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Old 09-10-2019, 03:55 PM   #21
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Originally Posted by Crisfole View Post
Awesome. That's super helpful. So doing this would require a completely A/C separate system for running from the engine (including ductwork, etc?)
Yes - but...

In the mini-split world it is not uncommon to run multiple evaporators and even multiple compressor/condenser units in one system. So we could do the same here.

Install the components of a conventional vehicle A/C system in the bus to cool the driver area, add additional evaporators for other parts of the vehicle (this is fairly common in buses), and then add one or two parallel compressors that are driven by electric motors. The reason why I say "one or more" is that the cooling capacity of a battery/solar powered system is at least one order of magnitude less that what generator or grid hookup can provide. Using the same compressor for both is not going to be efficient or even feasible unless that compressor has variable displacement. So the choice is one variable displacement compressor or two compressors matched to the respective power input.

If you have only battery/solar power available, you would run only the bedroom evaporator(s) with the refrigerant flow supplied by the small displacement compressor. With generator, shore power, or engine power driving a bigger compressor, you could crank up additional evaporators in the bus.

An evaporator with TXV valve will adjust the refrigerant flow according to the temperature AND volume of air flowing through the evaporator fins. If you turn the evaporator fan off, the core will get very cold and the TXV will severely restrict the refrigerant flow to prevent icing. If it turns out that the refrigerant flow through multiple unused evaporators is too big, solenoid valves can be added to in the liquid lines feeding the evaporators.

After thinking about this, I decided to make the micro-controller board of my battery/solar powered system expandable for systems with multiple compressors, condenser fans, and evaporators.
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Old 09-10-2019, 05:24 PM   #22
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look dont confuse this stuff.. its awesome for your own bus to build a complex system... my home system is quite fun and complext and works well.



but for the average rookie out there.. if you build him something complex he has no idea how to adjust, service, etc..



install SEPARATE SYSTEMS that you can RUN TOGETHER when needed..


install engine driven A/C up front for the driver area.. and any parked A/C you also want to install.. minisplits are also my choice if you can find room for the condensors.. remember a double decker bus is pretty tall.. I dont know how the bridges are around europe.. but not sure id want mini split condensers sitting on the roof.. solar panels YES!..


so now your single engine driven A/C cools you up front while driving... if you have enough batteries / generator / solar then you can also run your electric A/C for extra cooling and for other areas if needbe while driving..


parallel compressor systems require check-valves/ refrigerant valves as No compressor stops all back flow).. micro-controlled fans and compressors to get the coorect expansion esp if you arent running them all at the same time... this stuff is really fun.. i love to do it.. but it isnt for the novice.. for the average guy keep the A/C systems as a single compressor and to manufacturer guidelines.. ie multi minisplits are cool because they are made that way and their controllers handle the heavy hitting..



engine driven A/C separate because its simple and just that... for when driving...



-Christopher
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Old 09-10-2019, 06:00 PM   #23
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Quote:
Originally Posted by cadillackid View Post
look dont confuse this stuff.. its awesome for your own bus to build a complex system... my home system is quite fun and complext and works well.



but for the average rookie out there.. if you build him something complex he has no idea how to adjust, service, etc..



install SEPARATE SYSTEMS that you can RUN TOGETHER when needed..


install engine driven A/C up front for the driver area.. and any parked A/C you also want to install.. minisplits are also my choice if you can find room for the condensors.. remember a double decker bus is pretty tall.. I dont know how the bridges are around europe.. but not sure id want mini split condensers sitting on the roof.. solar panels YES!..


so now your single engine driven A/C cools you up front while driving... if you have enough batteries / generator / solar then you can also run your electric A/C for extra cooling and for other areas if needbe while driving..


parallel compressor systems require check-valves/ refrigerant valves as No compressor stops all back flow).. micro-controlled fans and compressors to get the coorect expansion esp if you arent running them all at the same time... this stuff is really fun.. i love to do it.. but it isnt for the novice.. for the average guy keep the A/C systems as a single compressor and to manufacturer guidelines.. ie multi minisplits are cool because they are made that way and their controllers handle the heavy hitting..



engine driven A/C separate because its simple and just that... for when driving...



-Christopher
Funny that you say this. I was just thinking over dinner who I would consider to be the right candidate for a more complex, custom A/C system in a travel bus. You were among the handful of people I could identify on this forum.

Knowledge of basic control theory and programming of embedded systems is pretty much a must in order to be happy with the end result. Due to the vastly variable operating conditions (engine rpm, temperature, humidity, sun load, etc.) there will be some fine-tuning necessary after the systems works in the drive way and that is not everyone's cup of tea. Since the OP hinted that he is in the IT business, I decided to err on the optimistic side.

But realistically, the number of threads reporting on the mindless drudgery of destructively removing bolts/rivets/rubber/plywood will continue to outweigh by a factor of at least 100 the really interesting stuff like your transmission swap and other DEV bus adventures. Maybe it's time for dev.skoolie.net where the focus is on what has NOT been done yet.
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Old 09-10-2019, 07:27 PM   #24
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Originally Posted by alpine44 View Post
The ability to edit a post on this forum expires after a certain time. Maybe somebody knows what that time is.

I'll check your photos this evening and hopefully respond with some ideas.
It's only anout 5-10 minutes.
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Old 09-10-2019, 08:25 PM   #25
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I'm definitely technically inclined, but much less mechanically inclined. I'm a software engineer. I think simple sounds better. Even if it means giving something up. I'd rather have high quality and easily fixable. KISS if the easiest principle to achieve that goal.
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Old 09-11-2019, 06:13 AM   #26
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Ok, so I think everyone has convinced me that, as unpleasant as it sounds, a generator running a beefier A/C both over the road and while parked is the way to go. Adding an engine driven system sounds more complex than it's worth if I can just run a larger mini split with a generator for both situations...

