A/C Ducting?

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A/C Ducting?

Postby g00s3 » Mon May 16, 2016 9:27 pm

Hi All,

I'm working through my plan b a/c design (rooftop unit will not work out - I did kind of expect it) and would like to put a petcool/climate right unit in my tongue box similar to aggie79's design

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except that I will duct both supply and return through the front and the headboard. I wanted to see if anyone has some advice on the type of ducting/tubing I should be using for this and where to get it from? I'm not having much luck on google and I suspect its because I am searching for the wrong thing.

Anyone know if the climate right uses 3" or 4" connectors?

Thanks all.

-goose
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Re: A/C Ducting?

Postby noseoil » Mon May 16, 2016 11:09 pm

I would get the unit first, then decide how to hook it up. What about ABS pipe & some flex hose connections?
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Re: A/C Ducting?

Postby aggie79 » Tue May 17, 2016 8:28 am

I checked the manual for the ClimateRight units. They use a 3.3" size duct. As I recall, that is about what the PetCool used.

The PetCool blower is not very powerful. The CFM rating is sufficient but like most blowers, it does not handle back pressure well. You'll want to minimize the resistance by keeping the duct runs as short as possible and with as few bends as possible.

The ClimateRight uses flanges at the unit like the PetCool. If your runs are short, I would consider using the hoses that come with the unit.

On my install I had longer runs. I used hoses and fittings designed for dust collection for woodworking tools. I used the 4" hose diameter: http://www.rockler.com/clear-flexible-dust-collection-hose-optional-sizes. To make up the difference in diameter, I used weatherstripping around the flanges and slipped the dust collector hose over the flanges and weatherstripping. I held everything in place with foil duct tape. After the hoses/ducts were in place, I insulated them with two layers of "bubble wrap" insulation and wrapped the insulation with the foil duct tape.

My PetCool worked very well in high heat and high humidity conditions for a long time. It recently, however, has quit functioning. I will be replacing it with a window unit air conditioner. Unfortunately, I am going to have to build a new tongue box to accommodate the A/C unit. I mention this, not to discourage you from using the ClimateRight, but to recommend that you build flexibility into your tongue box to "future proof" it in case you ever need to replace the ClimateRight.
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Re: A/C Ducting?

Postby g00s3 » Tue May 17, 2016 11:10 am

aggie79 wrote: I will be replacing it with a window unit air conditioner. Unfortunately, I am going to have to build a new tongue box to accommodate the A/C unit. I mention this, not to discourage you from using the ClimateRight, but to recommend that you build flexibility into your tongue box to "future proof" it in case you ever need to replace the ClimateRight.


Thanks for the great info Tom. Are you planning to use Shadow Catcher's hack on the window unit?http://tnttt.com/viewtopic.php?t=44561 I am nearly done with my cabinets and galley so my next task would be to build my tongue box and work through the a/c challenge so if this is something you are planning soon I'd love to collaborate with you on it. The window unit definitely appeals to me because it is a much lower cost option than the ClimateRight and since I am yet to purchase a ClimateRight I am definitely open to alternatives.

As always, I really appreciate the great information on this forum and everyone's willingness to share what they know.
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Re: A/C Ducting?

Postby aggie79 » Tue May 17, 2016 11:52 am

g00s3 wrote:Thanks for the great info Tom. Are you planning to use Shadow Catcher's hack on the window unit?http://tnttt.com/viewtopic.php?t=44561 I am nearly done with my cabinets and galley so my next task would be to build my tongue box and work through the a/c challenge so if this is something you are planning soon I'd love to collaborate with you on it. The window unit definitely appeals to me because it is a much lower cost option than the ClimateRight and since I am yet to purchase a ClimateRight I am definitely open to alternatives.


I appreciate all of the work Shadow Catcher did and will use his experiences for my approach. The primary differences are that I want to use supply and return air duct work that is the same cross-sectional area as it is when it leaves the A/C unit (to hopefully prevent freezing of the evaporator coils), and that I am doing a permanent installation rather than a portable solution.

