KOOL-TEMP ™
MARINE REFRIGERATION/FREEZER
UNITS
INSTALLATION INSTRUCTIONS
AND OWNER’S MANUAL
PRODUCED BY:
MERMAID MANUFACTURING OF
S.W., FL, INC.
2651 PARK WINDSOR DRIVE
SUITE 203
FORT MYERS, FL 33901
800-330-3553
239-418-0535 – P
239-418-0538 – F
SECTION 8 (ELECTRICAL)
A. Power Supply
B. Wire Size
C. Overload Protection
D. Connections, Power
E. Connections, Thermostat
F. Connections, Fan
SECTION 9 (TROUBLESHOOTING GUIDE)
A. Note
B. Compressor Not Running, No Start Attempt
C. Compressor Attempts To Start, Or Starts And Stops Shortly After
D. System Runs, Box Temperature Too High
E. System Runs, Box Temperature Too Low
F. Excessive Frost Build Up
SECTION 1
(OVERVIEW)
A. Introduction:
Congratulations!! You have just purchased one the most dependable Marine
Refrigeration/Freezer units available 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, refrigeration, and
dehumidification needs.
Mermaid refrigeration/freezer systems 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 refrigeration/freezer units are modularized, self contained, pre-
wired, pre-charged and mounted on a solid foundation of stainless steel. All electrical
parts are standard refrigeration components and are available across the entire country,
and around the world.
As you will come to find, Mermaid Marine takes great pride in the products and services
they provide to their customers. Mermaid believes there is no such thing as enough
customer service and, in today’s market, this is a must! Whether you purchased
Mermaid’s 12/24VDC model or our 12/24VDC & 110V with Auto Change-Over model,
we are sure you will be pleased with their performance.
Mermaid provides a one-year warranty on the refrigeration/freezer products and a five-
year warranty on their marine air conditioning line. In the unlikely event of any issue,
Mermaid will take the necessary steps to ensure your complete satisfaction.
Thank you for the business and we look forward to hearing of your success!
Regards,
John D. Trotter
Vice President
SECTION 2
(CONDENSER INSTALLATION)
A: Mounting Position:
These units should be mounted in a cabinet or area where they will not be susceptible to
physical or water damage. There should be adequate ventilation of the compartment to
allow the warm air to be expelled, but not so that it can be immediately drawn back in.
The efficiency of the system depends mainly on the temperature of the air entering the
condenser. Re-circulating the heated air back into the condenser in a sealed or poorly
ventilated cabinet will result in poor system performance, as will drawing in air from a
heated space, i.e. engine room.
B: Installation
These units are designed to be mounted on a surface where adequate ventilation can pass
around the unit. This can either be from an adjacent cabinet or a custom “return air”
grille no smaller than a 6” x 6” grill.
Mount the unit by securing with screws through the base, making sure that the condenser
lines up with the ventilation hole. Best results are achieved with the unit if the condenser
frame is sealed against the bulkhead with foam rubber tape or equivalent. The ventilation
hole should be covered with a suitable grill to protect the condenser fins from damage, &
for aesthetic appeal. The grill must be of sufficient size & construction so as not to
impede air flow.
SECTION 3
(CONTROL MODULE)
A: Electronic Control Module:
The Electronic Control Module is an integral part of the Danfoss BD35/50F compressor
system. It transforms direct current power from the vessels batteries into alternating
current to run the compressor. Never attempt to run the compressor directly from the
batteries or other power source.
B: 12/24VDC, 12/24VDC & 110V w/ Auto Change-Over
A supply voltage of either 12 or 24 volts dc is required, & the Module will run from
either without any special settings or adjustments, switching to 24v mode if the voltage is
above 17v. The Mermaid unit is also available in 12/24v & 110v with Auto Change-
Over. Should this be your model, the unit will automatically detect either 110v or
12/24v. The unit will run on the stronger of the two power sources. Should 12/24v be
available and 110v is introduced (via shore power or generator) the unit with
automatically switch to this power source. If 110v is lost, the unit will wait 60 seconds
before automatically switching back to 12 or 24 volts dc.
