Anyone ever used High Pressure A/C & Heat?

[oldmansax]

Please forgive me if this subject has already been covered, or if I make any "newbie" mistakes! I have been interested in bus conversions for about 3 years but have yet to "take the plunge". Has anyone ever used a high pressure system, such as UNICO or SPACE PAC,  to heat or cool a bus? I have been installing the UNICO system in historic houses for a number of years and it appears the same characteristics that make them a good fit for old houses would apply to buses. The systems have a small footprint when compared to other house type systems, the main trunk is 6.5" x 6.5", the runs are only 4" and can be installed in a 4" hole made with a hole saw. UNICO is also excellent at removing humidity and can be used to heat with the addition of a hot water coil. The engineering is somewhat tricky but can be done with a little foresight & perseverance.  Has anyone used this type of system?

[gumpy]

Not familiar with them, but I'm guessing if they are designed for house installation that they are probably 240v, and probably have fairly high current requirements?

May not be suitable for bus connection which typically isn't wired for 240v appliances. Not to say it couldn't be, though, but you might be restricted to generator or 240V/50A shore line.

I like the idea of using it for heat with the addition of a coil, though, if it could be used on a 30 amp 110V shore connection. Probably wouldn't work well on batteries due to current draw by the fans.

Again, I'm not familiar with the specific units you posted, so this is all speculation and generalization based on common house units.

[oldmansax]

They are designed for house applications and have 240v motors. The motor could be replaced with a 1/2HP 110v if you so desired. I am not sure how to get around the 240v condensing unit though. You can generate 240v from 110v using a capacitor bank.  I have done that in situations where I had  3 phase equipment and only single phase service.  I was interested in this because I see some busses for sale advertise they have 2 or 3 ton house type systems. Do they just use the gen set all the time? The hot water coil is a pretty neat feature as you could use hot water from the engine, or gen set if it is water cooled, or from a Wabasco or like unit. I had thought the 240v problem would be easier to solve than the space problem duct work causes. BTW, anyone can view specs at www.unicosystem.com

[Len Silva]

I think the busses you are seeing that have house type AC are entertainers, they run the generator 24/7.

Len

[DrivingMissLazy]

As far as I can tell, this is only the air handling portion of the system, you still need a compressor/condenser system. It says to use your own which I would assume could be either 240 or 120 volts.

It would be relatively easy to provide a step up transformer to supply the 240 volts for the air handler fan which is apparently only 1/2 hp. The motor may also be re-connectible for 120 volts.

I do not think you could use capacitors in this application to get the voltage you need. The system you are talking about uses a capacitor to provide starting current for the third phase of the motor, but then drops out after it starts. You would already have the necessary single phase 240 volt voltage available. BTW, using this system you will lose 1/3 of the hp rating of the three phase motor.
Richard

They are designed for house applications and have 240v motors. The motor could be replaced with a 1/2HP 110v if you so desired. I am not sure how to get around the 240v condensing unit though. You can generate 240v from 110v using a capacitor bank.  I have done that in situations where I had  3 phase equipment and only single phase service.  I was interested in this because I see some busses for sale advertise they have 2 or 3 ton house type systems. Do they just use the gen set all the time? The hot water coil is a pretty neat feature as you could use hot water from the engine, or gen set if it is water cooled, or from a Wabasco or like unit. I had thought the 240v problem would be easier to solve than the space problem duct work causes. BTW, anyone can view specs at www.unicosystem.com

[TomC]

I would think it would be fairly easy to set up two one ton systems, or could use a 2-2.5 ton system (probably all you'd need in a well insulated bus considering the superior air flow characteristics).  Use their evaporator mounted inside in the middle of the bus and then use the Cruiseair condensing/compressor units (two of them) since they are designed for mobil operation.  While this is a novel approach, I could easily see you spending towards $5,000 on a system like this, when you could buy three roof tops (much easier to install, service and you don't sacrifice any basement storage-and can duct these also) for less than $2000-plus roof tops are proven, and your system would be completely custom-never used.  Personally, I like my three roof tops and the fact that in the 11 years they've been up there, I have done zero maintenence except for cleaning the filters periodically and replacing one exterior shroud.  All three cost $1500.  Can hardly beat that-except for them being on the roof (a bit unsightly, but practically all RV's have roof tops)  Good Luck, TomC

[oldmansax]

While this is a novel approach, I could easily see you spending towards $5,000 on a system like this, when you could buy three roof tops (much easier to install, service and you don't sacrifice any basement storage-and can duct these also) for less than $2000-plus roof tops are proven, and your system would be completely custom-never used.  Personally, I like my three roof tops and the fact that in the 11 years they've been up there, I have done zero maintenence except for cleaning the filters periodically and replacing one exterior shroud.  All three cost $1500.  Can hardly beat that-except for them being on the roof (a bit unsightly, but practically all RV's have roof tops)  Good Luck, TomC

I agree with you concerning the rooftops, but I see others using various other systems and have been weighing the benefits and liabilities of each. One of the reasons I have not either bought or converted a bus (other than lack of time) is I have a tendency to over-think and over-engineer things. It's my ONLY vice! 

