Why do the Aussies get better air conditioners?

[richard5933]

I had Crusiair in our Eagle 2 in the spare tire compartment an 1 at the rear nice and quite loved those units the fans were adjustable from 0 to high

Our 4106 had a Cruisair - we also thought it was a good unit. Our current bus has two units built by Custom Coach, both modeled after the Cruisair and work as well. When I needed to have them serviced a few years ago, it took a while to find a tech who knew what they were. In the end it was a commercial refrigeration tech who was able to help. He told me that everything on those units was made from off-the-shelf (and top shelf) components, all of which are still available 46 years later.

Wouldn't be difficult for a bus nut to make one himself, with the advantage of being able to shove it into whatever space was available. There are also some much more efficient options for components out right now than 46 years ago, so I'd guess one could be built that would run off and inverter or a little Honda gennie with no problem.

[lostagain]

There isn't a lot of space left in the baggage tanks after all the plumbing and heating is installed. AC downstairs uses up even more space. I don't mind them on the roof. If ducted, they aren't noisy. In the Country Coach, there are diffusers on the ceiling that make them quiet. Also the roof units are easy to replace when necessary.

[chessie4905]

Yeah, all that great baggage storage space gets eaten up by all the new ideas. Just needs remembering that all that stuff will need fixed or replaced eventually and as we age, crawling around down there trying to remember how everything is wired and connected and parts aren't available anymore. Well, they'll see.Depends whether the hobby is travelling or just have something to occupy your time repairing hobby.

[richard5933]

Lots of options on this, and to me the choice one makes is all about what the priorities are and how much space is available. To someone like me trying to keep the outer appearance as bus-like as possible keeping the roof free of a/c units is important.

Since I have large bays, using some space for a/c units is not a problem. With newer components, these could be even smaller than mine. Without a doubt, what I've got installed takes up lots less space inside the bay than a mini-split. The photo showing the inside of the cabinet doesn't show the last 3" at the bottom where the actual condensing coil is. That can be seen on the photo with the closed aluminum cabinet.

For someone working with smaller bays or without trying to maintain the original appearance, rooftop a/c units certainly present a viable option.

[Jim Blackwood]

I know I really shouldn't promote an idea before it's been proven so you know, open season if y'all want to flame me for this but I'm going ahead anyway.

A lot of the above is why I kept the OTR air system, which I know is usually the first thing converters yank out so, "You're Doing It All Wrong!" applies here... but maybe not.

The DL had really good OTR air with an overall capacity in the range of 13 to 14-1/2 tons depending on how you measured it, clearly well beyond what any RV needs under just about any conditions except going up the Rockies in the summer desert with a serious overload of passengers. In the spirit of too much is still not enough that has some potential benefits.

First the distribution. Based on the thermal expansion valves at each evaporator it has 3 separate 1-1/2 ton or 18,000 btu air handlers, and of course the main 10 ton unit. IF 4-1/2 tons or 54,000 btu is enough for stationary use that would seem like a good start. Just have to get around a few issues. First among these is the requirement to remove the overhead storage bins so they can be replaced with overhead storage bins. What? Yep, that's right they gotta go, because they were designed and built for something that moves. Sorta like the ones in airplanes, you know? I mean they have latches that keep them closed for god's sake, what's that all about? And you can walk past them when the doors are open. And they are roomy. And they are built into the curve of the roof. And have lights under them. And A/C nozzles. And speakers. And maybe even power, all of which should be done differently. Why? Because -plastic-. Can't have that in a modern vehicle now can we?

True there are some places where we wouldn't want them, like the shower, bedroom and bathroom but aside from that really why not? Which allows you to keep what? The overhead air handlers. 36,000 btu's of cooling. Plus another ton to a ton and a half in the dash air. And if needed, the main evaporator. About that, are those stainless ducts at the sides of the floor really that bad? I mean they run behind the cabinets and couch in wasted space, take a little foot room beside the toilet, squeeze in the shower tub just a little, then go through the wardrobes into the bedroom maybe using those as the grille, why exactly is it that they have to go? They look like a bus? But you don't SEE them, and where you do they are polished stainless.

Which gets us to the rest of the system. OK the condenser is huge. Absolutely monstrous. But is that a bad thing? Generally speaking the condenser is the limiting factor for how much heat can be removed and it is passive so aside from the needed volume of freon the only reason to worry about it is due to the power drain of the fans. That's a valid concern that must be dealt with but there are advantages to a large condenser such as a large passive heat dispersal capacity. It'll get rid of a lot of heat even with the fans off.

