MrCool Signature MAHM CTA Series Quick start guide

The Signature Series is NOT designed for amateur installation. Installation SHOULD be performed by an authorized technician.
Please read this manual carefully before installation and keep it for future reference.
The Signature Series is NOT designed for amateur installation. Installation SHOULD be performed by an authorized technician.
Please read this manual carefully before installation and keep it for future reference.
Owner & Installation
Manual
MAHM*CTA AIR Handler
Signature Series

507787-01C mrcool.com Page 1 of 22
Save these instructions for future reference
INSTALLATION INSTRUCTIONS
MAHM*CTA Series Air Handler
(P) 507787-01C
Manufactured By
MRCOOL LLC
Hickory, KY 42051
This manual must be left with the homeowner for future reference.
This is a safety alert symbol and should never be ignored. When you see this symbol on labels or in
manuals, be alert to the potential for personal injury or death.
Table of Contents
......2
Shipping and Packing List ...........................................3
General........................................................................3
Requirements ..............................................................3
Installation Clearances ................................................4
Installation ...................................................................4
Condensate Drain........................................................7
Duct System and Filters ..............................................8
Brazing Refrigerant Lines............................................9
Sealing the Unit .........................................................12
Electrical Connections...............................................12
..............................16
Check-Out Procedures..............................................18
Operation...................................................................18
..........................................19
Repairing or Replacing Cabinet Insulation ................19
Professional Maintenance .........................................20
Use of Air Handler During Construction.....................20
IMPORTANT INFORMATION FOR INSTALLER
This unit has a delay relay that delays the supply blower “ON” for 1 second and keeps the blower “ON” for 45
seconds on all fan and cooling demands. For more details, refer to page 18 for unit sequence of operation.
1
SECOND
DELAY
OFF
100%
CFM 100%
CFM
45
SECS
COOLING
DEMAND
12
3 4
*P507787-C*1

507787-01Cmrcool.comPage 2 of 22
A
B
FRONT VIEW SIDE VIEW
LINE VOLTAGE
INLETS
(Top and Right Side)
LOW VOLTAGE
INLETS
(Either Side)
SUCTION
LINE
LIQUID
LINE
FILTER
ACCESS
3/4
(19)
AIR FLOW
CIRCUIT
BREAKER
COVER
D
1-1/8
(29)
1/2
(13)
C
LINE VOLTAGE
INLETS
(Top and Left Side)
LOW VOLTAGE
INLETS
(Top and Right Side)
1 (25)
SUPPLY AIR
OPENING
TOP VIEW
OPENING OPENING
1 (25)1 (25)
1-1/8
(29)
1-1/8
(29)
20-3/8
(518)
22
(559)
14-1/2
(368)
DETAIL OF PIPING PLATE
LIQUID
LINE CONDENSATE
DRAINS (2)
(Horizontal)
1-3/4
(44)
3/4 (19)
2-3/4
(70)
3-1/2
(89)
PIPING
PLATE
4-3/4
(121)
4-3/8
(111)
2-3/8
(60)
CONDENSATE
DRAINS (2)
(Upflow and
Downflow)
SUCTION
LINE
CONDENSATE DRAIN
PIPING PLATE (3)
(2-1/4 x 3-3/4)
MAHM*CTA
Dimensions 018 024 030 036 / 042 048 060
in. mm in. mm in. mm in. mm in. mm in. mm
A43-1/2 1105 45-1/2 1156 47 1194 53-5/8 1362 55 1397 59-3/4 1518
B18-1/2 470 18-1/2 470 18-1/2 470 21-1/2 546 21-1/2 546 21-1/2 546
C16-1/2 419 16-1/2 419 16-1/2 419 19-1/2 495 19-1/2 495 19-1/2 495
D16-1/4 413 16-1/4 413 16-1/4 413 19-1/4 489 19-1/4 489 19-1/4 489