I want to keep the same ducting arrangement as I have with the PetCool. The supply air will go from the tongue box through the front wall of the teardrop and turn up to flow out of the top of the headboard cabinet. The return air will collect at the bulkhead and flow under the teardrop back to the tongue box.

I have purchased a 5000 Btuh Frigidaire window unit with mechanical controls. (http://www.amazon.com/Frigidaire-FFRA0511R1-Window-Mounted-Mini-Compact-Conditioner/dp/B00W2KG92Y?ie=UTF8&psc=1&redirect=true&ref_=oh_aui_detailpage_o00_s01) My first hack will be to remove the front cover and take measurements. I want to relocate the front panel controller to the interior of the teardrop, so my next hack will be to cut the wiring and add about ten feet of wire length to see if the additional wiring will work. I think - I'm not an electrician or electrical engineer - and am hopeful that the mechanical controls and their line voltage will be less sensitive to voltage drop of the longer wiring than "digital" controls.

If this pans out electrically, then I will construct the tongue box, build the ducting - probably galvanized metal insulted EPS insulation - do the electrical work relocate to the controller, etc. If it doesn't then I'll need to think about leaving the controls on or near the unit and figure out a different tongue box arrangement.

As you can see, this is still a mental exercise for me and a work in progress. As it also turns out, my WFCO converter has failed on the DC side of things, so I have purchased a PD converter and will be installing it too. That will be my first priority and then I will refocus on the A/C install.

g00s3 wrote:As always, I really appreciate the great information on this forum and everyone's willingness to share what they know.


I echo your comments. Without the information sharing on this forum, I never would have been able to build my teardrop.
Last edited by aggie79 on Tue May 17, 2016 6:23 pm, edited 1 time in total.
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Re: A/C Ducting?

Postby Shadow Catcher » Tue May 17, 2016 12:22 pm

I was concerned that there would be too much line loss for the control wiring but it does not seem to have been a problem. I ran it through the outlet duct because I had to use the bilge blower.
Less mechanical connection will mean less translated sound and I like to be able to leave ours at home.
I do btw have some duct that fits the Climate right which did not work well enough for us if any one wants it.
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Re: A/C Ducting?

Postby g00s3 » Tue May 17, 2016 9:36 pm

Thanks for the feedback and info all. I think it's definitely worth re-visiting the window shaker hack. Anyone see any issues with making the adapter part out of wood and fiberglass instead of sheet metal? I thoughts at the moment are that I could potentially integrate that part into my tongue box.
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Re: A/C Ducting?

Postby KCStudly » Wed May 18, 2016 6:38 am

Noise transmission may be one issue. In larger HVAC systems there is usually a skirted flex joint (short fabric hoop coupler) that joins the unit to the duct. this helps keep NVH (noise, vibration, harshness) isolated to the unit.

Will your TB be hard connected/built in to the cabin?
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Re: A/C Ducting?

Postby aggie79 » Wed May 18, 2016 8:11 am

KCStudly wrote:Noise transmission may be one issue. In larger HVAC systems there is usually a skirted flex joint (short fabric hoop coupler) that joins the unit to the duct. this helps keep NVH (noise, vibration, harshness) isolated to the unit.

Will your TB be hard connected/built in to the cabin?


My Petcool is held in place in the tongue box by a nylon strap. To minimize vibration, I placed the PetCool on top of a foam exercise tile (with a cutout for the condensate drain) and placed a section of the exercise tile underneath the top of the strap. As previously mentioned, the initial duct connections were made with flexible dust collector hose. This was quite effective. Although the PetCool was a "shaker" when running, there was no vibration felt or noise heard - other than the sound of moving air - inside of the teardrop.

In my new install, I plan to use the exercise tiles again to isolate vibration for the window unit. I will also have some sort of flexible duct connection but haven't worked out that detail yet. I'm leaning toward either a thick foam weather stripping between the window unit and the supply/return air plenum or fabricating a flex joint out of sheet rubber or rubberized fabric.
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Re: A/C Ducting?

Postby g00s3 » Wed May 18, 2016 12:45 pm

KCStudly wrote:Will your TB be hard connected/built in to the cabin?


