Built in AC Units - Remove?

[Brad_SwiftFur]

Originally Posted by cadillackid

Brad - my A/C is in the back of redbyrd and I need more up-front, and im just a 6 window bus.. on those hot southern summer trips im not sweating but im not freezing either.. and can be on the warm side if im heading into the sun.. I looked into moving my unit over the front. however being that my bird isnt a high ceiling it would end up being a head-bumper all the time.. so im going to add a second evaporator up-front and do the custom Dash-air thing I like I did in my DEV bus..

the side mount units are nice.. you can put it near to the middle or front, and even duct a couple vents up to you pretty easily.

-Christopher

This is the type of insight that is *VERY* helpful to me. Mine's not a high-roof either and I likewise figured a front-mount evap would be a headache - both figuratively and literally. For those same reasons I figured a side mount would be my best bet, plus I can route the hoses/electrical right down the wall behind the driver's seat.

[Kubla]

There are several drop in replacements for R22, do not even need to change the oil, so do not get rid of a unit if it runs R22

[MarkyDee]

Originally Posted by Kubla

There are several drop in replacements for R22, do not even need to change the oil, so do not get rid of a unit if it runs R22

I've heard of R-407 as a drop-in for R-22, but the compressor lubricant has to be changed. What drop-ins are there for R-22 that the lubricant doesn't need to be changed?

[cadillackid]

synthetic RS-44b is the main one I know of that doesnrt requirew lubricant changes.. its classified as an HFC.. it matcxhes the discharge pressures better than 407 and 427 as well.. ive not used it as I no longer have any 22 systems out there..

for Fixed (non mobile) R-22 systems I ran ES-22A. and it had much better COP numbers than R-22 but it was flammable so i couldnt use it in a mobile application..

-Christopher

[MarkyDee]

Originally Posted by cadillackid

synthetic RS-44b is the main one I know of that doesnrt requirew lubricant changes.. its classified as an HFC.. it matcxhes the discharge pressures better than 407 and 427 as well.. ive not used it as I no longer have any 22 systems out there..

for Fixed (non mobile) R-22 systems I ran ES-22A. and it had much better COP numbers than R-22 but it was flammable so i couldnt use it in a mobile application..

-Christopher

Thank you!

[cadillackid]

occasionally with a drop-in ive had to adjust the TxV slightly.. you can look up the PT chart for anything you want to use.. and NEVER mix them!! always evac and recharge... remember if your system is even 1/2 charge you'll have ;latent liquid in the oil that takes TIME to boil off.. so i always recommend the vacuum pump being on a couple hours before I attempt to recharge.. some of the drop-ins also have a different weight than their original... most manufacturers will post it if weigfht difference is needed... ie "charge 85% of R-22" etc... I didnt read this one to see what the glide (if any) is but I always charge with a liquid bleed as opposed to pulling gas from the cylinder.
-Christopher

[JDOnTheGo]

Originally Posted by PNWorBUST72

Can I ask why anyone would want to get rid of the AC units that are built into the bus?

Every situation is different so I don't believe in a single "right answer".

The common approach in the RV world is an engine driven A/C system for the cab area. This is usually insufficient for the whole coach so they also have a generator that provides AC power for roof mounted A/C units (hows that for mixing confusingly similar acronyms?!?). The roof A/C's also run from shore power when it is available - so dual purpose (driving and sitting still). The roof mounted A/C units are self contained and cost about $1k or less each. The generator however; is usually a bit of coin. So, while I think this is the best option, it certainly does not work for all skoolies - either from a cost or equipment perspective.

My coach comes with a massive A/C system that runs from a 24 V, 270 amp alternator. However; the system is reportedly very expensive to maintain. So, when it fails, I'm more inclined to invest in roof A/C and generator (if I can't run them via the big alternator - I haven't researched that yet) than into a system that only runs when the engine is running.

I think I'm rambling... I think my point is that you have to decide how much A/C you require while driving, how much while sitting still/camping, and decide how you are going to power them.

[MarkyDee]

JD, Chris, or anyone else who knows:

Any way to get variable flow rates out of an engine-driven compressor?

[cadillackid]

what are you trying to do? multiple evaporators? you can do that if you have TxV's. they vary the flow of regirgerant based on the call for cooling...
-Christopher

[MarkyDee]

Originally Posted by cadillackid

what are you trying to do? multiple evaporators? you can do that if you have TxV's. they vary the flow of regirgerant based on the call for cooling...
-Christopher

Just musing to myself about how to do my build-out.

The roof-mounted HVAC blower pulls air in from a central return, over the coils, and back out through the baggage bins (they double as ducting). I'm removing the bins, so I have a big decision:

1. Remove the HVAC and go all minisplits (I gain weight savings, roof space for solar, and space in the engine compartment for an extra alternator, plus I use one HVAC system for driving or parking).
2. Keep the HVAC and determine how to replace the "ducting".
   1. Install minisplits for when I'm parked.
   2. Determine/mod the current HVAC for when I'm parked.

Although 2-1 is the "easy way out"; I'm still drawn to 2-2. Oh, and I'm concerned that the compressor won't have enough flow to stay cool in the engine compartment....