507787-01C mrcool.com Page 3 of 22
Shipping and Packing List
Package 1 of 1 contains:
Check the air handler for shipping damage; if found,
immediately contact the last carrier. Check the unit rating
NOTE: Special procedures are required for cleaning
the all-aluminum coil in this unit. See Page 20 in this
instruction for information.
Improper installation, adjustment, alteration, service
or maintenance can cause property damage, personal
injury or loss of life. Installation and service must be
performed by a licensed professional HVAC installer or
equivalent, service agency, or the gas supplier.
The Clean Air Act of 1990 bans the intentional venting
of refrigerant (CFCs, HCFCs and HFCs) as of July
1, 1992. Approved methods of recovery, recycling or
may be levied for noncompliance.
The MAHM*CTA series air handler with all-aluminum coil is
designed for indoor installation only. As shipped, the unit
hand or right-hand air discharge applications. Electric
accessories are available and listed in the Product
This instruction is intended as a general guide and does
authorities having jurisdiction before installation.
sheet metal edges can result in personal injury. Take
and protective clothing.
Requirements
can result in back or other type of injury.
MAHM*CTA units include a factory-installed check/
capacities. These units must be installed as a part of
a matched system as outlined in the MAHM*CTA Product
These instructions are intended as a general guide and do
authorities having jurisdiction before installation.
pertaining to this type of equipment should be determined
as the instructions supplied in separate equipment, before
starting the installation.
In addition to conforming to manufacturer’s installation
instructions and local municipal building codes, installation
(NFPA) standards: “Standard for Installation of Air
Conditioning and Ventilation Systems” (NFPA No. 90A)
and “Standard for Installation of Residence Type Warm Air
Heating and Air Conditioning Systems” (NFPA No. 90B).
All models are designed for indoor installation only. The
must conform to the requirements of the National Electrical
Code, ANSI/NFPA No. 70 (latest edition) in the United
Local authorities having jurisdiction should be consulted
before installation is made. Such applicable regulations
or requirements take precedence over the general
instructions in this manual.
the Installation of Warm Air Heating and Air-Conditioning
Systems (latest edition).
The air handler is shipped from the factory completely
connection of the duct system.

507787-01Cmrcool.comPage 4 of 22
Do not remove the cabinet knockouts until it has been
the installation.
conditions. Consider required clearances, space, routing
requirements for refrigerant line, condensate disposal,
information.
materials and vapors, such as gasoline,
that heating elements are at least 18 inches
instructions can result in death, explosion,
Excessive condensation may occur if the unit is installed
unconditioned space, apply sealant around electrical
Apply sealant on the inside of the cabinet at the
electrical controls.
This unit is approved for installation clearance to
combustible material as stated on the unit rating
plate. Accessibility and service clearances must take
precedence over combustible material clearances.
The air handler must be installed so that free access is
compartment.
•
humid space.
• If installed in an unconditioned space, sealant should
cabinet.
•
they exit the conduit opening. Sealant is required to
prevent air leakage into, and condensate from forming
inside of, the air handler, the control box, and on the
electrical controls.
• This unit is approved for installation clearance to
combustible material as stated on the unit rating
plate. Accessibility and service clearances must take
precedence over combustible material clearances.
• The air handler must be installed so that free access
control compartment.
bottom to form a return air plenum. It may also be installed
single-story buildings.
When a MAHM*CTA
be:
• 320 square inches for -018 and -024 models;
• 360 square inches for -030 and -036 models;
• 450 square inches for -042 thru -060 models
determine if the open area meets the minimum open area
listed above.
If a return air plenum is used, the return air grille should be
the opening, there must be adequate clearance around the
and controls in an insulated galvanized steel factory-
For ease in installation, it is best to make any necessary
place.
Refrigerant Metering Device
MAHM*CTA
expansion valve or an RFC device.

