Mermaid MERMAID MARINE AIR CONDITIONING Operating instructions

MERMAID MARINE AIR
CONDITIONING
INSTALLATION
&
OPERATIONS GUIDE
Mermaid Manufacturing of Southwest Florida, Inc.
2651 Park Windsor Drive, Suite 203
Fort Myers, FL 33901
[phone] [phone]
Fax [phone]
E-mail: [email protected]
Web site: http://www.mmair.com

TABLE OF CONTENTS
SECTION 1
(OVERVIEW)
A. Introduction to Mermaid
SECTION 2 (INSTALLATION and OPERATION)
A. Air Conditioner Installation
B. Operation
SECTION 3 (OPERATION and PROGRAMMING)
A. Digital, Programmable Thermostat
SECTION 4 (PUMP RELAY BOX)
A. Introduction
B. Installation
SECTION 5 (MAINTENANCE and WINTERIZATION)
A. Maintenance
B. Winterization
SECTION 6 (THEORY of OPERATION and TROUBLE SHOOTING)
A. Theory of Operation
B. Trouble Shooting
FIGURES:
1. Typical Ducting and Venting Scheme
2. Operational Block Diagram
3. Typical Cooling Water Installation
4a. Wiring Diagram "Cool Only" Models
4b. Wiring Diagram "Electric Heat and Cool" Models
4c. Wiring Diagram "Reverse Cycle Heat and Cool" Models
5. Typical Bleed Off Valve Installation
SECTION 1

(OVERVIEW)
A. Introduction:
Congratulations!! You have just purchased one the most dependable Marine Air
Conditioners on the market today, a MERMAID.
Mermaid supplies pleasure boat owners, custom boat builders, yacht brokers, boat dealers
and marinas around the world with their marine air conditioning needs.
Mermaid air conditioners are manufactured to the highest of quality standards using only
top of the line components and materials assembled by long-term technicians. All of our
air conditioners are modularized, self contained, prewired, precharged and mounted on a
solid foundation of stainless steel. All of our air conditioning components, such as the
evaporator, compressor and condensing coil are manufactured in the USA. All electrical
parts are standard refrigeration components and are available across the entire country,
and around the world. Any four wire 24Volt digital thermostat will operate any standard
Mermaid air conditioner. Don’t forget to see our NEW flush mount digital controller
on our website – www.mmair.com.
Our standard electrical control box does not contain any printed circuit boards or solder.
All electrical connections are "snap on" color coded wires, making part replacement
simple and fast. The electrical box can be unplugged for ease of assembly and service
and the entire installation can be accomplished with standard shop tools. Our upgraded
controller uses state of the art electonics eliminating any contactor or relay noises.
Our warranty is also unsurpassed. For the first 5 years, the Mermaid factory
warranty covers all issues with your air unit. After 5 years, any certified air
conditioner technician, marine, household or commercial, can service any Mermaid
air conditioner model.
SECTION 2
(INSTALLATION and OPERATION)

A. AIR CONDITIONER INSTALLATION:
First, and of foremost importance, the air conditioner and electrical box must be installed
in a non-explosive, dry environment. SEE THE FOLLOWING WARNING.
WARNING
IF THE AIR CONDITIONER OR ELECTRICAL BOX ARE PLACED IN AN
EXPLOSIVE ENVIRONMENT OR EXPOSED TO AN EXPLOSIVE ENVIRONMENT
OR EXPLOSIVE MATERIALS, EXPLOSION COULD OCCUR RESULTING IN
SERIOUS INJURY OR DEATH AND/OR DESTRUCTION OF THE BOAT. THIS
COMPONENT DOES NOT MEET FEDERAL REQUIREMENTS FOR IGNITION
PROTECTION. DO NOT INSTALL IN SPACES CONTAINING GASOLINE
ENGINES, TANKS, LPG/CPG CYLINDERS, REGULATORS, VALVES OR FUEL
LINE FITTINGS. FAILURE TO COMPLY MAY RESULT IN INJURY OR DEATH.
Typical unit mounting spots are under the vee berth, under settee seats, in hanging
lockers, in cabinets or in outside dry lazzeretts and sail lockers. The selected spot must
accommodate the following eight requirements. Everything must fit in and/or be
accessible to the selected spot:
(a) The physical size of the unit and electrical box.
(b) Water in and out hoses.
(c) Electrical power cable for the unit and pump connections.
(d) Air ducting and air splitters.
(e) Mounting of the return air grill to insure the proper volume of return air.
(f) Access to the high pressure switch.
(g) Condensation removal.
(h) Thermostat installation and wiring.
IMPORTANT
READ THE ENTIRE INSTALLATION INSTRUCTIONS BEFORE YOU
COMMIT TO CUTTING OR DRILLING ANY HOLES. REMEMBER
" HOLES ARE FOREVER". MEASURE, MEASURE, THEN MEASURE AGAIN
BEFORE PICKING UP ANY TOOL WITH A SHARP EDGE.
IMPORTANT
LEAVE AMPLE EXCESS OF HOSE, WIRE AND DUCTING WHEN ROUTING
INTO THE AIR CONDITIONER MOUNTING COMPARTMENT TO ALLOW
FOR FINAL POSITIONING OF THE AIR CONDITIONER AFTER ALL
INSTALLATION TASKS ARE COMPLETED.

