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Old 04-29-2016, 12:21 AM   #1
Mini-Skoolie
 
Join Date: Mar 2016
Location: Cypress, Texas
Posts: 52
Year: 1996
Coachwork: International Thomas
Engine: DT466E
Rated Cap: 71
Air conditioner wiring to generator, also how to run when driving

OK so I don't know much about electrical stuff. I need advice about air conditioning and generators. In a 72 passenger bus, I feel like I'm going to need at least two AC units. The AC is very important to keep staff, pets and clients at least somewhat cool. That's the whole point of turning a bus into a mobile vet clinic. I have looked at the choices of window units in Windows (seems to ratchet- this needs to look at least somewhat professional). I have looked at window units in basements (general research seems like these don't do so well with cool going up and all that). And I have looked at RV top mounted AC units (expensive, hole in the roof and all that). I am very curious about the mini split ductless but heard that they can't take the bouncing of a bus.
So I need help with these things:
1) can I do a mini split
2) if I do a roof top, how big a generator do I need to run two 13500 units.
3) how do I wire it once I get it? Do roof top or mini splits have places you can wire a plug that can then run to a generator?
4) how can I run it while driving to keep the driver cool? I have read about people running a unit off of their engine (alternator?) while driving but I am completely mystified by that.

I know these questions may sound stupid. I just have no clue so forgive me. I'm a fantastic veterinarian and I can build stuff (ok maybe a little). Just electrically and mechanically (in regards to a Diesel engine) challenged.

***I am also very willing to barter vet services for bus help in the Houston area***
Thanks
Virginia
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Old 04-29-2016, 06:32 AM   #2
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Join Date: Mar 2016
Location: Danglebury, Tejas
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Year: 1999
Coachwork: Blue Bird
Chassis: IH 3800
Engine: Navistar DT466E
Rated Cap: 72 passenger
If you do large animals, I've got a Suffolk Punch draft and will keep you in mind when foaling time comes. Hehehe

Back to the bus...

The first step is figuring out how much cooling power you need. In Houston, in the summer, in a long bus, you'll need at least three units. The reason I say that is because you dont have a lot of time to pump-down the occupied space when you arrive somewhere. As I envision your practice, you need to pull-up to a clients home, flip a switch for central genny and air, and honk. You'd have just a couple of minutes (max) until the client and a companion animal appear at your doorstep for service. So a quick pump-down would be a good thing. And since this is a professional service, you shouldnt keep the client waiting while things take 15 minutes to cool down. Further, it all HAS TO WORK. Every time, all the time. No excuses. Or your clients will find another vet.

I'm going to go out on a limb and suggest you use three (or four) roof-mounted 16k BTU RV units. These are basically made for the job and can be quickly swapped-out in case of failure. Correctly installed they wont leak and they do a good job of dehumidification (very important here in Houston!). Price the units on Amazon and you can save a bundle over the usual brick and mortar bandits. And you can easily install them yourself. Cutting the hole isnt frightening. You simply install a standard roof-vent ring, seal it well, and drop the unit into place over the ring. Tighten a couple of retaining clips and you are done except for power.

Assuming this scenario would work for you, the next question is what other gear do you need to power? Portable xray? Exam lights? Refrigeration? Hot water? What other loads are on your list and what do the surge currents look like? Once we get this info, and perhaps an idea of what you have for budget, we can make some suggestions on power source options. Personally, I'm a big fan of diesel gensets for permanent installations, but the $$$ may make you cringe.

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Old 04-29-2016, 07:09 AM   #3
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Join Date: May 2009
Location: Columbus Ohio
Posts: 7,949
Year: 1991
Coachwork: Carpenter
Chassis: International S3800
Engine: DT360
Rated Cap: 7 Row Handicap
you have a lot of options when it comes to air conditioning.. for what you do, your bus will be a mix of driving and parked.. for many reasons you will want a generator to run your in-bus 110 volt equipment including the air conditioning..

Rooftop air units make sense for what you are doing... I dont know how many things you will have running but at least 2 if not 3 will probably be required...

if your generator is mounted to the bus and not sititng on the ground while parked, there is no reason you cant run your generator while driving and keep the bus air-conditioned.. the rooftop units are made to run in both stationary and non stationary situations...

if you are gunshy about cutting holes in the roof due to the possiblility of leaks, etc.. you can go with portable units...

Climax Air | DC Inverter Portable Air Conditioner w/ Dual Hose | Worlds Most Efficient Portable AC

that one is pricey however the only requirement for it is 2 (4 or 6 inch) hoses that go to the outside.. either holes in the side of the bus or perhaps if you are replacing some of your windows with metal, the holes could be cut in that metal..

these units disadvantage is they will take up space inside your bus. they need to sit indoors and cant easily be basement mounted.. the SPECIFIC UNIT I linked above is generator friendly as it is an inverter.. which means no power surge on compressor start.. and no on / off cycling to speak of as it simply varies its compressor speed as required for the cooling load.. very similar to the operation of a mini split...

now onto Heat, im sure you will need some at some point.. in my opinion portable space heaters are Dangerous so some type of built in heat should be provisioned.. your bus already has an EXCELLENT heating system if you havent torn it out yet.. granted its main design is to run off of the engine, but its not a requirement.. devices like this

Proheat ? X45 School Bus

are designed to run up the bus's built in heating system without idling the engine... if your generator is running you can easily provide a 12 volt charge to the battery packs from the generators to run the bus heater fans...

many other solutions exist for heat... if you have a strong enough generator you can place an electric heater... if you are driving from one location to another, the built up engine heat in your bus may be enough to heat while stopped depending on average stop time.. many busses have a "boost pump" which will circulate coolant through the heater loops with just the key on / engine off.. and turning on one or more heater fans will run heat for awhile... esp from a large iron diesel engine...