507787-01C mrcool.com Page 5 of 22
1. The air handler must be supported on the bottom only
frame.
2.
horizontal drain pan.
NOTE: The horizontal drain pan is not required in
3. Place the unit in the desired location and slope unit.
Connect return and supply air plenums as required
4. Install units that have no return air plenum on a stand
air return.
HORIZONTAL DRAIN PAN
(MUST BE REMOVED)
UP-FLOW /
DOWN-FLOW
DRAIN PAN
Figure 1.
Horizontal Applications
When removing the coil, there is a possibility of danger
of equipment damage and personal injury. Be careful
in right- or left-hand applications. The coil may tip into
the drain pan once it is clear of the cabinet. Support the
NOTE: When the unit is installed in horizontal applications,
codes.
NOTE:
air discharge horizontal applications. Adequate support
panels if installing in the horizontal position.
Right-Hand Discharge
1.
connections.
2. With access door removed, remove drain line plugs to
install drain lines.
3.
end of the unit and level from front to back of unit (see
Figure 6).
4.
Drains
AIR FLOW
PLUGS
RIGHT‐HAND DRAINS
Figure 2.
5. If the unit is suspended, the entire length of the cabinet
must be supported. If you use a chain or strap, use a
piece of angle iron or sheet metal attached to the unit
air plenums as required.
FRONT WEIVDNEWEIV
ANGLE IRON OR SHEET
METAL
E
ANCE 4 IN. (102 MM)
MAXIMUM 1/2"
LONGSCREW
AIR FLOW
Figure 3. Suspending Horizontal Unit
Left-Hand Air Discharge
1. Remove access panels and the corrugated padding
corrugated padding.
2. Pull the coil assembly from unit. Pull off the horizontal
drain pan.
3. Remove the drain plugs from back drain holes on
horizontal drain pan and reinstall them on front holes.

507787-01Cmrcool.comPage 6 of 22
After removal of drain pan plug(s), check drain hole(s)
to verify that drain opening is fully open and free of any
debris. Also check to make sure that no debris has
fallen into the drain pan during installation that may plug
up the drain opening.
4. Rotate drain pan 180º front-to-back and install it on the
opposite side of the coil.
5.
6. Remove plastic plug from left hole on coil front end
seal and reinstall plug in back hole.
90º
BEND
CABINET
SUPPORT
COIL SHOWN IN UPLOAD POSITION FOR EASY CONVERSION
TOP CAP SCREWS
DRAIN PAN
REINSTALLED
HERE
DRAIN PAN
SHIPPING
LOCATION
TOP CAP ROTATED TO
CORRECTPOSITION
———— DRAIN PLUGS ————
REINSTALLED HERE REMOVED FROM HERE
BACK COIL END SEAL
TOP
CAP
90º
BEND
ALIGN HOLES WITH
HOLES IN COIL END
PLATE. STARTING WITH
THE ROUND HOLES ON
THIS END.
Figure 4.
7.
back coil end plates. The top cap has a 45º bend on
one side and a 90º bend on the other. The 90º bend
must be on the same side as the horizontal drain
pan as illustrated in Figure 4.
DOWN-FLOW RAIL FRONT EDGE OF HORIZONTAL
DRAIN PAN
Figure 5.
NOTE:
into the coil end plate engaging holes. Misaligned
8.
support rail as illustrated.
9. Install the horizontal shield (-060 model) on the front
edge of the horizontal drain pan as illustrated in Figure
5.
NOTE:
of humid air.
10. Knock out drain seal plate from access door. Secure
11. Flip access door and replace it on the unit.
12.
end of the unit. Connect return and supply air plenums
13. If suspending the unit, it must be supported along the
entire length of the cabinet. If using chain or strap,
use a piece of angle iron or sheet metal attached to
illustrated in Figure 3. Connect return and supply air
NOTE:
kit.
If electric heat section with circuit breakers (ECBA25) is
installed in a MAHM*CTA unit in a downflow application, the
circuit breakers must be rotated 180° to the UP position.
See ECBA25 installation instructions for more details.