We will now address each of the above eight requirements in detail:
1. Installing the Air Conditioner Unit:
AIR CONDITIONER DIMENSIONS
UNIT BTU WIDTH LENGTH HEIGHT
5,200 Cool Only 11.5 Inches 15 Inches 11.5 Inches
5,200 Reverse Cycle 12 Inches 18 Inches 11.5 Inches
6,500 11.5 Inches 16 Inches 11.5 Inches
9,000 11.5 Inches 16 Inches 11.5 Inches
12,000 13 Inches 19.75 Inches 13.75 Inches
16,500 13.5 Inches 19.75 Inches 13.75 Inches
24,000 17 Inches 23 Inches 13.75 Inches
The air conditioner needs to be mounted in an area where it will physically fit, as well as
accommodate a properly sized return air grill and any ducting or splitters (Wyes) which
would be attached to the air output collar. In addition, you need to insure there is space
for the water hoses to be connected.
The air conditioner must be securely mounted on a flat surface. If the sole of the boat
(cabin floor) cannot accommodate the size of the air conditioner base plate, a mounting
shelf or platform must be built. Typically the shelf will be made from 3/4 inch marine
grade plywood which can be either fiberglassed or mechanically attached to the boat’s
sole or superstructure. Never screw directly into the hull.
When attaching the unit to the sole of the boat, the superstructure or a fabricated
mounting shelf, always make absolutely positive that the length of the screws being
used to mount the unit will not engage the hull. If there is any question as to whether the
hull may be compromised, an alternative mounting method must be used or another
mounting spot must be located.
The electrical box, unlike the air conditioner, can be mounted in any attitude. It is
attached to the air conditioner by a detachable 40 inch electrical cable allowing it to be
mounted above the unit, on a side wall or bulkhead and, if needed, in a totally inverted
position.
IMPORTANT
IT IS NOT UNCOMMON IN AIR CONDITIONING SYSTEMS FOR
CONDENSATION LINES OR PANS TO BECOME BLOCKED OVER
PROLONGED USE. WHEN SELECTING THE ELECTRICAL BOX
MOUNTING SPOT MAKE SURE THAT IT IS NOT LOCATED WHERE

CONDENSATION WATER CAN COME IN CONTACT WITH IT SHOULD THE
CONDENSATION WATER OVER FLOW ITS PAN. NEVER PLACE THE
ELECTRICAL BOX BELOW THE AIR CONDITIONING UNIT.
WARNING
IF CONDENSATION WATER CONTACTS THE ELECTRICAL BOX
ELECTRICAL SHORTING COULD OCCUR CAUSING FIRE WHICH COULD
RESULT IN SERIOUS INJURY, DEATH AND/OR DESTRUCTION OF THE
BOAT.
We suggest that once you are satisfied that the unit and electrical box, along with all of
the other items required in the air conditioner compartment will fit, that you remove the
air conditioning unit and electrical box or cover them completely until all holes and
construction in the compartment are completed and the area cleanly vaccuumed.
2. Cooling water in and out:
All central marine air conditioning and heating units are water cooled. Cooling water is
provided to the air conditioner via a foot scoop, sea cock, water strainer and pump
assembly all of which are mounted below sea level. Typically the sea cock, water
strainer and pump are installed remotely to the air conditioner (SEE FIGURE 3).
Water In:
Generally, in power boats, the sea cock will be installed in the engine compartment. In
sail boats, because of their more uniform draft characteristics, it is usually installed under
a settee seat or some other compartment more convenient to the air conditioner.
Water is then routed to the air conditioner from the pump via 5/8 inch marine water hose
(also known as ½” I.D. hose) where it is connected to the air conditioner condensing
coil's "water in" connection. Make sure that space is allowed around the unit to make
this connection. The water hose is easily kinked, restricting water flow. If needed, use a
hose barb 90 degree fitting to eliminate any kinking. (These can be found at any pvc
supply store).
An additional length of 5/8 inch marine hose (again, ½” I.D.) is connected to the
condensing coil "water out" connection. Cooling water passes through the condensing
coil and routed through this hose to the "water out" thru-hull fitting which will be
installed above water level in the side of the boat’s hull (SEE FIGURE 3).
IMPORTANT
THE SEA COCK, WATER STRAINER AND WATER PUMP MUST BE
INSTALLED BELOW SEA LEVEL. THE SEA WATER PUMP IS NOT SELF
PRIMING AND RELIES ON WATER SEEKING ITS OWN LEVEL ALONG
WITH THE HYDRAULIC PRESSURE OF THE BOAT TO ATTAIN PRIMING
OF THE PUMP.

