Coach a/c

[Bus Wannabe]

Coach a/c (if it has one) compressor is disengaged when magnetic clutch is not energized. Has anyone seen electric motor or gasoline motor connected to bus a/c compressor and cooling the bus while main engine is off? Why have another a/c when bus already has one? What are the complications? I have never seen It done. Why not?

[Njsurf73]

Originally Posted by Bus Wannabe

Coach a/c (if it has one) compressor is disengaged when magnetic clutch is not energized. Has anyone seen electric motor or gasoline motor connected to bus a/c compressor and cooling the bus while main engine is off? Why have another a/c when bus already has one? What are the complications? I have never seen It done. Why not?

Some coaches have separate engines for a/c.
I am no expert, but it should be doable.
Well anything is possible with a little imagination​ and a lot of money lol

Sent from my XT1254 using Tapatalk

[Robin97396]

AC driven by smaller engines was common years ago. It just sounded like a generator running, and it produces a constant speed to power the AC unit. You don't warm up when you're idling in traffic on a hot day.

[Bus Wannabe]

Originally Posted by Njsurf73

Some coaches have separate engines for a/c.
I am no expert, but it should be doable.
Well anything is possible with a little imagination​ and a lot of money lol

Sent from my XT1254 using Tapatalk

May be the space restrictions or too much money? Can't say that rooftop a/c units are cheap though.

Some have separate engines because either the bus doesn't have originally a/c unit or in some cases It is technically difficult to have in running on main engine. The more expensive newer coaches don't have that any more. The bus original a/c is a good one usually and powerful also. I am trying to think why haven't bus converters done It. The reason I would not do It is that I don't know how to make It tecnically work. In priciple It cannot be that hard

https://www.youtube.com/watch?v=3m8mzKErvZU

.

I don't have a buus yet, I am doing my research now and I have all kinds of silly qestions but this one is not silly IMO

[MarkyDee]

Interestingly enough I've been thinking the same thing. Put a clutch on the compressor and an electric motor (it'll freewheel if not powered or acting like a generator, although a clutch on it as well would keep it from spinning needlessly), and good things happen....

[Bus Wannabe]

Originally Posted by MarkyDee

Interestingly enough I've been thinking the same thing. Put a clutch on the compressor and an electric motor (it'll freewheel if not powered or acting like a generator, although a clutch on it as well would keep it from spinning needlessly), and good things happen....

Yes, the compressor is "freewheeling" separate from the main engine now unless the clutch is energized. So I am thinking there must be a way to connect an electric motor to the clutch . It doesn't have to be automatic and hight tech, once you park your rig, you can pull some lever in engine compartment to connect the electric motor to the compressor through the clutch that is now not engaged with main engine. In order not to have the compressor running constantly and freezing you, you could use the same relay system that engages and disengages the clutch now, It would turn your AC motor on and off (inside the coach would be a thermostat). It can be done theoretically but my question is why hasn't anyone done It. There are all kinds of geniuses who have converted buses. Why haven't they done It? AC electric motors are not expensive. You probably don't have to run the air conditioner to full power since modern bus air conditioners are very powerful (I consider modern 20-25 years old, full of electronics already) so I figure 2-3 kw AC motor would do fine? I am in Europe and you could get a less than 20 years old coach with less than million km on It for 10 000 euros. It has even floor (most have middle part lower), It is close to 400 hp diesel pusher with air suspension, working toilet, working air conditioner, Webasto hydroponic heater, refigurater, inverter for coffee makers etc. So I am thinking of using as much as possible the technology that is on the bus already. Air suspension can be configured with solenoid valves to work as a leveling system (that has been done). Still wondering why double your air conditioning system with another system?

[MarkyDee]

My guess is the type of pump chosen for the A/C system. The A/C system that came on my bus seems to be a piston-style pump thats designed to run at a minimum speed and produce a specific pressure and flow rate with little deviation. I don't think it can run efficiently at a lower speed or pressure because the valves are specifically set for that pressure and flow.

The A/C that can run at lower speeds and pressures (mini- and multi-splits) use a different kind of pump (scroll pump) driven by an AC motor on a variable-frequency inverter and has computer controlled valves. The computer controls the speed of the motor/pump and the valves for a given cooling demand. So I don't think its as easy as it looks.

But I'm just speculating based on what little I know. We'd need an A/C technician to really give us the information.

[Bus Wannabe]

"My guess is the type of pump chosen for the A/C system. The A/C system that came on my bus seems to be a piston-style pump thats designed to run at a minimum speed and produce a specific pressure and flow rate with little deviation. I don't think it can run efficiently at a lower speed or pressure because the valves are specifically set for that pressure and flow."