507787-01C mrcool.com Page 7 of 22
Condensate Drain
in the condensate drain lines (primary and auxiliary,
through the drain lines into the air supply.
pipe to the outside of the building, is required in all
pan. In some localities, local codes may require a
secondary drain pan for any horizontal installation.
Sloping The Unit
THISCORNER SHOULD BE 5/8" (+/- 1/8") HIGHER
THAN DRAIN CORNER
DRAIN CORNER
LEVEL PLANE
Figure 6. Sloping the Unit for Proper Drainage
ABOVE
FINISHED
SPACE?
OVERFLOW DRAIN LINE
ALWAYS RUN AN OVERFLOW DRAIN LINE. IF NOTPOSSIBLE TO
ROUTE OVERFLOW DRAIN LINE, INSTALL LOW VOLTAGE
OVERFLOW SWITCH KIT. WIRE KIT TO SHUT DOWN
COMPRESSOR PER INSTRUCTIONS.
NO
YES
PART #
X3169 CLEAN OUT
VENT
PRESS IN
(DO NOT GLUE)
VENT MUST EXTEND
ABOVE HEIGHT OF
COIL DRAIN PAN BY
TWO INCHES (51MM)
1” X 3/4” X 3/4”
REDUCING
TEE WITH
PLUG
1P-TRAP
49P66, J-TRAP #
91P90 OR ANY
PVC SCH 40 P- OR
J-TRAP 3/4”
OVERFLOW
DRAIN
AIR HANDLER DRAIN PAN
WHEN A COIL IS LOCATED ABOVE A FINISHED SPACE, A
3/4” (19.1MM) SECONDARY DRAIN LINE MUST BE:
CONNECTED TO SECONDARY DRAIN PAN
OR
CONNECTED TO THE OVERFLOW DRAIN OUTLET OF
THE AIR HANDLER DRAIN PAN.
TRAPS MUST BE DEEP ENOUGH TO OFFSET MAXIMUM STATIC DIFFERENCES —
GENERALLY, TWO INCHES (51MM).
DRAIN LINE SHOULD
SLOPE A MINIMUM OF
ONE INCH PER 10
FEET (25MM PER 3
METERS)
NOTE — WHEN A AIR HANDLER IS LOCATED
ABOVE A FINISHED SPACE THE SECONDARY
DRAIN PAN MUST HAVE A LARGER FOOTPRINT
THAN THE AIR HANDLER.
MAIN
DRAIN
TO APPROVED
DRAIN
FOR NEGATIVE PRESSURE COILS (BLOWER
AFTER COIL) TRAPS ARE REQUIRED ON ALL
DRAIN LINES CONNECTED TO COIL.
COMPACT OVERFLOW SWITCH WITH 3/4” FEMALE SLIP INLET
AND MALE ADAPTER, TWO PART DESIGN FOR USE WHERE
OBSTRUCTIONS PREVENT DIRECT THREADING
SECONDARY
DRAIN PAN
2”
(51MM)
TRAP DEPTH
1P-TRAP 49P66 REQUIRES A LARGER INSTALLATION SPACE THAN THE J-TRAP 91P90.
2PIPE NIPPLE PROVIDED IN BAG ASSEMBLY - SCH 80, 3/4” I. D. X 5” - 34K7401 (1): CUT THE PIPE IN HALF AND USE IT TO ROUTE THE MAIN DRAIN.
MAIN
DRAIN
PROVIDED
PIPE NIPPLE 2
CUT TO
REQUIRED
LENGTH
SIDE VIEW
Figure 7.