WARNING
BEFORE DRILLING THE MOUNTING HOLE FOR THE SEA COCK THE
ENTIRE BOAT MUST BE OUT OF THE WATER. DRILLING THE SEA COCK
MOUNTING HOLE WITH THE BOAT IN THE WATER COULD CAUSE
EXTREME FLOODING AND SINK THE BOAT OR CAUSE SEVERE WATER
DAMAGE TO EQUIPMENT IN THE BOAT.
IMPORTANT
WHEN SELECTING THE SPOT FOR THE SEA COCK, BEFORE DRILLING
THE HOLE, MAKE SURE THAT THE PUMP AND WATER STRAINER CAN
BE INSTALLED IN THE SAME ADJACENT AREA AND REMAIN BELOW SEA
LEVEL. ALSO CHECK THE OPERATION OF THE BALL VALVE SHUT OFF
HANDLE ON THE SEA COCK FOR ANY POSSIBLE INTERFERENCE ONCE
INSTALLED.
When selecting your sea cock mounting spot, you should also try to select a spot where
the pump and water strainer are a maximum distance of 2 feet from the sea cock. We
realize that in some boats it is not possible to incorporate the two foot rule. However,
remember the closer you keep these three items together, the fewer pump priming
problems will be experienced.
Once you are sure that all components will fit in the spot selected and remain below sea
level and the boat is totally out of the water, you are ready to cut the sea cock mounting
hole. (SEE WARNING ABOVE)
IMPORTANT
BEFORE CUTTING YOUR SEA COCK MOUNTING HOLE CHECK THE
OUTSIDE HULL IN THE AREA YOU WILL BE CUTTING TO MAKE SURE
THAT THERE ARE NO RIBS OR OTHER HULL VARIATIONS WHICH WILL
NOT ALLOW THE SEA COCK FOOT SCOOP TO MOUNT FLAT AGAINST
THE HULL. IF THERE IS ANY CONCERN, WHAT-SO-EVER, DRILL A
SMALL PILOT HOLE FIRST WHICH CAN BE EASILY SEALED IF
INTERFERENCE EXISTS.
If you are using a sea cock assembly furnished by Mermaid, we recommend that a 1-1/16
inch hole saw be used to make this hole. If you are using a sea cock purchased
elsewhere, you must use the appropriate hole saw for that specific sea cock.
IMPORTANT
DRILL THE 1-1/16” SEA COCK MOUNTING HOLE AND PILOT HOLE AT
THE SAME ANGLE AS THE HULL. THIS WILL INSURE THAT THE FOOT
SCOOP LIES FLAT AGAINST THE HULL.
Once the sea cock hole is drilled, inspect the hole to determine if your boat has a
"corded" hull. That is, a hull not of solid fiberglass, but two layers of fiberglass
separated by balsa or foam. When not properly sealed, “cording” acts like a wick,

absorbing sea water into the hull. If the hull is "corded," obtain a fiberglass sealing kit
from your local marine supplier to seal the cording before installing the sea cock,
eliminating the possibility of "water logging" your hull. This is also true of water out
thru-hulls.
IMPORTANT
FAILURE TO SEAL A “CORDED” HULL MAY RESULT IN SERIOUS
DAMAGE TO THE BOAT’S STRUCTURE.
Note: The threads on the foot scoop end about 3/8 of an inch from the actual foot scoop.
If after drilling the hole for the foot scoop you discover that your hull is thinner than 3/8
inch, you will need to reinforce the hull with a 6” x 6” pad to “shim up” to insure the nut
tightens correctly. We usually use ¾ inch marine grade plywood to fashion the pad.
Apply fibreglass on both sides of the pad and affix to the inside of the hull. After the
fiberglass has cured, assuming that you had already drilled the hole for the foot scoop
through the hull, then drill through the pad from the outside of the hull to insure proper
alignment through the pad and hull. Do not attempt to drill through the pad from the
interior of the boat.
Before installing the sea cock, apply a bead of marine sealant around the foot scoop and
mounting post. We recommend "3 M" 5200 brand or a sealant brand of equivalent
quality.
Insert the foot scoop up into the boat with the scoop intake facing toward the bow
(foreword) and secure it to the hull with (2) 1/4 inch flat head s/s screws. We
recommend that the screw holes be predrilled with the appropriate size drill bit to
eliminate cracking of the outer gelcoat of the hull. When drilling the holes, take care not
to drill through the hull. Use a hand held screwdriver to eliminate stripping the hole out.
These screws are intended only to keep the foot scoop from turning under the boat when
the inside fastening nut is tightened down.
Inside the boat, attach the bronze retaining nut to the sea cock threaded post. Using an
appropriate size tool or slip jaw pliers, tighten the nut to the hull snugly to insure that it
will seal against the hull. After tightening the nut completely, cover it with a thick coat
of marine sealant from the post out to about 1 inch from the nut onto the hull.
Now that the foot scoop is mounted, the ball valve (shut off valve) can be attached.
Generously coat the foot scoop post threads with marine sealant and screw the ball valve
onto the post. After the ball valve is fully tightened on the post, check the action of the
shut off arm to make sure it can be fully opened and closed without interference with the
boat structure, the water hoses when they are attached or any other obstruction. If
interference is encountered, turn the ball valve on the post to a position that allows proper
operation. CLOSE THE VALVE, REPEAT, CLOSE THE VALVE!
To connect your water hose you will need a 90 degree "thread to hose barb" fitting and a
¾ inch “closed end nipple.” Using 3M 5200, thread the ¾ inch “closed end nipple” to