They are piston compressors. You might be correct that too powerful AC motor would be needed. Those draw 3 times more amps than normal operation while starting also.

This is a thread I could find 12v single shaft motor to run A/C by belt? - DIY Electric Car Forums

There is not much about this topic out there.

My gues is also that bus air conditioning systems are very powerful, the motors needed would be too much (may be 10 kw?).

[Bus Wannabe]

ok, here is one

https://www.transarctic.com/media/co...ygwtmzzb2t.pdf

Revolution range: 600-4000 RPM
Displacement: 635 cubic centimeters/38.75 cubic inches
So they are powerful. You really don't need such a powerful air conditioner on RV.

[cadillackid]

the reason people dont piut an electric motor on the compressor is capacity... if you think of a Coach A/C system, its design is to cool a bus down while moving and full..

a full size school bus like a 12-14 row bluebird will typically be outfiited with 2 A/C systems for a total of 120,000 BTU.. thats right nearly 10 TONS of A/C..

a moving bus is much different to cool than a stationary bus parked in the shade.. you have road heat, wind blowing in the windows, engine heat (esp in an FE or conventional), sunload, plus the desire to drop the temperature of the bus fairly quickly.. just like a car you get in start it up and want cool air.

a little DC electric motor is not going to push a pair of 5 ton compressors.. you may need upwards of 20 HP. (more under heavy load)..

thus a Pony engine was used for busses that needed to idle a lot.. in a full size converted coach 4 or 5 13000 BTU electric roof airs arent uncommon.. and those are fully insulated coaches with less windows.. Plus those coaches have Dashboard /
Driver A/C thats usually 20k BTU on average..

-Christopher

[Bus Wannabe]

Yes It is too powerful. You would need somewhere like 10+ KW AC motor that draws may be triple the amps while starting. If you had a connection at home that could handle this, It could be done but most people like to travel with their motorhomes and campground breakers wouldn't do. It is not neccesarily very inefficient since the AC motor is turned off when desired temperature is reached. Inefficient compared to the inverter mini splits sure.

I've seen people running 12 kw diesel generators on their buses, something to think about.

Any way thanks everyone, I got rid of my obsession.

[Robin97396]

So those 60,000 btu heat pumps the military keeps selling off wouldn't actually be that outrageous if we could find a way to power them. They are probably designed to be running on three phase from military generators. Right now there seems to be a lot of 5k diesel generators for sale, soundproofed in a box approximately the size of a small desk.
These heat pumps are also about the size of a small desk because they're in a sound deadening box. They'd fit in a basement pretty well but might be a little intrusive in medium or short buses without the basement.
I like military equipment because it's extremely durable and can be bought for peanuts compared to what uncle Sam paid for it, often in new condition.

[Seriousracer]

Apu off of semi's.

[Seriousracer]

https://www.vanderhaags.com/Search-R...typesetid=6030

[Rameses]

Originally Posted by Seriousracer

Apu off of semi's.

That's exactly what I was thinking of too.

They're made to keep a larger volume of space at a lower temperature than what we want to.

Might be overkill, but it'll definitely get the job done.

[Rameses]

Wait, are those for AC in a sleeper without idling the truck?

I was talking about a reefer unit for a trailer.

[Seriousracer]

You are thinking reefer unit
Apu will go about 12 to 15000 btu hot or cold
With about 2000 watts electric. Off a single cylinder Diesel engine. Most are really quite.
Watch which one you buy.
And 2000 they are cheap. Add a geni a roof air and a heater and you are not far off

[Bus Wannabe]

I am thinking about mini splits and generators. Propane generator is within my reach, brand new diesel one is not.

https://www.youtube.com/watch?v=8zw9F15jaeI

https://www.youtube.com/watch?v=IHDT5ZEpKkw

With those old apu-s you don't know what youu are getting, for the same money you can get brand new equipment.

[bry899]

I have been following this (Coach A/c) Thread and others.
I have an E350 Super Duty Shuttle Bus (12 P, 1WC). With dash & Rear Air working off the engine mounted compressor, & underneath condenser.

This might be a stupid question, but is their any way to incorporate a Mini split Compressor/Condenser to work with the bus rear Inside unit?
Maybe with some switches and some kind of electric valves to switch from either when the vehicle is running or when it is parked.

In other words all A/C would operate as normal when engine is running.
When parked the rear A/C could run off the Mini split Compressor, with valves closing so the freon cannot go to the engine compressor & Condenser, but loop back to the Mini split.

I love the idea of the mini split, but then I would lose Full A/c when driving

[Seriousracer]

Possible
It would be the same as some apu