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OTR or Prevost Air?
Hi Everyone,
My wife and I are looking at all the different converters and attempting to digest all the differences before we make our purchase. I have been reading here and seen many references to the OTR or Prevost Air and would like to know if there is any difference between to the two and if so which is better.
In addition from what I am reading it would appear the Prevost experiences serious heat gain and am curious to hear from you all regarding your experiences regarding this topic.
Currently we have a Wanderlodge that does not have dash air so we use the front roof top a/c while on the road and it provides more than enough comfort. I have also read the roof top front air does not do a good job of cooling the cockpit in the Prevost, is this true or converter specific?
All in all I have seen a lot of attention paid to the OTR air system and it would appear that it has significant challenges and high failure rate, would be curious to hear your all’s thoughts on this subject.
Thank you.
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11 Replies
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Getting into a discussion about A/C on Prevost coaches is akin to poking a bee hive with a stick. It has the potential to get exciting.
Let’s first define some terms. Prevost OTR or over the road air is a whole coach system. It ranges from a little over 80,000 BTU on early models to as much as 109,000 BTU on later models. It has a driver’s or front air system component that can be set at a different temp than the balance of the coach, but the driver and coach systems share a large Carrier type compressor. It is only available on coaches with up to 2 slides. Coaches with 3 or 4 slides will only have driver’s air and a much smaller compressor.
Some converters have coaches with Prevost installed driver’s air only that is supplemented with a converter installed system that might have one or two evaporators to cool the house portion of the coach. The output of that supplemental system is less than the Prevost OTR system. This smaller system has also been called an OTR system so when discussing the various systems everyone in the conversation has to be sure to understand what is being discussed.
Some conversions have only driver’s air, and any additional A/C while driving will come from the house A/C units which could be a roof air, Cruiseair or a basement package unit.
Those are likely the options available to a buyer of a new or used coach.
What works for one owner may be overkill or inadequate for another owner. We can debate what is best, what is needed, or what is too little or too much but that is something that is determined by personal needs. I am heavily biased towards Prevost OTR because I prefer cool temperatures and I know the OTR system will keep the entire coach at whatever temperature I desire.
I know for a fact I am outnumbered by owners who are satisfied with their A/C systems even though the total capacity might be less than half that of the Prevost OTR.
The same debate regarding what is acceptable for an A/C system when driving can take place regarding the house systems. The bottom line is how an owner defines comfortable. If an owner is comfortable at 70 degrees more A/C system capability is going to be required to satisfy him than that which will keep an owner who is comfortable at 75 or 80. The discussion can also include a recognition that Cruiseairs are likely to lack performance as the ambient temps go up and the highways get heated by the sun because in excessively hot temps with a lot of heat radiating from the highway the condensing units are not going to get sufficient cooling air. Roof mounted units will perform much better under those conditions, but the objection to them is the noise level.
It makes no sense to have OTR if the coach spends most of its time at a RV resort and is used as a second home and driven rarely. A coach that is going to be driven a lot, especially in the southwest would be a good candidate for OTR. There are any number of issues to cloud the discussion such as use of space, cost of replacement, number of units to have, etc with almost every single owner claiming the system they currently have in their coach is all you need or is best.
OTR is a mechanical system, and because of that it requires service. But it is not a maintenance hog. Many of us with OTR have never had to service the system. And those of us that have probably did the first service after it had been in service for 15 or 20 years. A typical issue is the eventual need to replace the seal on the compressor and to recharge the system.
Roof airs are viewed as throw away devices because their cost is relatively low and after they fail some don’t even have a means of recharging the system. Newer roof airs are especially difficult to repair and while they are serviceable to an extent the cost when compared to the cost of a new one makes repairs less cost effective.
Cruiseair split systems are much more expensive, but they are very serviceable. It is hard to say which is more reliable, but those with Cruiseair units favor them for the quieter operation than roof airs, but also understand they are not the best option for A/C while driving in hot areas. The output on Cruiseairs is the same as roof air units with both types in the 13,500 BTU range. Some roof airs have as much as 15,000 BTU output, but they have been reported as noisy and prone to problems.
The bottom line is there is a seat for every butt. No matter how a coach is configured as far as its A/C system somebody will find it not only acceptable, but desirable.
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Jon, great summary. It is responses like yours that make this site so valuable for future Prevost owners.
If I may add a couple of items. As a Country Coach owner, I am familiar with the Country Coach “OTR” system. I put it in paretheses because it is a poor cousin of the Prevost OTR system. We have this system on our coach, where it cools the driver compartment and the bedroom. We have 3 15k Btu roof ACs which does a good job of cooling the coach, but as you say, are very noisy. All Country Coach Prevost conversions I have seen have the CC OTR system, which to the best of my knowledge is about 30k Btus. The difference between our system and that installed on CC Prevost converion is on ours the OTR does both dash and bedroom, the CC Prevost have their own driver’s AC, so the entire capacity is available for the OTR system. But 30k Btus is still far short of the 80k to 108k Prevost OTR system. CC Prevost owner will have to chime in on the effectiveness of their OTR system. -
When owners respond to how they like their system most of the debate or confusion relates to how different people have different views of what constitutes comfortable. I use my aunt and uncle as an example. When I visited them I quickly learned they go out in 70 degree weather pretty well bundled up, and their home AC would not be turned on until the temps in the house were at least 85.