507787-01Cmrcool.comPage 8 of 22
connections.
On some pans, the primary and secondary drain holes
have knockouts.
1. MAHM*CTA
includes green (main drain) and red (secondary drain)
DRAIN PAN RED SECONDARY
DRAIN PLUG
UNSCREW PLUGS
AND CONNECT
PROPERLY SIZED
FIELD-PROVIDED
FITTINGS AND
DRAIN LINES.
GREEN MAIN
DRAIN PLUG
Figure 8. Drain Line Connections
2.
and connect primary drain line to the main drain pan
connection.
NOTE:
connections on the drain pan.
3. If the secondary drain line is to be used, remove the
plug or the knockout and route the drain line so that
requirements on the secondary drain line.
4. Check again to ensure drain ports and drain pan are
free of all debris.
5. Plug and check any unused drain pan openings for
leaks or seepage from the drain pan.
6. Install a 2” trap in the main (primary) drain lines as
close to the unit as practical (see Figure 7). Make sure
NOTE:
NOTE:
7. Route the drain line to the outside or to an appropriate
drain. Drain lines must be installed so they do not block
service access to the front of the air handler. A 24”
and service access.
NOTE:
Test Condensate Drain
Test the drain pan and drain line after installation:
1.
2. Check the installed drain pan. Drain pan must be
leaking. Water must be draining from the end of the
primary drain line.
3. Correct any leaks found.
Duct System and Filters
Duct System
of the supply plenum.
Supply and return duct system must be adequately sized
to meet the system’s air requirements and static pressure
conditioned areas or 2” minimum in unconditioned areas.
extend at least 3 ft. from the air handler before turning or
branching off plenum into duct runs. The plenum forms
Filters
Model Filter Size – in.
-018, -024, -030 15" x 20" x 1"
-036, -042, -048, -060 18" x 20" x 1"
Table 1. Unit Air Filter Size Chart

507787-01C mrcool.com Page 9 of 22
and performance may be reduced. The pressure drop
may also cause the limit to trip more frequently during
resulting in an increase in the number of service
against the data given in the appropriate Product
Service and Application Note ACC002 (August 2000).
handler. If an isolation connector is used, it must be
Field-Fabricated Return Air Duct Flange for
Horizontal Applications
A return air duct system is recommended, but not factory-
closet, run a full-size return connection to a location outside
the closet.
BOTTOM OF
CABINET
DUCT
ADAPTER
1−1/2
(38)
”A”
BRAKEDOWN90 DEGREES
1/4 (6) DIA.
2−HOLES
"A"
1−1/2(38)
3/4
(19)
3/4
(19)
1−1/2
(38)
3/4
(19)
1/2
(13)
3/4
(19)
DUCT
FLANGE
CABINET
DOOR FLANGE
UNIT SIZE
Cabinet and Duct Flange
-018, -024,
-030
-036, -042,
-048, -060
18-3/8"
21-1/2"
Figure 9. Cabinet and Duct Flange
Brazing Refrigerant Lines
Refrigerant lines must be clean, dry, refrigerant-grade
copper lines. Air handler coils should be installed
combinations.
Handle the refrigerant lines gently during the installation
restriction.
Do not remove the caps from the lines or system
connection points until connections are ready to be
completed.
absorb moisture very quickly. It is very important that the
refrigerant system be kept closed as much as possible.
DO NOT remove line set caps or service valve stub
caps until you are ready to make connections.
charge from only the high side may result in
suction tubing. Application of a brazing torch
to a pressurized system may result in
ignition of the refrigerant and oil mixture.
applying heat.
When using a high pressure gas such as
nitrogen to pressurize a refrigeration or air
conditioning system, use a regulator that
(6.9 to 13.8 kPa).

507787-01Cmrcool.comPage 10 of 22
hazardous to your health.
Avoid breathing vapors or fumes from brazing
areas.
Wear gloves and protective goggles or face shield to
protect against burns.
prevent oxidation and the introduction of moisture into
the system.
NOTE:
.
1.
the lines in a direct path, avoiding unnecessary turns
and bends.
2. Make sure that the suction line is insulated over the
entire exposed length and that neither suction nor
3. To avoid damaging the rubber grommets in the cabinet
source.
NOTE:
suction line connections.
4. Connect the suction and liquid lines to the evaporator
coil. Take care to protect the cabinet and internal
components as detailed in Figure 10.
5. Braze using an alloy of silver or copper and phosphorus
NOTE: Do not use soft solder.
6.
NOTE:
7. Reinstall the rubber grommets into the refrigerant
piping panel.
NOTE:
not touching metal edges or copper tubing.
8. Make sure outdoor unit has been placed according
to the Installation Instructions and is connected to the
refrigerant lines