So what's left? Controls, plumbing, and the pump. all of which are standard A/C things and can be configured in the standard A/C ways to get the desired result. Sealed solenoid valves are a common element. So, want 3 tons of A/C? Run a 3 ton compressor to the overhead air handlers. Want 4 or 4-1/2 tons? Same story but with the dash air. Want BIG cooling? fire up the main engine.

I really don't see the problem here.

Jim

[richard5933]

I know I really shouldn't promote an idea before it's been proven so you know, open season if y'all want to flame me for this but I'm going ahead anyway....

...So what's left? Controls, plumbing, and the pump. all of which are standard A/C things and can be configured in the standard A/C ways to get the desired result. Sealed solenoid valves are a common element. So, want 3 tons of A/C? Run a 3 ton compressor to the overhead air handlers. Want 4 or 4-1/2 tons? Same story but with the dash air. Want BIG cooling? fire up the main engine.

I really don't see the problem here.

Jim

In theory you may be right in thinking that the OTR system can be scaled down for use when the bus isn't filled with passengers or when camping. In practicality you might run into a few problems. None insurmountable, for sure.

The amount of cooling needed to keep a bus comfortable going down the road is often underestimated, especially if you are planning to keep a good number of the windows. If you add adequate insulation AND remove enough windows, then perhaps a down-sized system will work. Of course, if you're still planning to run it as a parallel system with the OTR compressor and condensing coil fan in place, no problem here.

Another issue will be if you are going to rely on the bus engine to keep cool in really hot weather, at least if you ever plan to camp next to other RVs and/or people. Running the bus engine all day or night will not win you any friends, for sure.

The other thing is the lack of redundancy. Not a problem is everything is rock steady and reliable, but otherwise it's nice to have backup methods of heating and cooling.

Where I can see a real positive to this approach is if you can come up with a way to run the OTR system using a 120v or even a 240v compressor for when you're camping. This would make it possible to run the whole thing from a pedestal or generator and avoid having to add all the extra hardware for a separate house a/c system.

[Jim Blackwood]

Another issue will be if you are going to rely on the bus engine to keep cool in really hot weather, at least if you ever plan to camp next to other RVs and/or people. Running the bus engine all day or night will not win you any friends, for sure.

The other thing is the lack of redundancy. Not a problem is everything is rock steady and reliable, but otherwise it's nice to have backup methods of heating and cooling.

Where I can see a real positive to this approach is if you can come up with a way to run the OTR system using a 120v or even a 240v compressor for when you're camping. This would make it possible to run the whole thing from a pedestal or generator and avoid having to add all the extra hardware for a separate house a/c system.

They might not mind too much if you only run the main engine in the middle of a hot day when you get back from the beach to pull down the heat soak. Can't much see using it for anything else except while driving. At least you wouldn't be interrupting their sleep.

If 4-1/2 tons isn't enough It might be time to rethink either your insulation plan or your location. That's enough cooling for a pretty large house, say 3 bedrooms, full downstairs, and large sun room. Equivalent to 4-5 roof warts. Should be plenty for a stationary bus under normal conditions. The limiting factor really is the amount of amperage available from a pedestal. Otherwise you're on a genny or OTR both of which are noisy. So this is where you devote your efforts to get the most efficient possible compressor and reduce the draw of the fans. Some of the new sealed scroll compressors really are quite good (such as those used in mini-split systems), and pulse width modulated motor drivers can run the fans only as much as is required.

As for redundancy, you already have that with your evaporators (4 total) and would have it with your compressors (2 or more) and your condenser fans (2) leaving only the common plumbing and if that fails it has to be because you did something wrong. Not very likely.

Jim

[windtrader]

If the OTR A/C system only runs while the bus engine is running, then this comparisons is apples and shoes. There is no way in any practical viewpoint that running the engine is an acceptable power source for 90% of the typical owners who use them for recreation.

I can't think of any campground that would not suffer a barrage of complaints if you run the bus during the day or evening. Most of us here are so concerned we use small quiet compressors so we shorten the time from engine start to getting out of the campground.
The 10% that park in the desert, have at it but that is a small case overall where noise is not nearly an issue.

