OTR Air Operations

[Mark]

I have not purchased my bus yet but I would like to know from those of you that have OTR air your rule of thumb using your OTR air vs roof top/Cruise airs. I know when driving there's no questions running the OTR air as thats why you have it, but when you stop for lunch/dinner or any hour or two do you leave your bus running with the OTR air on or do you switch over to generator and roof/cruiseair? I'm not concerned with the diesel burn of the bus engine vs the generator but I dont know if idling the bus for extended periods is good or not. I know the truckers idle all night in the truck stops.

[garyde]

Hi Mark. On my Coach the Cruise aires are split units with the condensors down below in the cargo area and front spaces . 3 fan coils are behind walls in different areas of the coach and one above the front door entrance steps. If I stop for just an hour or less I use the OTR usually.

[Jon Wehrenberg]

Mark,

I use the OTR when driving. If we pull into a rest area for lunch I usually have the generator running when I am on the ramp to the rest area and the AC units running just before I shut down the bus. I'm a firm believer in the adage "use it or lose it" so I exercise all my AC units and the generator any time I get a chance.

I do not run the OTR with the engine idling just to keep the bus cool as long as I have the generator. But that is just my preference. Seated coaches have no choice and we all have seen them sitting on high idle with the OTR running so the coach is cool when the passengers get back on.

[Kenneth Brewer]

OTR while driving, generator and cruise-airs when stopped. OTR when first starting up to drop or help drop temps inside. If starting up for first time, and stationary for an extended period for some reason, use OTR, but always on high idle, which should not harm engine (not the primary reason for high idle feature; the main reason is current load of fans and reasonable loaded rpm for compressor), unless it - engine - is cold.

[Kenneth Brewer]

Correction;

OTR while driving, generator and cruise-airs when stopped. OTR when first starting up to drop or help drop temps inside. If starting up for first time, and stationary for an extended period for some reason, I use OTR, but always on high idle, which should not harm engine (not the primary reason for high idle feature; the main reason is current load of fans and reasonable loaded rpm for compressor), unless it - engine - is cold.

[Will Garner]

Mark,

First, welcome to POG.

You go, you have the full range of responses to pick from. I use the generator to run the Cruisaires while provisioning the bus (food, paper products, clothes, shoes, etc.). That way when I'm ready to go the bus is cool even if I am hot. When on the road and the OTR is not keeping up on a hot day, I have a CC, I simply reach the overhead switches and turn on the generator and a couple of the cruisaires and keep going down the road. When we pull into a rest area for lunch, the generator comes on for the cruisaires and the big motor goes off. We are usually stopped for less than an hour and the coach stays nice and cool. Then its turn off the generator and start the big engine and get rolling!

Hope that helps. Maybe we should conduct a poll?

[Jon Wehrenberg]

Mark,

I'll likely get flamed for this, but in the context of your question OTR (over the road air conditioning) it is understood to mean the Prevost system that uses a large Carrier compressor located on the curb side of the engine compartment.

When Will refers to an OTR system not keeping up with the heat he is referring to a Country Coach installed system. As every owner of the Prevost installed OTR system will attest that system is so large I don't know of anyone that couldn't keep cool with that system. If you inquire about bus AC systems from a salesman, depending on the product they have you will hear different versions of why the Prevost OTR is important to have or why you do not want to have the Prevost OTR system. Very few who have, or have had the Prevost OTR system would not want it again.

[Kenneth Brewer]

We looked at several (older) CCs before we bought our coach. It is my understanding that CC, and other converters, used a similar, but clearly not the same, engine powered compressor 'bus air' system system called an RVAC. It has/had a significantly smaller btu rating. Rather than comment on the performance, since I have no experience with it, I invite those who have to weigh in on this.

[GDeen]

I usually have the bus so cold with the OTR there is little need to run anything for a short lunch or dog walk break. One thing about running the OTR on high idle vs the cruiseairs or roof airs is the noise. OTR and high idle gives a little more background noise which may or may not bother you.

[Seabyrd]

I have to agree with Jon here.. It is amazing.. we are in Texas and it has been scorching hot day and night some days well over 100 degrees.. the OTR from Prevost is just unbelievable.. I have to get a blanket to keep warm.. it will freeze you out !! (even with an outside temp over 100 !!
We had a 45' Navigator with 3 roof airs and burned up here in TX... couldn't get the temps below 85-90 during the day !! It was miserable.. Let's hear it for OTR !!
It will" freeze the balls off a brass monkey" !!
Now having said that please "google" what "Freeze the balls off a Brass Monkey" really means before you think I'm being rude !!
Not that I wouldn't however, hehehe.

[Jon Wehrenberg]

Just so the numbers can be put in perspective, the Prevost OTR system is about 80,000 BTU. It was designed to cool a coach with 45 passengers. The human body generates a little more than 250 BTU to 400 BTU when at rest (a maximum of 18,000 BTU), so the OTR is overcoming the heat generated by passengers plus the heat from outside. It is no wonder why in our coaches that we can stay comfortable with OTR.

To put this in perspective roof airs and Cruise Airs have a BTU rating of 13,000 to 15,000 per unit.

Going further, there are some considerations for owners. Excess capacity means an owner can get a coach cooled down. Having no excess capacity means the coach has to be cool and kept cool before the heat of the day or the temps will not come down. Entertainer coaches may have OTR (not always), but in general they also have 5 roof airs. The apparent excess of AC capacity is for a reason. They not only can get cool and keep cool, but they also can remain comfortable if one should fail. They may not have the time for repairs.

OTR in conversions is going to go away. As the demand for more slides increases, there is just no way to engineer a duct system for the OTR that can work with slides in and slides out. In my opinion if you get a coach with slides and no OTR, opt for an excess of AC units because the silliest thing in the world is a megabuck coach that can't keep you comfortable under any conditions.

[Jerry Winchester]

Yep nothing better than the jet engine sound of the OTR with the engine on high idle. It's a timing issue with me. If I am fueling or stopped for less than 15-20 minutes, then I leave the OTR on. Anything longer usually gets the generator / Cruisair or I will just run two Cruisairs off the inverters and not mess with the generator if it is not too hot. I also try not to let the bus get hot at anytime during or before the trip. Trying to un-hot-soak the big stainless hulk is a pisser when the temp is in the high 90's, so I have taken to cooling it down while it is still in the hanger tied to the shore power then quickly moving over to the OTR as we head out the door. I would not stop the bus and have no AC on if it were as hot as Loc's 5th Ring of Hell and I was going to have to get back in shortly.