"Hybrid" Air Conditioner and Heat?

[zimmysurprise]

I've spent a lot of time reading up on the old posts about air conditioning for a bus. My OTR air and heat still work, but  the AC charge isn't lasting very long so I am guessing that the compressor seals are at the end of their life. I need a long term solution that involves basement air or a split system rather than rooftop units. Now that I've pulled every cover off the HVAC compartment on my GM 4108, I see a perfectly good set of 24v blowers already ducted into a distribution system I currently use, along with a condensor and evaporator that would be the envy of any kid for show-and-tell in HVAC school.

My question is- Would it be possible to use the existing coils, change the fan motors to 120v, and install an electric compressor to create a hybrid basement air system? The advantages appear to be that the evaporator is bigger (more effective?) than one you would buy, and it's already installed. The system layout is proven, and it may even be able to be reversed for use as a heat pump. The OTR heat would still work as designed, but AC would require the generator on. Nick- am I nuts?

[Iceni John]

Or maybe do something similar to what this wonderful young lady in Las Vegas has done to her Van Hool:  http://www.skoolie.net/forums/f32/1998-vanhool-45-coach-conversion-12097.html   She's doing something that makes most other conversions look rather amateurish!   Essentially, she's designed and made a 7-ton water/glycol heat exchanger system for five zones.   She begins to describe it at post 37.   I can hardly believe what she's achieved so far, doing almost everything herself.

John   

[TomC]

You would need at least a 10hp electric compressor-or 10ton compressor. To run that you'd need a 20kw generator minimum.
I know roof tops are ugly-but there is a real good reason they are used by everyone now-they are easy, effective, and cheap to replace. I have three 13,500btu Colemans that usually two keep my bus cool. And they are my only A/C, so I run the 10kw genset going down the road. Good Luck, TomC

[kyle4501]

A good HVAC designer can best advise what you will need. The size of the compressor will be determined by many things - insulation, neat loading, etc

[robertglines1]

those huge high output dc motors would be overkill for your application.  They pull up to 50 amps of power.  Just a thought,no free ride on power.

[luvrbus]

There are a couple of bus that have been around for years with the chiller setup,I never heard how the systems hold up but they are bullet proof in commercial building

[chessie4905]

Chillers are ok out west where the heat is dry.q Works well at high outside temps Too humid here in the Northeast.

[chessie4905]

Chillers are ok out west where the heat is dry.q Works well at high outside temps Too humid here in the Northeast.

[chessie4905]

Also, think down the road a few years when something fails....at least with rooftop AC/heat pump, simple to repair or replace about anywhere in the country.

[eagle19952]

Also, think down the road a few years when something fails....at least with rooftop AC/heat pump, simple to repair or replace about anywhere in the country.

you have the replace part right...eager and competent repair not so much.

there are 100's of service choices when the system is residential/commercial.

one or two if rv.. and a crap shoot that nets most waving goodbye to a wallet full of cash.
i would rather deal with a used car salesman/dealer than a mobile rv tech.

[Iceni John]

Chillers are ok out west where the heat is dry.q Works well at high outside temps Too humid here in the Northeast.

The Van Hool I mentioned has a water/glycol chiller system similar to large commercial installations.   It's not a simple evaporative cooler (the so-called "swamp cooler" that ironically would not work in a humid swampy environment!).   At work we have a water chiller system that provides A/C to the entire facility, and it uses a 950,000 gallon tank to store chilled water for use during the day  -  this system is much more efficient than the previous A/C system, and in terms of lower electricity usage it has quickly paid for itself.

John

[luvrbus]

They use chillers in the high humidity in Texas,it won't be long before the solar powered Ammonia absorption AC's come here the technology is getting better everyday  JMO   

[Lin]

Chillers are the standard for larger installations everywhere.  I used to work for an HVAC engineering company in Louisiana, and they were used there too.  The chill water storage system that John referred to takes advantage of cheap night time electrical rates to cool the water to use during the day and avoid paying day rates for the compressors.  They can go all day on just pumps and fans.

BTW, swamp coolers get there name because they raise the humidity so much that some people consider it like being in a swamp.  They will not work in humid areas like swamps though.  You must have relatively dry air.  Many, like myself, are so used to refrigerated AC that evaporative coolers (swamp) just are not acceptable.

[TomC]

I had a friend of mine that was in air conditioning in Florida. When the Soverign of the Seas came out, he had to do some A/C work. He said the sea water chiller was 4 decks high! Good Luck, TomC

[Nick Badame Refrig/ACC]

Hey Zimmy,

I like your thinking, Anything is possible.. however you need to think about factors that some have mentioned. 

The more complicated your system is the harder it will be to repair and or obtain parts when needed.  I have built

several basement systems for myself and others in the past. They are all installed in very tight quarters and engineered

to work well but, as time goes by things tend to wear out and need replacing as I have done twice now in my own coach.

Systems have changed and now it's very hard to replace equipment once 10 years old or more. I have had to rebuild my

basement systems with similar parts because originals are no longer available. I made it work but, you not being in the field

might have quite a challenge doing so. 

With all that being said, Roof tops or ductless splits may be a better choice for you.  or just have me come along on all your

bus outings... Lol  I don't like roof warts at all however there are always low profile penguins that are a bit less intrusive.

I always thing Redundancy...  What ever I can have as a back up, I will do.. Trial and error usually ends up the latter most

of the time.  The next bus I convert will have (2) 230v conventional systems with air handlers in the coach and condensers

in the bay. 2.5 tons each and ducts running down each side of the inside roof line. Just like Florida Coach did it for many

years in their entertainer coaches.  Seems every time I use my bus, it's hot as hell out and my two 15,000 btu basement

units are never enough!

Hope this helps
Nick-