Adding roof A/C to supplement basement A/C

[Old Grape]

Howdy all,
I have read tones of forum posts about folks that added a roof AC where their kitchen vent was to supplement their basement AC. One thing that have not found is if they did any additional roof bracing or just let the roof as is support the new AC. So if any of you all have done this how did you handle the support and bracing question?

[binkley2]

I did this on my Vectra 40 a few months ago. My installer told me the factory bracing was sufficient for the additional AC. I am very pleased with the install except one thing. In my coach the vent was directly above the over sink cabinet, and there is a wall with a slider in it that separates the bathroom from the galley and living room. The header that covers the track for the slider door blocks the rearward facing vent on the new AC so it doesn't blow into the bedroom and bathroom. This wouldn't be a problem if the Ac were simply a supplement to the basement air, however my thermostat for the basement air is on the side of the cabinet directly below the new AC, so the basement air shuts off and the bedroom gets pretty warm. The other not so great thing about the roof air is, my installer told me my diesel generator does not have sufficient capacity to run both the basement air and the roof air, so there is an additional outlet in my basement in the power compartment that I plug the roof air into a 110 v outlet on the shore power pedestal at the park. I plan to have an electrician verify this need for me soon, but haven't gotten around to it yet. Other than these two items, I love the additional cooling and the rooftop air cools my rig way beyond the ability of the basement air in 100+ degree Texas heat.

[Keith K]

I agonized over this problem and went another way by buying a Toshiba portable A/C unit: https://www.homedepot.com/p/Toshiba-...290367#overlay
The exhaust vent fits the window next to the passenger seat and it fits perfectly behind the seat for travel. The vent hose snaps off allowing the window to be closed and the hose stored beside the A/C. It plugs into the receptacle for the fireplace. At 8000 BTU in concert with the basement air has kept the coach in the low 80s during 100 degree temperatures. For $300 it's been an easy fix & I'm very happy with it.

[Ray,IN]

Your Winnebago Grand Tour WILL cool sufficiently with the basement air unit(24K BTU) IF it is properly maintained, including using pleated air filters instead of the green mesh that was OEM.
You may need to pull the basement unit and clean the evaporator coil. use a bright light and mirror to inspect the ductwork behind the rear cap; use metal duct tape to patch and cracks and leaks (an IR heat gun is good for this)


Other suggestions for improving performance are: do not open windows in the morning then close everything up after it begins to get hot, that's too late, by then everything fabric or stuffed has absorbed ambient humidity and temperature. This puts the basement unit behind the curve-so to speak, and it is trying to catch up the rest of the day.
Use something to block the sun from shining in the windshield and windows on hot days. I'm sure others have equally good advice to offer.


Finally, binkly2's installer is wrong. On a 50A shore power breaker I have no problems(never) running my basement air unit (24-26A) and the microwave (10.1A) at the same time. Since a microwave and a 15K roof air conditioner(14.1A) pull nearly the same running amps, you should be OK.
reference: https://rvtechlibrary.com/electrical...eloadchart.php

[Old Grape]

Originally Posted by Keith K

I agonized over this problem and went another way by buying a Toshiba portable A/C unit: https://www.homedepot.com/p/Toshiba-...290367#overlay
The exhaust vent fits the window next to the passenger seat and it fits perfectly behind the seat for travel. The vent hose snaps off allowing the window to be closed and the hose stored beside the A/C. It plugs into the receptacle for the fireplace. At 8000 BTU in concert with the basement air has kept the coach in the low 80s during 100 degree temperatures. For $300 it's been an easy fix & I'm very happy with it.

I tried the portable unit idea already. Helped some but not much. The only ones I could find were all 8K BTUs, Also the vent tube strung up to the window is somewhat in the way. Glad it has worked for you.

[Old Grape]

I some what disagree with "Ray,IN" on a couple items. "Cooling sufficiently" is subjective. I have read more posts than I can count about how basement air units just don't get the job done when temps start exceeding the mid to upper 90s. I just spent 3 weeks in Yuma, AZ where temps hit 118f and stayed above 113 for numerous days. My couch inside hit 92F on the bad day and hovered between 88 & 90 on the other days of triple digit temps. Many RV techs have told me that the 2 ton unit is just a little under powered for a large coach. Also pulling the unit out is a pretty big chore. The wiring has to be disconnected, support frame disconnected, and then the 150 to 200 pound unit has to be slid out of its whole. That may take a little jockeying. Also it will require two of us average folks to manhandle it out. also stick with the green mesh filters. They don't restrict airflow like the pleated ones do. Reduced airflow is not good for ACs.

I have decide to add a 15.5k roof AC. I'm mounting it where my kitchen powered vent is. I will run it off of a separate 20 amp breaker.

[binkley2]

Originally Posted by Ray,IN

Your Winnebago Grand Tour WILL cool sufficiently with the basement air unit(24K BTU) IF it is properly maintained, including using pleated air filters instead of the green mesh that was OEM.
You may need to pull the basement unit and clean the evaporator coil. use a bright light and mirror to inspect the ductwork behind the rear cap; use metal duct tape to patch and cracks and leaks (an IR heat gun is good for this)


Other suggestions for improving performance are: do not open windows in the morning then close everything up after it begins to get hot, that's too late, by then everything fabric or stuffed has absorbed ambient humidity and temperature. This puts the basement unit behind the curve-so to speak, and it is trying to catch up the rest of the day.
Use something to block the sun from shining in the windshield and windows on hot days. I'm sure others have equally good advice to offer.


