Custom Air Conditioning Retrofit

[rubicon327]

I sense some very good design and engineering skill on this forum so I want to bounce this idea off of you folks. Like many others out there we are tired of the absurdly loud overhead Dometic A/C unit (especially at night) and I gather that they are all pretty similar in noise level until you get up to very high end with ducted units. I have procured a 120V 9,000 BTU/H Fujitsu 9RL2 mini-split system at cost through a contractor friend. I plan to mount the condensing unit on a custom mount on the tongue (covered by a hard plastic propane cover when not in use) and mount the indoor unit semi-recessed within the front cabinet blowing lengthwise down the trailer. These are very quiet and efficient. The bonus is this can also provide heat and can easily be run on a Honda EU2000i gen. Internet searches show this has been done successfully on an old Boler, a few Airstreams and a Silverado 37QB 5th wheel, but not an Escape. I have thought about this extensively and have an HVAC engineering background. I don't see any issues personally, but are there any thoughts or constructive criticism before I take this on? Thanks!

www.fujitsugeneral.com/PDF_06/Submittals/Submittal9RL2.pdf

 

[SFDavis50]

Very interesting!!! I am trying to decide between a 21 and a S.0TA but I really don't want a lot of stuff on the roof although the Dometic looks a lot more aerodynamic on the 5.0 since it is mounted on a down slope of the roof.
The only concern I have is that my son plans on doing a lot of weekend winter camping at the Colorado ski areas and the heat pump gets less efficient as it gets colder, so would it work on really cold nights? The propane heater is still there so it may be a moot issue and with power he could augment with an electric ceramic heater.
Most of our RV camping will be in the high country so the air conditioner would get little use. I was thinking of rigging up a little cooler using a 6 gal. plastic bucket, several blue ice blocks and a 12v fan. That should work when the temps get to an intolerable mid eighties.
My freezer would probably be constantly filled with some form of ice.

 

[MyronL]

Copy that. I self installed the 11,000 btu Dometic on my roof at a huge personal savings but with a huge personal loss, in hearing.

Though I can't see sacrificing tongue box space (if you have one) for a/c parts or how transmission lines would enter the cabin, or how an a/c unit fits anywhere in the front cabinets, unless you mean under the seats, I look forward to watching your work. Take pictures.

 

[padlin]

I take it you have room on the tongue and have looked into the added weight there.

Says it's 47db, did you check the Dometic?

What the amperage draw? is that what they call MCA?

 

[padlin]

The only concern I have is that my son plans on doing a lot of weekend winter camping at the Colorado ski areas and the heat pump gets less efficient as it gets colder, so would it work on really cold nights? The propane heater is still there so it may be a moot issue and with power he could augment with an electric ceramic heater.

Don't know if it'd be the same, but I've heard the down side to using the heating element in the Dometics AC is that you have to run the noisy blower. Would be nice to know how loud the proposed AC is on the inside of the trailer.

 

[cpaharley2008]

I assume you are not getting the optional front storage box as this unit is adding maybe another 90 lbs to your tongue weight. Plus you will have to relocate the battery someplace. In addition, a heat pump below freezing is no longer efficient and needs to be supplemented with electric heat.
The stock a/c supplied by Escape with the digital thermostat has a 2 speed blower option, something others may not have if they elected otherwise. On the lower speed, it is a lot quieter than conventional one speed units. Just my $.02 worth.

 

[tractors1]

I plan to mount the condensing unit on a custom mount on the tongue (covered by a hard plastic propane cover when not in use) and mount the indoor unit semi-recessed within the front cabinet blowing lengthwise down the trailer.

www.fujitsugeneral.com/PDF_06/Submittals/Submittal9RL2.pdf

Other than adhering to the standoff requirements for the outdoor units for the intake/exhaust I don't see a problem. I have a similar unit on my shop and the outdoor noise is pretty quiet. You might give some thought to mounting them on isolation pads to further reduce any noise transmitted through the frame when mounted.