SECTION 4
(SAFEGUARDS)
Protection from the following is provided
A: Low Voltage:
To prevent the batteries from being totally discharged, the compressor will be stopped if
the voltage at the terminals on the Module falls below 10.6 volts (23.4), & will not re-
start until the voltage rises above 11.7 (24.0) volts.
B: High Voltage:
If the voltage exceeds 17v, the Module stops the compressor & switches into 24v mode,
but will not attempt to start the compressor until the voltage reaches 24v.
C: Compressor Non-Start:
If the compressor does not start, the Module will stop the starting process, & attempt a re-
start every 60 seconds.
D: Compressor Speed Too Low:
If the compressor speed falls below 1900 RPM the Module will stop the compressor.
E: Fan Protection:
If the current draw across the fan terminals exceeds 0.7 amps 12v dc, the compressor will
be stopped & a re-start attempted every 60 seconds.
F: Module Overheat:
If the heat sink on the module exceeds a preset temperature, the compressor will be
stopped & will be re-started when normal operating temperatures are resumed.
G: 4 Alarm Indicator:
A LED may be installed across the + & D terminals of the Module to indicate a failure
condition as follows:
LCD will “Blink” up to 5 times every 5 seconds.
1 Blink; Supply voltage low, below 10.4v (22.8)
2 Blinks; Excessive load on fan terminals, above 1.0 amps
3 Blinks; Compressor non-start – Refrigerant pressure too high
4 Blinks; Compressor speed below 1850 RPM
5 Blinks; Module heat-sink temp too high. Re-sets on cool-down. IE: Module too hot.
NOTE ONE
After power is applied to the Module there may be a delay of up to 60 seconds before the
compressor starts.
NOTE TWO
The Electronic Module, although designed for harsh & marine applications, can be
damaged from either direct or incidental contact with water, & by water flowing down
wires attached to the terminals. When attaching wires to the terminals on the Module,
make sure that all wires approach from below the terminal, & endeavor to mount the
Compressor & Module combination in a location that is clear of existing & potential
water leaks.
SECTION 5
(EVAPORATORS)
A: Location:
All types of evaporator need to be located as high as possible in the ice-box/refrigerator
to maintain the correct temperatures. The series of flat evaporators may be carefully bent
on a 2” radius to follow the shape of the ice box. A section of PVC piping with an outside
diameter of 2" may be used for this purpose. This must be done slowly & with great care
to avoid excessive kinking of the channels in the evaporator. The channels will look like
tubing inside the evaporator. The evaporators must also be mounted on the walls of the
compartment with the indicator arrows pointing upwards (if present). Mounting the
evaporator on the bottom of the compartment will result in damage and inadequate
cooling of the compartment.
B: Installation:
All evaporators have approx. 6' of copper tubing attached, with dust-plugs in the end
fittings that must remain installed until the connections are ready to be made. A 1 1/2"
hole needs be drilled in the wall of the ice-box, as high as possible, & through successive
bulkheads as required. Carefully unroll the tubing & feed it through the holes to the area
where the compressor/condenser is located. Some evaporators have sections of aluminum
tubing close to the body of the evaporator that must be handled very carefully & not bent.
Warnings to that effect are attached to the evaporators in question.
Any bends that need to be fashioned in the tubing must be made carefully & of as large a
radius as possible to avoid kinking . The section of insulation that is free to slide on the
tubing should be positioned so that it covers the tubing starting at the point where it exits
the ice-box. Once the evaporator is installed, this exit hole must be sealed with expanding
foam, refrigeration putty, or other suitable material. Any excess tubing may be carefully
rolled up & fastened out of the way in a horizontal orientation.
