How do you use a rooftop ac as a basement ac?

[dougg]

Tom C said "I took 15,000btu (straight A/C, no heat or heat pump) Penguin's and converted them from roof to basement units.  They cost $850.00 apiece.  Savings of almost $2,000.00 (when running two).  Course the conversion took a bit of engineering, having custom duct work made, making a platform for them to sit on, and creating an evaporator drain.  But-sometimes that's the fun part.  Good Luck, TomC"
Can you give us more details and maybe some pictures?

[TomC]

I'm going out to the bus this Sunday and will take some pictures of the one that is installed and the one I haven't installed yet.  The one I installed, I ran it for my wife.  The air coming out of the duct into the bedroom was just about silent.  Will now be able to sleep with the A/C running, compared to the roof airs I have now.  Good Luck, TomC

[rampeyboy]

Ha! And my wife has to have some kind of fan running (for the noise, not the air), or she can't sleep!
Boyce

[chrome dome]

We have gotten so used to the noise also , I don't think I could sleep with silence now.

Dave5Cs

[Scott Crosby]

Also Intrested in seeing this...

[foohorse]

Ditto, I have 5 roof units ready for the knife.

[FAST FRED]

For a basement system to work , weather its 2 units in a box or a chopped up carbunkle the hassle is still working out the return air duct work.

No return air , not much cooling .

Hot air rises , so the noisy ugly carbunkles actually do fine at cooling a coach area by recirculating the air..

I would like to find a split system that works on 120v where the evaporator is simply hung in the cabin, getting its return air from the cooling space.

?  With heat pump config is prefered.

FF

[Oonrahnjay]

(snip) I would like to find a split system that works on 120v where the evaporator is simply hung in the cabin, getting its return air from the cooling space. (snip) 

       My bus design makes some *very* complicated needs for the design of an air conditioner system.  I've looked at a number of "mini-split" systems and they all provide this feature (in the design of the "air handler" components) or at least provide the flexibility for you to install the parts so that they work this way.  I agree entirely with your assessment on the importance of the proper provision for the return air but it appears to me that that's been pretty well considered in the "mini-split" design.  Or am I missing something?

[George Todd]

Bruce,

I don't think you are missing anything, a ductless mini on a wall will pick up plenty of warm air from around it and direct the cool air across the room where it will displace the hot air and move it back to the unit for the next pass.

Circulation is the key, and the reason rooftop units do a good job is because they can't go wrong, they are in the hottest air in the bus.

Actually the comment "No return air, not much cooling" isn't correct, it should be no return, NO cooling.

Circulation is the key, look at all of the air conditioned highway coaches in service.  None of them have a high return air, almost all of the return air intakes are in the front stairwell, until the recent buses which take some air in under the middle seats.  This tends to cause a cold draft complaint though, even if it saves on ducting.  The conditioned air is supplied evenly around the bus below the windows, and obviously it works well.

In putting a rooftop in a basement, I would try and separate the supply and return as far as I could, to avoid hot and cold spots, and make the ducting as big as possible, and avoid sharp turns, because the fan is not made to move air thru ducts.  If the unit hasn't been purchased yet, buy the ducted rooftop type, because it will be able to cope with the air restriction better.

Many of the basement types are made as splits, with the air handling, or indoor portion made to be mounted over the top portion of a floor to ceiling cabinet.  They are about a 2 foot cube, and take return air in on one side, and put the supply out the other where it can be ducted.  Being mounted over a cabinet allows the freon,  power connection, and condensate drain lines to run down to the floor.
G

[Oonrahnjay]

  (snip) , a ductless mini on a wall will pick up plenty of warm air from around it and direct the cool air across the room where it will displace the hot air and move it back to the unit for the next pass.

Circulation is the key, a (snip) 

     Thanks, George.  Very clear and valuable comment (as usual).  My experience with designing "add-on" air conditioning systems for Land Rovers is that a centrifugal "squirrel cage" blower provides much stronger air flow through restrictions - are these systems available with a choice between blade fans and  centrifugal blowers?

[robertglines1]

I'm using mini -splits in the 45 xle and they preform from the teens to 100F  actually better than I expected. Total load for all three is 19.5 amps@120volts max. My cost for the 3  was $1450.  They  have a sweep function that fans the air side to side and up and down.  For what it's worth. Tested by me.  Total Btu out put 30,000 btu. 2ea 9000 and 1 each 12,000 btu.  at 100F outside the two 9,000 keep up on their own.  I actually got the ideal from another bus nut. He is in the Hvac   business.    The inverter technology lets them run more efficiently. inside noise is at 35 to 44 ddb.  Bob

[Oonrahnjay]

    I appreciate the info, Bob -- real world experience is always very useful.  However, I'm really impressed with TomC's adaptation of rooftop airs.  I can install one in a similar way under a couch in my upstairs sitting room and have it blow down on the driver/passenger traveling compartment and also direct into the kitchen and dining area downstairs.  In this way, it's "on the roof" of the downstairs area.  It may not be the "Best Way" or it may not work out to be "My Way" in the end, but his adaptations are very good.
    And getting that kind of BTU-age on the low number of amps as Bob has done is very impressive.

Thanks for the info.  BH

[buswarrior]

Oonrahnjay, for what its worth, the Van Hool double decker Megabuses have a tendency to be cold downstairs, while the AC on the upper deck is running flat out.

They have the added challenge of two sets of stairs to facilitate lots of cold slipping downstairs, so controlling air flow and temp layering must be the devil for their design engineers.

Of course, a seated coach has way more compromises in packaging biased towards maximum passenger loads, and a busnut is free to compromise in other directions.

Getting the feed and return air ducting right to defend against the big temp layering will be the trick. Or you can use this to your advantage capacity/efficiency wise and let it layer for going down the road, first floor cool, upstairs doesn't matter until you are stopped and engage another portion of the entire system.

Lots of fun using the physics as you see fit!

happy coaching!
buswarrior

[robertglines1]

If you would like to see some pic of the mini-split rough in   go to   prevostcommunity.com/forum       look under  hvac   2nd page   minni-split   go down  to pictures.   I haven't got on to posting on this site yet(pic)  Bob

[robertglines1]

pic