AC ducting ?????

[grantgoold]

Sure would like to get some ideas on ac ducting inside your bus? I have a basement model (3 ton) in the center driver's bay. 1984 MCI 9.  Did you use 6 inch, 4 inch, 10 inch ducts. How many registers? How about return air flow or size.  I have had some really good ideas to date. Nick has been awesome!!  How about you?

Pictures are always a plus!!!

Thanks in Advance.

Grant
Sacramento

[Sojourner]

Hang in there!

I am sure Nick will answer asap.

Sojourn For Christ, Jerry

[grantgoold]

Nick has already sent me his setup. I am looking for the rest of you who have built your ducting system inside the bus to chime in. I am looking to have four six inch registers along the top of the walls. I also have 2 return air registers (wall mount) that will help me recycle the interior air for faster cooling and cleaner air.

How about you?

Grant

[belfert]

Remember that you generally need as much return air ducting as supply ducting or the condenser will be starved for air and may freeze up or do other funky things.

You can get by with fewer return vents than supply vents, but the return vents need to be bigger than the supply vents.  Just as in a house, I would not put a return in the bathroom if you have a supply there.

[TomC]

This is where some simple algebra comes into play.  When you buy the A/C unit, the manufacturer will tell you the square inches needed for both the cold and return side.  Typically return is a rectangular opening so simply length times width will get you to the equation.  Usually the outlet side is already a round outlet.  It is very important that you never go smaller than what the manufacturer recommends, or you risk problems like evaporator freeze up.  Make sure to include an air filter. 
Personally, instead of using a basement unit, I am going to use a roof top that is mounted on a shelf in my basement.  The Duotherm Penquin will work since it uses a squirrel cage blower for the condenser that can be ducted outside.  I will buy the ducted remote thermostat unit and then just use duct work of proper size for the air.  There is a big difference in price from a roof top (around $6-700) compared to a basement unit ($15-1800).  When multiplied by three, it is alot.  Good Luck, TomC

[JackConrad]

We purchased our basement AC from RonTheBusNut. It is a scratch&dent 24,000 BTU unit made by RVP (formerly Coleman) that was around $800.  We made all ducts per RVP installation specs. I think the supply was 48 sq.in. and the return was 54 sq.in. (these figures are not guaranteed as I have slept since then). I was told the return should always be slightly larger because the returning air is warmer and less therefore less dense.  I do know our system has worked flawlessly for 8 years.  Jack

[grantgoold]

Jack, I have the exact same set up and story. I was hoping for some detail on exactly how you distributed your supply lines inside and how you managed the return lines.

Thanks

Grant

[JackConrad]

Grant,
  My supply is a 3" tall X 16" wide duct that runs almost the entire length of the bus just slightly to the drivers side of center in the ceiling. Vents are located  as follows: 1 in bedroom, 1 in bathroom, 1 in kitchen area, 1 in living area and 1 just behind drivers/co-pilots seats. Return vent/with Filter is in bathroom area. Return duct is 3" tall X 18" wide.  Both supply and return ducts go across top of closet on passenger side of bus in bathroom area, down the back wall of closet and into the rear bay to attach to the unit. 
  The duct were made from a product called UltraDuct.  It is about 3/16" thick and consist of a 1/8" layer of high density closed cell foam with a layer of heavy aluminum foil on both sides. I cut it with a utility knife and used the aluminum AC duct tape to seal the joints. All joints were then covered with AC duct caulking compound to insure a 100% seal.  Jack

[TomC]

You might re consider placing the return in the bathroom.  You'll then be recirculating all that wonderful bathroom smell especially after dropping a big one.  Good Luck, TomC