Roof Airs

Hello folks! Lee and I are the new people on the block and have a problem with Prevosts. Problem is I drove one. Toast now. Must have one. Besides that I have joined POG forum.
I am considering a 99 Marathon which only has 3 15K BTU ac units on the roof. I have a friend who owns a Liberty and hammers me daily that I better get one with bus air or you will regret it. Question is, how well do the 3 units handle the heat during the hight of August weather in the South? Down the road? Sitting? Is 4 better? 5? Cruise Airs? We will not be hot!
Thanks for the input! Great Site!

Doug and Lee
New Port Richey, Fl

You will get multiple answers on this. The Liberty gang will say that getting OTR air is the only way to go, and about the only way you will find it is on a Liberty. I have a 4 roof air setup and have not had any trouble so far, but have not spent a great deal of time in very high heat areas yet. I have been in 100+ degree heat and have not had trouble cooling the coach to my satisfaction. One thing you have to be sure on is how many roof airs you can run from your inverters while going down the road without running the generator. I can run 2 (any 2) off the inverters or all four on genset or shore power. I have found that running 2 with the dashboard air going down the road seems to be ok most of the time. I have fired up the genset and run all 4 a couple of times and it did get cooler, so that is always an option.

I do not have any direct experience with Cruise airs on a coach so I can not comment on those...they have different issues that other can address.

I would find the coach you like and not worry so much about one thing. You may pass up what could be the perfect coach for you if you hold out for OTR air and it is the only thing missing...just my opinion for what that is worth. <g>

If you spend a lot of time in the South, South West or the East Coast in the summer months OTR will keep you very cool. Temp in the Coach will remain in the 70's while its over 100 outside.
I actually have to turn the temp up at times because its too cold. My kids sometimes throw a blanket on while watching tv in the bedroom.
OTR uses up bay #3 on both sides of the coach so you'll have to decide if you need the added storage.
The OTR blows cool air up onto the windows so it keeps the heat off the windows and circulates thru out the coach.

We live in TX and it's very hot here.. We had a 45' Navigator with 3 roof airs and nearly died from the heat. I personally do not believe that 3 roof airs can cool a 45 footer consistantly in the South .. I understand that we're not comparing apples to apples.. but you should listen to your friend... go with 4 or bus air. We upgraded to a 45' H3-45 with bus air and it will freeze you out on the hottest day. We love it !!
Welcome to POG !!

Hello Doug and Lee,

We had two Prevosts with out OTR, and now our present "H" with OTR is the winner !

Alek

Thanks for the replies. No doubt OTR air is the ticket. So taking the OTR out of the picture, will the three 15K roof airs handle 45' going down the road? We all know these things dont cool as well while in motion as they do while stationary.

Short answer....no.

The bus absorbs a lot of heat, and Marathon which has a lot of glass, black glass at that, on the sides, acts like a rolling solar panel.

The best you are going to get per AC unit is 15,000 BTU (13,000 BTU most common) for a total of 45,000 BTU. At the very least get a coach with 4 AC units. If you can, get OTR which has a capacity in excess of 80,000 BTU.

Here are some things to consider. If the coach does not have OTR consider you are going to have to run the generator so the entire coach stays cool. Running one or two off an inverter seems to be what a lot of folks consider, but at the end of the day you may have a heat soaked bedroom because the two units operated while driving tend to be the front ones.

With marginal AC capacity available you can never let the coach get warm because trying to cool down a heat soaked coach with only three AC units is a challenge. It is a challenge for four units.

Your comfort level may be such that 3 AC units will be OK. I am comfortable when the temps are 70. At 75 in the coach I am starting to get warm. At 80 I am suffering. But I have an aunt and uncle that live in south Florida and they won't turn their house AC on until it gets to 85 so different people have different interpretations of what is acceptable.

You are correct about differences in performance when in motion and stationary. It can be compared (in heat terms) to the difference between a conventional oven and a convection oven where the flow of air makes a huge difference in how fast something heats up.

