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The Newbie Thread
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Look at this article it will explain the different A/C systems used.
There is a lot of information in the “Article” section that will be of help to anyone considering a Prevost conversion.
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“Is that really just the ability to run the roof A/Cs on the road?”
No Mike, but a good question. Over the road air (aka OTR and “bus air”) is what you’d find a seated coach. The bus engine turns a large Carrier (at least is what I think is on my 1999 Liberty Prevost) compressor. The conditioned air (cooled or heated as you desire) is discharged through a duct system and grills just below the windows from one end of the coach to the other. It would be rare to see a motorhome Prevost with OTR and roof airs, at least I think it would be.
Mike, did you know that as an alternative to roof airs some Prevosts (like Liberty’s) use Cruise-Aire heat pumps to provide heating and cooling either off of shore power or the generator? Our Liberty had two Cruise-Aire mounts in a mid-coach bay and two behind the front bumper. Some of the newer coaches with Cruise-Aire might be able to run one or two of them off the invertors, but I’m only speculating.
If you feel like your drinking information from a fire hose, then you’ve got company. We all started out that way.
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It’s going to be for sale Geo, only 36k miles!
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Mike, you hit upon one of the reasons for OTR. We all have house HVAC. In all coaches the HVAC systems can be powered via the generator, and in a lot, maybe most, some if not all HVAC can be powered through inverters.
As was mentioned I am a big advocate of OTR because the entire coach is made comfortable regardless of outside air temps. Dpending on the vintage coach that OTR will range from 80,000 BTU all the way up to 109,000 BTU. That cooling capability is very important because in the summer southwest with the coach at speed it is difficult keeping the coach cool with less BTU power. There is a great deal of heat loss or gain through the windows, and moving the coach at highway speeds increases that loss or gain.
OTR is a no-brainer. set it, and forget it. You will not have to try to cool a heat soaked bedroom at the end of a long day.
But let’s start thinking of redundancy because nothing can screw up a vacation trip faster than to find you have to drive down the road suffering from the heat because you have no alternative. A 45 foot coach likely has 4 house AC units. One for the front, one for the rear and two for the middle. Each one is likely going to have a maximum of 15,000 BTU. So compared to the available capability of OTR the house units are going to work harder. And if the one in the bedroom or the one serving the front quits it could get uncomfortable. I like knowing my entire time driving or living in the coach is not dependent upon only one way of keeping me cool. That’s a personal choice and I understand if someone is happy with their non-OTC coach they don’t need OTR.
OTR has been criticized as sucking fuel and robbing power. Both are true, but no matter how you opt to set up the HVAC on a coach keeping the interior cool is going to use the same amount of power and fuel. Instead of using fuel for the generator you use it for the inverters, which in turn are taking battery power to run the AC units and using alternator power to keep them charged.
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Thanks for the great insight and the helpful article on OTR air. I can appreciate the benefits having suffered in previous coaches while driving on high temperature days where the roof A/Cs were unable to keep up. This seems like an ingenious solution to high A/C demand on the road, and explains to me how commercial buses are doing it.
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Someone once told me the human body is the equivalent of a 500 watt heater.
If you have a busload of people driving through Arizona in August you have a serious need for cooling power, so the seated coaches are equipped with systems that overcome both inside and outside heat. Those of us that have OTR know the systems are both robust and very capable.
I know from experience that once a coach gets heat soaked the available house AC systems have a very hard time cooling the coach down. They may work well if starting with a cool clach, but once they get behind they do not seem to have the capacity to handle the total heat load.
But keep in mind we are all different and what someone may consider warm may be just right for someone else. My definition of comfortable is if I need to run the wipers to clear the condensation from the outside of the windshield it is just about perfect. So I am one of those who likes a vey cool coach.
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Mr Mike
I rest my case, commercial bus is what we are built on, not an RV chassis.
I am located near MCCC close to Indio, if you are in the desert I would be more than happy to let you look and drive my bus so you understand.