507787-01C mrcool.com Page 11 of 22
REMOVE ACCESS PANEL
A
REMOVE RUBBER PLUG FROM BOTH LIQUID
AND SUCTION LINES
B
NITROGEN
HIGH
LOW
EITHER REMOVE OR PUSH PIPE WRAPPINGBACK
THROUGH HOLEIN PIPING PLATE BEFORE LINE
SETCONNECTION AND BRAZING.
C
DCONNECTPIPESECONNECT GAUGES AND
START NITROGEN FLOW
FPLACE A WET RAG AGAINSTPIPING
PLATE AND AROUND THE SUCTION
LINE CONNECTION.
GBRAZE CONNECTION. ALLOW PIPE TO
COOL BEFORE REMOVING WET RAG
FROM CTXV SENSING BULB AND PIPING
PANEL AREA.
HREPEAT PREVIOUS PROCEDURE FOR LIQUID
LINE.
NOTE - REFRIGERANT LINE SETS
SHOULD BE ROUTED TO ALLOW
FILTER ACCESSIBILITY.
NOTE - MAHM*CTA SERIES UNITS USE NITROGEN OR DRY AIR
AS A HOLDING CHARGE. IF THERE IS NO PRESSURE WHEN
THE RUBBERPLUGS ARE REMOVED, CHECK THE COIL FOR
LEAKSBEFORE INSTALLING.
REFER TO INSTRUCTIONS PROVIDED WITH OUTDOOR
UNIT FOR LEAK TESTING, EVACUATINGAND CHARGING
PROCEDURES
FLOW REGULATED NITROGEN (AT 1 TO 2 PSIG)
THROUGH THE REFRIGERATION GAUGE SET INTO THE
VALVE STEMPORT CONNECTION ON THE OUTDOOR
UNIT LIQUID LINE SERVICE VALVE AND OUT OF THE
VALVE STEMPORT CONNECTION ON THE SUCTION
SERVICE VALVE.
PIPING
PLATE
NOTE - REFER TO OUTDOOR UNIT INSTALLATION
INSTRUCTIONS FOR REFRIGERANT PIPINGSIZE
REQUIREMENTS.
PLEASE READ IMPORTANT ISSUES CONCERNING BRAZING
OPERATIONS IN THE BRAZING REFRIGERANT LINES SECTION
BEFORE PROCEEDING.
NOTE - Use silver alloy brazing rods withfive or six percent
minimum silver alloy for copper-to-copper brazing, 45
p
ercent alloy for copper-to-brass and copper-to-steel
brazing.
Figure 10. Brazing Connections

507787-01Cmrcool.comPage 12 of 22
Sealing the Unit
installed in an unconditioned area.
If installed in an unconditioned space, sealant should be
sealing strips, caulking, or equivalent sealing method
Use duct tape and/ or Permagum to seal closed any
any gaps or holes in the cabinet.
Electrical Connections
supplies before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical
shock.
in one opening.
Electric Shock Hazard. Can cause injury or
death. Unit must be properly grounded in
pole contactors. Disconnect all remote electric
Electric Shock Hazard.
Can cause injury or death.
Foil-faced insulation has conductive
characteristics similar to metal. Be sure there
insulation. If the foil-faced insulation comes in
provide a path for current to pass through
to the outer metal cabinet. While the current
produced may not be enough to trip existing
electrical safety devices (e.g., fuses or circuit
breakers), the current can be enough to cause
an electrical shock hazard that could cause
personal injury or death.
• Wiring must conform to the current National Electric
Code ANSI/NFPA No. 70, or Canadian Electric Code
Part I, CSA Standard C22.1, and local building codes.
for minimum circuit ampacity and maximum over-
current protection size.
•
protection are to be supplied by the installer. Refer
to the air handler rating plate for maximum over-
as operating voltage. Select the proper supply circuit
17 in the National Electric Code, ANSI/NFPA No. 70 or
tables 1 through 4 in the Canadian Electric Code, Part
I, CSA Standard C22.1.
•
•
single phase, 60 cycles. For 208-volt applications, see
“208 Volt Conversion” later in this section.