When considering what works for you, keep in mind a few things. No matter how the coach is cooled while in motion you are going to use similar amounts of energy. Whether using an inverter, a generator, or OTR the watts of energy required translate directly into horsepower to drive an alternator, a big compressor, or the running of the generator so if someone trying to sell you one coach over another suggests somehow the way the coach they are selling is more efficient be suspicious. I am talking apples and apples here. Once a coach is at a comfortable temperature for you, no matter what system you have for cooling the BTU loss is going to be the same and the energy to compensate only varies slightly.

I won't own a coach without OTR because I like the ease of use and its unmatched ability to maintain any temperature I want regardless of outside temps, hot or cold. The space it takes up is the equivalent of 1/2 bay. That space behind the AC condenser and evaporator is used for the fuel tanks so even without OTR you don't gain significant space and usually those coaches without OTR eat up whatever space is saved with more batteries to handle the load of trying to run AC units off inverters so again its a toss up.

One last comment about 3 versus 4 AC units. Presuming 3 AC units handle the temps satisfactorily, when one quits you may not be comfortable. The units for the most part are reliable, but the only time they fail is when we are on the road using them. They don't quit at home in our garages where we can deal with the failure without discomfort. Having 4 AC units allows that failure to happen (if it happens) and you can at least complete a trip without a visit for repairs or suffering in heat. I think 3 units in a 40 footer without slides will be OK, but not a 45 footer.

Doug,

Here's my take on OTR after owning 3 Prevosts with no OTR...

94 Liberty 40 - 3 Cruiseairs - Stationary they worked great, in extreme road heating on generator, they shut down and all you have is dash air.

97 Marathon 40 - 3 Cruiseairs - Stationary they worked great, 2 ran off inverters while driving, but again, extreme road heat they shut down and dash air only.

00 Country Coach 45 - 3 Roof Airs - Stationary and on the generator they worked great , CC's version of bus air did the job and generator usage was not necessary.

Keep in mind that my usage is mainly east of the Rockies mostly in the southeast and if I was doing the desert thing, OTR would be the only option. So the bottom line for me would be roof airs or OTR. I really liked the Cruseairs, but 90+ degree's in GA during the summer afternoon will have you looking for a cold one!

Howdy Doug and Lee:

Deb, Jay, and I had a 92 Angola with over the road air, plus 3 roof airs. In Nevada, I think late summer 2008, our over the road air breaker tripped and we didn't know how to reset (we were still kind of new to this bus thing). So we ran generator and the three roof airs as we crossed some Nevada desert. Outside temps around 100. Three roof airs running lowest temp setting on thermostat wouldn't cool below 85. It was toasty. That was extreme situation, I think.

That experience gave us a very direct comparison of over the road air (very effective until the breaker tripped) versus three roof airs (totally ineffective) in the heat of the Nevada desert in the summer. This is not a sales pitch for getting over the road air. You will enjoy whatever you buy. Happy bus searching.

Eric Faires
Huntsville, TN

Since I don't know, I have one question...what is the normal setup for buses with OTR air for when you are stationary? Roof airs or bay mounted Cruise Airs?? Have you ever had a failure of the OTR air when on the road and how has the "other" setup work for you when actually driving?

The Liberty Coach has 4 Cruise Air split units. The condensor and evaporating coils are located in the bays. (2 in the center of bay #2, 2- in the front behind the bumper.) The bedroom has 1 fan coil and contol, the Galley & living have 2 fan coils & contols and the the driver and passenger have 1 fancoil and control. They run off of Shore power and/or Generator power.
Because the condensor coil is beneath the floor , it recieves its air from below the Coach. This can be a problem if the outside air temp is too hot and the road is hot. It will shut down the A/C units.
These same units can also be used for heating the Coach.

Similar to these Marine units: http://www.dometic.com/enus/Americas...ctdataid=85332

Quote:

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Originally Posted by Jon Wehrenberg

Short answer....no.