Finally, binkly2's installer is wrong. On a 50A shore power breaker I have no problems(never) running my basement air unit (24-26A) and the microwave (10.1A) at the same time. Since a microwave and a 15K roof air conditioner(14.1A) pull nearly the same running amps, you should be OK.
reference: https://rvtechlibrary.com/electrical...eloadchart.php

Thanks for the info and the link. I am pondering adding a second AC to the roof in the bedroom and using the two circuit breakers attached to the basement air to power them. Last week my basement air gave up the ghost altogether. I'm kind of over the basement air saga. It has been regularly serviced and highly inefficient in my opinion. Previous to the MH we had a 42 foot fifth wheel and you were able to hang meat with two rooftop ACs. IMHO, basement air was and is a bad idea on Winnebago's part.

[SuperGewl]

Well before you go to all that fuss. have done a hand over hand check of all the ducting? In most cases, some of the ducting has come loose and is sending cold air into the neverland thus not getting into the coach where it belongs. also verify both compressor are working and get the junk from under the bed that is blocking the intake. Clean the condenser coils also, they get a lot of road crap in them along with the critter nest. A little Preventive maintenance goes a long way. but then a gain what do I know

[Old Grape]

Originally Posted by SuperGewl

Well before you go to all that fuss. have done a hand over hand check of all the ducting? In most cases, some of the ducting has come loose and is sending cold air into the neverland thus not getting into the coach where it belongs. also verify both compressor are working and get the junk from under the bed that is blocking the intake. Clean the condenser coils also, they get a lot of road crap in them along with the critter nest. A little Preventive maintenance goes a long way. but then a gain what do I know

I have checked the ducting as far as I can reach and have taped up all leaks I found. Only way to do the entire duct is to remove the rear cap. Not an easy or cheap task. The basement air is a good concept but better in smaller coaches and more temperate climates. It hit 108 degrees here in Tucson and my coach was 88 degrees inside. 40 ft of coach with thin walls, single pane windows, and darkish exterior pain is just a lot for a barely 2 ton system to keep cool.

[Wild Card]

Originally Posted by Old Grape

I have checked the ducting as far as I can reach and have taped up all leaks I found. Only way to do the entire duct is to remove the rear cap. Not an easy or cheap task. The basement air is a good concept but better in smaller coaches and more temperate climates. It hit 108 degrees here in Tucson and my coach was 88 degrees inside. 40 ft of coach with thin walls, single pane windows, and darkish exterior pain is just a lot for a barely 2 ton system to keep cool.

It's actually 26500 btu/h. Each compressor is 13500btu/h

But yes for a 40ft multi slide its barely adequate.

My 08 Horizon dark gray 3 slide in 100* heat index will creep from 74* setpoint to 75-76 during heat of day.

My plan is to add 15kbtu/h in my kitchen fan spot. It's 1.5ft to my 1 place panel between kitchen and bath. I can bore a hole over for electrical and stat wiring. I also plan to open up to make it ducted into the original ducts.

I then will have true supplement and some back up.

I also plan to abandon the basement ac and add another 15kbtu rooftop when the time comes or if my basement needs a lot of work.

[Ray,IN]

Originally Posted by Wild Card

It's actually 26500 btu/h. Each compressor is 13500btu/h

But yes for a 40ft multi slide its barely adequate.

My 08 Horizon dark gray 3 slide in 100* heat index will creep from 74* setpoint to 75-76 during heat of day.

My plan is to add 15kbtu/h in my kitchen fan spot. It's 1.5ft to my 1 place panel between kitchen and bath. I can bore a hole over for electrical and stat wiring. I also plan to open up to make it ducted into the original ducts.

I then will have true supplement and some back up.

I also plan to abandon the basement ac and add another 15kbtu rooftop when the time comes or if my basement needs a lot of work.

My service manual states it is a 2-ton cooling unit; that equals 24,000 BTU.
I've never seen a larger basement Coleman-Mach unit.

[BCam]

See post #10 in this Winnieowners.com thread if you haven't already seen it:

https://www.winnieowners.com/forums/...ng-361521.html

Also here (post #13):

https://www.winnieowners.com/forums/...ml#post3900346

[Old Grape]

Today most of the 40' DPs come with at least 3 roof top ACs. Each are 13.5K BTU or greater. So at a minimum that's 40.5K BTU total. The 2 ton or 24K BTU basement AC just is not really big enough on its own to handle the hotter weather. Mine keeps my coach at 20 degrees cooler than the outside. On 105 days that means 85 and 115 days mean 95 inside the coach.

[Ray,IN]

Originally Posted by BCam

See post #10 in this Winnieowners.com thread if you haven't already seen it:

https://www.winnieowners.com/forums/...ng-361521.html

Also here (post #13):

https://www.winnieowners.com/forums/...ml#post3900346

Explain why the service manual states it is a 2 ton unit. One ton in air conditioning equals 12,000 btu.