Meet Goldilocks

[paulnack]

...or as my girlfriend calls her, Ricitos de Oro. We'll make it easy and nickname her Rizi. She earned her name by being an 11 row flat nose. In my months of hunting (and neck-breaking for every school bus seen on the road) I've only found one other of this configuration in Florida. She's got just enough interior space, but still only a 15' wheel base!

My name is Paul and I'm finally actualizing an idea that's been swimming around upstairs for over 3 years. I just picked up an IHC with a DT466e.

It's super early in my build (I just got the title transferred this week). So far its just been a lot of bus stripping... gotta pay for this process somehow amirite?

Over-arching plans are:
• roof raise 12"-15" for 7'6" interior height
• roof deck w/ removable railing and fold-open tent (aka penthouse)
• solar with battery bank
• closed-cell spray insulation and rigid polyurethane insulation for hot Florida weather
• reuse original split a/c and power compressor with electric motor
• garage bay w roll up door in place of handicap lift door
• queen bed adjacent to garage
• composting toilet with porcelain bowl
• 2 person shower stall with 2x glass walls
• combination fold-away work desk/ book shelf/ entertainment center
• built-in couch with slide out base to convert to guest bed
• 4 person dinette adjacent to couch, converts to 2 person dinette and L-couch
• kitchen counter w/ double basin sink, gas range, mini oven, fridge

So the concept is to build a permanent residence, that also has boon-docking abilities (although this is secondary). And I plan on making this a luxurious 190 sq ft.

I'm excited to share this project with yall! Seems like a great, active community. Also, my friends are pretty much useless in this realm

[paulnack]

You didn't I would leave all that text and no photos, did you??

Here's some exterior, some interior, my engine being strangled by A/C hoses, rat's nest electrical box, and some gratuitous innards splayed out.

[paulnack]

Bonus! Floor plan rough draft. Looks a little cramped

[Rusty]

Dang. Gonna be an epic build.


Ricitos del Oro.


Bienvenidos y Buena suerte !!

[david.dgeorge07]

Nice size! What did you use to plan you layout? Sketchup?


Sent from my iPhone using Tapatalk

[paulnack]

I used SolidWorks for the floor plan. I'm a mech engineer, so it's like my second language. Although for just roughing out where the big things will live, I think it might have been simpler to use Sketch Up.

[Summ1]

Are you going to keep the existing AC or do you have a different plan?

[cadillackid]

if you are going to travel much id keep one of those A/C's! flat nose front engine busses make a LOT of engine heat and camper A/C;s wont touch it..

However I would reroute those crapily insytalled refrigerant lines that the coach builder installed.. im a definite A/C guy and those make me cringe.. (lets just locate the A/C hoses next to the hottest point on the engine.. the TURBO)..
-Christopher

[paulnack]

As of now my plan is to keep one of the TWO Carrier split systems that came w the bus. I'm actually worried 1 won't be enough to keep it cool in Florida summers. Need to do some rough heat calcs and see if I'm in the ball park.

I will need to do something with the compressor tho. It needs to be electric so I can run it while parked. I'm going to mount it all in the rear and cut down about 40' of lines from the system.

Now some questions for y'all! Any idea how much hp it takes to turn that compressor? And if I sell my second system, any idea of the value?

[Rusty]

Originally Posted by paulnack

Now some questions for y'all! Any idea how much hp it takes to turn that compressor? And if I sell my second system, any idea of the value?

More than you want to hear:

A common GM A6 compressor operating at it's max. Head pressure needs around 7 hp.

[cadillackid]

more than 7 HP to move the volume of that carrier..

that A/C system is for travelling.. you wont be able to run it with an electric motor efficiently.. keep One of the 2 for when you are travelling as the engine makes a TON of heat.. then install 2 minisplits in a well isulated bus for when you are parked and on shore power or are boondocked on generator.
with an insulated bus and keeping the front system you'll be nice n cool while driving..

-Christopher

[Rusty]

Originally Posted by cadillackid

more than 7 HP to move the volume of that carrier..



-Christopher

That's what I figured- that was just for a car a/c compressor. 7 hp electric motor isn't a slouch, either.

Ever turn on the A/C and hear the engine load, then adjust? That alone should tell you the draw.

[cadillackid]

On a side note.. ever wonder why the old GMcA6-bases air was wicked cold? That compressor ha a 276cc displacement. It's more than most compressors in our busses...
GM wanted the ac at full capacity even when idling .. valves in the EEVIR kept constant pressure across the evaporator to prevent high speed freezing
Christopher

[paulnack]

Rusty and Cadillac, thanks for the reality check. So I guess I can throw the idea of re-purposing that compressor right out of 1 of my 22 windows... How about getting a 110V compressor designed for home use to move the refrigerant? The Carrier system was design for R134a.

I'd really like to avoid having 1 A/C system for driving, and 1 for stationary use. The evaporator and the condenser each take up so much space. Also, I already have these units and that makes my wallet happy.