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What he said. We have had 3 roof airs on a 35' coach, and they were sufficient for that length, but we had to run all 3 (to keep the bedroom, kitchen, and bathroom cool and the ammonia cycle refrigerator happy), and that required the generator (no inverter/s). We have had 1 fail on one occasion, and 2 fail on another occasion. In those cases, of course, running or parked, 3 roof airs are insufficient. OTR will cool a heat soaked coach (over 110 outside) in relatively short order, and then seem to loaf. In those conditions, parked, do not consider any roof air (or cruise-air, for that matter) coach with less than four units. Or you will regret it, in my opinion, for my 2 cents.

have 45 foot with 4 roof airs and have never run more than 3. Only run 1 plus dash air while moving. have traveled thuout the South. Tx. La. Ms. Ga. Fl. Tn. Al Sc. Nc. Co. Nm. I do beleive You could have a problem in the desert with just 3.

Quote:

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Originally Posted by garyde

The Liberty Coach has 4 Cruise Air split units. The condensor and evaporating coils are located in the bays. (2 in the center of bay #2, 2- in the front behind the bumper.) The bedroom has 1 fan coil and contol, the Galley & living have 2 fan coils & contols and the the driver and passenger have 1 fancoil and control. They run off of Shore power and/or Generator power.
Because the condensor coil is beneath the floor , it recieves its air from below the Coach. This can be a problem if the outside air temp is too hot and the road is hot. It will shut down the A/C units.
These same units can also be used for heating the Coach.

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So, from reading this thread, I guess that there is no "Perfect" system out there, and either roof airs or the combo of OTR air & cruise airs all have a potential downside. The original posters question about 3 roof airs I think has been answered as a big "NO" but 4 roof airs or the OTR /Cruise air combo would work ok.

I am happy with my roof airs, and it appears that some are happy with OTR air...looks like it is more of a personal preference thing and shouldn't be the sole reason to disqualify a coach from consideration.

I have had two buses with OTR and Cruise Airs. I have had the OTR quit for the same reason Deb and Eric's quit and that was a failed circuit breaker. But when it quit it was a day in the 90's and I found out that when heat radiates off of a heat soaked highway the cooling air available to the Cruise Air condensing units is insufficient to keep them operating and they shut down. If the coach had roof airs it would have been picking up clean air high off the highway that was not being heated from the highway.

Cruise Airs however have their place and when parked (or modified as described below) they work great because the ground beneath the bus is shaded so there is air capable of cooling the condenser effectively. Their benefit is they are relatively quiet and they are not built to be replaced so they tend to be reliable and have a longer life than the typical roof air. Some owners have made modifications to get good performance from Cruise airs. I know of one coach that has an improved condenser fan system to jam more cooling air across the condenser. I know of one that has had a pressure switch installed and that switch controls mister sprays when internal pressures creep up keeping the units functioning. So the short answer is Cruise Airs are not the best thing if you need to fall back on them. Having said that I had a relay quit on my current coach last summer and I needed to run the Cruise Airs. I was surprised when they worked very well despite high ambient temperatures and did not shut off like my Cruise Airs did in my first coach. So maybe those that do fail to function are either in excessively hot temps or something has changed.

I don't know of anyone whose roof airs shut down when the highway temps are excessive.

The extra bay space used for the Cruise Airs could be an issue for some I guess, otherwise I don't see any downside either way. Since my bus is parked until spring, I don't have to worry about air-conditioning for awhile yet..<g>.

The IDEAL set up is OTR, 4 Roof airs, and Driver/dash air. Should your OTR fail, start the genset, run the dash air (especially if headed west in the summer) to keep the driver and co-pilot cool. Sort of like wearing a belt and suspenders! Trust me, headed west in the afternoon sun, even 4 roof airs will not keep the driver and co-pilot cool without dash air! You hardly ever see this set up...but it would be ideal. Next best set up is OTR with 4 roof airs for back up.

In both cases I applaud Liberty for the Cruise Air placement. They were located behind the bumper (2 units) or centrally located behind the 2nd bay. Neither location seems to rob valuable storage space yet when necessary all units in either location are easily accessed for service.

I don't know where other converters locate the condenser units.

Pete nailed it for a belt plus suspenders set up.