[Twigg]

Odd as it might sound, propane can be used as a replacement for R22

For refrigeration I believe it is sold as R290.

It stinks, deliberately. However, the concentration of air/propane to provide an explosive mixture is very narrow, making it rather safer than non-believers would have you believe.

I'm not getting into a debate over this. Do your own research and make an informed decision. I am not a heating engineer.

[MarkyDee]

Originally Posted by Twigg

Odd as it might sound, propane can be used as a replacement for R22

For refrigeration I believe it is sold as R290.

It stinks, deliberately. However, the concentration of air/propane to provide an explosive mixture is very narrow, making it rather safer than non-believers would have you believe.

I'm not getting into a debate over this. Do your own research and make an informed decision. I am not a heating engineer.

I'm not sure I'd want to do that in a mobile application. However, if you're carrying around propane anyway, what's the difference....

[cadillackid]

propane is closer to R22. but ytou need a tad bit of butane with it to drop the pressure slightly.. i did extensive experimentation on this subject back in the 90s early 00s.. both fixed "and yes mobile".. all I will say is i had the damn coldest A/C of any vehicles around at the time... i used a mixture of products..


anyway im a firm believe in parked A/C for being parked and road A/C for driving..

install minisplits for being parked.. mod the road A/C for driving...

theres a reason those 40 foot prevost coaches have 4-6 rooftop A/C's and strill have dashboard A/C for the driver... it takes a LOT of A/C to cool a bus going down the road..

when I drove those friends of mine 3/4 m illion dollar coach down to florida and back each year for them I was awfully glad to have that dash air.. yep we ran the Genny and they had 1 or 2 rooftops running depending on where they were in the bus.. and if I was driving into the sun on a warm day. i NEEDED the **SIX** (not just 4) vents blowing around in front to stay comfy... once we parked we closed off the driver area and ran the rooftops.. most times we only needed a couple.. so 2 minisplits at 12k each would be sufficient for most insulated coaches.. unless it got really hot inside first.. then it might take a while.. but hopefully you get to park in the shade.. you dont have the option of driving in the shade... heading southwest in july gets warm..
-Christopher

[Jdawgsfanasty]

Originally Posted by Twigg

Odd as it might sound, propane can be used as a replacement for R22

For refrigeration I believe it is sold as R290.

It stinks, deliberately. However, the concentration of air/propane to provide an explosive mixture is very narrow, making it rather safer than non-believers would have you believe.

I'm not getting into a debate over this. Do your own research and make an informed decision. I am not a heating engineer.

True...most compressible gases could work as refrigerates...

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[cadillackid]

Originally Posted by Jdawgsfanasty

True...most compressible gases could work as refrigerates...

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not so much... you need to look at the specific heat of said substance.. and at what pressures it will be in the temperature range you are operating.. each substance is different in both respects..

just punching a gas into a system isnt the way to get the best and most efficient results... not to mention you need to be concerned about the ability of a refrigeranrt to circulate the lubricant.. there are different lubcricants used in A/C.. certain ones are better for being circulated with various refrigerants...

your compressor and tubing need to be designed to handle the pressures and required volume flow for the space you are conditioning...

its not hard to cobble together some pieces of kit and charge a bit of gas into a pipe... then you'll surely get some cooling... but at what efficiency and longevity??? thats why these systems are designed carefully when new...

-Christopher

[Jdawgsfanasty]

Originally Posted by cadillackid

not so much... you need to look at the specific heat of said substance.. and at what pressures it will be in the temperature range you are operating.. each substance is different in both respects..

just punching a gas into a system isnt the way to get the best and most efficient results... not to mention you need to be concerned about the ability of a refrigeranrt to circulate the lubricant.. there are different lubcricants used in A/C.. certain ones are better for being circulated with various refrigerants...

your compressor and tubing need to be designed to handle the pressures and required volume flow for the space you are conditioning...

its not hard to cobble together some pieces of kit and charge a bit of gas into a pipe... then you'll surely get some cooling... but at what efficiency and longevity??? thats why these systems are designed carefully when new...

-Christopher

Yep...totally agree...the ones in common use are probably the cheapest/safest/most efficient...

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[skoolertobe]

Is there a way to setup a generator to run the existing ac in the school bus when parked besides running the engine?

[cadillackid]

Originally Posted by skoolertobe

Is there a way to setup a generator to run the existing ac in the school bus when parked besides running the engine?

not a generator per se.. the bus A/C is driven by a belt... you would need to use a small engine and spin one of the compressors.. joe blasck is building such a setup as we speak... some busses come with a setup like that... many trucker APU's have a small diesel engine and an A/C compressor..

custom building a setup if you cant find a bus that has the secondary engine for the A/C and power..
-Christopher

[MarkyDee]

Originally Posted by skoolertobe

Is there a way to setup a generator to run the existing ac in the school bus when parked besides running the engine?

See "Not A Skoolie" build thread. He set up a small pony engine to run the compressor....

I've got a similar setup to his and I'm following with great interest.

[Jdawgsfanasty]

Originally Posted by MarkyDee

See "Not A Skoolie" build thread. He set up a small pony engine to run the compressor....

I've got a similar setup to his and I'm following with great interest.

I thought that would work...probably wouldn't need more than 4hp...

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