507787-01C mrcool.com Page 13 of 22
•
voltage and line voltage. Refer to the dimension
•
provided caps to seal holes not used.
•
installed electric heat) is given in Figure 14. Refer to
for proper installation.
USE COPPER CONDUCTORS ONLY
1.
2. Remove the air handler access panel.
3.
connection box.
4.
5. Replace the air handler access panel.
SIDE
TOP
Figure 11. Electrical Connections
NOTE:
in Figure 12.
TOP
SIDE
Figure 12. Control Panel Relocated to End Panel
208 Volt Conversion
1.
2. Remove the air handler access panel.
3.
panel as a reference, move the 2 connected black
transformer leads from the 240 volt terminal on the
transformer to the 208 volt terminal on the transformer.
Electrically ground air handler. Connect
Failure to do so can result in death or electrical
shock.
208 / 240 VOLT TRANSFORMER
PRIMARY SECONDARY
240 Volts
208 Volts
Figure 13. Converting Unit from 240VAC to 208VAC

507787-01Cmrcool.comPage 14 of 22
Figure 14. Typical Wiring Diagram MAHM*CTA

507787-01C mrcool.com Page 15 of 22
Figure 15. Typical Wiring Diagram MAHM*CTA

507787-01Cmrcool.comPage 16 of 22
R
G
AIR
CONDITIONER
UNIT
R
R
G
G
BU
W
W
BK
COOLING‐ONLY APPLICATION
AIR HANDLERTHERMOSTAT
HEAT‐ONLY APPLICATION
AIR HANDLERTHERMOSTAT
COOLING APPLICATION WITH
ELECTRIC HEAT
AIR HANDLERTHERMOSTAT
HEAT PUMP APPLICATION WITH
ELECTRIC HEAT
NOTE - Connect common wire only if required (Refer to the appropriate thermostat installation instructions).
BU
BU
SEE
NOTE
SEE
NOTE
SEE
NOTE
Y
Y
AIR CONDITIONER
UNIT
R
G
BU
W
BK
CONNECT COMMON
WIRE ONLY IF
REQUIRED
(REFER TO THE
APPROPRIATE
THERMOSTAT
INSTALLATION
INSTRUCTIONS)
AIR HANDLER
THERMOSTAT HEAT PUMP
UNIT
Figure 16.
Air Flow – Cooling Blower Speed
capacity rating of the air handler.
If the outdoor unit is smaller than the maximum cooling
chart in Table 2.
supplies before servicing.
Replace all parts and panels before operating.
Failure to do so can result in death or electrical
shock.
Change Blower Speed
1.
2. Remove the air handler access panel.
3.
4.
harness connector.
NOTE:
5. Replace all panels.
6.

507787-01C mrcool.com Page 17 of 22
2
BLUE (MED) RED (L0)
BLACK (HI)
YELLOW (COM)
5BLOWER RELAY
BLOWER RELAY
PLASTIC CAPS
4-PIN
BLOWER CONNECTOR
HARNESS
NOTE - Refer to wiring diagram located on the
unit
ance (table 2).
All air data measured external to unit with 1
inch non-pleated air filter in place.
All factory settings are medium speed.
All data given while air handler is operating
with a dry DX coil.
All downflow applications run on high speed
when utilizing electric heat.
Figure 17. Changing Blower Speed
NOTE:
Air Handler Model Blower Speed .10"WC .20"WC .30"WC .40"WC .50"WC
-018
LOW 538 525 503 471 418
MED 688 670 639 603 548
HIGH 919 881 855 788 710
-024
LOW 677 673 657 629 592
MED 1011 979 942 803 742
HIGH 1106 1045 999 917 857
-030
LOW 871 870 853 812 769
MED 1078 1057 1024 987 936
HIGH 1311 1261 1214 1154 1086
-036
LOW 1020 972 956 909 806
MED 1276 1240 1191 1148 1086
HIGH 1559 1521 1446 1395 1327
-042
LOW 1300 1273 1250 1211 1155
MED 1527 1493 1452 1390 1345
HIGH 1816 1756 1693 1605 1528
-048
LOW 1257 1212 1157 1116 1053
MED LOW 1486 1448 1411 1364 1330
MED 1721 1675 1630 1594 1553
MED HIGH 1721 1675 1630 1594 1553
HIGH 1840 1794 1754 1721 1681
-060
LOW 1098 1049 1001 926 831
MED LOW 1624 1594 1565 1520 1492
MED 1815 1783 1758 1730 1685
MED HIGH 1903 1869 1837 1809 1764
HIGH 1981 1957 1923 1893 1861
•
•
•
Table 2. MAHM*CTA

