Cooling the Aft Deck with Isinglass

Brian,

You are trying to condition the outdoors, a difficult task.  I have never calculated a BTU requirement for your situation.  I usually install the largest units I can fit into the area taking into account the unit location is generally in a cabinet.  Sometimes two cabinets are available and I go with two air handlers of the largest size that will fit.  Because outside temperatures can fluctuate to an extreme, you don’t have to worry about overcooling the area with too large of unit.  If you could get 6 tons of cooling to the area I think it will keep the area comfortable for most times. 

There are a couple of things to look out for.  Make sure your chiller unit isn’t maxed out for capacity.  Installing air handlers without having the capacity of the chiller to support it will de-rate the new aft deck unit and can also affect the air handlers inside the vessel.  Make sure you have large enough chilled water lines to support the new units.  Six tons of air handler will require 18 gallons of water per minute.  The correct pipe size to accommodate the amount of water would be a 1 ¼ pipe.  If a smaller pipe size is used your air handlers will not perform as rated.  Since the units and water lines are exposed to outside conditions make sure the pipe insulation has a large enough thickness.  If possible install a 1 inch wall thickness onto the chilled water lines.  Insulate the drain lines with ½ wall thickness and add additional insulation to the air handler unit to prevent condensation.  The air handler coil can be protected from the salt air atmosphere by coating it.  I’ve used a brand named Heresite before.  It is designed for salt air environments and will extend the life of the coil.  It is best to disassemble the unit and spray both sides of the coil making sure you get to the middle section.

Matthew