the seacock, then fasten the 90 degree thread to hose barb, with 5200 on to the ¾ inch
nipple. The “closed end nipple” is the bronze threaded pipe open on either end.
The water strainer and pump can now be mounted, but first you must get each component
fully assembled and ready to mount. The water strainer and pump brackets must be
securely mounted on a flat surface. Do not mount on the sole of the boat (cabin floor). If
a nearby bulkhead cannot accommodate the size of the mounting brackets, a mounting
shelf or platform must be built. Typically the shelf will be made from 3/4 inch marine
grade plywood which can be either fiberglassed or mechanically attached to the boats
sole or superstructure. Never screw directly into the hull.
When attaching the mounting brackets to the superstructure or a fabricated mounting
shelf, always make absolutely positive that the length of the screws being used to mount
the bracket will not engage the hull. If there is any question as to whether the hull may
be compromised, an alternative mounting method must be used or another mounting spot
must be located.
The Water Strainer:
If you are using a Mermaid furnished water strainer, it will come with (2) 3/4 inch thread
to hose barb hose fittings. Attach these fittings to the strainer using an ample amount of
marine sealant on the threads. Again, if you are using a Mermaid strainer, locate the
strainer mounting bracket. This is the bracket with a large hole in it. Unscrew the plastic
bowl from the strainer body and place the strainer body in the hole. Replace the plastic
bowl on the strainer body to lock the strainer in the bracket. This is meant to be a loose
fit to facilitate cleaning when the strainer is dirty.
Water will flow from the sea cock through the strainer into the inlet of the pump. Ideally,
the strainer and pump will be mounted so the water flow is at a slight upward grade to
help eliminate air locks. Once you have settled on the mounting locations of the strainer
and pump, attach each of their mounting brackets with (2) 1/2 inch s/s pan head screws.
Note that the strainer is directional. Take notice of the stamped arrow on the top of the
strainer when installing and insure the arrow is pointed toward the flow of water to the
air conditioner unit
Ideally, the pump should be mounted with the external 5/8” water discharge (the line that
goes TO the air conditioner) pointed vertically. However, there is an alternative position.
The pump can be mounted with the external 5/8” water discharge on the side. To
accomplish this successfully, it is IMPERATIVE to have the actual pump discharge at
the highest level. In this position, the external 5/8” discharge will be located on the
upper right corner of the pump with the ¾” intake facing you. In this alternative position,
the pump will still operate as originally designed. Failure to follow either of these
recommendations will void any warranty with the pump.

Never screw the pump directly to the hull. If a stringer or other structure is not
handy, you may have to fiberglass a mounting board to the hull to accept the
mounting screws.
Note: If you are supplying cooling water to more than one air conditioner a larger
GPH pump is required. Follow the mounting instructions furnished with the larger
pump. Also a “tee fitting” must be used on the discharge side of the pump to run
cooling water to each unit.
Using the appropriate length of the 3 feet of 3/4 inch red stripe marine hose and (2) s/s
hose clamps per connection, connect the sea cock, water strainer and pump together.
The Pump:
IMPORTANT
ON DUAL AIR CONDITIONER INSTALLATIONS, AN IN-LINE SHUT OFF
VALVE MUST BE INSTALLED IN EACH OF THE “WATER IN” LINES TO
ALLOW OPERATION OF EITHER AIR CONDITIONER IF ONE UNIT IS
REMOVED FOR SERVICE.
WARNING
ALL HOSE CONNECTIONS MUST BE SECURED USING TWO (2)
STAINLESS STEEL HOSE CLAMPS. FAILURE TO DOUBLE CLAMP ALL
HOSE CONNECTIONS MAY RESULT IN A HOSE DISCONNECTING WHICH
COULD CAUSE FLOODING DAMAGE AND /OR SINKING OF THE BOAT.
DAMAGE TO THE AIR CONDITIONER FROM EXCESSIVE AND
RECURRENT LEAKING DUE TO FAILURE TO DOUBLE CLAMP ALL
CONNECTIONS WILL VOID THE WARRANTY.
The 5/8 inch blue stripe water hose (or black reinforced hose – deluxe kits) and the pump
power cord may now be routed to the air conditioner compartment. If the power cord
that is permanently attached to the pump is not long enough to be routed to the air
conditioner compartment it must be extended using 16 gauge boat power cable. Cut off
the connector on the end of the pump power cord (if present) and splice in the 16 gauge
boat power cord. Appropriate electrical splicing must be used and the connection must
be water proof and secured well above the bilge water level to insure that the connection
will always remain dry. We have provided a piece of heat shrink tubing to ensure proper
insulation after connectors are applied.
WARNING
FAILURE TO KEEP THIS ELECTRICAL CONNECTION DRY COULD CAUSE
FIRE AND DESTRUCTION OF THE BOAT.
Note: Loss of prime on the water pump is a common occurrance. An optional
"Bleed Off " valve is available that aids in regaining pump prime. If you are using
this option, it must be installed at this stage of the installation at the output of the

pump (SEE FIGURE 5). Remember, all water hose connections must be secured
using double stainless steel clamps.
To install the bleed off valve, attach a short length of blue tracer hose to the water-out on
the pump and secure the bleed off valve on the other end of the hose. Attach the blue
tracer hose that you are running up to the air conditioner unit to the other end of the bleed
off valve. Close the bleed off valve. At each connection point, use two stainless steel
hose clamps to properly secure the attachment.
WARNING
AFTER INSTALLING "BLEED OFF" VALVE, MAKE SURE VALVE IS IN THE
"OFF POSITION". THAT IS, THE POSITION WHERE WATER CANNOT
FLOW INTO THE BILGE. FAILURE TO CLOSE THIS VALVE WILL RESULT
IN FLOODING WHEN THE BOAT IS PLACED BACK INTO THE WATER
POSSIBLY CAUSING SERIOUS WATER DAMAGE OR SINKING OF THE
BOAT.
After cutting off the three prong plug, temporarily tape the pump power cord to the end
of the water hose and route both items together to the air conditioner compartment (See
Following Note). Secure both items along the way at (1) to (2) foot intervals to
eliminate sagging or kinking due to boat or wave action. We will connect the cable and
hoses to the air conditioner later in the installation.
Note: If you are using a single pump to supply cooling water to two air conditioners,
you must install a Pump Relay Box. Before running pump power cable please see
Section 3 entitled "Pump Relay Box".
Water Out:
The "water out" thru-hull can be mounted any place on the boat’s hull that is a
minimum of (6) inches above the water line. If using a Mermaid supplied thru-hull
fitting, the required hole size is 1-1/16 inches so the same hole saw used for the "water
in" sea cock can be used. Typically the "water out" thru-hull will be mounted close to
the air conditioner to eliminate the extra work of having to route the water hose in
difficult places.
The water line on the outside of the hull will give a good base line to determine the lower
limit of the hole location. If your boat is new or kept high and dry, you will have to place
it in the water to determine the water line. Once you know the water line you can
determine where on the inside of the boat you can drill, staying above the water line and
out of view. This hole should always be drilled from the inside of the boat. Once you
have settled on a location for the hole, check outside again to insure you will be above
water level and that you will be clear of any outside ribs or other interference which will
not allow the outside lip of the fitting to lay flat against the hull. Always drill a pilot
hole and check outside before committing the larger hole.

