Powering Coach AC While Engine is Off

[sledhead]

I am waiting for the day someone builds a split unit outside unit made to mount on it's side so the air vents up and then the line set could go inside to the head unit where ever you wanted to put it .

the seer on the newer units is way up there and the amp draw is very low so one could put 3-4 units up on the roof and have more a/c then you would ever need with out a problem of large amp draw

how hard could it be maybe we just need a bus nut to build it

dave

[jap42]

Use a setup like this: https://www.alpinehomeair.com/viewproduct.cfm?productID=453078036

You could remount the compressor and lay this down flat. The compressor is the only part that would not like being on its side. In my case the current air flow actually works. Although backwards from the OTR system because the air will vent out the side and come in through the bottom. I could take the condenser off the door and mount the mini split in its place. I am going to check the dimensions.

The air handlers can be mounted under the floor. I would probably run return air from one side and vent air on the other side to create circulation. I could add some hydronic heat exchangers on the intake side with valves to use engine heat to heat the bus. Place the air handler in fan mode and circulate the heat.

There are 3 of these to one condenser you can actually have up to 5 I think with this brand. That kit has 3X 12K concealed duct units. Evenly spaced with an extra duct off the front one to the drivers area for A/C and defrost.

Again, the OTR compressor could then easily be replaced with a large generator to power the unit over the road and/or Charge Batteries for an off grid system. They run off inverters nicely.

[Fred Mc]

"Grease Monkey isn't the source i would be using for my information."
Well, I'm sure there are better sources except that

"he's been there and done that".
And that's where "I" would be looking.

[luvrbus]

"Grease Monkey isn't the source i would be using for my information."
Well, I'm sure there are better sources except that

"he's been there and done that".
And that's where "I" would be looking.

People have done it long before the grease monkey Yvan has been doing it for 2 years with Ion batteries anyways bring those suckers to AZ in a 112 F heat and give them a test bet you cold one he would uncomfortably hot
 

[brettpearson67]

Do the coach ac units work well in 115 degree heat?

[luvrbus]

they do ok the condenser, fans and dc motors are large enough to draw enough air over the condenser to keep the head pressure in check some of the buses have 2 of the big @$# DC motors running fans ,lol but a 10,000 but mini split will not keep a bus cool here 

[dtcerrato]

We have been running a single 13500 btu roof top ac on our one & only bus for over 40 years now. The bus has full timed us in every type of environment including 115° desert heat. The word successfully has more to do with the owner(s) than the equipment IMO. When our bus is at 85° interior temp during 115° ext. Temps - that is perfectly fine with us so in our opinion our setup is fine. Catch our drift... 

[luvrbus]

The average temp drop here with standard AC is 22 degrees unless you have a unit large enough to over power the heat lol when we hit a 122 degrees our unit really works and it shows on the power bill all the units here are oversized I have 6 tons where in Idaho our house was 2 story and more sq ft and a 3 ton unit did fine,it nothing to see a house here with out 2 or 3  units.Our rv has 3 15.000 btu units and well insulated 2 will freeze you but sometimes I need to run all 3 to drop the temperature in a hurry so 1 or 2 units can keep up       

[Jim Blackwood]

The mini-split separates the hot side from the cold side. So does every other well designed system. So does the OTR air, so do standard residential units.

The mini-split is ductless. But this may not be that great of an idea. Sure, you don't have to cool the ductwork but that generally doesn't add much of a heat load and gives way better distribution of the cold air.

The mini-split is smaller. But newer units are now at 3 tons and more. That is well into the residential range.

So let's face it, the only real advantage the mini-split might have is packaging and that is questionable.

You could just as well call the OTR system a Maxi-split. Except that it has air distribution ducting that the mini-split lacks. It also has a much larger condenser than you will ever see on any mini-split system, and the limiting factor in any AC system is the ability to get rid of heat. The large condenser is not a limitation, to the contrary it is a huge advantage. So I really don't understand the push to throw it out and replace it with something that doesn't have a hope in hell of ever doing as good of a job.

I do get that is looks simpler. Looks. Not the same as being.

Jim

[windtrader]

So let's face it, the only real advantage the mini-split might have is packaging and that is questionable.

From what I gather the newer mini-splits are measurably more efficient than rooftops. Those pioneering full off-grid electric source seem to indicate they consume less energy.

[jap42]

The problem with the factory otr is the engine has to be running, and in my case at high idle or moving to actually work. So the question is add ac power to the factory or replace it with something that works all the time. Mini split and ductless are two different things. You can get ducted minisplits.

[TomC]

There's a real good reason why the studio buses use 5 roof top A/C's-because they work and are simple to replace. Just install 3 rood tops and be done with it. I have 3 on my 40ft'r and usually 2 do the job just fine. Good Luck, TomC

[richard5933]

If a regular mini-split doesn't work for you, it's also possible to do like Custom Coach did and build your own. They used off-the-shelf commercial refrigeration components to build their systems, using a Copeland compressor and a condensing unit down in the bay, and an evaporating coil/fan upstairs. The added ducting to some, as needed.

These compressors can be bought in many sizes and capacities.

[Jim Blackwood]

Richard, that's exactly what I've been trying to tell these guys. A good Copeland compressor is guess what? The exact thing they use in mini-splits.

You already have the best condenser you will ever find sitting right there in the side of the bus. It's only job is to cool down the compressed gas going through it and for that, bigger is most certainly better. As long as there is no resistance to the freon flowing through it it is as efficient as it can ever get.

On the evaporator side, the TXV controls how much liquid goes in and therefore how much cooling. All the evaporator does is trade that for heat. If it is too small it will freeze up. If it is too big? What? How can it be too big? The only consideration here is making sure the TXV will never flow more liquid than the condenser puts out, and that's a function of the compressor. Lines are lines. Bigger ones flow more and do it easier but hold more. The only thing that leaves for efficiency improvements are to prevent heat losses (or cold). So good insulation and separation in the right spots. As BW said, roof air units will never come close to matching one where the evaporator is separated out. That's why residential units are made the way they are.

And now with ducted mini-splits, when compared to the existing maxi-split where is the efficiency advantage? All you are doing is comparing an efficient small system to an efficient larger system.

With a Copeland and a little plumbing you have the option of configuring the system as you choose and making it switchable. Solenoid valves in the right places and multiple compressors along with TXVs on the main evaporator that can be switched in and out to match the compressor would let you have a fully configurable system for anywhere from 3 tons or less clear up to the full system capacity of 14 tons in stages.

That's a more complex system but each aspect is simple. You have two 1-1/2 ton evaporators in the bins so that's 3 tons and each one already has it's own properly sized TXV. So add a solenoid valve to shut off flow to the main evaporator (if there isn't one already), add in a parallel Copeland past the belt driven compressor, and voila! You have your 3 ton system. Put a PWM driver on the condenser fan with a thermocouple or other temp senser so that it only works hard enough to get rid of as much heat as it needs to and you have your efficient 3 ton AC system.

It shouldn't be hard to sort out how you go up from there. You have a driver's evaporator rated for 1 ton (but it is fitted with a 1-1/2 ton TXV so you should be able to get more out of it) and then the main 10 ton evaporator. You could easily run that one at 5 tons by switching in a 5 ton TXV with a solenoid valve or two. I don't understand why some guys try to make it so hard to understand. But I guess that's business.

Jim

[luvrbus]

AC and refrigeration units are simple to build they all start with a compressor,what he trying to do using the engine driven compressor then driving it by electricity  is going to take some thought out planning .I don't think a sealed compressor like Copeland could handle the oil charge reqired for the Carrier bus system