C: Thermostat Sensing Tube:
Check to see where you need to attach the thermostat sensing tube before mounting the
evaporator. The capillary tube (silver capillary tube) coming off the thermostat is the
sensing device. Upon delivery, the sensing tube will be coiled up near the body of the
thermostat. The entire unit – including the dial – may be installed in the
refrigerator/freezer box if necessary. If you choose to mount the controls external of the
box, ensure that a majority of the capillary tubing is inserted into the box. Without the
capillary sensing tube, the thermostat will not operate effectively. You may use items
like tie straps or small plastic cable clamps to mount the capillary sensing tube inside the
walls of the refrigerator/freezer. It is also acceptable to mount the capillary sensing tube
just behind the evaporator plate on the white nylon stand-offs provided for the plate
installation. Tie straps work well for this mounting application. Should the entire unit be
installed inside the refrigerator/freezer, leaving the capillary tubing coiled up next to the
body of the thermostat IS acceptable. Simply ensure the capillary tubing (body included
or not) is in an area where the inside temperature created by the white evaporator plate
can be felt.
D: Mounting:
The evaporator has numerous mounting holes along the top & bottom edges. Do not drill
or attempt to drill holes in any evaporator for any purpose. Always use the nylong
mounting spacers (stand-offs supplied) to protect the tubing & to provide adequate air
circulation behind the white evaporator plate. Mounting the evaporator directly against
the icebox wall with no spacers will diminish the heat removing surface area and lower
its efficiency.
SECTION 6
(THERMOSTATS)
Refrigerator & Freezer Thermostats:
B: Mounting:
As mentioned above, the thermostat can be mounted either inside the ice-box, or in an
alternative location that is within the length of the capillary sensing tube. This capillary
tube controls the thermostat by the pressure of the gas it contains, & must not be kinked,
broken or cut. Any excess tubing may be carefully coiled up & secured out of the way to
avoid damage. Care must be taken to ensure that the sensing tube does not come into
contact with any electrical component either inside or outside the ice-box. If the sensing
tube needs to be bent within the confines of the refrigerator or freezer box, it must be
done with great care, heeding the warnings above.
C: Operation:
The thermostat knob is marked from 1 to 7. The coldest setting is 7, & from this position
the knob can be rotated counter-clockwise to setting 1, which is the warmest. If the knob
is rotated further counter-clockwise, beyond setting 1, some initial resistance is felt &
then the thermostat will click into the OFF position. On initial system start-up, it is
recommended that you set the thermostat to number 4 & let the system run through a few
cycles while monitoring box temperature before any adjustments are made.
TEMPERATURE RANGES FOR EACH MODEL THERMOSTAT
MODEL
WARM IN/OUT
51.7/40.9
MIDDLE IN/OUT
44.5/32
COLD IN/OUT
36.4/23.9
FRIDGE ONLY
FREEZE ONLY
COMBO UNIT
28.4/12.2
38.2/26.6
22.1/5
32/19.4
14/-4.8
23.9/10.4
Temperatures above are in Fahrenheit and are a range from warmest to coldest. The “in”
temperature is when the unit will turn on during that setting. The “out” is the temperature
when the unit will turn off during that setting. The temperature is measured by the silver
capillary sensing tube on the thermostat. Each thermostat is stamped with the model
number indicating the thermostat range. See below:
077B0028 = Refrigerator Only
077B0021 = Freezer Only
077B0028 = Combination Unit
SECTION 7
(QUICK CONNECT REFRIGERANT CONNECTIONS)
A: Note:
Each component of the Mermaid condensing system is fitted with one male & one female
Quick Connect fitting that connects with a corresponding fitting on other components of
the system. The individual items (condenser and evaporator) are charged with the correct
amount of refrigerant at the factory, & when the Quick Connect fittings are joined
together, they allow the refrigerant to flow through the system without leaking out to the
atmosphere. If needed, they can be undone to enable a faulty component to be removed
& replaced without leaking refrigerant.
Never run the compressor unless all components of the system are connected together.
