this was an add-on in case we need to use the ac with a Honda 2200 on our travels.
Attachment 400545

The ac is bolted down from the roof and I used some leftover Tempro 635 to seal the spaces under the foam blocks where the 4 bolts go in. The hardest part of the install was lifting the new ac on to the trailer roof.

I hope this helps the next person who is considering an ac replacement or has issues with airflow.
Thank you for your post. I have a 2016 27fb International. My AC has always had a hard time cooling. After reading your post, I went out and looked at my intake. I could see all the duct work. I turned on the unit and it would barely hold up the cheap foam filters. I sealed the opening with aluminum tape, like you did. Turned the unit on and I can actually feel the air being pulled in. Running now and It feels cooler. Can't wait to get it out and see the difference .
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Old 07-28-2021, 01:51 PM   #10
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2015 25' FB Flying Cloud
Redmond , Washington
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A couple other things I'd like to call out. One is finding out how to crimp the power cable into the Molex connector. There was no information in the Penguin II installation manual but it shows up on pages 13-15 on the Brisk II evolution 3314850 manual. The one I purchased was part no. 19403-1010 and the specs said that it was rated for 12gauge wire. The other half that came installed on the ac was a compatible fit. I do wish Dometic would send this just like the included low voltage Molex connector.

The other was that before I started up the new ac, I let the lubricant in the compressor settle for 24 hour after installation. I didn't find any specific guidelines on the Dometic site but did this out of an abundance of caution.



Quote:
Originally Posted by firemed509 View Post
Thank you for your post. I have a 2016 27fb International. My AC has always had a hard time cooling. After reading your post, I went out and looked at my intake. I could see all the duct work. I turned on the unit and it would barely hold up the cheap foam filters. I sealed the opening with aluminum tape, like you did. Turned the unit on and I can actually feel the air being pulled in. Running now and It feels cooler. Can't wait to get it out and see the difference .
I had fun holding all kinds of objects up to the return vents to see if they would stay up with the suction. I tried a light piece of foam and then a small metal cover for a junction box, both of which stuck very easily but my cellphone didn't stick! Earlier, I would hardly feel a draft with my hand held up there but it is very noticeable now. Did you feel/see the gasket blocking/dividing the return from the supply side? You should be able to see the gasket material all around the return air cavity. And the gasket that was missing in my situation was the one facing the back of the trailer looking up at the return air cavity. It should be just behind the drain tube.





Quote:
Originally Posted by GCinSC2 View Post
Seen the satellite view yet?





Quote:
Originally Posted by wulfraat View Post
This is helpful thank you. Now Iím gonna go inspect my 2017 for leaks at the air intake!
In addition to the return cavity, I think it would be worth resealing the plastic plenum up on the roof if someone really wants to get a cleaner and more efficient airflow. The ac is already on the roof, it's a matter of removing 4 bolts lifting the ac up resealing the duct work/plenum nice and proper and then re-tightening the bolts down with some sealant. If climbing the roof isn't something you want to do then it would be worth paying an hour or two of labor to have it done the next time you take it in for repairs. If your setup has quick disconnects already in place for the low voltage wires and power cable, it really shouldn't take more than an hour. The Penguin II units are around 100lbs, so definitely be careful!
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Old 07-29-2021, 03:22 PM   #11
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Quote:
Originally Posted by wanderingduo View Post
I had fun holding all kinds of objects up to the return vents to see if they would stay up with the suction. I tried a light piece of foam and then a small metal cover for a junction box, both of which stuck very easily but my cellphone didn't stick! Earlier, I would hardly feel a draft with my hand held up there but it is very noticeable now. Did you feel/see the gasket blocking/dividing the return from the supply side? You should be able to see the gasket material all around the return air cavity. And the gasket that was missing in my situation was the one facing the back of the trailer looking up at the return air cavity. It should be just behind the drain tube.
yes the gasket is there.
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Old 07-29-2021, 03:52 PM   #12
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Thanks for the very useful thread
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Old 08-10-2021, 11:32 AM   #13
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I made some more modifications to aid airflow in the ducts. The idea here was to reduce leakage of conditioned air between the duct vents and the upper cavity of the trailer. I used aluminum foil tape and a sharp blade to notch the tape to fit the circular shape of the vents.

While doing this I also taped some seams within the duct area that were easily accessible. I found it's best to do this after taping the vent cutouts - makes for less sharp edges to cut your hands and fingers up.

After doing this I don't find the need to make any modifications to the existing vent registers by cutting the plastic fins, etc. Plenty of airflow in the trailer now.

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Old 08-12-2021, 06:17 PM   #14
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2015 25' FB Flying Cloud
Redmond , Washington
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We are having a real warm spell in the NW. Temps were up in the high 90's today.
The new ac works well. We set the thermostat at 73F - The awnings were not extended but the ac still did a pretty good job of keeping the trailer cool. It just goes to show that a single well charged ac (15000BTU), properly installed on a FC25 can be trusted to cool the cabin sufficiently.
I can't help but wish that there was a way to tape a few of the seams inside the duct work. Most are hard to reach or simply impossible to reach through the vent cut outs. This needs to be done at the time of install at the factory. It would make the system that much more efficient, creating better airflow, causing less usage of the ac, less electricity wastage and better air quality inside the cabin overall.
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