Carrier 48N Series Guide

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Catalog No. 04-53480193-01 Printed in U.S.A. Form 48N-2SO Pg 1 7-19 Replaces: 48N-1SO
User’s Information Manual
NOTE TO INSTALLER:
This manual should be left with the equipment owner.
Your combination heating/cooling rooftop unit is equipped
with an automatic direct spark ignition system and induced-
draft power combustion blower.
WARNING
If the information in this manual is not followed exactly, a
fire or explosion may result causing property damage, per-
sonal injury or loss of life.
Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or any other appliance.
WHAT TO DO IF YOU SMELL GAS
• Do not try to light any appliance.
• Do not touch any electrical switch; do not use any
phone in your building.
• Immediately call your gas supplier from a neighbor’s
phone. Follow the gas supplier’s instructions.
• If you cannot reach your gas supplier, call the fire
department.
Installation and service must be performed by a qualified
installer, service agency or the gas supplier.
AVERTISSEMENT
RISQUE D´INCENDIE OU D´EXPLOSION
Si les consignes de sécurité ne sont pas suivies à la lettre,
cela peut entraîner la mort, de graves blessures ou des dom-
mages matériels.
Ne pas entreposer ni utiliser d´essence ni autres vapeurs ou
liquides inflammables à proximité de cet appareil ou de tout
autre appareil.
QUE FAIRE SI UNE ODEUR DE GAZ EST DÉTECTÉE
• Ne mettre en marche aucun appareil.
• Ne toucher aucun interrupteur électrique; ne pas
utiliser de téléphone dans le bâtiment.
• Quitter le bâtiment immédiatement.
• Appeler immédiatement le fournisseur de gaz en
utilisant le téléphone d´un voisin. Suivre les
instructions du fournisseur de gaz.
• Si le fournisseur de gaz n´est pas accessible, appeler le
service d´incendie.
L´installation et l´entretien doivent être effectués par un in-
stallateur ou une entreprise d´entretien qualifié, ou le four-
nisseur de gaz.
WARNING
Do not use this furnace if any part has been under water. A
flood-damaged furnace is extremely dangerous. Attempts
to use the furnace can result in fire or explosion. A quali-
fied service agency should be contacted to inspect the fur-
nace and to replace all gas controls, control system parts,
electrical parts that have been wet or the furnace if deemed
necessary.
AVERTISSEMENT
Ne pas utiliser cet appareil de chauffage s´il a été en partie
immergé dans l´eau. Un appareil de chauffage endommagé
par une inondation est extrêmement dangereux. S´il est
utilisé, un incendie ou une explosion peut se produire. Il
faut avoir recours à une entreprise d´entretien qualifiée
pour faire inspecter l´appareil de chauffage et remplacer
toutes les commandes de gaz, les pièces du système de
contrôle, les pièces électriques qui sont entrées en contact
avec l´eau ou l´appareil de chauffage lui-même, si cela est
jugé nécessaire.
WARNING
Improper installation, adjustment, alteration, service or
maintenance can cause injury or property damage. Refer to
this manual. For assistance or additional information con-
sult a qualified installer, service agency, or the gas supplier.
WARNING
Before performing recommended maintenance, be sure
main power switch to unit is turned off and lockout tag is
installed. Electrical shock could cause personal injury.
WARNING
Burners will light automatically. Do not attempt to light by
hand; personal injury may result.
48N 75-150 Ton
Gas Heating/Electric Cooling Units
with ComfortLink Controls

2
TO LIGHT UNIT
See Fig. 1 for location of gas valve(s). Refer to Fig. 2 while
proceeding with the following steps.
1. Turn off the unit demand for cooling or heating by using
the Navigator™ device. The Navigator device is located in
the control box.
a. Push the key until “Select a Menu Item” is
shown.
b. Push the key until the SERVICE TEST LED is
lit.
c. Push the key.
d. Push the key to move the flashing cursor to
STOP.
e. Push the key again. The NO/YES display
will flash.
f. Push the or key to toggle the display to YES
and then push . The unit will be locked off
from heating, cooling or any operation. The controls
will still function and the display will still operate.
2. Close the field-installed manual gas shutoff valve.
3. Turn off the electrical power to the unit using the optional
disconnect or the field-installed disconnect and lock off
using proper lockout and tag-out procedures.