Later
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Before we had Prevo bus air, I didn’t get it. Now that we do I get it. It’s whole bus Climatrol and a last resort. Our Vantare has bus air, a 2.5 ton basement unit and 2 cruise airs. Last Oct. at the Prouds rally in Al. 1 leg of the basement air went out and shortly after the front cruise air took a crap. In the heat of the day we were able to run the bus for a few minutes to get it real cool (like 55deg) and then what was left of the basement air and the rear cruise air kept everything quite liveable. If not for the bus air we would have cut the rally short to get home and get everything fixed. Like the Monkees..I’m a believer ! Geo.
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I will chime in too about Prevost OTR bus air. I love it and so does my family. Nothing cools the bus like it. I plan to keep this bus until I either do not need it, can not drive it or Jesus comes, whichever comes first. But, IF I was looking for another bus it would have bus air if at all possible.
Davy
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I would say the choice is simple, if you want storage space go with roof air,if you only need minimum storage space go with OTR or cruise airs, both of these take up a ton of bay area. My previous coach was an XL40 with three roof airs,my present XLV 45 has three Cruise airs. I sure miss the storage space.
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I own a Bus with 4 rooftop units. I have traveled in almost every state in summer and have always been cool with one unit and dash air while traveling. When parked have never had to use all 4 units, only 3! My 2 cents.
Have owned bus for 8 years.
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Is there such a bus configuration of OTR, and Roof Airs. How much bay space does OTR take up.
would that be an option to have full coach comfort when driving, and also keep bay space by going with roof airs.
Do roof airs equal bay space and simplicity of maintenance & repair. -
Is there such a bus configuration of OTR, and Roof Airs. How much bay space does OTR take up.
My old 93 has Prevost OTR air (5 ton carrier compressor) and 3 roof airs (40 ft). The OTR takes up a half length bay. The Evaporator on one side and condenser on the other. These are not full width of the bus since the fuel tank sits in the middle between the two bays. The storage space given up is not that great.
I don’t have basement nor cruise air.
When the OTR air is out as is currently the case (compressor head leak per Jeff) then I have to run the run the generator to run the roof airs while traveling. The roof airs are not powered thru the inverter.
Rather than investing in a new compressor, I can either buy diesel to run the generator or install a new inverter and run the front roof air via the separate 12V alternator and house batteries. A third alternative would be to convert the condenser bay to an inverter bay and use the 24 volts from the 50 DN alternator (currently driving the condenser blower) to supply power to more than one roof air. I need to give those later two methods some more thought. I expect the later is a lot more work to implement.
We loved the OTR air but it’s expensive to maintain in a 22 year old coach.
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I have OTR and 4 cruiseairs. My OTR costs me 1/2 of a bay as has been mentioned above. My cruiseairs occupy space behind the front bumper where two units are located. The remaining two are stacked, one on top of another so the bay space they occupy is about 2 feet by 2 feet, full height. Other converters locate cruiseairs in different spaces or in a different manner, but the total space lost is not that important to me.
My set up is close to ideal for me based on how I use the coach. If my use of the coach differed I might consider a completely different HVAC set up. For example if I did not have OTR I would use roof airs (4) because they perform better while on the road than cruiseairs because they are in clean cool air and are not drawing the superheated air radiating from the highway through the condenser. The roof airs are likely to be noisier than cruiseairs.
If I used the coach as a second home and most of the time it was parked at an RV resort the OTR would get little use and therefore the space it occupies would be more valuable for storage. I would lean towards cruiseairs for that type of use because of less noise associated with their use, as long as the coach got limited driving. Cruiseairs also do not require roof pentrations which seem to impact all of us over time due to potential leaks.
There is no perfect way to control the environment in a coach. Every single system or combination of HVAC systems is a compromise with good and bad features.
As to maintaining a OTR system, Joe is correct in that there is a cost. The heart of the system is the compressor and it might periodically need a seal around the shaft or it might need to be rebuilt or replaced. I think a new compressor is going to cost somewhere between $2200 to $3000. The evaporator and condenser blower motors will occasionally need brushes or might even need replacement. But the bottom line is there are going to be costs associated with owning a coach and they can be expected and planned for.
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You right on the money John, Jeff quoted me $2,500 for new one.
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