[cadillackid]

those units are by design as coach A/C systems.. with a Front engine bus it takes a LOT more cooling to cool it when you are driving than it does when you are parked.. think of your bus in a 70 MPH windstorm each time you drive it.. and then add big diesel engine making heat.. and yeah you can insulate and dynamat and seal.. but lot of that engine eat will make it into the driver area wile driving.. esp that big windshield into the florida summer sun..

those evaporators and condensors should be separate for each system.. take one out keep the other... minisplits or rooftops for parked A/C.. I vote for minisplits because they are inverter friendy and much more efficient (BTU / watt) vs rooftop or window units.. those coils are designed for the pressures and temperatures of 134A.. R-22 ran at somewhat higher pressures but is not made and Tough to get.. you may be able to find electric R134A compressors.. but not sure what kind of capacity you will find. R410A is out of the question.. its pressures are MUCH higher than the design pressures of those coach A/C coils..

many people here dont mind driving windows open and then having A/C when parked.. its a personal decision.. me personally I wouldnt want to drive a bus in hot weather without Good A/C keeping me cool..

if you were Rear engine you would have a lot less heat load upfront.. and you could do what somewhereinusa did which is put a 1 minisplit right above the driver area and one in the rear of the bus.. I believe he runs his when driving with some success.. again there's no engine upfront in his..

your coach A/C system likely topped out over 100,000 BTU(combined).. a window unit is 5000 BTU, a minisplit is 12,000 BTU.. a rooftop unit is 12,000 BTU..

insulating and swapping bus windows for either skinned over areas or good RV windows mean when parked you wont need anywhere near 100,000 BTU of A/C, nor would you need all of that while driving. but its not a stretch to think you might need half of that to be comfortable driving..
-Christopher

[paulnack]

Chris, that's incredibly helpful info. Thank you. So an estimated cooling load of 50k BTU with engine running, maybe 25k BTU while parked?

Using those numbers here are some rough calcs- that equates to a 4 ton/ 2 ton system respectively. Lets just focus on the parked scenario for now. From what I see 2 ton systems running on 230V require ~25 amp breakers. That's 5.8 kW, or 7.7 hp (excellent estimating on your part).

Now I'd need to estimate the A/C duty cycle to calculate the necessary battery requirements. But with a pair of 6V batteries only providing 12V, 200 AH... this only gives about 25 mins of run time. How does anyone run A/C off battery?!?

I also took a quick look at solar radiation numbers. Peak loading looks to be about 1 kWh/m2 (at 100% absorption). My roof is about 21 m2 and probably has about .25 absorption coefficient, so my heat load at worst may be 5 kW/h (confirming our original estimate of cooling load).

So what am I missing.... do people who run A/C offgrid just have enormous battery banks??

Another question: what happens if I put a smaller capacity compressor on my existing large evap/ cond?

[Twigg]

Originally Posted by paulnack

Chris, that's incredibly helpful info. Thank you. So an estimated cooling load of 50k BTU with engine running, maybe 25k BTU while parked?

Using those numbers here are some rough calcs- that equates to a 4 ton/ 2 ton system respectively. Lets just focus on the parked scenario for now. From what I see 2 ton systems running on 230V require ~25 amp breakers. That's 5.8 kW, or 7.7 hp (excellent estimating on your part).

Now I'd need to estimate the A/C duty cycle to calculate the necessary battery requirements. But with a pair of 6V batteries only providing 12V, 200 AH... this only gives about 25 mins of run time. How does anyone run A/C off battery?!?

I also took a quick look at solar radiation numbers. Peak loading looks to be about 1 kWh/m2 (at 100% absorption). My roof is about 21 m2 and probably has about .25 absorption coefficient, so my heat load at worst may be 5 kW/h (confirming our original estimate of cooling load).

So what am I missing.... do people who run A/C offgrid just have enormous battery banks??

Another question: what happens if I put a smaller capacity compressor on my existing large evap/ cond?

The answer is in your question. No one runs effective AC from batteries. It's possible that a small window unit could cool a bedroom on a hot night, but that's about it.

AC is run from shorepower or generator.

[PNW_Steve]

Originally Posted by Twigg

The answer is in your question. No one runs effective AC from batteries. It's possible that a small window unit could cool a bedroom on a hot night, but that's about it.

AC is run from shorepower or generator.

There are some folks out there that are running A/C from solar/batteries.

It is a tough endeavor but there are a few who have been successful.

A generator is a much simpler solution.

[cadillackid]

remember keep your parked and driving A/C separate... also puting a smaller compressor on your driving A/C will cause it to malfunction.. it wont be able to keep up the required flow.. over-sized compressors dont generally hurt anything because the expansion valves handle the flows of refrigerant..

2 12,000 BTU minisplits will cool most busses.. somewhereinusa is running 2 minisplits in his bus when he is parked and says it stays nice and cool in there.. he has a rear engine bus thats moderately insulated and using RV windows ..

is your dual coach A/C units on a single compressor instead of on 2? most school bus systems have 2 compressors.. running a TxV expansion device allows the compressor to run at lower load on the engine when the cooling load is low.. again this is just for driving..

Inverter mini-splits dont have a real duty cycle on the compressor as they are designed to run nearly continuous at a low capacity.. so a minisplit slowly ramps up from a stop and then runs at the capacity it needs to cool the space.. mini-splits running at 80% or less of their rated capacity are in their super efficient operating zone.. they can run up to 120% (most of them) but are inefficient there.. however its nice to have the extra capacity in case you need it on rare occasions..

-Christopher

[paulnack]

Hey Steve, is there any particular action or setup in common amongst all those with successful battery-powered A/C systems?

Chris, so that 25,000 BTU number was pretty accurate . I have 2 complete systems- 2 compressors, 2 evaporators, and 2 under-bus condensers. I am certain I will sell one set. One system alone is rated 60,000 BTU/hr (IMACA). I cant let go of the idea of employing it for parked A/C just yet...