Mars Air Systems L-2254 - Manual (Page 7)

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English L-2254 Installation
duct diameters and their corresponding supply and
return air grille minimum area in square inches. If a
transition box is used, the total area of supply air ducts
going out of the box should at least equal the area of
the supply duct feeding the box. To calculate the square
inch area of a round duct, multiply the radius by itself (r
2 )
and multiply that number by 3.1416( π). See Figure 8.
The following is a summary of proper ducting connections:
1. Pull back the fiberglass insulation exposing the inner
mylar duct hose.
2. Slide the mylar duct hose around the mount ring until
it bottoms out.
3. Screw 3 or 4 stainless steel sheet metal screws
through the duct hose into the transition ring.
Make sure to catch the wire in the duct hose with the
heads of the screws. Do not use band clamps, as the
hose will slide off.
4. Wrap duct tape around the ducting and ring joint to
prevent any air leaks.
5. Pull the insulation back up over the mylar to the ring
and tape this joint.
6. Remove excess ducting and use the same connection
method at the supply air grille.
All ducting should:
• Be appropriately sized for each application.
• Run as smoothly and taut as possible.
• Have as few bends or loops as possible.
• Be securely fastened to prevent sagging during boat
operation.
• Have all excess ducting lengths trimmed off.
• Not be flattened or kinked.
• Insulated when located in high heat load areas (hull
side, mechanical compartments, etc.).
• Be properly protected against potential damage
when routed through open areas.
Seawater Pump and Plumbing
Several guidelines should be followed during the installa-
tion of the seawater system. Since the circulation pump
is centrifugal and not self-priming, it must be mounted so
that it is always at least one foot below the water line
regardless of which tack the vessel is on. Pump may be
mounted horizontally or vertically, however the discharge
must always be above the inlet. Pump head should be
rotated toward the direction of water flow.
Install the
seawater speed scoop intake as far below the water
line and as close to the keel as possible in any
application, but especially on a sailboat, to keep the
intake in the water when the boat heels over so that
air does not get into the system.
(See Figure 7 for
proper installation.)
The speed scoop intake must face forward and not be
shared with any other pump. A seawater strainer is
mandatory between the shut off valve (seacock) and the
pump to protect the pump from any foreign matter.
Failure to install a seawater strainer will void the
pump warranty.
The seawater system should be in-
stalled with an upward incline from the speed scoop &
seacock, through the strainer, to the inlet of the pump
and then up to the inlet of the a/c unit’s condenser coil.
The discharge from the a/c unit should then run to the
seawater outlet thru-hull fitting which should be located
where it can be visually checked for water flow and as
close as practicable to the waterline to reduce noise. All
hose connections shall be secured by means of double/
reversed stainless steel hose clamps. Use teflon tape on
all threaded connections. The following is a summary of
the seawater system installation:
1. Install the speed scoop thru-hull inlet as close to the
keel and as far below the water line as possible, facing
forward. Bed the scoop with a marine sealant de-
signed for underwater use.
2. Install a bronze, full flow seacock on the speed scoop
thru-hull inlet.
3. Install a seawater strainer below the level of the pump
with access to filter.
4. Mount the pump above the strainer and at least one
foot below the waterline.
5. Connect the seacock and strainer with an uphill run of
reinforced marine grade hose.
6. Connect the discharge from the pump uphill to the
bottom inlet of the a/c unit’s condenser coil with 5/8"
hose. Connect the discharge from the condenser coil
to the overboard discharge thru-hull fitting with 5/8"
hose.
7. Avoid loops, high spots or the use of 90° elbows with
seawater hose (each 90° elbow is equivalent to 2.5' of
hose and a 90° elbow on the pump outlet is equivalent
to 20' of hose).
8. Double clamp all hose connections with stainless steel
clamps, reversing the clamps.
9. Use teflon tape on all threaded connections.
10. Connect all metallic parts in contact with seawater
to the vessel’s bonding system including the
speed scoop inlet, strainer, pump and the air
conditioner. Failure to do so will void warranty.