First of all Doug and Lee, WELCOME to this family!!:D

Ed and I have 2 buses:confused:, and both have roof airs (3)each. We have NOT had any problems with cooling. Both our buses are Royales. One is 40ft. (which by the way is for sale just down the road from you at Luxury Coach Brokers with Ken Robertson)He is one of our Sponsors. The current bus we have is a 45ft. with 3 roof airs. So far we have not had any problems with cooling while sitting or underway. We use the dash air while underway. I don't think, as one has already stated, that this is what you need to FIRST consider when buying your bus. You will know the one instanly when you see it. There are alot other decisions which you will be making and I'm sure you will understand what all are saying after looking and looking!!

That is my 2 cents now.
Again, welcome to this FUN, INTERESTING, and CRAZY family. You could join us at the Oysterfest in March at Bella Terra and I'm sure there will be a variety of conversions there. I'm sure we could give you tours of all our buses.
Sandy

Jon,I heard recently that when Liberty did the first 3 slide which does not have OTR that they found that there is a vacuum created under the coach at a certain speed(like ground effect on a flat bottom race car).With this new information,assuming that it is true,temperature may not be the problem while underway but instead no air flow to cool the condenser.Also there might be certain speeds that there is air flow and other speeds that the vacuum is created.

Let me say that just because of the response from you folks makes it worth joining the website. The group of people here are quick to give good honest opinions helpful to those of us not yet experienced in certain topics like say, 3 or 4 roof airs? Its one of those things that you have to experience to know the outcome because both look good on paper. Experience can be an expensive thing to learn on our own not counting the multiple attempts at the same problem. I appreciate everyone taking the time to make a post and hopefully others with some of the same questions may have picked up another little morsel to file somewhere.
I am a master class Sporting Clays shooter and am planning on using the bus for travel to events around the country, not that I will win anything but its entertaining and a good bunch of people there to shoot with. My wife is an excellent needle-pointer and also we plan on trips around the country for classes offering advanced teaching of the art for her. I just don't want to arrive HOT and IRRITATED!!!!

Quote:

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Originally Posted by jack14r

Jon,I heard recently that when Liberty did the first 3 slide which does not have OTR that they found that there is a vacuum created under the coach at a certain speed(like ground effect on a flat bottom race car).With this new information,assuming that it is true,temperature may not be the problem while underway but instead no air flow to cool the condenser.Also there might be certain speeds that there is air flow and other speeds that the vacuum is created.

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Jack, While I can understand and appreciate how a vacuum can develop beneath the coach, I cannot accept that the two condensing units behind the bumper are affected by a vacuum. Don't interpret my skepticism as being anti Cruise Airs or disbelief that the vacuum is the real problem. It may in fact be a number of issues that impacts the ability of a Cruise Air to function while on hot highways.

Ironically when the bad relay caused my OTR to quit last summer I ran the Cruise Airs by accident with the front shutters closed and they were putting out cold air despite it being in the mid nineties, the first time and only time they worked well while traveling on a hot road.

I agree that the front two should work with the impact of air to the condenser from 60+ mph but almost everyone that has ever run cruise airs under way has had a problem(myself included).I lost a voltage regulator 2 years ago and it shut the OTR down and I cranked the generator,opened the shutters and the front cruise air shut down with hi pressure in 10 minutes or so.My coach with the shutters open has a loud buffeting sound at certain speeds,like the air is not flowing through the area.I know that Liberty modified the airflow on the 3 slide coaches and they did not do it on the first one and it has been a problem as far as cooling while under way.Unless we have actually measured the pressure or vacuum at a particular place we are just guessing at whether there is positive or negative air flow.

The ambient air temperature should not change whether the coach is stationary or moving. The ability of the fan to cool the condensor is obviously the issue. My coach has a deflecter on the front of each outlet which should increase the vacuum at the outlet thus increasing airflow. I'm not sure if all coaches have the same arrangement or not. When I purchased my coach the OTR did not work and I used the cruisairs while driving in 100 degree plus weather. The front and mid worked perfectly but the rear shut down because the condenser and fan were caked with dirt.
The large squirrel cage fans move a lot of air and part of regular maintenance the fan and condenser coils should be cleaned regularly.