4. Open the burner section hinged access door.
5. Move the switch on the gas valves to the OFF position and
wait 5 minutes.
NOTE: If this is the first installation of the unit, the gas flue hoods
must be installed before operating unit. These must be installed for
the unit to run properly.
6. Move the switch on the gas valves to the ON position.
7. Close the burner section hinged access door.
8. Turn on the electrical supply to the units.
9. Open the field-installed manual gas valve.
10. Using the Navigator™ device, enable the unit to run using
the following procedure:
a. Push the key until “Select a Menu Item” is
shown.
b. Push the key until the SERVICE TEST LED is
lit.
c. Push the key.
d. Push the key to move the flashing cursor to
STOP.
e. Push the key again. The NO/YES display
will flash.
f. Push the or key to toggle the display to NO
and then push . The unit will return to nor-
mal operation and exit SERVICE TEST mode.
11. To test the operation of the gas section, use the Navigator Ser-
vice Test routine to energize the gas outputs and to turn on the
gas. Refer to the unit Controls, Start-Up, Operation, Service
and Troubleshooting literature for more information.
12. For normal operation, make sure that units with a conven-
tional thermostat are set to heating control temperature.
On VAV (variable air volume) and CV (constant volume)
units with a space temperature sensor, make sure that the
set points are at the normal heat set points.
WARNING
CARBON-MONOXIDE POISONING HAZARD
Failure to follow instructions could result in severe personal
injury or death due to carbon-monoxide poisoning, if
combustion products infiltrate into the building.
Check that all openings in the outside wall around the vent
(and air intake) pipe(s) are sealed to prevent infiltration of
combustion products into the building.
Check that furnace vent (and air intake) terminal(s) are not
obstructed in any way during all seasons.
AVERTISSEMENT
RISQUE D’INTOXICATION AU MONOXYDE DE
CARBONE
Si ces directives ne sont pas suivies, cela peut entraîner des
blessures graves ou une intoxication au monoxyde de car-
bone pouvant causer la mort, si des produits de combustion
s’infiltrent dans le bâtiment.
Vérifier que toutes les ouvertures pratiquées dans le mur
extérieur autour du ou des tuyaux d’évent (et de la prise
d’air) sont scellées de manière à empêcher l’infiltration de
produits de combustion dans le bâtiment.
Veiller à ce que la ou les sorties de l’évent de l’appareil de
chauffage (et la prise d’air) ne soient, en aucune façon, ob-
struées, quelle que soit la saison.
WARNING
Should overheating occur or the gas supply fail to shut off,
shut off the manual gas valve to the unit before shutting off
the electrical supply.
AVERTISSEMENT
En cas de température excessive, ou s´il est impossible de
couper l´alimentation en gaz, fermer le robinet manuel
d´alimentation en gaz du générateur d´air chaud avant de
couper l´alimentation électrique.
DANGER
1. Do not turn off the electrical power to unit without first
turning off the gas supply.
2. Before attempting to start the gas heating section,
familiarize yourself with all the procedures that must
be followed.
3. Never attempt to manually light the burners on the unit
with a match, lighter, or any other flame. If the electric
sparking device fails to light the burners, refer to the
shutdown procedures, then call your dealer as soon as
possible.
If you do not follow these instructions exactly, a fire or ex-
plosion may result, causing property damage, injury, or loss
of life. WARNING
If the main burners fail to light or the blower fails to start,
shut down gas heating section and call your dealer for ser-
vice. Failure to follow these requirements could result in
serious personal injury.
