Over the Road Air

[Richard and Rhonda]

I am sure that some or most of us also looked at Prevosts at one time or another. Much ado is made about the OTR A/C systems that come with the Prevost shell.

This is an interesting thread that you have to read all the way through to get to the meat of the post.

The poster, Sean, makes an excellent point in debateing OTR versus the generator driven AC systems that Newell uses as standard. The poster is quite an mechanical and electrical guru, just visit his own site and look at the rig he built.

Anyway, I thought it was interesting reading. http://www.busconversions.com/bbs/index.php?topic=15769.0

[folivier]

Yeah, running the genny and a/c's is much less complicated. Plus the genny is getting the necessary exercise. Most of the stuff I've read show that the genny uses about the same fuel as turning the large alternators to power the OTR's.
What I'm thinking of doing is adding solar panels to the roof so that I can boondock. Of course I don't plan to do this where I would need a/c. I'd just like to park in some out of the way places away from the crowds.

[chockwald]

Same here, Forest. Now that we have got the car hauler issue out of the way, I want to add solar panels. Like you I don't plan to boondock where it is NOT hot, so being able to run the A/C while I am boondocking is not important, but being able to use all my other appliances is.

How is retired life going?

Richard....that was quite a technical discussion....I'm still trying to uncross my eyes....LOL! Seriously, it was an interesting discussion.

[folivier]

My coach has the Raritan electric water heater. So in order to have hot water while I'm boondocking I'll probably buy a small portable propane tankless water heater and put hookups directly into my coach's systems. It shouldn't be too difficult to make a stand to set the heater outside (unless Richard designs it :))
Seriously this should work pretty well and shouldn't cost much over a couple hundred.
Retirement is great! No problems, no stress, have to remember to grab my cellphone when I go somewhere. I'm actually completing some projects that I started years ago! Got the coach all waxed, front & rear compounded and waxed, small freezer installed. Haven't had a chance to be bored yet.

[larryweikart]

Forest, I need to replace my bay fridge/freezer. Is that what you just installed and, if so, Where did you purchase? The Norcolds appear to run about $1400. Is there a better or different solution. Thank you for any input.

[folivier]

Larry, I looked at those and others but ended up buying an Edgestar for about $160 at compactappliance.com
http://www.compactappliance.com/CRF150SS-EdgeStar-Compact-Stainless-Steel-Freezer-With-Lock/CRF150SS,default,pd.html?cgid=Appliances-Freezers-Upright

It's a 1.5 cuft and only runs on 120vac but is very quiet and was the only one that would fit, my coach had a dishwasher under the pantry originally. Last owner removed it and put in a small refrig. which died shortly after we bought it. I'll put in a drawer above it to fill the remaining space.
I figured with the difference in cost I don't care if it only lasts a few years. What's neat about this small freezer is that it has dual thermostats, it can freeze down to -16 degrees (checked that out) and it can also be used as a refrig. and cool from about 32-48 or so. The insulation is pretty thick so if I'm not plugged I can run it off the inverter or only plug it in for a couple hours a day.

[fulltiming]

Richard, I agree that the OTR air is overkill for most folks. It was designed for a bus load of people (40 or 50) during very hot weather. It does an excellent job and can literally freeze you to death in a coach with 2 or 3 people in it. As I recall, OTR air is 10 tons (120,000 BTU) or the equivalent of 8-10 roof airs. Most OTR's also generate about 150,000 BTU of heat.

There is no question that OTR air is BIG (takes up the equivalent of 1 to 1-1/2 bays), EXPENSIVE to buy and to maintain and HEAVY. For the vast majority of RV'ers, OTR air is way overkill. It takes space, load carrying capacity and $'s that would be better spent on things more useful (like a BIG generator that you will actually use).

I have the 12.5 KW genset on my coach (most of you with newer coaches have 17.5 KW or 20 KW) and can run my 4 basement airs without trouble going down the road. I can run the genset non-stop for days at a time if needed and I do run it continuously when traveling if the outside temperature is above 75. In theory, you should shut the generator down every 6 days or so of continuous running for long enough to change the oil.

OTR air is another case of a product designed for a specific purpose (OTR bus) becoming more of a liability when put to a different task (RV). That said, it still gives some bragging rights to be able to cross the desert during the summer in the hottest part of the day with the temperature inside the coach cold enough that you have to wear a coat to be comfortable.

No question that Newell made the best decision.