Lee, I suspect Jack's newer coach, my middle aged coach and your vintage coach have the Cruise Airs all installed alike. While I agree moving or stationary should not have an impact what happens when we are moving is the air temperature 12 to 15 inches above a heat soaked highway that is radiating heat is going to be different than at the roof line, or beneath a coach that is stationary and has shaded the ground below the coach.

When we had the OTR failure in our first coach and the Cruise Airs would shut down, it was daylight and sunny and ambient temps were in the 90s. As soon as the sun set all three came roaring back to life and we went from sweltering in the heat to freezing. Admittedly the temps dropped, but from mid nineties down to about 85 isn't a significant drop, but I surmise the temp down near the highway went from 120 plus to closer to ambient.

I am now curious so I am going to compare temps outside to temps just above the road when it gets hot out. Too many of us have had exactly the same experience for this to be related to a single coach.

I clean my coils routinely, but admit some portions of the coils are never going to get clean without removal of the entire condensing unit.

If your coach is close to the same as mine the outside air temperature sensor is in the spare tire compartment on the passenger side almost at interior floor level. As you know this is where the condensers draw there air from, so in my case the condenser cooling air must be the same temperature as the outside air. It would lead me to believe that it is an air flow issue rather than a air temperature issue.

Its a theory.

I would guess the only way we will know if it is air flow related will be if we hook a manometer up to measure the pressure differential on one side of the condenser to the other while moving and stationary.

LOL isn't that what I said

Yup...............

Ledo -
I thought I warned you about this group - I said, " Don't ask about A/C, plastic shields, or nitrogen in tires ", But you went and did it anyway! Welcome aboard.

Ken,

I know you are one of the good guys, so why don't you tell us from your perspective how a bus should be equipped regarding ACs, plastic shields, and nitrogen in the tires.

This I want to see.

And why aren't you and Mel out at some romantic dinner instead of posting on this site?

Romanticism is way overrated. :) Oops, did I just tip my hand? Dang, I should've made reservations...

Ledo,

Please don't ask them about toilet paper, know what I mean!:p

I pulled into a RV site several years ago and the cruise Air would not work. The Temp outside was over 100 degrees and the site pad was very hot. Troy from Liberty recommended watering down the
cement pad under the coach to cool the pavement below my A/C condensors. It works.

Guess we could expand that a bit, by just "watering down" the entire coach to cool the skin. Then , of course, it would need to be tenderly dried and buffed back to its shine.

Sorry John - I sell coaches with and without OTR air, plastic shields, and, probably, nitrogen, as well. It's best if I keep my opinions closely guarded. BTW, Mel and I went to a movie and had a lovely dinner on Saturday to celebrate Valentines Day early.

Trying to free up our schedule to make the oyslerfest. Hope to see you there.

Ken

I am one of those "M" guys so take what I say with a grain of salt. My 99 Cruise Air shut down one time in the 3 years we used it. We travel from CA to the East during the summer months, July, August and September. My 01 has never shut down, but I will say the last few years was not that hot, mabe only 100 a few times. I have never had on shut down when parked and again only one time with the 99, I would guess it was north of 115 at that time.
We run with 2 wwhen driving with the 270 AMP alternator thru the Trace 4000 invertors and the standard dash air. I keep both always tuned up and life is good! I personaly would not pass up the "bus" of my dreams due to lack of OTR. Anyway, I guess it's a mute point on all the new ones, no matter who builds them!

Quote:

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Originally Posted by kenrobertson

Sorry John - I sell coaches with and without OTR air, plastic shields, and, probably, nitrogen, as well. It's best if I keep my opinions closely guarded. BTW, Mel and I went to a movie and had a lovely dinner on Saturday to celebrate Valentines Day early.

Trying to free up our schedule to make the oyslerfest. Hope to see you there.

Ken

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Ken - I do hope you and Mel can make Oysterfest! Please post to the Oysterfest thread as soon as you can confirm so I can add you to the running attendee list!

Thanks Michael, will do.

Doug,

Look at this one:

http://www.prevost-stuff.com/2000Roy...stCKusilek.htm

It has OTR and 4 roof units. At this asking price it is a steal !

Alek