[Jim Blackwood]

OK Don, I completely agree with you but are you really paying attention here? We aren't talking about using the big engine driven compressor in the campground. If ever it would only be used to draw down the inside temp after baking all day in the hot sun with nobody home taking 5 minutes or so, but that might never happen. So what are you complaining about?

Jim

[richard5933]

What specifically are you considering for a compressor to run parallel to the OTR compressor? Will it run from inverter or will pedestal/generator be necessary?

What about for the fan on the condensing coil? The onboard one I've got draws 70 amps @ 24v, so it's unlikely that's a keeper. What are you thinking about to take its place?

I see where you're going with this concept, but it might be one of those times that possible doesn't equate to practical.

[Jim Blackwood]

Well first, 70A @24v is about 15A @ 115v and since you aren't trying to exhaust 14 tons of heat it can run at low speed and load, proportionally about 3-4A for the heat you have to get rid of. Even for two fans that is manageable. You have to add in the load of the air handler fans of course. This requires an inverter/charger and a PWM motor speed controller, preferably with a thermocouple input so it only runs when the condenser is hot. My math may not be perfect but the idea is to see if it isn't feasible.

As for the compressor, like I said something like the mini-splits use, probably a sealed modern scroll compressor with soft start, maybe some sort of variable speed drive, and a high seer number, something up in the 20's. That should get the current demands down to where a shore line can power it. One option would be to use a pair of compressors each running on 115v so if that's all there is available you can still have AC. If a mini-split can do it why couldn't that? All you really have that is different is a really big freon reservoir and a bunch of inside units.

Seems like there are plenty of ways to skin this cat.

Jim

[richard5933]

So, in the end what are you actually sharing between the two systems other than the refrigerant and some copper lines?

Those reduced capacity components may work while camping, but wouldn't do the trick while on the road so you'll still need the OTR equipment in place.

Seems like for a whole lot less effort and money you could add a totally parallel system using one like Custom Coach did. Or, if you want to maintain the OEM ducting system you could just add another coil to the stack for the smaller system to use while camping.

That larger system will still be needed for keeping cool going down the road, especially if most of the windows are in place. I think that many underestimate the amount of cooling necessary on the road. Probably the reason lots of entertainer coaches run 4 to 5 roof top units with a 20KW generator.

[luvrbus]

I have 3-15000 btu Colemans with heat pumps Country Coach did a hella of job making those quite,then I have 48,000 btu dash air engine driven with a condenser in the rear under the bed with separate controls ,the passenger can control her comfort level too   last summer driving was nice with the dash air 

[windtrader]

Jim,
Didn't mean to come across as complaining other than saying other campers would be complaining if a OTR 2 stroke bus starts up in the campground.
And yes, maybe dropping in when I should be doing something else. Just confusing myself just what you are trying to accomplish and various options with different benefits and such. 

[Jim Blackwood]

Appreciate your input Don and maybe I was overly brusque.

Common elements would include all the evaporators, the lines, the freon, the accumulator, the condenser (a biggie right there) the solenoid valves and the controls. Also the compressors but you would only use the one or more that applied at the time. Definitely less work than installing a complete new system because all you are adding are the compressor(s) and a solenoid valve or two. And modify the controls of course. Everything else is already there. You have to evacuate the system and do some plumbing, and find a place for the new compressor and then recharge of course. But that can be done.

Don't worry if you can't see the vision here, not many can get past the A/C hype to understand that anybody is capable of working on this stuff. There's been a long and concerted effort to portray it as Rocket Science, but it really isn't. Especially on the MCI where you have an accumulator tank that'll let you charge anywhere from 10 to 30 lbs of freon into the system and has sight glasses for the top and bottom. To go wrong there you have to be trying real hard.

So the advantages are:
Minimal changes to the existing system
Minimal expense
Retention of OTR capabilities
Use of OTR system for camp air without the noise
Interior ductwork already in place
Use of system at reduced capacity for camp air in efficiency mode
Retention of robustness of OTR system
Ability to supplement camp air with OTR air if needed.

There may be more if I spent time thinking about it but for me that's enough to give it a try.

Like I said, the key is finding the appropriate sealed compressor for the camp air side. This would undoubtedly be different for different buses and owners. Some might want a single compressor that ran on 220v and that would be the easiest. Some would want a pair of 110v compressors. I probably fall into that group.

A company like Goodman down in Texas might be a fair source. When you can buy a complete 4-1/2 Ton residential system charged and ready to install for $600-700 the cost of just the compressor should be acceptable, even for the high efficiency models.

Jim