[larryweikart]

Thanks for the info Forest, that may be a good alternative. While on the subject of OTR and air conditioning, has anyone found an acceptable solution to the almost impossible task of maintaining the split air conditioning system Newell installed in the early 90's coaches. I know some appear to be going to roof airs, but I find that to be a very expensive solution and I can't imagine cutting thru my roof. I continue to have problems with the system and at this time we have actually shut down unit #3 to use as spare parts to keep the other 3 operating! (#2 has problems now)

[folivier]

I just upgraded the circuit boards and thermostats (digital) on 2 of mine. I found a guy on ebay that had 2 for $350. The circuit board is also available at Northwest RV Supply http://www.nwrvsupply.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=NWRV&Product_Code=3311557&Category_Code=ele
for $119 but doesn't include the thermostat. My local a/c guy serviced mine last year and is coming out to clean/service them next week. He said that he should be able to get parts if needed. He also said that he could build a system to replace one if he couldn't find the parts. I plan to nurse mine along for as long as I can. Then I'll replace them with roof-tops. Steve Magown did his and ran the wire outside along the roof. I was thinking maybe run the wire (especially for thermostat) in wiring races along the metal trim strips to a nearby cabinet. You can get the races in a color that would match pretty close to the headliner.
Another thought would be one of the mini-split units that are becoming popular. You might be able to adapt one by destroying the cabinet and mounting it in place of the basement units. You could utilize your existing wiring, tubing and ductwork. Neither option would be cheap, but would retain the features of the basement unit.

[smagown]

Forrest:

I've still got my basement units installed if anyone wants them for parts. Two new boards. One for a single compressor and one for a twin compressor unit. After replacing the boards one of the condenser fans seized and I gave up.
Thanks,

[tuga]

As some of you may know, I am a member of POG (Prevost Owners Group). It is a great organizaiton made up of 99% Prevost owners, 2 Newell owners, and a Blue Bird guy. Anyone who is interested in learning about Prevosts can join.

The subject of OTR air comes up often, and as you would imagine there are pros and cons discussed. The only real advantage I can see to an OTR system is redundancy; if your roof/basement ACs break down you have a back-up with OTR. In my 1987 Newell (3 roof ACs) and in my 1993 Newell (3 basement ACs) I have had 2 of the 3 break down at the same time! Guess what month they broke in; yep August, in Texas. I sure wish I would have had a OTR AC then. Keep in mind, that both of these Newells had crap for dash ACs. They never put out cold air - they didn't even put out cool air. I had Newell work on them and other AC shops try to repair them - the result was always the same - THEY DIDN'T WORK! Some time in 1996 or later Newell began using a really good dash AC. I have one in my coach (1999).

The dash AC in my 1999 works so good that I don't have to use the basement ACs until the temps get to 90 degrees. This dash AC is far superior to the old units. The subject of dash ACs brings me to my next point.

Marathon Coach around 1994 and later began converting Prevost shells with a different kind of OTR air. Instead of a 10 ton Carrier OTR AC (belt driven by the engine) they used 2 regular AC compressors like you would find on your car. Each compressor ran off of the engine and they cooled the inside of the coach nicely in average hot weather. So here you had the best of both worlds: a good back up to the basement/roof ACs and yet an inexpensive belt driven system run by the engine AC that could cool the entire coach without running the generator. RVers are cheap; they don't want to spend the money to run the generator. They want free AC using engine driven systems like OTR.

IMO this is the best set up I have ever seen for cooling a coach.

I would like to suggest to Karl to consider building a coach with the automotive compressors and evaporators - one in the dash area and the other in the middle of the coach to be used while driving down the highway. With Newells being insulated as well as they are I think 2 units would work. If not, put 3 units in; I'm sure the 650 hp engine could easily handle the little compressors. If you are going to have redundancy, the ACs are the place to have it. Nothing can ruin your day faster than driving a hot motorcoach!

Just my .02

[afrench45]

My second coach was a 1989 Prevost shell with a 2000 conversion. The coach did have bus air but was missing something so I never used it. After reading forums on it, I wish I would have spent the money to fix it, because I had more problems with the generator on that thing. The problem I have with my Newell is on a hot day (80+) its hard to keep from the galley back cool with the basement units Im assuming the coach picks up road heat and the engine heats the inside. Once the coach is slid out, it cools immediately.

does anyone else have this problem?

[larryweikart]

Thanks for the input. My problems have not been circuit boards (not yet) but finding replacement compressors. Newell had found some, but they barely fit the area allowed and one didn't even last a year. Maybe I'll just winter in Mi. and summer in Canada! Instead of a snowbird, I'll become a snow snail!

[fulltiming]

One of the big reasons for the switch to roof airs by Newell was the difficulty in adequately ducting basement AC's in multiple slide coaches.

I believe a prime motivator for Steve to switch to roof airs was the reduced efficiency of the basement air conditioners with the slide in. It doesn't surprise me that a triple slide unit with the slide in could display issues with air circulation. Since I don't have slides, I don't have any air circulation issues and the rear of my coach stays nice and cool traveling in the summer with the basement air in the bedroom.

