Wiring bus for 50amp 240 for mini split

[DoubleEagle]

The three mini-splits might do a good job of cooling while parked, but will they be able to keep you cool while going down the road? A lot depends on whether you are well insulated, have fewer windows, and whether you are going across the West in August. Three traditional roof tops are not enough in many situations, so I have my doubts about three 12,000 btu mini-splits. If you go through all this effort and discover that they are not enough, have a supplemental plan B. 

[Jcparmley]

So perhaps I should use a step up transformer for the front driver unit.  Do you think 18 or 24k.  What are your thoughts about a 12k unit in the bunk (middle of the bus) and a 12k for the bedroom?

The three mini-splits might do a good job of cooling while parked, but will they be able to keep you cool while going down the road? A lot depends on whether you are well insulated, have fewer windows, and whether you are going across the West in August. Three traditional roof tops are not enough in many situations, so I have my doubts about three 12,000 btu mini-splits. If you go through all this effort and discover that they are not enough, have a supplemental plan B. 

[buswarrior]

What did the coach have for stock BTU in the dashboard?

That had little to do with the passenger load and everything to do with sun load on the driver...

Also, regarding exterior mounting of equipment:

You may not want to unwittingly fit the undesirable profile that "loose outside bits" puts you and coach into?

Figure out how to get everything inside the lines of the coach.

happy coaching!
buswarrior

[DoubleEagle]

So perhaps I should use a step up transformer for the front driver unit.  Do you think 18 or 24k.  What are your thoughts about a 12k unit in the bunk (middle of the bus) and a 12k for the bedroom?

The more the better, up front, otherwise have a paper towel dispenser close by to mop up the sweat (and fans). Entertainer coaches that go everywhere usually have big central airs or five rooftops joined together duct-work wise. 12k's in the rear areas are fine when parked, going down the road in the heat is the problem, especially up front. The cool air tends to sink to the floor and gravitate to the rear where it meets the heat generated by the engine and transmission. If you cannot afford more cooling, then it would be best to stay out of Arizona, Texas, and Death Valley in the summer. 

[richard5933]

...If you cannot afford more cooling, then it would be best to stay out of Arizona, Texas, and Death Valley in the summer. 

Why would anyone want to be in those places in the summer? That's why these things have wheels - to get to places like northern Wisconsin where we slept with the windows open in the middle of August with temps in the 60s.

[DoubleEagle]

Why would anyone want to be in those places in the summer? That's why these things have wheels - to get to places like northern Wisconsin where we slept with the windows open in the middle of August with temps in the 60s.

Well, you would have ask Cliff about that. I've been to Wisconsin and Minnesota in August, and it was not always in the 60's. It was even hot at times in Canada this year.

[eagle19952]

Well, you would have ask Cliff about that. I've been to Wisconsin and Minnesota in August, and it was not always in the 60's. It was even hot at times in Canada this year.

Yup, left FL end of May it was 94. Got north of Minneapolis it was 105. In fact, it was over 96 all the way there.

[richard5933]

Yup, left FL end of May it was 94. Got north of Minneapolis it was 105. In fact, it was over 96 all the way there.

Do we have warm and even hot spells? Of course we do. By and large though, weather in the summer is much more pleasant in Wisconsin and Minnesota than in Texas and Death Valley. Unless one just enjoys the excessive heat.

[RJ]

JC -

Our "new to us" 40' Prevost has three 15,000 BTU CruisAire units, which are basically similar to the mini-splits you're considering.  The coach is also spray foamed for insulation, the best you can have.  Two units are in the spare tire compartment up front, the third in the second bay, passenger side.

It will not maintain 75º when it's 100º outside. Moving or parked.

The 45' Entertainer cars are using five low-profile 15,000 BTU roof units in an interior ducted format for a couple of reasons: 1) The clients stay cool in all kinds of weather, and 2) If one unit fails, the coach will still stay relatively cool and the RV dealer at the next gig can throw another unit up there in one day, compared to searching out a service center for basement or mini-split systems, thus putting the coach out of service.

I'm not fond of carbunkles on the roof either, but the newer low-profile models tend to negate that eyesore.  Your genset will easily handle three 15K BTU units, especially the newer, energy-efficient Colemans, but one of the real keys is to spray foam the interior for the best insulation, thus reducing the workload on the HVAC systems. Not to mention it's a lot easier to wire in three rooftops than the mini-splits!

Buswarrior makes a good point about being extremely careful about what you "hang" off the exterior of the bus - you don't want your C3 looking like a backyard shade-tree mechanic hacked together something to make it work.  RV parks and campgrounds do not tend to look at that type of workmanship favorably.  OTOH, if you can integrate the HVAC into the rear roof cap similar to what today's transit buses are doing, that might be a viable solution - IF you can work around the engine radiators!

Anyway, that's my nickel's worth of suggestions, altho it's probably only 2¢ in today's economy.

FWIW & HTH. . .

[richard5933]

JC -

Our "new to us" 40' Prevost has three 15,000 BTU CruisAire units, which are basically similar to the mini-splits you're considering.  The coach is also spray foamed for insulation, the best you can have.  Two units are in the spare tire compartment up front, the third in the second bay, passenger side.

It will not maintain 75º when it's 100º outside. Moving or parked....

