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Old 11-11-2016, 11:46 AM   #1
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Adding road a/c to a rear engine bus?

Mornin' Everyone,

I am considering solutions for road a/c in a Bluebird 72 passenger RE bus.

On my last bus I relied on running the generator and typical RV roof a/c's. While driving in the Southwest I roasted. It was fine in moderate climates but 95F and bright sun was near unbearable.

I want to do better on this one. I want something that will keep me comfortable while I drive.

I have been looking at all sorts of electric a/c solutions that will likely require generator operation. Now I want to take a look at engine driven a/c.

The biggest challenge that I see is the 40 foot run from the engine to the drivers seat. I have no clue what the limitations are on refrigerant line length.

Another option would be to keep the evaporator at the rear of the bus and duct it up to the driver. Maybe run a duct the full length of the bus and place vents periodically along its length and have the last vent blowing directly on the driver?

Another variant would be an inverter connected to the coach charging system to run an electric a/c for the drivers area.

I know we have some a/c Guru's out there. What do you all think?

Thanks

S.
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Old 11-11-2016, 12:01 PM   #2
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No matter what you do, it is not going to be cheap. I do not know if there is a length restriction on A/C lines, but front to back on a full size RE bus would be pushing it. I would fear loosing too much pressure to the lines needing to be flexible.
I will throw out another crazy idea. What if you got an Automotive style A/C system from a place like Vintage Air, and powered it off of a small Honda GX gas engine, like you would see on a go-cart or rototiller. Honda Horizontal OHV Engine with Electric Start 270cc, GX240 Series, 1in. x 3 31/64in. Shaft, Model# GX240UT2QAR2 | 241cc - 390cc Honda Horizontal Engines| Northern Tool + Equipment
Then you could find a place near the front of the bus and mount it. They do offer electric starters for them, so it could be started from the drivers seat. You could mount the engine under the bus at the front, add a larger fuel tank, maybe 5 gal and you got A/C.
So, a crazy idea, but it could work. Yoou would just need to find out the HP draw of a Sanden A/C compressor. I would guess less than 5hp.
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Old 11-11-2016, 12:43 PM   #3
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nope shou;dnert be any length restrictions on refrigerant lines... at least not 40 feet anyway... the Liquid line is the most critical and holds them ost refrigerant... if you are looking for multiple units we just have to locate your condensor in the spot that makes sense for both evaporators.. if you just want dash air then we want your condenser coil as close to the front od the bus as we can get it...

since oyu are converting and insulating we should be able to get you buy with one compressor / condenser and then up to 2 evaporators... I run such a setup in the DEV... custom built Dash air and rear unit...

yes its very pricey unless you find some take-off parts.. the condenser and evaporator are the priciest parts.. and then any fancy electronic controls you might want for temperature control.. paerts can be mixed and matched by brands, however the capacities must add up to be a close match..

compressor - Selttec 8390 / TM-16 (good for Max 50,000 BTU)couple hundred bucks.. brackets? can be pricey but likely find take-offs here or in a bus boneyard pretty cheap..

freon lines.. varies on how much you end up needing.. I used the slightly pricier Burga-Clip fittings because its a very simple leak free and still rotateable fitting once installed.. (i'll gladly loan out the Tool to crimp the fittings on)...

freon? my guess is about 10 lbs in a system on a full length bus iof the condenser is closer to the front...

vintageair and companies systems are typically only 9000 BTU and made for a car..

a typical full size FE / RE 12-14 row school bus with white roof and tinted windows will run 120,000 BTU of A/C... you dont need near that much since you arent looking to cool it in 3 minutes and there wont be 84 screamin demons aboard... and will be insulated...

horsepower calculations are out there for how much a compressor uses in a bus enviornment.. remember an auto environment is 9000- 12000 BTU and so those HP calculations are not what your compresor will pull in a bus..

-Christopher
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Old 11-11-2016, 01:20 PM   #4
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Cadillac can definitely tell you more on this subject than me or probably anyone else here...but...what I can add is that the lines for several mini-splits here at my studio were easily 40+ feet and functioned just fine. The only issues I can imagine are price and keeping the necessary lines well insulated along the length.
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Old 11-11-2016, 01:20 PM   #5
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I am getting ready to pull the condenser and evaporator (carrier) out of an E450 5 row. I wonder if I might re-task those pieces?

Perhaps mount the evaporator facing forward just aft of the drivers seat.

I did see some Thermo King APU's for $600-$900 for just the APU. No condenser or evaporator. Than would be a bit more flexible but I am back to running a second engine while running down the road.