Thanks for being patient with my questions! Maybe in renovation 2 of this bus...
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Old 09-11-2019, 07:51 AM   #27
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Originally Posted by Crisfole View Post
Ok, so I think everyone has convinced me that, as unpleasant as it sounds, a generator running a beefier A/C both over the road and while parked is the way to go. Adding an engine driven system sounds more complex than it's worth if I can just run a larger mini split with a generator for both situations...

Thanks for being patient with my questions! Maybe in renovation 2 of this bus...
I do not know who else chimed in behind the scenes but neither Christopher (cadillackid) nor I recommended omitting a vehicle A/C that is driven by the bus engine. I fact, he tries to stop a growing madness in the skoolie community with this thread.

There are many commercially built buses that have A/C while driving and when parked like class-A RVs, mobile libraries/bloodbanks/imaging centers, etc. NONE of these runs without a traditional vehicle A/C and you can be sure if the manufacturers could save a buck, they would.

A functioning vehicle A/C has become a safety critical item for operating the vehicle in all weather conditions. Aside from guaranteeing sheer survival in the summer, the vehicle A/C also provides expedient defogging of windows in wet weather. I do not see how you could achieve that with a wall mounted mini-split evaporator without some serious hacking.

The other question is how long will the mini-split and the generator last if neither one was ever designed for substantial acceleration in all directions while operating. With acceleration I do not just mean bouncing but also questions like what will happen to the generator's lubrication systems in tight turns and when braking. And why do we use R-134a refrigerant in vehicle A/Cs if the R-410A used in a mini-split is thermodynamically more efficient? Because the higher pressures of the R-410A cycle could become a reliability issue in a vehicle environment. (BTW, the different capitalization of the letter "a" is intentional and conveys whether the refrigerant is a pure substance "a" or a blend "A").

Using mini-splits for every use case of the vehicle is not inherently impossible. But you would have to delve deeply into mechanical experimentation/modification and I would not want to venture there, even as a trained and experienced mechanical engineer, unless this is a well-funded job assignment.

The phrase "buy once, cry once" should be extended to "think/design/acquire/build once, cry once". Cobbling together off the shelf components in an ill-understood context may result in a lot of tears later. Minimizing risk generally requires effort.

How painful is the alternative of installing a traditional vehicle A/C? I just put a dual evaporator (factory front and aftermarket rear) R-134a system with all new components in my 1984 Chevy Blazer. Since this is the military version with already two alternators on the diesel engine, I needed to fab brackets and a pulley system for the A/C compressor similar to what would be needed for your Leyland. The whole project took about $750, a few weekends, and some occasional curses to make everything fit and work. But now I am confident that this system will reliably cover the next 35 years of the vehicle's life if necessary. I am cool/happy, the dogs in the back are cool/happy, and I call this the second best upgrade of the vehicle, right after replacing the original 3 speed automatic with a locking 4 speed.
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Old 09-11-2019, 09:52 AM   #28
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@Christopher I'm in New York state, just around the ... corner? ... from you. The bus is 13'6". So nothing goes on top, not even solar. I think my plan is to create a pair of solar awnings which can double as shade.

But, being 13'6" it is safe for all US states except where posted and except my driveway. (I'm doing battle with the power, cable, and telephone companies to get my lines raised. I'll let you konw when they've finally killed my will to fight). Three cheers for roof rakes that can temporarily raise the height while I get in and out.

@alpine44 OK, so you managed to retrofit A/C there...but it was already setup for A/C. Since I _do_ have engine driven heat in the bus (over all doors and windows to form a sort of 'envelope' of warm air), can I make the ductwork do double duty?
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Old 09-11-2019, 11:29 AM   #29
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Quote:
Originally Posted by Crisfole View Post
@Christopher I'm in New York state, just around the ... corner? ... from you. The bus is 13'6". So nothing goes on top, not even solar. I think my plan is to create a pair of solar awnings which can double as shade.

But, being 13'6" it is safe for all US states except where posted and except my driveway. (I'm doing battle with the power, cable, and telephone companies to get my lines raised. I'll let you konw when they've finally killed my will to fight). Three cheers for roof rakes that can temporarily raise the height while I get in and out.

@alpine44 OK, so you managed to retrofit A/C there...but it was already setup for A/C. Since I _do_ have engine driven heat in the bus (over all doors and windows to form a sort of 'envelope' of warm air), can I make the ductwork do double duty?
The vehicle where I installed the A/C is a M1009 CUCV, the military version of the square body Chevy Blazer. While I could use a under-dash air handler from the civilian model, that still required modifications of the firewall, relocation of the rear battery tray, etc. and fighting for every inch of space. It is most likely less work to put an A/C into a bus due to more empty space there.

If I had already duct work in a bus I would definitely put an evaporator 'coil' in there. That's common practice in coaches and transit buses.

I am going to be in Elkton, MD about 5 hours from you until Christmas to finish my build and then head for Quarzite. If your concerns are how to get the A/C installed in the bus, I would not mind driving up to NY for a couple of day to help. Have all the necessary tools plus a welder to build the rack for the mini-splits. 'Leaf peeping' season would be ideal or sometime next spring. Depending on Christopher's interest and schedule we could have a small build party in upstate NY.
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Old 09-11-2019, 01:55 PM   #30
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Wow, I'd take you up on that for sure! NY leaf season is way prettier than New England's, just don't let them hear that I said it.

Not sure what I can trade you for the help, but an extra pair of hands and a quiet place to park out in the country can go a long ways...let me know...
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