507787-01Cmrcool.comPage 18 of 22
Check-Out Procedures
NOTE:
instructions.
Pre-Start-Up Checks
• Is the air handler properly and securely installed?
•
• Will the unit be accessible for servicing?
• Has an auxiliary pan been provided under the unit
could cause damage?
• Have ALL unused drain pan ports been properly
plugged?
• Has the condensate line been properly sized, run,
trapped, pitched, and tested?
• Is the duct system correctly sized, run, sealed, and
insulated?
•
• Is the indoor coil factory-installed TXV or RFC properly
sized for the outdoor unit being used?
• Have all unused parts and packaging been disposed
of?
•
•
• Is the unit properly grounded and protected (fused)?
•
location?
• Are all access panels in place and secure?
Check Blower Operation
1.
come on.
Check Cooling Operation
1. Set thermostat to force a call for cooling (approximately
2. The outdoor unit should come on immediately and the
later.
3.
system is moving cooled air.
4. Set the thermostat 5ºF higher than the indoor
should cycle off.
1. Set thermostat to call for auxiliary heat (approximately
minimum of 3 minutes for all sequencers to cycle on.
2. Set the thermostat so that it does not call for heat.
Operation
Time Delay Relay
1. When cooling demand is initiated, there is a 1 second
motor-on delay.
2. After the motor-on delay expires, motor ramps up
3.
seconds.
4.
1
SECOND
DELAY
OFF
100%
CFM 100%
CFM
45
SECS
COOLING
DEMAND
12
3 4
Figure 18. Blower Time Delay
When the thermostat calls for cooling, 24 volts is put on
relay energizes. The normally open contacts close, causing
and Y is completed, closing the circuit to the contactor in
the outdoor unit, starting the compressor and outdoor fan
motor.
On heat pumps, circuit R and O energizes the reversing
reversing valve remains energized as long as the
and outdoor unit should cycle off. Air handler should cycle
off 45 seconds after the outdoor unit shuts off.
and W is completed, and the heat sequencer is energized.
on the thermostat sub-base, or they may also be connected
to a second stage on the sub-base.

507787-01C mrcool.com Page 19 of 22
When the thermostat calls for heating, 24 volts is applied
the circuit to the contactor in the outdoor unit, starting the
compressor and outdoor fan motor.
If the room temperature continues to decrease, the circuit
room thermostat. Circuit R-W1 energizes a heat sequencer.
thermostat. They may also be connected to a second
heating stage W2 on the thermostat sub-base.
on the thermostat sub-base so that the electric heat control
Homeowner Maintenance
duct by the installer.
•
cause of inadequate heating or cooling performance.
•
•
sized for it.
•
REPLACED before the unit is put back into operation.
separated or torn.
Matte- or foil-faced insulation is installed in indoor
conditions (surrounding ambient temperature and humidity)
and the varying conditions inside the unit. If the insulation
inside surface temperature of the cabinet.
and outside of the cabinet can cause condensation on the
corrosion and, subsequently, component failure.
Areas of condensation on the cabinet surface are an
indication that the insulation is in need of repair.
condition, the insulation should be cut in an X pattern,
and placed back against the cabinet surface, being careful
to not overly compress the insulation so the insulation can
retain its original thickness. If such repair is not possible,
replace the insulation. If using foil-faced insulation, any
cut, tear, or separations in the insulation surface must be
1. CUT INSULATION IN X PATTERN
2. APPLY GLUE
3. PRESS GLUED TABS AGAINSTCABINET
GLUE - Make sure there is
full coverage of glue on the
metal or insulation so there
are no areas where air
pockets may form which
can lead to sweating.
Figure 19.