B: Connecting the Quick Connect Fittings:
Leave the clear plastic dust plugs installed until you are ready to connect the system
together. After you have removed the plugs, keep them in a safe place in case you need to
remove or replace a component later. Push the male & female fittings together & then
carefully rotate the collar on the female fitting until it starts on the thread on the male
end, making sure that the fitting is not cross-threaded & the male end does not rotate.
Continue making up the collar of the female end, either by hand or with a crescent
wrench, while preventing the male end from rotating by restraining it with another
wrench. It is most important not to let the male end rotate at all during this whole
process. Tighten the collar until it nearly covers the threads on the male fitting. It is not
necessary to use excessive force as the seal that stops the refrigerant from escaping is
made with an o-ring & does not depend on the fitting being wrenched down hard. If there
is a continuous hiss after the connection has been completed, disconnect the fitting &
check that the o-ring has not been damaged.
SECTION 8
(ELECTRICAL)
A: Power Supply:
The power supply to the Electronic Control Module must given particular attention to
prevent nuisance problems & compressor non-operation, shutdown, or failure. All
incoming power electrical connections should be either soldered or made with good
quality crimpers & crimp connectors of the correct size & type. All switches, breakers &
connections must be in good condition & be designed & constructed for marine use. It is
suggested that during the initial start-up the supply voltage be monitored at the terminals
on the Module before, during, & after the compressor starts, to ensure that the voltage
stays steady & does not fall appreciably. This test should be conducted with as many
other DC loads turned on as is practical. Each model Mermaid produces is pre-wired and
tested for voltage drop. It is not necessary to change any wiring connections made at the
factory unless damaged during installation. This section is to ensure your incoming
power (12VDC, and/or 110V) is wired properly to the pre-stripped connections from the
Mermaid factory.
B: Wire Size:
Consult ABYC tables for 3% volt drop. Never use less than 10 gauge wire.
C: Overload Protection:
Use either a breaker or fast-blow fuse with 15 amp rating for a 12/24v supply, and/or a 8
amp fuse for the 110v a/c side. (These items are provided on new installations from the
Mermaid factory).
D: Connections, Power:
If wiring from the factory needs to be removed, connect the power supply to the Module
to the top two terminals, observing the correct polarity. Reversing the polarity at the
terminals will prevent the compressor from running but will not harm the system.
12/24VDC & 110V Auto Change-Over units have clearly marked 110v (+) and (N) – DO
NOT incorrectly put the 12/24VDC lines to here. It will not cause permanent damage
however, the unit will not operate. Follow the wiring schematic carefully. SEE LAST
PAGE OF MANUAL FOR WIRING SCHEMATIC
E: Connections, Thermostat:
Connect the two slip-on connectors from the thermostat to the corresponding terminals on
the Electronic Module, color & polarity are important. One connector must go on the “C”
terminal, & the other to the “T” terminal. Again, follow the enclosed wiring schematic.
SEE LAST PAGE OF MANUAL FOR WIRING SCHEMATIC
SECTION 9
(TROUBLESHOOTING GUIDE)
A: Note:
(1) The voltage must be checked at the terminals on the Module, with the supply wires
attached.
(2) Start-up may occur up to one minute after power is supplied & thermostat is on.
(3) Run all applicable tests before assuming Module or Compressor to be faulty.
B: Compressor Not Running, No Start Attempt.
Probable cause
Action
1
2
Supply voltage too low
Check voltage with a digital multi-meter
at the terminals on the Module. This
must be 11.7v or more for a 12v supply
& 24v or more for a 24v supply. Inspect
power supply, ground connections &
components for integrity. Check wire
sizing. Charge batteries if necessary.
Supply voltage too high If a 12v supply is faulty & delivers over
17v, the compressor will not run. If it is
over 24v, it will assume that it is a 24v
supply & act accordingly.
3
4
Polarity incorrect
Faulty thermostat
Check that the polarity is correct at the
Module.