 

[Rossue2]

OP has a 2010 19, don't think front storage box option was even available then was it?

 

[Brian B-P]

I think it's a great idea, for noise, keeping mass low, and avoiding extra height. When I've looked at the details, my concerns are usually the bulk of the outside unit (but the tongue is a great place for it), the total weight, finding the right size, and of course the cost.

This is an interesting unit. For its heating feature it runs as a heat pump, not just a resistance heater, a feature generally not available on small conventional RV air conditioners. It runs at variable speed, not just on-off.

The linked specs are only for the outdoor unit, so total system weight and power are higher.

As a split unit it inherently fixes the problem that most RV air conditioners have of running both inside and outside fans whenever one is needed, because they are on one motor - the inside and outside fans are in entirely separate units.

Sorry I don't have any useful suggestions at this point, Dave, but it looks like you have already thought this through. I would be interested in following the project and taking at shot at any detail issues that might be encountered.

 

[tractors1]

Most heat pump units stop functioning below 34-36F and an auxiliary set of contacts close normally used for calling for the backup electric heat coils in the house furnace to activate; this is normally a relay contact signal. One could possibly tie that into the furnace as a means to hand off the heating demand to the propane furnace, but it would take a bit of research to figure out how to electrically make that work downstream of the thermostat. Might take another relay in the final 12V leg to the furnace, but I'm sure it could be done. I have 40 years of heat pump engineering in my background.

 

[Brian B-P]

I assume you are not getting the optional front storage box as this unit is adding maybe another 90 lbs to your tongue weight. Plus you will have to relocate the battery someplace.

The outdoor unit is 64 pounds (so adds maybe 55 pounds to the tongue weight) and the inside unit will be further back, so the tongue weight addition would be much less than 90 pounds.

If the battery or batteries are mounted on the tongue in a box or boxes, the outdoor unit could be above them, or to one side. Mount and packaging design will be important.

 

[rubicon327]

The only concern I have is that my son plans on doing a lot of weekend winter camping at the Colorado ski areas and the heat pump gets less efficient as it gets colder, so would it work on really cold nights? The propane heater is still there so it may be a moot issue and with power he could augment with an electric ceramic heater.

The heating side of this is secondary and as you point out can easily be supplemented or not even used at all. The unit can operate in heating mode down to 15F and the rating of 10,000 BTU/H is at 47F, but to your point this capacity likely drops off fast as it gets colder. It would not be considered a primary heat source.

Though I can't see sacrificing tongue box space (if you have one) for a/c parts or how transmission lines would enter the cabin, or how an a/c unit fits anywhere in the front cabinets, unless you mean under the seats, I look forward to watching your work. Take pictures.

Tongue box space is a non-issue because the trailer didn't have one and we did a custom installation of a Stowaway box on the rear. The plan is for the lines to come in underneath the trailer into the front dinette storage space and then up the wall behind the corner padding. The unit should fit semi-recessed into our upper front cabinet based on my dimensions. I went with the Fujitsu because it is the smallest available indoor unit.

I take it you have room on the tongue and have looked into the added weight there.
Says it's 47db, did you check the Dometic?
What the amperage draw? is that what they call MCA?

I'm not claiming this is easy but should have a big payoff. We are likely going to relocate the batteries and move the dual propane back. The unit will sit where the propane does now. The outdoor unit is 65 lbs. So very similar in weight to one Interstate GC2 6V battery. The 47 db is on high. In the quiet and low mode the indoor unit is 23 and 33 db respectively. I've used these at work and they are insanely quiet. The biggest issue with rooftop is the noise level and vibration of the unit with the compressor running. The mini-split with inverter technology only has the compressor running as much as it needs to to meet the load. MCA is listed as 13.5 amps, but this would be the absolute maximum it would be expected to draw.

