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Old 07-15-2013, 09:49 PM   #15
Senior Member
Yukon Jack's Avatar
Monaco Owners Club
Join Date: Oct 2010
Location: Colleyville, TX
Posts: 165
A few weeks ago after spending a weeks vacationing in 97 - 101 degree temps, with a lot of shade at the camp site, I was not satisfied with the cooling of the Duo-Therm Penquin 13.5 btu ACís in my 2001 Monaco Dynasty. Even though I make it a habit to annually clean the condenser and evaporator coils and replace the interior recirculation filter I was not satisfied with its performance.

After arriving back home I embarked on a mission to evaluate ALL aspects of these two roof mounted AC units and do everything possible to improve the operating performance of them. I have attached a series of photos that illustrate the modifications that I made to my AC system which included the following areas:

1. Thoroughly cleaning condenser and evaporator coils and combing the fins on both sides.

2. Oiling both ends of the electric fan motor bearings

3. Verify the condition of the isolation insulation between the condenser and evaporator sides of the AC, and using plugging putty to plug any and all holes where wires pass through the sheet metal walls in each compartment . This is to make sure that no air hot ambient air can cross over into the evaporator compartment prior either where the interior recirc air passes into the evaporator coil or into the cavity where the cooled air is discharged into the cooling ductwork.

4. Adding insulating material to the exterior sheet metal which encapsulates the evaporator cavity of the AC system, which included the sides and top cover. The top cover already had a 1/8 inch foam type of insulation on the underside of the top cover but I felt this was not adequate for hot weather operation. I used REFLECTIX reflective insulation material that uses an insulation layer resembling bubble wrap material sandwiched in between two layers of aluminum foil, that I purchased at Home Depot. This insures that the evaporator compartment is kept as cool as possible by reducing the heat load in the interior recirc air that is sucked up and through the evaporator coils. I attached this REFLECTIX insulation to the sheet metal top cover, I elected to use standard ľ inch nylon push rivets, rather than glue, which are used in the automotive industry. I purchased these from OíReilly Auto Parts which are made by Dorman under the part number 458220BP. I drilled the holes with a 17/64" drill bit and used 6 rivets on each top cover to securely hold the insulation material in place and would not have to worry about any glue possibly releasing its grip since it is exposed to some real adverse temperature swings, plus if I needed to replace the material, it can be done much more easily than working with previously glued items.

5. Added some insulation to assure that there was no HOT discharge air from the condenser that could loop around and re-enter into the inlet of the condenser coils. The condenser discharge air must be expelled to the atmosphere and NOT allowed to re-enter the condenser or evaporator coils. As most everyone knows, the cooler the air is entering a properly cleaned condenser coil, the more efficient the AC system will operate, as this is required to maximize the heat transfer in these coils.

6. Removing all six of the AC duct registers and modifying them to allow for added air flow due to the restrictions that are unfortunately designed into the underside of these registers. There are two reasons for reduced air flow: a) the configuration of the sheet metal in these registers to allow the louvers to fully operate greatly reduces the air flow through them. b) The size of the 4 x 6 register sheet metal inlet sleeve is undersized compared to the duct opening in the ceiling which further reduces air flow. As the photos illustrate, in 5 of the registers, I carefully removed all the louvers and increased the size of the inlet opening to snugly fit into the existing duct opening in the ceiling. After completion, and performing a before and after test, the increase in air flow was a huge improvement. The 6th register, which is used in the bedroom, I modified it by eliminating the sheet metal restrictions but left two of the original 3 louvers in so I could somewhat control air flow during the night.

7. After removing the air duct registers, I re-taped each air duct opening to make sure I have smooth air flow into each register. I also re-taped the front and rear terminal ends of each duct to make sure I was not loosing any air into the roof of the RV.

8. I cut open a hole in the bottom of the air duct directly under the evaporator fan outlet and re-taped the transition area between the vertical duct from the evaporator and the horizontal duct way that runs the length of the RV in the ceiling. This assured me that I would have good, smooth air flow coming out of the AC and entering the duct runs in the ceiling.

At least in my 2001 Monaco Dynasty, these changes made a definite improvement in the performance of cooling efficiency and a huge improvement in air flow through the air ducting system. Hopefully this may be of assistance to anyone desiring to improve the cooling efficiency of their roof mounted AC systems.

Good Luck and Happy RVíg


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Old 07-16-2013, 10:59 AM   #16
Senior Member
YC1's Avatar

Holiday Rambler Owners Club
Join Date: Jun 2011
Posts: 4,568
Those registers can be made even less restrictive by straightening the louvers and if you really want max performance break out every other one. I did this at my business and the air flow increase was dramatic.

When we had our AC replaced in the sticks and bricks they suggested changing all of the vents to a lower restriction kind. Huge difference and they too can be straightened for less restriction.
Attached Files
File Type: pdf Register modification.pdf (395.7 KB, 22 views)
File Type: pdf Register 2.pdf (115.3 KB, 23 views)

Myron & Deborah
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