Back to what you said Christopher, if I engine mount the compressor and run lines all of the way forward then mount the evaporator directly above the first baggage bay and place the condenser in the first (modified) baggage bay. That would place both pieces as far forward as I can and within about eight feet of each other.

Do I understand correctly then that I would need: compressor, receiver-dryer and expansion valve? Those would all live in the engine compartment?
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Old 11-11-2016, 01:50 PM   #6
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Quote:
Originally Posted by PNW_Steve View Post
I am getting ready to pull the condenser and evaporator (carrier) out of an E450 5 row. I wonder if I might re-task those pieces?

Perhaps mount the evaporator facing forward just aft of the drivers seat.

I did see some Thermo King APU's for $600-$900 for just the APU. No condenser or evaporator. Than would be a bit more flexible but I am back to running a second engine while running down the road.

Back to what you said Christopher, if I engine mount the compressor and run lines all of the way forward then mount the evaporator directly above the first baggage bay and place the condenser in the first (modified) baggage bay. That would place both pieces as far forward as I can and within about eight feet of each other.

Do I understand correctly then that I would need: compressor, receiver-dryer and expansion valve? Those would all live in the engine compartment?
the evaporator in your van should have a TxV valve built in depending on how they tied it into the factory dash A/C.. the receiver dryer you will want to buy brand new they should not be re-used.

your evaporator may have a freeze-thermostat built in, if not those are easy and cheap.. the dryer goes in the Liquid line between condenser and evaporator.. it can be near either.. the TxV expansion valve goes at the evaporator inlet...

what you want to do sounds very viable..
you can go as elaborate or as simple as you want on your temperature control..

the Trans/AIR in my bluebird has 2 fan speeds (resistor block) and 2 temperature settings.. cool and cold.. the cold setting keeps the coil temp at just above freezing.. the cool setting keeps the coil temp about 45 or so... both are simple mechanical tube thermostats mounted on the evaporator and wired to the driver control.. 45 coil temperature means it cycles the compressor when the coil temp reaches about 45 (usually means I get about 55 degree air out opf the vents)...

freon Lines.. you will have a line that goes from the compressor to the condenser inlet.. from the condenser outlet you go to the receiver dryer.. then from their to the evaporator inlet (TxV inlet)... then from the evaporator outlet you go back to the compressor...

most times on the receiver dryer theres a schraeder valve where you screw on a Trinary pressure switch that goes in series to the power for the compressor... if your freon leaks out it disables the compressot.. and also disables the compressor if the pressuer goes too high.. (fans quit or such)...


back to your E450 Van, if you plan to keep the dashboard A/C in it after removing the rear... it mah not have a condenser in front of the radiator... not all of the busses with rear units also have that front condenser.. a trip to the boneyard for a ford condenser and you can re-connect just your dash air in that Van... if you are lucky it already has one...
-Christopher
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Old 11-11-2016, 02:07 PM   #7
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This sounds simple enough to accomplish, even if a little pricey.... but would be worth it to have A/C going down the road.... and powering it from a smaller gas or diesel engine it would be operable even when the bus is not being driven (power the blower from the house batteries). With a large enough engine you could also drive a generator head so you could do double duty... and in the winter when you don't need the A/C just remove the belt that drives the compressor.
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Old 11-11-2016, 03:36 PM   #8
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Originally Posted by AlleyCat67 View Post
This sounds simple enough to accomplish, even if a little pricey.... but would be worth it to have A/C going down the road.... and powering it from a smaller gas or diesel engine it would be operable even when the bus is not being driven (power the blower from the house batteries). With a large enough engine you could also drive a generator head so you could do double duty... and in the winter when you don't need the A/C just remove the belt that drives the compressor.
compressors are on a magnetic clutch, the outer pulley spinning uses almost no resources... no need to yank the belt if you are running it with a genny engine. the indoor fan on mine pulls about 15-20 amps and the condenser fans pull about 30-35 or so..compressor clutch is like 5-10 amps i think..

-Christopher
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Old 11-11-2016, 06:04 PM   #9
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So.... what I would need to undertake this.....

- Evaporator
- Condenser
- Compressor
- Filter/Dryer
- Tubing to connect everything together
- Freon to charge the system
- Blowers and ductwork
- Switches and such to control the system

Did I miss anything?
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Old 11-11-2016, 08:23 PM   #10
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The Thermo King APU has a small (10hp?) diesel engine, an a/c compressor and a small alternator.

Take a look: Thermo King TriPac Auxiliary APU unit, 2014 model year NO RESERVE | eBay

The idea intrigues me but I think stuffing that into my bus may be a bigger project than I want to add to an already hefty to do list. We will see....
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