When installing the thru-hull fitting apply an ample amount of marine sealant to the
outside lip of the fitting and its mounting post. If possible, have someone hold the
outside of the fitting to keep it from turning when you attach the retaining nut from the
inside. Be careful not to over tighten the nut. Use two (2) s/s hose clamps to attach the
hose to the thru-hull fitting. Route this hose into the air conditioner compartment where
it will eventually be connected to the condensing coil "water out" fitting.
3. Electrical Power:
Both the air conditioner and pump require 115 vac, 60 hertz power to operate. (220v
models are available) This power is obtained from the master 115 vac Circuit Breaker
Panel in the boat. Power is routed from this panel to the air conditioner. The air
conditioner will then supply power to the pump as required.
WARNING
BEFORE PROCEEDING FURTHER, CHECK TO INSURE THAT ALL 120 VAC
POWER HAS BEEN DISCONNECTED FROM THE BOAT AND CIRCUIT
BREAKER PANEL. FAILURE TO DO SO COULD CAUSE ELECTRICAL
SHOCK RESULTING IN SERIOUS INJURY OR DEATH
Using 12 gauge boat power cable, beginning on the inside of the Main Circuit Breaker
Panel, route the cable to the air conditioning compartment. Leave ample excess before
cutting to allow for positioning of the unit’s electric box at time of final hook up.
Connection of this cable to the air conditioner electrical box will be covered later.
At the circuit breaker panel locate a blank hole and install a 20 amp circuit breaker of the
same style as those breakers currently in the panel. Note that all of the breakers are
connected together on one side by either a buss bar or individual jumper wires. Connect
the new breaker in the same manner. Remove about 12 inches of the outer insulation
from the end of the boat cable to expose the inner wires. This cable contains (3) inner
insulated wires which are "BLACK", "WHITE" and "GREEN' in color. Using the
appropriate wire connectors, as those currently used in the panel, connect the wires as
follows: "BLACK" to the remaining terminal on the circuit breaker, "WHITE" to the
buss bar connecting all "WHITE" wires together and the "GREEN" to the buss bar
connecting all "GREEN" wires together. Included in the installation kit, if you purchased
that option, is a small Mermaid A/C sticker. Place this on your breaker panel to properly
denote the air conditioner circuit breaker. The Main Circuit Breaker Panel can now be
closed up.
FOR 220V UNITS THAT HAVE A 4 WIRE SYSTEM WITH RED, BLACK,
WHITE, AND GREEN WIRES, THE FOLLOWING APPLIES:
BLACK GOES TO BLACK (HOT)
RED GOES TO WHITE (NEUTRAL)
GREEN GOES TO GROUND
WHITE GETS CUT OFF AND NOT USED

4. Air Ducting and Splitting:
Regardless of the btu size of the air conditioner, at least one vent must be within 4 to 5
feet of the unit. Insure though, that the airflow is not directed back towards the return air
grill. In the case of the 16,500 btu unit, the largest grill is required to be the closest grill.
Improper ducting accounts for the majority of marine air conditioning problems. Though
there are exceptions to the rule, the following rule of thumb applies to the number and
size of the supply air grills required for each btu size air conditioner:
5,200 btu unit: (2) four inch grills.
6,500 btu unit: (2) to (3) four inch grills.
9,000 btu unit: (3) to (4) four inch grills
12,500 btu unit: (Cool only) (3) or more four or six inch grills.
(With electric heat) Same as cool only.
(With reverse cycle heat) (1) six inch grill and (2) or more four inch
grills.
16,500 btu unit: (1) six inch grill and (2) or more four inch grills
24,000 btu unit: Minimum of three 6 inch vents/grills
When it comes to ducting, a general rule is that more grills are always better. Any time
more than one supply air grill is used, an air splitter is required. Air splitters come in a
variety of sizes and styles. Splitters may be mounted directly on the unit output air
collar, or placed in line a short distance from the unit where space restrictions preclude
mounting the splitter on the unit. Additional air splitters may be used at various intervals
along the duct routing to distribute air to multiple cabins. Wye’s are always preferable to
Tee’s. We do not use Tee’s for air splitters. Refer to FIGURE 1 for a typical ducting
scheme.
When surveying the boat for your air conditioner mounting spot, you must also decide
what size supply air grills will be used and where they will be mounted. The size of the
grill will dictate the size of the ducting. It is also important that you decide upon using
insulated or non-insulated air duct before beginning. Generally the ducting will be 4
inch, 5 inch or 6 inch diameter non-insulated duct. If you decide on insulated duct, add 2
inches to the outside diameter of the non-insulted duct. Typically power boats will use
non-insulated duct and sail boats insulated. Except for passing through a hot engine
room, the only benefit in using insulated duct is preventing condensation forming on the
exterior of the duct (sweating) which could cause water staining on fabrics. Because sail
boats generally sit lower in the water and have less glass than power boats, they tend to
produce more duct condensation than the power boat, however, space restraints may not
allow the total use of insulated duct and you may need to use a combination of the two
duct types. Some situations will require the use of non-insulated duct, but will require
insulating the duct after the installation with a insulation wrap. All duct runs should be
as short and straight as possible. Every 90 degree turn in a duct run reduces
performance by about 14%. Ducting should be tied to a permanent structure every foot