ESCAPE
ENTER
ENTER
ENTER
ESCAPE
ENTER
ENTER
ENTER

3
Fig. 1 — Heat Section Details
GAS VALVE
TYPICAL IN
EACH SECTION
75-105 TON SIZES CONSISTS OF
2, 3, OR 4 HEAT SECTIONS
120-150 TON SIZES CONSISTS OF
3, 4, OR 5 HEAT SECTIONS
GAS VALVE
TYPICAL IN
EACH SECTION

4
Fig. 2 — To Light Unit
STEP 1
STEP 5
STEP 4
STEP 3
STEP 2
STEP 7
STEP 6
STEP 10
STEP 8
LOCK-OUT
TAG
ON
OFF
MAIN
STEP 9
Run Status
Service Test
Temperatures
Pressures
Setpoints
Inputs
Outputs
Configuration
Time Clock
Operating Modes
Alarms
ENTER
ESC
MODE
Alarm Status
TIME
EWT
LWT
SETP
12.58
54.6F
44.1 F
44.0F
NAVIGATOR
ComfortLink
Run Status
Service Test
Temperatures
Pressures
Setpoints
Inputs
Outputs
Configuration
Time Clock
Operating Modes
Alarms
ENTER
ESC
MODE
Alarm Status
TIME
EWT
LWT
SETP
12.58
54.6F
44.1 F
44.0F
NAVIGATOR
ComfortLink

5
TO SHUT UNIT OFF
Refer to Fig. 1 for location of gas valve(s). See Fig. 3 while
proceeding with the following steps.
1. Turn off the unit demand for cooling or heating by using
the Navigator device. The Navigator device is located in
the control box.
a. Push the key until “Select a Menu Item” is
shown.
b. Push the key until the SERVICE TEST LED is
lit.
c. Push the key.
d. Push the key to move the flashing cursor to
STOP.
e. Push the key again. The NO/YES display
will flash.
f. Push the or key to toggle the display to YES
and then push . The unit will be locked off
from heating, cooling or any operation. The controls
will still function and the display will still operate.
2. Close the field-installed manual gas shutoff valve.
3. Turn off the electrical power to the unit using the optional
disconnect or the field-installed disconnect and lock off
using proper lockout and tag-out procedures.
4. Open the burner section hinged access door.
5. Move the switch on the gas valves to the OFF position and
wait 5 minutes before doing any service in the section or
on the piping.
6. Close the burner section hinged access door.
7. If unit is being shut down because of a malfunction, call
your dealer as soon as possible.
If unit is being shut down because the heating season has ended,
restore electrical power to the unit and reset the Navigator device
to RUN mode to ensure operation of the cooling system during the
cooling season. Refer to the unit Controls, Start-Up, Operation,
Service and Troubleshooting literature for more information.
Do not use this unit if any part has been under water. Immedi-
ately call a qualified service technician to inspect the unit and
to replace any part of the control system and gas control that
has been under water.
Fig. 3 — To Shut Unit Off
WARNING
1. Do not turn off the electrical power to unit without first
turning off the gas supply.
2. Never attempt to manually light the main burners on
unit with a match, lighter, or any other flame. If the
electric sparking device fails to light the main burners,
refer to the following shutdown procedures. Call your
dealer as soon as possible.
Failure to follow these procedures can result in serious fire
or personal injury.
ESCAPE
ENTER
ENTER
ENTER
CAUTION
Ensure clearances are in accordance with local installation
codes, the requirements of the gas supplier and the manu-
facturer's installation instructions.
ATTENTION
Assurez-vous que les dégagements sont conformes aux
codes d'installation locaux, aux exigences du fournisseur de
gaz et aux instructions d'installation du fabricant.
STEP 1
STEP 2 STEP 3 STEP 4
STEP 5 STEP 6 STEP 7
LOCK-OUT
TAG
ON
OFF
MAIN
Run Status
Service Test
Temperatures
Pressures
Setpoints
Inputs
Outputs
Configuration
Time Clock
Operating Modes
Alarms
ENTER
ESC
MODE
Alarm Status
TIME
EWT
LWT
SETP
12.58
54.6F
44.1 F
44.0F
NAVIGATOR
ComfortLink

6
MAINTAINING YOUR UNIT
All maintenance should be handled by skilled, experienced per-
sonnel. Your dealer can help you establish a standard procedure.
For your safety, keep the gas heating area clear and free of
combustible materials, gasoline, and other flammable liquids
and vapors.
To ensure proper functioning of the unit, flow of combustion and
ventilating air must not be obstructed from reaching the gas heat-
ing area. Clearance of at least 4 ft on all sides is required.
ROUTINE MAINTENANCE AND CARE
FOR THE EQUIPMENT OWNER
Before proceeding with those things you might want to main-
tain yourself, please carefully consider the following:
Air Filters
Air filters should be checked at least every 3 or 4 weeks and
changed or cleaned whenever they become dirty. Table 1
indicates the correct filter size for your unit. Open the hinged
filter access door to replace or inspect the filters. All units have
filter tracks into which the filters slide. Remove the filters by
pulling outward from the track. See Fig. 4.