Don't know if it'd be the same, but I've heard the down side to using the heating element in the Dometics AC is that you have to run the noisy blower. Would be nice to know how loud the proposed AC is on the inside of the trailer.

With a mini-split you have no compressor noise to deal with and vibration should be dampened with a tongue mount. The inside unit varies from 23 db on "quiet" to 43 db on "high". 4 speeds total. I bought a higher end unit. Some of the cheap ones out there are not as quiet.

 

[rubicon327]

I think it's a great idea, for noise, keeping mass low, and avoiding extra height. When I've looked at the details, my concerns are usually the bulk of the outside unit (but the tongue is a great place for it), the total weight, finding the right size, and of course the cost.

Sorry I don't have any useful suggestions at this point, Dave, but it looks like you have already thought this through. I would be interested in following the project and taking at shot at any detail issues that might be encountered.

Thanks Brian. I was hoping you chimed in because your suggestions helped us get to perfect solution on the rear storage box regarding mounting and departure angle. I will certainly post as I proceed to get some feedback from you and others on this. By the way, I was able to procure this package (at cost) for $810 which includes a 15' line set. This isn't too bad when you consider the Dometic option on the new trailers is $1,100 (installed) and the cheaply made mini-splits available at Home Depot are more expensive. I would love for this to get to the point that Escape would maybe even consider it during a build for customers that know the rooftop is not ideal for them for one reason or another.

 

[jxoco]

Sounds like a really good idea.
I hope it works fantastic for you.
Post some pictures for us when you do it.
The only thought I have is that it might not like the vibrations that occur on a towed trailer. Maybe the Dometics are beefier, I don't know.
So mount it on some rubber mounts so that the metal parts inside don't crack.

 

[SFDavis50]

I would love for this to get to the point that Escape would maybe even consider it during a build for customers that know the rooftop is not ideal for them for one reason or another.[/QUOTE]

I agree, I want insulation up there for the really cold nights without hookups.

 

[rubicon327]

The only thought I have is that it might not like the vibrations that occur on a towed trailer. Maybe the Dometics are beefier, I don't know.
So mount it on some rubber mounts so that the metal parts inside don't crack.

Good point. We plan to mount with some heavy duty rubber isolators. The road harshness is another reason why I think the tongue is the best place for the outdoor section. I think the life of the unit would be reduced significantly on the rear.

 

[rbryan4]

The road harshness is another reason why I think the tongue is the best place for the outdoor section. I think the life of the unit would be reduced significantly on the rear.

These type of units are designed for a stationary home installation with no constant bumping or movement. I don't see any technical reasons why you couldn't do it, but the fact that the unit isn't designed for motion might affect the durability.

But, being able to greatly reduce the noise is certainly appealing.


Sent from my iPhone using Tapatalk

 

[rubicon327]

I don't see any technical reasons why you couldn't do it, but the fact that the unit isn't designed for motion might affect the durability.

We are going to see! There are not enough out there in use to know how they hold up long term. I bought a quality unit and have a few HVAC technician friends as insurance.

 

[Brian B-P]

These type of units are designed for a stationary home installation with no constant bumping or movement. I don't see any technical reasons why you couldn't do it, but the fact that the unit isn't designed for motion might affect the durability.

That's a good point, although having looked at the guts of my RV air conditioners it is not obvious that anything has been done to handle road vibration in them.

There are small split 120V AC driven systems used for air conditioning of highway truck cabs, which are obviously suitable for the conditions. It would be interesting to know if there is any difference in the construction of those and of the one Dave has chosen.

 

[Brian B-P]

Don't know if it'd be the same, but I've heard the down side to using the heating element in the Dometics AC is that you have to run the noisy blower.

True, but much of the noise problem of the blower is the blower for outside air, rather than the one for inside air...

As a split unit it inherently fixes the problem that most RV air conditioners have of running both inside and outside fans whenever one is needed, because they are on one motor - the inside and outside fans are in entirely separate units.