or two to eliminate sagging. Using tie wraps, insure ducting is appropriately fastened to
each supply air grill.
Another important consideration is the physical size of the supply air grills. Four inch
round grills require a 4.5 inch hole and the duct merely slides over the neck of the grill.
A four inch rectangular grill usually measures 4x8 inches for the hole size but also
requires a plenum or transition box behind the grill, also measuring 4x8 inches and
extending approximately four inches behind the wall. These boxes are needed to attach
the air duct to the grill and are required for every size rectangular supply grill.
We suggest that you lay out a simple sketch of your boat on paper and then over lay your
ducting scheme. Take this diagram on board and make measurements to be assured that
the scheme is attainable. Remember once committed, "holes are forever". If you need
help or would just like to discuss your installation with an experienced technician, give
us a call. Mermaid will be happy to aid you in the layout of your duct and venting
scheme.
5. Return Air :
Sufficient cabin "return air" back to the air conditioner is just as important to the cooling
of the boat and the performance of the air system as "supply air" is going into the cabin.
Air conditioning is just that, conditioning of the air in a closed environment by
continually pulling it back into the air conditioning unit, removing heat and moisture and
sending it back into the room or cabin.
It is important that the same volume of air being forced into the cabin is allowed to return
to the air conditioner. As long as the physical opening of the return air grill is at least the
minimum size specified below for your specific air conditioner, the actual shape of the
grill is not important. Where it is not possible to have a single return grill multiple grills
may be used. Make sure that the air conditioner evaporator (the front of the air
conditioner resembling an automotive radiator) is not blocked or restricted from
receiving the cabin return air. It must always be at least 3 or more inches from any bulk
head or structure. Never stow items such as life preservers, bedding or other items of this
nature between the evaporator and the return air grill. To allow better access to the air
conditioner compartment during installation, do not attach the return air grill until the
unit has been completely installed.
RETURN AIR REQUIREMENTS
MODEL BTU SQ. INCHES OF RETURN
M-5 5,200 96
M-6 6,500 96
M-9 9,000 96
M-12 12,000 140
M-16 16,500 140

M-24 24,000 140
6. High Pressure Switch Access:
All Mermaid marine air conditioners utilize a manual High Pressure safety switch. This
switch monitors the system’s high pressure any time the compressor is running. If a
condition occurs that causes the system high pressure to rise to a level that could damage
the compressor, the switch will activate and remove power from the compressor and
pump. Once activated, this switch must be manually reset. The switch is a green
cylindrical object with a red button . You must provide enough space to reach your
hand into the compartment or cut an access hole in the cabinet above or alongside
the switch to reset it after activation.
When the air conditioner is operating in the cooling mode only the lack of sufficient
cooling water can cause high pressure. In reverse cycle heat pump units operating in the
heating mode, high pressure can only be created by over heating of the evaporator which
is generally caused by insufficient return air or restricted supply air. The trouble
shooting guide covers these and other problems.
7. Condensation Removal:
Depending on the btu rating of your unit and the actual run time, the air conditioner will
remove from one to five gallons of water (condensation) from the air in a 24 hour period.
This water collects in the condensation pan to be drained out. Most boat owners will
drain this water into the bilge for removal overboard by the existing bilge pumps. When
running your condensation hose remember that condensation flows only by gravity and
the hose must never rise up any where along the way or condensation will backup into
the pan and overflow. This will not sink your boat, but it can get the surrounding area
very wet. In many boats it is not possible to drain to the bilge, and the condensation must
be removed by other means, such as a “Mermaid Condensator Kit”. Please contact your
Mermaid dealer or the factory for other options to remove condensation.
8. Mounting The STANDARD Thermostat: (Programmable + Non-Programmable)
NOTE: SEE SEPARATE FX-1 THERMOSTAT OWNERS AND OPERATIONS
MANUAL FOR INSTALLATION AND INSTRUCTIONS PERTAINING TO THIS
PRODUCT. THIS MANUAL WILL BE INCLUDED UPON THE PURCHASE OF
THIS PRODUCT
The 24v thermostats come with a 20 foot power cable. One end of the cable attaches to
the BLACK terminal board on the side of the air conditioner electrical box. The other
end is wired into the black teminal board inside the thermostat itself.
The thermostat may be mounted on any flat wall surface with space behind the wall to
run the thermostat power cable out of view and still reach the air conditioner electrical
box. Ideally, the thermostat will be about 2/3 up on an interior wall, out of direct sun