-Christopher
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Old 04-29-2016, 11:25 AM   #4
Mini-Skoolie
 
Join Date: Mar 2016
Location: Cypress, Texas
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Year: 1996
Coachwork: International Thomas
Engine: DT466E
Rated Cap: 71
So I am attaching a pic of the roof top RV AC unit we are thinking about. It is a Dometic Brisk II 15000 btu unit, 115v. We would start with two of those. Can I run these off of a 5000w generator? Also looking at a 6500w Honda EU.

The vet clinic will be used as a mobile stationary clinic. Basically, the bus will drive to a location and park for 5-6 hrs. People with dogs and cats come to the bus, then go through for services. Ideally come in the front and go out the back for good flow. Only other equipment on the generator would be a small dorm sized refrigerator, some fans for circulation, some computer equipment.
Thanks
Virginia
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Old 04-29-2016, 11:28 AM   #5
Mini-Skoolie
 
Join Date: Mar 2016
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Engine: DT466E
Rated Cap: 71
Sorry here are the pics



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Old 04-29-2016, 11:39 AM   #6
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
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Chassis: International S3800
Engine: DT360
Rated Cap: 7 Row Handicap
ive never been a Huge fan of dometic but lots of people use them without issue.. (ive just had to fix my neighbors dometics a number of times)..

I didnt see the run current listed anywhere on those.. the starting surge is the hardest part of an A/C to a generator.. i dont know what their surge current is, or what your gennie will handle as far as surge current..

i'll let others chime in that have real-life experience with camper A/C and generators..

-Christopher
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Old 04-29-2016, 11:52 AM   #7
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Join Date: Apr 2013
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i just replaced one of my roof top units with that dometic one last year. it works great. the weight difference between the old and new air conditioners is surprising. the old one was like a boat anchor.

i have a 12k generator belly mounted under the floor that runs the air conditioning and anything else i need.

the newer more efficent a/cs will take less power than older equipment like mine.

there are some heating calculators that you could use to determine your needs when sizing your system.

i have 30k btus of both heating and cooling on board.
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Old 04-29-2016, 12:04 PM   #8
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The Honda EU6500 I believe is no longer available new and has been replaced with the EU7000is, which I can attest is a beautiful machine. You won't regret buying that generator, unless of course you end up with too much load. (Then buy two!) It's the quietest unit in their whole line and the only portable from Honda, and I believe the only from any make, with fuel injection and push-button start. Not just electric start, but literally press the button momentarily and it'll take care of starting on its own.

Having done no heat analysis, but having seen many similar-size class A coaches with two rooftop A/C on them, and supposing you're not going to be removing any windows (solar heat gain) and will have lots of door-open time with customers coming and going (warm moist air coming in), plus occupancy of people and pets giving off heat and vapor, I can imagine you'll find that 3 rooftop units would be necessary. Of course you can start with one or two and add more if/when the need arises.

You probably could run two of the A/C on a 5000W generator, but if it turns out that 3 are needed you might be looking for a new generator too. Better to be oversize on the generator I think. Considering it's a business and the roar of a relatively inexpensive open-frame contractor generator could discourage repeat customers, plan on paying the premium for a quiet generator. EU7000is or, if you need larger, probably an 8-10kW diesel fueled RV model. I don't know yet whether the EU7000is will run reliably while the bus is in motion. Several forum members have found that some smaller generators won't run reliably in certain places on the bus while the bus is in motion. For my own use I'm banking on it working though!

As for the wiring: rooftop A/C units expect the supply wiring to be connected in the 14x14 inch hole the air passes through. They just have wire leads and would be wire-nut connected to building wire. If you aren't removing interior bus wall panels then you could at least snake a wire through the ceiling to the edge above a window and emerge from the ceiling/wall into a surface-mount conduit there. It's probably a good idea to use BX cable (the stuff with the spiral-wound metal armor on the outside) at least for the part going through the ceiling where regular conduit won't go. Plain plastic-jacket romex would be vulnerable to being cut on unseen sharp sheet metal edges inside the wall/ceiling. The blue plastic "smurf tube" flexible ENT conduit would be a fine alternate for BX cable in the ceiling. Once the conductors are out of the ceiling and down the wall you can bring them together in some way and connect to a male cord(s) end to match the generator's receptacles.
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Old 04-29-2016, 12:25 PM   #9
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If you are getting into the 30-45K btu range, you might consider a small diesel genny. No need for a second fuel source and loads of output options. Definitely run the numbers on your total usage before investing in any genny/inverter system. Better to have too much than too little because you will always be adding more stuff that draws juice.
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Old 04-29-2016, 02:03 PM   #10
Mini-Skoolie
 
Join Date: Mar 2016
Location: Cypress, Texas
Posts: 52
Year: 1996
Coachwork: International Thomas
Engine: DT466E
Rated Cap: 71
I can't find any of the Onan generators around here right now, so I may go ahead with the less expensive Honda EU 7000 or a slightly used Honda EU 6500.
I understand that I may end up needing three roof top units, but I'm going to start with two and see how this goes.

The two 1981 International Wayne buses do not have escape hatches but the 1996 International Thomas has escape hatches. Any advice about mounting a roof top AC through the escape hatches?
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