Our bus has two split systems, which all signs point to having been made from commercial refrigeration units similar to those found keeping walk-in beer coolers cool. Compressor & condensing coil in the bay, evaporator & blower up above. At 100 degree with high humidity, they will drop the interior temperature from over 100 to the low 70s in just over an hour. If they ran on high all day it would be a meat locker. Each of these consumes as much as 19 amps when working full steam. It's a purely mechanical system with no electronics and just a few large relays. Original to the bus from 1974.

While you may not want to create such a system for your bus, I bring it up to remind you that sometimes it's necessary to think outside the box. Instead of sticking with something like the modern mini-split and trying to force fit them into the space on your bus, why not use off-the-shelf HVAC parts to just make a system that works best for your situation?

Do you have a relationship with a local a/c tech? This would be my suggestion - find a local guy that knows his refrigeration business inside and out. One that works on commercial refrigeration units as well and not just the cookie-cutter residential units. Buy the six pack, and have him over to brainstorm this project. Do this before you commit to something that down the road (literally and figuratively) won't do what you need. You might be surprised at some of the suggestions and what these guys can do with standard parts.

After all, an a/c system consists of only a few moving parts: compressor, condensing coil, evaporator, and blower. Add a few miles of tubing, a thermostat, some valves & relays, and you've got an a/c system.

When ours was serviced last spring the guy said that all the parts on our 44-year-old system are still available off the shelf. That's the advantage of not using a foreign made inexpensive system.

[luvrbus]

All the AC's are off the self except the newer mini splits,RJ has some top of the line AC units with his CruisAirs those 3 units cost almost 10 grand and if installed and serviced  right you can make Popsicles with those. 
I used 3 CruisAir for 20 years here in the AZ heat in a 40 ft Eagle never ran but 2 at the most.A residential AC or RV service can screw one up in hurry by overcharging they have a sight glass and about the only AC that requires bubbles in the Freon.
Keep the outside unit clean to prevent head pressure and have a marine CruisAir dealer service the units they were the best on the market,the fan speeds where from 0 to full none of the 2 or 3 speed crap they have a speed for everyone         

[eagle19952]

My AC was designed to service Condo high rise units in Dallas,TX and retro fitted to the bus.
FirstCo is the maker. Mine is a 2.5T. unit.
https://hdsupplysolutions.com/shop/p/hvac-00-65/equipment-00-65-15/packaged-units-00-65-15-40/first-company-20-ton-thru-the-wall-condensing-unit-p259478

Depth   25.5 in
Height   34.5 in
Width   19.5 in
And is slightly different dimension than this one.


With the air handler in the coach.
Been in service since the early 90's It has had the compressor replaced in 2012, is R22, and because of the way the AC regs have evolved I decided to replace the A-Coil in 2014. It is 240v. But, I'm not hesitant to run my generator, tho I don't do Death Valley in July, I have summered in Houston, Ft. Myers and Prescott, AZ.

[Jcparmley]

RJ
Do you think 3 15k units will keep the bus cool?  What about the driver?

JC -

Our "new to us" 40' Prevost has three 15,000 BTU CruisAire units, which are basically similar to the mini-splits you're considering.  The coach is also spray foamed for insulation, the best you can have.  Two units are in the spare tire compartment up front, the third in the second bay, passenger side.

It will not maintain 75º when it's 100º outside. Moving or parked.

The 45' Entertainer cars are using five low-profile 15,000 BTU roof units in an interior ducted format for a couple of reasons: 1) The clients stay cool in all kinds of weather, and 2) If one unit fails, the coach will still stay relatively cool and the RV dealer at the next gig can throw another unit up there in one day, compared to searching out a service center for basement or mini-split systems, thus putting the coach out of service.

I'm not fond of carbunkles on the roof either, but the newer low-profile models tend to negate that eyesore.  Your genset will easily handle three 15K BTU units, especially the newer, energy-efficient Colemans, but one of the real keys is to spray foam the interior for the best insulation, thus reducing the workload on the HVAC systems. Not to mention it's a lot easier to wire in three rooftops than the mini-splits!

Buswarrior makes a good point about being extremely careful about what you "hang" off the exterior of the bus - you don't want your C3 looking like a backyard shade-tree mechanic hacked together something to make it work.  RV parks and campgrounds do not tend to look at that type of workmanship favorably.  OTOH, if you can integrate the HVAC into the rear roof cap similar to what today's transit buses are doing, that might be a viable solution - IF you can work around the engine radiators!

Anyway, that's my nickel's worth of suggestions, altho it's probably only 2¢ in today's economy.

FWIW & HTH. . .

[buswarrior]

RJ

Get those units serviced, inspect the physical condition of ductwork, etc

You aren't getting near 45k BTU out of 'em.

Happy coaching!
Buswarrior

[RJ]

Do you think 3 15k units will keep the bus cool?  What about the driver?

JC -

It all depends on where you place the forward unit.  The further back, the worse it gets. A ducting kit to direct all the discharge air forward will help, too.

If you really want to keep the driver cool, find a RedDot dealer (they specialize in custom car AC units), and have them rig up a system down in the spare tire compartment and then using the existing driver's AC that your MC-9 came with.  (This would be for over-the-road use, obviously.)  Going this route would allow you to more evenly space the roof units.

Buswarrior -

Getting them serviced is high on the priority list.  Trying to find a marine service center in the Seattle area, per Clifford's suggestion.

FWIW & HTH. . .