light and not directly in front of a "supply air" vent, nor next to a hatch. It is important
that the thermostat be located where it is sensing “true” cabin temperature rather than a
“dead” spot, or getting incorrect readings from sunlight or sampling air near a constantly
opening/closing hatch thereby reading “outside” air rather than inside air.
Once you have selected the spot, remove the face of the thermostat from the back panel
and install by following these instructions:
1. Depress the thumb tab on the bottom of the thermostat and carefully pull the two
pieces apart.
2. Lift the thermostat up and off the subbase.
3. Drill a 1/4 inch hole in the wall and feed the cable through. With the cable behind
the wall, the thermostat back plate can be pressed flat to the wall. Now mark the
mounting hole spots on the wall. Only two 1/2 s/s screws are needed to secure
the thermostat. Predrill the holes before screwing to the wall. (Exact vertical
mounting is necessary only for appearance).
4. Route the thermostat power cable, out of view, back to the air conditioner
compartment. Secure the cable at appropriate spots along the way to prevent
sagging or looping so it will not be inadvertently snagged by stowed equipment.
5. To connect your gray thermostat wire to the thermostat AND the black electrical
box, follow these procedures:
A. On both ends of the gray wire, cut away the gray insulation being
careful not to cut into the RED, GREEN, WHITE, AND BLACK
wires.
B. Intall the four fork terminals (provided) by stripping back ¼” of each
of the colored wires and crimping the terminals to the wires. Ensure
with your crimp that you have a solid grasp of the wire, not insulation.
C. The four fork terminal connection will be connected to the black
terminal block on the upper side of the black electrical box for the air
conditioning unit. Follow the R = RED, G = GREEN, W = WHITE, B
= BLACK color code for the connections at the electrical box.
D. For connections at the thermostat, install (if already not done so) the
RED “jumper” wire (provided) between the “RH” and “RC” terminals
inside the subbase of the thermostat.
E. Carefully insert the other end of the previously ¼” stripped gray wire
into the appropriate locations. Follow the chart below for guideance.
•Red wire = “RH/RC” connection on thermostat – either “RH” or “RC”
lead is acceptable as the red jumper wire (provided) connects these
terminals together. This is the unit’s 24 volts from the transformer when
heating or cooling is called for.
•Green wire = “G” connection on thermostat. This is the fan operation
wire.
•White wire = “W” connection on thermostat. This wire is for heat – if
your system is a heating/cooling unit.

•Black wire = “Y” connection on thermostat. This wire is for the cooling
mode.
9. Putting it all together:
At this point the unit can be placed back into its compartment, and all the power, water
hoses and ducting should be available and ready to connect:
IMPORTANT
DO NOT CUT ANY EXCESS WATER HOSE , WIRE OR DUCTING BEFORE
DETERMINING THAT ALL REQUIREMENTS CAN BE MET WHEN UNIT IS
SECURED.
Position the air conditioner unit so "water in" and "water out" hoses can be attached
without kinking. Now check the air splitter and ducting for fit. Make sure that all
ducting bends are as slight as possible to keep air restriction to a minimum. Once you are
satisfied with the compromises you have made between the water and the air
connections, locate a place for the electric box. Remember this box may be mounted
in any attitude, but must never get wet. Now, before cutting any excess hose, etc.,
check to see that all four air conditioner mounting screws can be installed without
making contact with the hull.
Note: Enclosed in the kit is a "S" shaped flat metal bracket with a hole drilled in
one end of the "S". This is the "hold down bracket" for the fourth mounting screw.
This bracket will slip over the side of the evaporator condensation pan and the
fourth mounting screw will be used to secure it. Because this bracket can be placed
anywhere on the pan, you have a good deal of latitude in tight situations for
installing the screw.
The air conditioner unit may now be secured. For vibration reduction, ensure the
included foam insulation mounting pad is under the air conditioning unit. Do not secure
the electric box at this time.
Next, cut the water hoses to fit and attach each hose with two s/s hose clamps. Make sure
that each hose is placed on the proper end of the condensing coil as marked ("water-
in/water-out"). BE SURE TO REMOVE THE PLASTIC CAPS ON THE WATER-
IN/WATER-OUT ENDS OF THE CONDENSING COIL. THESE WERE
INSTALLED FOR SHIPPING PURPOSES ONLY.
Connect the clear 3/8 inch hose to the nipple on the condensation pan. This hose
generally fits snugly without a hose clamp.
Using the full length of the electric box cable or unpluging the cable, bring the box out to
where it is more convenient for you to work with in making all the required connections.
(SEE WARNING BELOW)