Remove the thermostat wires & jumper
the terminals that they were on together
temporarily. If the system then runs,
make the connection permanent &
control the system manually from the
breaker on your supply panel. Replace
thermostat as soon as possible.
5
Thermostat wired
incorrectly, or faulty
connections.
Refer to the installation instructions &
confirm that connections are as they
should be. Ensure that the thermostat
connectors are pushed firmly on to the
Module terminals.
6
7
Multi-speed board
incorrectly installed (if
fitted)
Check to make sure that the 2
connectors at the rear of the multi-speed
board are attached to the C & T
terminals of the Module.
Multi-speed board faulty Remove board & jumper terminals C &
(if fitted)
** Optional Part **
T on the Module. Note; If the thermostat
wires are connected directly to C & T on
the Module, the compressor will run at
its slowest speed.
8
Compressor plug not
Disconnect the Module by removing the
connected
retaining screw & then ensure that the 3-
pin plug is seated firmly on the pins of
the compressor.
9
Faulty compressor
Remove the Module as above, & unplug
from the compressor. Check that ohm
readings are the same across all
terminals of the compressor.
10 Heat sink overheated
11 Compressor too cold
Allow components to cool down before
attempting re-start.
If compressor is below freezing
temperature, allow to warm up before
attempting re-start.
C: Compressor Attempts to Start, or Starts Then Stops Shortly After:
1 Faulty or inadequate
power supply
Monitor the supply voltage at the
terminals on the Module during start
attempts to ensure that it does not fall
below threshold levels. If it does, check
power supply, ground connections &
components for integrity. Check for
correct wire sizing. Charge batteries if
necessary.
2 Faulty fan or pump relay Remove connectors from F & +
or unauthorized
component installed
terminals on Module & attempt re-start.
Maximum current draw on these
terminals is limited to 0.7 amps 12v
3 Quick Connect fittings not Check that all refrigerant fittings are
made connected together properly.
D: System Runs, Box Temperature Too High:
1 Thermostat setting
Rotate thermostat knob clockwise to a
higher number.
2 Speed setting
Check that thermostat leads are
connected to the speed setting
recommended for the evaporator that is
installed, & for its use i.e. refer or
freezer.
** Optional Part **
3 Thermostat type
If you are planning to convert your ice
box into a freezer, or as a spillover
system, a freezer thermostat (0021)
must be used.
4 Evaporator type & size
If the evaporator has an even coating of
frost, the thermostat is set on 7, & the
system is cycling, the evaporator may
be too small. Either replace the
evaporator with a larger model, add
insulation to the bottom of the box to
reduce volume, or re-locate the
evaporator lower in the box. The latter
may cause the temperature at the top of
the box to be above acceptable levels.
5 Excessive frost build-up
If an excessive layer of frost is allowed
to build up on the evaporator it will act
as an insulator & adversely affect box
temperatures. Defrost system by
interrupting power supply at the breaker
panel or by turning thermostat to the off
position. Restore power or reset
thermostat when evaporator is free of
frost. Never use any implement in an
attempt to loosen the frost on the
aluminum evaporator. A light frost is
acceptable.
6 Incorrect refrigerant
charge
If, after the compressor has been
running for an appreciable length of
time, the evaporator surface does not
have an even coating of frost, or it is
only cold & sweating to the touch, the
system may be low on refrigerant or
over-charged. Consult a marine
refrigeration specialist.
7 Drain left unplugged
If your ice-box is equipped with a drain
in the bottom of the box, it is suggested
that you block it off to prevent heat
loss. The drain should only be used if
you revert to melting ice, or after a
major clean-up.
8 Tubing hole left
unplugged
The hole that had been drilled to allow
the copper tubes on the evaporator to
pass through during installation must be
sealed.
E: System Runs, Box Temperature Too Low:
1 Thermostat setting
2 Thermostat type
Rotate thermostat knob to a lower
number.
Check that you are using a refrigerator
thermostat (0028) for a refrigerator
application.
