Adding roof a/c

My 2000 Winnebago JD 40 has only basement air.  Want to add a roof unit for boost on really hot days.  Hoping to add it to the opening replacing the front vent.  My question is how to get the wire from rear panel in bedroom to the front.  Is it a matter of cutting into the air duct using it for a raceway or is there another way?

Wire track along the ceiling would be the easiest way ...white wire track would not be terribly noticeable. Only other reasonable way I see would be to use the air duct.

Be sure your original unit is working up to its full capability ...both compressors running, no gaps in the output air duct starting at the unit and running up behind the rear cap. The duct has a strong record of needing the joingts re-taped from time to time.

I don't know if the Ultimates have the OnePlace where all of the meters, genny start, tank monitors, etc are located but I ran wire from the AC breaker box to the OnePlace and then punched a hole in the Styrofoam ceiling insulation to the AC. Here's my write-up.

Tell you what.  In my coach, I got a portable air conditioner.  Not a window unit, a free standing unit that has a flexible duct to lead to a window.  I then created a flat plate to put in the aft cabin window with a hole for the flexible duct to attach to.  WE put the free standing portable in the corer of the aft cabin.  Cheaper, easier than installing an overhead unit.  Not trying to divert your project, but consider this as an alternative.  Our basement unit seems to be working fine and we only need the help in intense heat.  We are headed to Vegas this summer and intend to use this approach.  With this aux unit, we have a total of about 36000 BTUs of air conditioning. 

Since the portable AC is in the aft cabin, I would try to find a site in Las Vegas where your stern faces west or southwest. Your cab area is probably going to get very warm; use some of that windshield thermal insulation which will reduce a lot of radiational heating. Consider a box fan to place on the floor to move some of that cold air to the salon.

The advantage of the roof mount air is its central location and being located on the roof/ceiling the cold air sinks. It's really quite effective in hot weather. One of the two best mods we've ever done (number two was installing a household fridge.)

Have you checked to see if you already have 110 Volt AC power there already?  A telltale will be a receptacle box on the ceiling with a blank plate on it.  Many manufacturers prewire just for that reason. 

With the basement air units, there is no 120V wiring in the ceiling but there is some nearby to the center vent fan.

Im no expert on this subject, but i read somewhere that they use dehumidifiers or humidifiers ,(not sure which one) to assist in making the air feel cooler. Does this work in very high temps like this. Just wondering.

muskoka guy said:

Im no expert on this subject, but i read somewhere that they use dehumidifiers or humidifiers ,(not sure which one) to assist in making the air feel cooler. Does this work in very high temps like this. Just wondering.

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An AC unit is in fact a de-humidifier ...that is why it drips water. In extremely humid climates additional de-humidifying might be helpful, but not likely needed in Las Vegas summers! 

Actually, many homes in dry climates use the old evaporative water coolers for "air conditioning" rather than true ac units because they work pretty well in dry climates. They were very common in NM and AZ when I lived in those states several years ago, and are likely common in NV too.

Here's a photo of my alternative, the portable unit.

John Canfield said:

With the basement air units, there is no 120V wiring in the ceiling but there is some nearby to the center vent fan.

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John, I see you added the overhead A/C unit and were happy with it.  I am currently happy with my portable unit, but we mostly rv in hot climates.  So the concept of adding a roof a/c is interesting.  I think the center vent fan in my Journey is 12V?
In my case, the biggest issue with A/C is the lack of vent outlets in the aft cabin.  There are only two small vents.  In the main cabin, there are 8.  So the biggest issue in the desert is likely the lack of air in the aft cabin.  which is why I put my portable unit there.  Where in the aft cabin could I mount an overhead A/C unit?  I would have to cut a new hole, since the closest vent is in the bathroom.  The bathroom has the very nice automatic fan that automatically opens the vent and turns on the fan that I'm reluctant to lose.  The main cabin has another overhead vent opening, but I don't need additional A/C in the main cabin.  Is there any way to add vents in the aft cabin for existing basement unit?  How would I locate the duct work overhead?
UPDATE:  re adding new vents in the aft cabin.  I just pulled the overhead A/C vent cover in the aft cabin.  There is basically no ductwork in the aft cabin ceiling.  There is an inner ceiling about 2" below the main ceiling.  Its held up by some boards (like 2x4s) between the inner and outer ceiling panels.  In that gap, air conditioned air flows and goes out various vents.  So cutting a new vent doesn't apparently need to find duct work.  It just needs to not hit one of the 2x4 boards that hold up the inner ceiling.  Has anyone else done this?

Call Owner Relations and ask them for the structural layout of your roof and designed roof loading in pounds. There's a good chance you can add a roof air in your aft cabin somewhere if you have roof space.

John Canfield said:

Call Owner Relations and ask them for the structural layout of your roof and designed roof loading in pounds. There's a good chance you can add a roof air in your aft cabin somewhere if you have roof space.

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Kewl.  I priced the A/C units online and they appear to be less than $500.  That's not a bad price.  Talked with wife and both powered vent fans are useful and don't want to give up.  Both the one in the kitchen and bathroom.  Looks like running the wire is the most difficult part.  Think I'll keep this one on the back burner and run a summer with the portable unit in the aft cabin and see how it works first.  The portable is 12K btu, so we have 36K total for the desert this summer.  And reserved the only rv site in the park in vegas with a tree for shade.

Sailorkane said:

Kewl.  I priced the A/C units online and they appear to be less than $500.  That's not a bad price.  Talked with wife and both powered vent fans are useful and don't want to give up.  Both the one in the kitchen and bathroom.  Looks like running the wire is the most difficult part.  Think I'll keep this one on the back burner and run a summer with the portable unit in the aft cabin and see how it works first.  The portable is 12K btu, so we have 36K total for the desert this summer.  And reserved the only rv site in the park in vegas with a tree for shade.

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For what it's worth, we got a 10k btu portable ac unit when we were stuck in 110+ temps and no afternoon shade one summer in Dallas and vented it out the driver side window. Spec say it pulls 9.5a. We were totally unimpressed with the performance.

afchap said:

Wire track along the ceiling would be the easiest way ...white wire track would not be terribly noticeable. Only other reasonable way I see would be to use the air duct.

Be sure your original unit is working up to its full capability ...both compressors running, no gaps in the output air duct starting at the unit and running up behind the rear cap. The duct has a strong record of needing the joingts re-taped from time to time.

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On mine the previous owner had a rooftop a/c added. The wiring was ran through the ceiling ducts. I'm not sure of the specifics on how the wire was pulled, but nothing shows and all wires are hidden. 2002 Ultimate Freedom

WE've used a portable AC in our Florida garage for some time.  HOA won't allow window units.  One large issue with preformance is the length of the discharge duct.  It gets very warm and hurts the cooling a lot.  I've tried to keep the duct as short as possible and will see how it works.