In my initial design the tongue box was completely separate, but now that I will be building the A/C into it I am leaning towards hard connecting it to the cabin. I'm still working through understanding all the pros and cons with that design, but it does solve a few other design issues for me.

Thanks for pointing out the noise transmission possibility. I understand that the where the actual ducting connects to the fabricated adapter it would need something to dampen the vibration. I believe Shadow Catcher used neoprene in his build
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Re: A/C Ducting?

Postby KCStudly » Wed May 18, 2016 2:43 pm

Just food for thought... I had planned to integrate my TB into the front wall of my cabin because I have a front locker/cabinet that sticks out and was going to share space. When I finished building my trailer I noticed that, naturally, there is a little up and down flex in the tongue relative to the attachment point under the front xmbr. Of course there is, if the tongue was so rigid that it couldn't flex it would break, right? (This is also the reason why aluminum trailers tend to have failure problems right here where they flex.)

I didn't like the idea of this constant motion using the TB as a lever in a can opener action against the front wall, so I decided to buy rubber mounts for between the TB and tongue. (Later, I decided to divorce it from the cabin completely, but since I already bought the rubber mounts and made the height adjustments for them, I will use them anyway.)
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Re: A/C Ducting?

Postby g00s3 » Wed May 18, 2016 5:17 pm

KCStudly wrote:Just food for thought... I had planned to integrate my TB into the front wall of my cabin because I have a front locker/cabinet that sticks out and was going to share space. When I finished building my trailer I noticed that, naturally, there is a little up and down flex in the tongue relative to the attachment point under the front xmbr. Of course there is, if the tongue was so rigid that it couldn't flex it would break, right? (This is also the reason why aluminum trailers tend to have failure problems right here where they flex.)

I didn't like the idea of this constant motion using the TB as a lever in a can opener action against the front wall, so I decided to buy rubber mounts for between the TB and tongue. (Later, I decided to divorce it from the cabin completely, but since I already bought the rubber mounts and made the height adjustments for them, I will use them anyway.)


Thanks KC. I had previously read about TB flex and movement on the forum (it may even be one of your posts) so it is definitely a consideration and the reason why I decided against it originally. I feel like I need to do it bit more research before I can say that I am definitely sold on the idea. At least I have decided to go with the window shaker A/C - about to place the order on Amazon.
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Re: A/C Ducting?

Postby aggie79 » Thu May 19, 2016 8:37 am

g00s3 wrote:
KCStudly wrote:Just food for thought... I had planned to integrate my TB into the front wall of my cabin because I have a front locker/cabinet that sticks out and was going to share space. When I finished building my trailer I noticed that, naturally, there is a little up and down flex in the tongue relative to the attachment point under the front xmbr. Of course there is, if the tongue was so rigid that it couldn't flex it would break, right? (This is also the reason why aluminum trailers tend to have failure problems right here where they flex.)

I didn't like the idea of this constant motion using the TB as a lever in a can opener action against the front wall, so I decided to buy rubber mounts for between the TB and tongue. (Later, I decided to divorce it from the cabin completely, but since I already bought the rubber mounts and made the height adjustments for them, I will use them anyway.)


Thanks KC. I had previously read about TB flex and movement on the forum (it may even be one of your posts) so it is definitely a consideration and the reason why I decided against it originally. I feel like I need to do it bit more research before I can say that I am definitely sold on the idea. At least I have decided to go with the window shaker A/C - about to place the order on Amazon.


I too will make allowances for the flexing of the trailer tongue. My current thoughts are to have the plenum hard-mounted on the front of the teardrop with the plenum extending into the tongue box. (The single plenum will be divided into return and supply air portions.) I plan to leave a 3/4" clearance around the plenum opening in the tongue box that will be sealed with rubber foam weatherstripping. There will also be a 3/4" clearance between the plenum and the window unit which I plan to seal the same way with weatherstripping. This should allow for any tongue movement.

Of course, all plans are subject to change once I take apart the window unit and start mocking up the prototype. :shock:
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