3 Faulty thermostat
If system is running continuously &
box temperatures are too low with
thermostat set on the lowest number,
first check for correct thermostat
connections at the Module, then remove
one connection. If compressor stops,
turn off breaker, replace connection &
then control system manually from the
breaker until the thermostat can be
replaced.
4 Holding plate over-sized If you are using a holding plate
evaporator that is over-sized for the
application, it will absorb more heat
than that which enters the box through
the insulation, & so lowers the
temperature. Experiment by covering
some of the plate surface with
insulating material until you achieve
correct box temperatures. This method
will also increase hold-over times.
5 Poor spillover system
construction
If you are running the evaporator as a
freezer, & cooling an adjoining
refrigerator compartment with some
spillover air, there must be an adequate
thermal barrier between the two, & it
must be properly sealed to prevent
unwanted air-flow. Temperatures in the
refrigerator side should be controlled
either with trial-&-error convection
holes, or a thermostatically controlled
fan. Two apertures are necessary, one
high & one low for adequate air
circulation.
F: Excessive Frost Build-Up:
Note: This is the result of moist air being allowed to enter the box. Problems are
compounded when cold air leaks from the lower area of the box & is replaced by warm,
humid air entering elsewhere.
1 Drains & holes not
plugged
Make sure all drains & holes in the
floor & walls of the box are sealed.
2 Circulating fan
If a small fan is used to circulate air in
the box, make sure that the cold air is
not being blown towards & out of a
door/lid seal. This could force cold air
out of the box & set up a circulation
pattern if the seals are leaking
2 Poor or damaged door/lid Check seals & replace if necessary. A
seals
good seal will grip a $1 bill when
inserted in the seal & the door/lid is
then closed. A front opening door / top
opening lid combination with poor seals
is likely to result in excessive frost
build-up on the evaporator, & extended
run times.
KOOL-TEMP ™
WIRING SCHEMATICS
DANFOSS COMPRESSORS 12/24V AND 12/24V W/ 110V
WIRING OF DANFOSS ELECTRONIC MODULE
12/24V
12/24V + 110V
FOLLOW THE WIRING DIAGRAM ABOVE AND DESCRIPTION BELOW TO MATCH WIRES.
THE 12/24 + 110V MODELS WILL HAVE AN ADDITIONAL POSITIVE (L) AND NEUTRAL (N)
SYMBOL FOR THE TWO 110V LEADS.
MM1 AND MM2 12/24V MODELS:
(-) NEGATIVE LEAD =
(+)POSITIVE LEAD =
(+)POSITIVE LEAD =
(F) NEGATIVE LEAD =
(D) FAULT LIGHT =
(C) THERMOSTAT =
(P) OPEN TERMINAL =
(T) THERMOSTAT =
BLACK WIRE (NEGATIVE 12/24V)
RED WIRE (INCOMING 12/24V POWER)
THIN RED WIRE (FAN)
THIN BLACK WIRE (FAN)
BROWN WIRE
GREEN WIRE
NO WIRE
PURPLE WIRE
MM1 AND MM2 12/24V + 110V WITH AUTO CHANGE-OVER MODELS:
(L) 110V LIVE WIRE =
BLACK WIRE
(N) 110V NEUTRAL WIRE =
WHITE WIRE
(-) NEGATIVE LEAD =
(+) POSITIVE LEAD =
(F) NEGATIVE LEAD =
(A) INTERIOR LIGHT =
(C) INTERIOR LIGHT =
(D) FAULT LIGHT =
(C) THERMOSTAT =
(P) OPEN TERMINAL =
(T) THERMOSTAT =
BLACK WIRE (NEGATIVE 12/24V)
THIN RED + 12V RED WIRE (FAN + INCOMING 12/24V POWER)
THIN BLACK WIRE (FAN)
NO WIRE
NO WIRE
BROWN WIRE
GREEN WIRE
NO WIRE
PURPLE WIRE
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