[Richard and Rhonda]

Larry,

Some of the bus conversion crowd have latched onto AC units called mini splits. You can google and learn all kinds of things. Here is one link http://www.harborpointac.com/ebay/ads/download/example_guide.pdf

On the rear bedroom issue, like Michael, I think it is simply an air flow situation. You can hang meat in our bedroom while cruising if you turn the thermostat down. I know, cause the teenagers crank it down, cover up with blankets, and sleep for hundreds of miles at a time.

Without the rear AC on, it does become warm from the engine heat.

[folivier]

One other thing to look at: in my '93 under the bed is a heat exchanger for heating the bedroom using engine heat. I found that just hot coolant circulating through the pipes would put out some heat, enough to make the bedroom warm if the a/c wasn't on. I added a valve to each pipe and insulated them so I can shut off the flow. It helps greatly.

[folivier]

I was just looking at that website Richard posted. Only $300 for a portable 12000btu 115v a/c that vents out of a window! I think that if I have a/c problems just before or during a trip this may work out in a pinch.

[encantotom]

the ductless split system that was in the manual richard attached require a permanent mounting. many years ago i used to define, and sell the inverter motor control microprocessors that were used in them for a long time. inverter motor control allows them to need much less power. they were designed originally for the japanese market where 100amp service was common and accomodations were smaller than here in the usa.

the indoor unit is basically an air handler with controls and no duct. they are now commonly used in large commercial buildings and churches where people need to be in a single office and not heat a large building to be ini it.

they are awesomely good units. Mitsubishi and Sanyo were the pioneers in developing them and i went to their facilities in japan many many times. in the late 80's early 90's.

the inside unit mounts on the wall, but has electrical and freon lines that run to the ouside compressor unit.

i struggle to see how they would work as well as our roof mounted units.

more than you wanted to hear i would guess.

later

tom

[larryweikart]

Thanks for all the great input. I'll continue to pursue solutions, with your help, until the final decision becomes necessary, which may be soon.

[Richard and Rhonda]

Thanks Tom for the insight.

I wasn't thinking of them as a better alternative to the roof units. I was thinking more in line of the mini split being a replacement for basement airs. And in that situation, adapting the mini split to work with existing basement air.

If my basement air was not repairable (hard to imagine after looking at it), then I would have to think really hard about taking a Sawzall to the roof :-) My first thoughts would be to cobble together a fix for what I have.

[jwe648]

Since I have no over-the-road Coach A/C unless I run the Gen & turn on the roof airs I've been thinking on how to supplement for the warm Arizona summer. Back in the day my company refurbished a number of corp jets. Typically the ole' bleed air system of cooling didn't work well on the ground or really below 12k feet. So I designed a 24v aux system for supplemental cooling. Their are such systems on the market for trucks, heavy equiptment, motorhomes and such. If your existing system is sound except the compressor etc. these could be incorprated into your system. The 24v option would use about 25 amp max under load which, should be doable with the batteries and alternators of the larger coaches. It could even be suplemented with some solar if you are somewhere the sun shines.. i have attached a jpg but there are many systems out there..

[encantotom]

hi jimmy,

how much are the rencool units? i looked and mostly came up with austrailian distributors.

tom

[jwe648]

Hi Tom,

This is the us link http://rencoolusa.com/dc-products/ i'm not sure what they cost... If I do it I'll just build one... not that difficult... My holdback is my alt size it's pretty wimpy... Could run on hyd but more issues and trouble.. Heading up the Mt in the am.. wish me luck.. on the down hill side.. I'll be in behind the slowest truck! In loading up found I need more room.. the little lady has filled it up for a two day trip..

Regards,

Jimmy

[Lewis and Clark]

Hello Forrest,
By any chance do you still have your old AC units and any parts available for sale? I need the board for the twin compressor. RVAC 305-2547 rev a. I know it is a long shot, as your post is 4-10-2010. How are the roof ACs working out? My coach is 96 #410.

Thanks.
Nando

[folivier]

I still have my basement airs. I was able to find the newer type board and thermostats.
But mine is the older Dometic single compressor, a '93.

[Lewis and Clark]

OK, thanks Forest for the reply.

Nando

[Nasser]

I have a friend who has a 1985 Prevost (nice wood interior just like new), he has an OTR A/c, and his coach is a wide body coach, but from inside just like 96" coaches! That OTR's AC is taking too much from the walls!! making the coach narrow in width from inside, when I measure it from wall to wall from inside, its 7.5" smaller than my coach (Newell 1988)!! This is too much!