[TomC]

Oldmansax- I agree with you.  My bus project, when I first started, was the way I kept my mind busy when I was driving cross country truck.  I would drive 9 months and take the 3 winter months off (me and that white stuff that falls out of the sky and collects on the ground don't get along) to work on the bus.  Hence, while driving, I'd be designing the next few steps in the building process.  Now that it's done, and I have a "normal" stay at home job, I still design my next project in my head before I go to sleep at night.  It's the one way I can turn off the problems of everyday living in my head and think happy thoughts on my continuing bus project.  Now let's see- I have to rebuild the toilet ball valve; need to call Sierra intercoolers on the cost of my air to air cooler for my turboing project; trying to work out the routing of the new plumbing for the turbo; possibly mount a split A/C system for quiet night time use-how will it by mounted and the plumbing run; need to service the genset; etc,etc,etc....Good Luck, TomC

[DavidInWilmNC]

AFAIK, the only unique thing about high pressure heat and A/C is the blower and ductwork.  I mean, a condenser, evaporator, and compressor are just a condenser, evaporator, and compressor.  I'm sure one could use a standard basement heat pump and supplement that with an additional blower, if needed, to achieve the high pressure and velocity for this system.  There was a fellow at the Timmonsville gathering with a '58 (I believe) Flxible that had a basement A/C mounted in the rear over the engine.  He built a duct on each side of the bus over the windows where many put a valance.  He installed 4" round louvered vents along the ducts.  There's a ton of air up at the front for the driver and passenger; he says it stays cool there while driving.  I'm considering a similar system for my MC-8.  I'm planning on ducting a 10K btu window unit from the rear bay to the bedroom too.  I like the looks of the original roof without A/C units, but mainly I like the silence.  The only thing I could hear was the quiet sound of air coming out of the vents.  Even in the rear bedroom, the system was extremely quiet.  This may not be exactly like a Unico system, but is similar enough to me to be the bus conversion equivalent.  

David

[kyle4501]

If I undrestand correctly, this high pressure air system moves the same amount of air thru a smaller duct system by increasing the air pressure. This increased air pressure requires more power to generate. This is the only real problem I see, as everything else is just a matter of preference.

If you are an off the shelf converter & are focused on the destination, well, sticking with off the shelf items may be the best route for you.

If you fancy yourself as a clever, crafty type who likes to re-invent the wheel because good ain't good enough & likes the journey as much or more than the destination, well invent on!

Most gensets can provide 240vac & most run their genset when A/C is needed.
Usually a 120vac motor can be found to fit your needs (it is just a matter of time & $$).
Cheap rooftop targets for tree limbs OR basement units & ducts that eat space - owner/ builder's choice.
Your ultimate goal for the coach you are converting is what counts.
While cost is a factor, but if I was driven by cost alone, I would have bought a tent.


The best thing I have found in this hobby is the many different ideas & ways of thinking of what is best. Those that take the time to point out the flaws in my ideas have saved me bunches.

Thanks YA'LL

kyle4501

[Nick Badame Refrig/ACC]

oldmansax,

Yes, my systems are "High Volocity" in my bus. They are not Unico or Spacepak but, I use SpacePak's defusers and tubing.

I constructed my own Hi V system! And it works very Well!  A couple of other members are doing the same as mine.

Nick Badame

[DrivingMissLazy]

I continually read on the various boards the complaints about noise. Trucks ideling all night, A/C fans too noisy, generators  and other noise complaints.

Well, Janet and I like some noise (white noise) and always run a fan or something to get rid of the quiet. A big truck in Flying J that idles all night is really no problem at all. Even our generator running all night provided a level of comfort noise and a little vibration as well.

How lucky can you get that we both liked this!

Richard

[Nick Badame Refrig/ACC]

Richard,

Noise is good. When I was a kid living in S. Philadelphia, I remember so many noises every night like, sirens, horns blowing, people yelling and screaming,
and dogs barking that when we moved to Jersey I couldn't sleep for a month. Too quiet, nothing but krickets!!

Nick-

[Christyhicks]

HA HA HA,  just shows how diverse our group is.  We live out in the country. . .and one of the best things about it is I'm finally away from the neighbor's barking dogs, loud, cussin' kids, cars, cars, cars, etc.  Due to a very tall roof and my tendency to go overboard with insulation, we can't hear ANYTHING in our home, and our bedroom is so remote, we can't hear the phones or the doorbell.  It's so quiet, that, one night when the a/c went down, we tried opening the windows, but couldn't sleep due to all of the noisy crickets, frogs, and coyotes.   hahahah, I'm SERIOUS! 

The hubby could sleep through wind and noise in his face, but you want to see ornery?  Make me do the same !  The only drawback is that we also can't hear storms, and often don't know a bad storm has come through until the next morning .  Larry used to stay up all night keeping various tornados away, now, he doesn't even hear the storms and therefore, just sleeps on through the night.  We do keep the cell phones next to the bed and our family knows to call us on the cell if they need us, so hopefully one of them will keep the tornados away. 

Knowing this, we designed our a/c system with quiet and peace in mind (to me the ideal hvac system does it's job with no one noticing it's even on).  We did the same for the generator, with the exhaust extending up through the roof to dissipate noise and fumes up, up and away.  Christy Hicks

[DavidInWilmNC]

Christy,

How are things going?  How are the modified A/C's working?  I'm planning something similar for my MC-8.  Like you, I like quiet air conditioners!

David