WARNING
MAKE SURE THAT ALL AC POWER TO THE BOAT HAS BEEN
DISCONNECTED. FAILURE TO REMOVE ALL BOAT AC POWER COULD
RESULT IN ELECTRICAL SHOCK CAUSING SERIOUS INJURY OR DEATH.
Determine which power cable is from the pump (16 gauge cable) and strip the outside
insulation back about six inches. Then strip each of the three individual wires back about
1/4 inch. Facing the WHITE terminal block on the side of the electric box, locate the
connection labeled "PUMP". Using the appropriate size flat blade screw driver, open the
connections marked "WHITE" and "BLACK" and slide the "BLACK" and "WHITE"
wires into the open connector slots for each color. Make sure that no bare wire is
exposed outside the connector slot and tighten the screw. Pull each wire to insure it is
tightly connected. Using an appropriate size electrical ring connector, attach the
"GREEN" wire to the "GROUND" post located on the mounting bracket.
WARNING
HAVING ANY BARE WIRE EXPOSED OUTSIDE THE WHITE TERMINAL
BLOCK COULD CREATE ELECTRICAL SHOCK CAUSING SERIOUS
INJURY OR DEATH.
Next, locate the 115 (or 220) vac power cable from the Circuit Breaker Panel (12 gauge
cable) and connect this cable to the electric box WHITE terminal block by inserting the
wires into the connector slots marked "POWER". To do this, follow the same procedure
as with the pump connections. (SEE ABOVE WARNING ON EXPOSED BARE
WIRE CONNECTIONS)
Locate the BLACK terminal strip on the outside of the electrical box (just above the
power terminal block) and attach the thermostat power cable. This terminal strip is color
coded for easy determination of which wire is attached to which connection ("RED" to
"R", "GREEN" to "G" etc.). Any excess cable may be neatly coiled next to the box or
cut off and shortened to fit. If excess is cut off, do not make connections with bare wires,
install new connectors on each wire.
IMPORTANT
MAKE SURE THAT YOU SECURE ALL LOOSE WIRING AND HOSES WITH
APPROPRIATE SIZE NYLON CLIPS OR CABLE TIES TO MAKE SURE THAT
BOAT OR WAVE ACTION WILL NOT CAUSE STRESS OR KINKING.
NOTE:
THE FX-1 THERMOSTAT CONTROL BOX IS PRE-WIRED FOR YOU. ONLY
ELECTRICAL (110V / 220V) AND PUMP CONNECTIONS ARE REQURIED ON
THE CONTROL BOX INSTALLATION FOR THIS PRODUCT.
Now connect the air splitter and air ducting. You may use appropriate size cable ties or a
high grade ducting tape. If the air splitter is attached directly to the unit air collar, we

recommend that you secure it with one or two 1/2 inch s/s screws along with duct tape or
foil tape.
Now, attach the return air grill and your installation is completed.
B. SYSTEM OPERATION:
Note: If the boat has not been placed back in the water, do so now. The air
conditioner requires proper cooling water to operate.
1. Priming The Pump:
a) Because marine air conditioner pumps are not self priming, generally, the pump may
need priming each time the boat is removed from the water and then placed back into the
water. Priming may also be required when the water strainer is cleaned or when the boat
has returned to the dock after being used. Normally, once primed at the dock, the pump
will retain its prime until used or taken in and out of the water as mentioned above.
b) To prime the pump, open the sea cock and view the water flow through the clear red
stripe hose. If the water flows into the input of the pump with no air bubbles in the
strainer or hose, the pump is primed. However, if air bubbles are present you must
loosen the hose clamps on the pump discharge hose (blue stripe or black reinforced) and
momentarily remove the hose. Water will immediately flow from the pump breaking the
air lock. Quickly replace the hose and retighten the hose clamps. The pump is now
primed. If you have installed the optional "Bleed Off" valve, it is usually not necessary
to remove the discharge hose from the pump. Open the "Bleed Off" valve until water
flow is observed and then close the valve. (Ideally this water should be directed to the
bilge or a container that can be later discharged overboard).
WARNING
AS STATED EARLIER, FAILURE TO CLOSE THE "BLEED OFF" VALVE
WILL RESULT IN FLOODING AND POSSIBLE SINKING OF THE BOAT.
Note: If water does not flow from the pump when the discharge hose is removed or
from the "Bleed Off" valve when opened, the pump is not below the water line of
the boat and must be remounted.
2. Power:
a) With the air conditioner circuit breaker in the "OFF" position connect the dock power
cord back to the boat.

b) Place the main circuit breaker and the air conditioner circuit breaker in their "ON"
positions.
3. Water Out:
a) Once the air conditioner starts, immediately go out on deck and check that water is
coming out of the "water out" thru-hull. Once all of the latent air is forced from the
hoses a steady stream should be present with enough force that the water stream clears
the side of the boat hull.
b) If the water flow is not present or weak, the pump was not properly primed. Shut the
air conditioner off and prime the pump as described above. (You may also attempt to
prime via the bleed off valve ONLY while the air conditioner is running – allowing for
the pump to function). If the air conditioner is allowed to run without water for more
than a minute, the High Pressure switch will activate and disengage power from the
compressor. Once the water problem is corrected, you will need to reset the High
Pressure switch by pushing the extended metal tab in with your finger. The High
Pressure switch is located on the top of the 6,500 BTU, 9,000 BTU, 12,000 BTU,
16,500BTU, or 24,000BTU air conditioner and is on the upper side of the 5,200 BTU
unit.
4. Checking Out The System:
a) Air Flow: Once the air conditioner is running and water flow is present, check each
supply air vent to make sure it is open and cooling air is present. If air flow is not
present, check ducting for good air tight connections and that kinking or sagging of the
duct has not occurred.
b) Water Connections: Check each water connection beginning at the sea cock, then the
water strainer, pump, the air conditioner and the "water out" thru-hull. No water leaks
should be present. Also, at this time, it is always good to check the hose clamps for
tightness in case one may have been overlooked during installation.
c) Condensation: By now the unit should be producing condensation. Check to make
sure that condensation is flowing freely into the condensation hose. If the unit has not
produced sufficient condensation to check the flow, pour water into the condensation pan
to see that in fact it is flowing freely.
d) The Air Conditioner Unit: The unit should be free of vibration noises and the sides of
the evaporator should be sweating and cool all the way up. If vibration noise is present,
adjust the unit mounting screws. If this does not correct the noise, use a socket wrench
with an extender or a large phillips head screwdriver (or 5/16 nut runner if applicable)
and tighten down the compressor mounting bolts until the vibration noise stops. In some
situations, although very rare, it may lessen the sound vibration to actually loosen the
compressor bolts a very, very small amount. In some boats where a mounting shelf was
installed, sound will travel through the board to the side walls and a "speaker effect" will