I’m OK wearing a T shirt when it is 50 degrees out, and I like our coach around 68 to an absolute upper limit of around 72. My aunt and uncle would be as uncomfortable at my temps as I am at theirs.
If members would express actual ambient and coach interior temps a lot of confusion could be eliminated. Another thing to help the discussions is knowing the specific coach systems. Some coaches have only 3 A/C units despite being 45 feet long and having 2 slides. If the coach is never allowed to get heat soaked it is entirely reasonable to understand on 90 plus days two AC units might be adequate, but if the coach has been driven all day with just AC on in the forward part of the coach, the heat in the bedroom due to the lack of cooling, plus the heat of the engine is going to tax all but the strongest AC system.
Regardless of how comfortable different people feel at different temps, our coaches are recreation vehicles. That means we want them to be enjoyable to be in. If 3 units are merely adequate, if one quits the other two will not be able to keep the occupants comfortable. So in that instance it is better to set a standard in which a coach of a given size has to have a minimum of 4 so if one fails there is ample capacity still available.
The model of coach makes a difference to this discussion also. XL coaches are single pane glass and with all the possible AC units operating you can still feel heat radiating into the coach through the glass when it is hot outside. Conversely, when it is cold out you feel the cold air spilling from the glass if you are sitting with your back to a window. H and XLII models have thermopane (double pane) windows and heat gain or loss on those is much different than an XL. If the windshield shades are black there is no AC unit that can overcome the heat pouring in as a result of the black shades acting like solar panels. Just the sun shining on on a southbound coach is a challenge to overcome.
We firmly believe in OTR. Despite the fact it is overkill in most instances, having such excess capacity has proven to be a real plus in providing the flexibility to heat or cool our coach anytime we experience the need. Once a coach is at the desired temp the energy required to maintain that temp is pretty much the same no matter what means is being used.
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I’ll chime in with our set-up.
First, we wanted four slides. You cannot get OTR air with four slides, two slides max.
We have driver’s air with an auxillary unit for the passenger side. Actually, the auxillary air has vents behind the driver’s and passenger’s seat along with a vent at the entrance door. The regular driver’s air has 3 vents for the driver and vents along the front windshield on both sides. Craig freezes all the time, so I point all the air vents on me as I drive.
While going down the road, I will run one or two roof airs just to keep the inside of the coach comfortable (about 74 degrees). If I run the front roof air, Craig freezes, so I will run #2 and #4 to balance. We have four 13,500 btu air conditioners with four 3,500 watt inverters so I don’t need to run the genny unless I want to.
Our recent jaunt to the desert in 105+ temps, two airs along with the dash air was fine to maintain 74 degrees inside the coach. Since we started off fairly early in the morning driving from Phoenix to Palm Springs, the coach was never really that hot on the inside from the start.
In a general sense, we are not in the south too often in the high heat but I think our systems can handle anything mother nature sends our way.
Mark
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Good info Mark. Just so anyone contemplating a coach is aware Mark’s driver’s air plus two 13,500 BTU air conditioners is keeping a coach at 74 degrees while driving, which is another element to take into consideration. Air moving across the coach surfaces imposes a certain additional load on the HVAC that is not present when the coach is stationary.
I think regardless of anyone’s bias for or against OTR there is ample agreement a working driver’s air plus two AC units will maintain reasonably comfortable temps when driving. I also think most agree when parked two AC units will also maintain comfortable temps.
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Mark, at the risk of thread drift I want to point out that one of the topics discussed at this weekend’s seminars was the Liberty rose petals. As a result of your original post regarding them most non-Liberty owners were looking for evidence of them around all the Libertys that were at the seminar.
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Jon,
All the Liberty owners will have to have our Rose Petal canisters re-energized at the next gathering.
LOL!
Mark
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Thanks everyone for the detailed information, very good feedback.
We are looking for a late 90’s CC Prevost, something without all the extra bells and whistles. My wife and I boondock frequently as currently our solar system allows us freedom from the plug.
Perhaps even an Angola as I understand these were much simpler products too. Although Angola can provide no support I am not worried. Bluebird isn’t around anymore either and via support from the forum have been able to keep our current bus quite healthy.
We are definitely open to any and all suggestions from the “Gurus” in the PC community, I have read hundreds of posts and from what I have read you guys and gals alike really know your Prevost.
So lay it on us and help us learn the product.
Thanks again to all who replied to our first post.
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One more point on roof ACs. The effectiveness of roof ACs are dependent on how they are set up. The coach we looked at today had four roof ACs with no ducting system–they just discharged air straight down. Not at all effective. Our system have 3 roof ACs sharing a duct system with two rows of 6 ducts throughout the coach. Seems like one of the Marathons we saw at the factory used a similar system. Air distribution is critical in any AC system.
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I’m replacing the big Carrier OTR compressor on our coach at ETLC.
While diagnosing the problems with it, Jeff Rowe educated me about the compressor. Three pairs of cylinders (total of six). As the thermostats are “satisfied” the system automatically drops pairs of cylinders to match the load on the compressor (and bus engine) with the demand for cooling. There are relays on top of both the left and right banks of cylinders which allow them to be dropped or brought into service as necessary. When there is no demand for cooling, the electric clutch on the compressor then shuts off the compressor.
How many of you out there didn’t know the Carrier OTR compressor had the ability to cut out cylinders to match demand? Or I am the only one?
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And how many know those solenoids on the compressor are protection against excessive system pressures and in addition to being controls, they are a very important safety feature.
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