Adding additional a/c capacity

[shields]

Its’ usually about 110 degrees when we drive through Las Vegas for our annual houseboat vacation. Our 1997 Monaco Dynasty has two rooftop Dometic Duo Therm air conditioners (13,500 btu each) and dash air too. Even with everything operating properly (recently serviced and checked) the temperature in the coach is still uncomfortably hot; probably in the upper 80s.

With each rooftop unit rated to draw about 12 amps, it seems we could run a third unit with the Onan 7.5 diesel genset. Otherwise, we could replace the two existing units with 15,000 btu units. Replacing the two existing units would take us from 27,000 to 30,000 btus. Adding a third unit would take us from 27,000 btus to 40,500. If absolutely necessary, we could do both and get up to 45,000 btus.

It seems like exchanging the two existing units with 15,000 btu replacements would be a simpler installation since the existing ducts and wiring could all be reused. The extra cost of cutting the roof, new wiring, and new controls for the third unit would probably offset the price (buying one unit instead of two). However, adding a third unit would provide the largest btu gain. I’m not sure the generator will actually handle all three units.

Am I going about this the right way? I don’t want to incur unnecessary expense, but we really need a cooler coach. Can anyone offer suggestions? Thanks so much.

Tim Shields

[wolfe10]

Tim,

Also consider adding window insulation along with upgrade from 13.5 to 15K BTU A/C's.

And verify that your dash HVAC is on recirculate. Taking in 110 degree outside air and trying to cool it is not a reasonable proposition. Taking in 80 degree air from the interior is a LOT better.

Brett

[garykd]

Hi Tim,

The move from 13.5K to 15K units can be a simple or difficult move. You'll need to get the professionals to tell you which one it will be. Depending on the original installation, the mechanical connections to the existing duct work is not necessarily a remove and replace situation. I've never heard where it was impossible, just letting you know it might cost more than originally thought.

[shields]

Brett, Gary;

Thank you for the suggestions. I'll certainly move forward with the window insulation and check the duct connections. Thankfully we don't have more desert trips scheduled until next June; so I have time to plan and work things out.

Thanks again!

Tim