If you have difficulty in locating your air filter in the return-air
duct system, or if you have questions concerning proper filter
maintenance, contact your dealer for instructions.
When replacing your unit filters, always use the same size and
type of filter that was originally supplied by the installer.
Units with outdoor air capability have a cleanable filter for the
outdoor air. This filter should be checked annually and cleaned
as necessary. Remove by removing screws in outdoor-air filter
retainer and sliding filters out of the unit.
Heat Exchanger
To ensure dependable and efficient heating operation, the heat
exchanger should be checked by a qualified maintenance per-
son before each heating season, and cleaned when necessary.
This checkout should not be attempted by anyone not having
the required expertise and equipment to do the job properly.
Checking and/or cleaning the heat exchanger involves remov-
ing the gas controls assembly and the flue collector box cover
and, when completed, reinstalling the gas controls assembly
for proper operation. Also, the flue collector box cover must be
replaced correctly so that a proper seal is maintained. Contact
your dealer for the required periodic maintenance.
Table 1 — Air Filter Data
NOTES:
1. See base unit Installation Instructions if field-supplied or optional
factory-supplied filters are used. When replacing filters, always use
the same type and size originally supplied.
2. When using pre-filters with bag filters, the pre-filters will be the
same number and dimensions as the bag filters.
WARNING
1. TURN OFF GAS SUPPLY AND THEN ELECTRI-
CAL POWER TO YOUR UNIT BEFORE SERVIC-
ING OR PERFORMING MAINTENANCE.
2. Do not turn off electrical power to this unit without
first turning off the gas supply.
3. When removing access panels or performing mainte-
nance functions inside your unit, be aware of sharp
sheet metal parts and screws. Although special care has
been taken to reduce sharp edges inside the unit, be
extremely careful when handling parts or reaching into
the unit.
Failure to follow these procedures can result in serious fire
or personal injury.
WARNING
Never operate your unit without filters in place. Failure to
heed this warning may result in damage to the blower mo-
tor and/or compressor. An accumulation of dust and lint on
internal parts of your unit can cause loss of efficiency and,
in some cases, fire.
48N BASE UNIT N P Q R S T
NOMINAL CAPACITY (tons) 75 90 105 120 130 150
MIXED AIR FILTERS
MERV 7 Pleated Filters 2 inch, MERV 7 2 inch, MERV 7
Quantity 28 28
Size (in.) 20x24x2 20x25x2
MERV 8 Pleated Filters 4 inch, MERV 8 4 inch, MERV 8
Quantity 28 28
Size (in.) 20x24x4 20x25x4
MERV 14 Pleated Filters 4 inch, MERV 14 4 inch, MERV 14
Quantity 28 28
Size (in.) 20x24x4 20x25x4
MERV 14 Cartridge Filters, 2 or 4-in. in Pre-Filters 12 inch, MERV 14 Cartridge Filters 12 inch, MERV 14 Cartridge Filters
Quantity 20 20
Size (in.) (15) 20x24x12, (5) 24x24x12 24x24x12
MERV 14 Bag, 2 or 4-in. in Pre-Filters 12 inch, MERV 14 Bag Filters 12 inch, MERV 14 Bag Filters
Quantity 20 20
Size (in.) (15) 20x24x12, (5) 24x24x12 24x24x12
MERV 15 Bag, 2 or 4-in. in Pre-Filters 19 inch, MERV 15 Bag Filters 19 inch, MERV 15 Bag Filters
Quantity 20 20
Size (in.) (15) 20x24x19, (5) 24x24x19 24x24x19
FINAL FILTERS
MERV 14 Cartridge Filters, 2 or 4-in. in Pre-Filters 12 inch, MERV 14 Cartridge Filters 12 inch, MERV 14 Cartridge Filters
Quantity 19 19
Size (in.) (14) 20x24x12, (5) 24x24x12 24x24x12
MERV 15 Bag, 2 or 4-in. in Pre-Filters 19 inch, MERV 15 Bag Filters 19 inch, MERV 15 Bag Filters
Quantity 19 19
Size (in.) (14) 20x24x19, (5) 24x24x19 24x24x19
MERV 17 HEPA, 2 or 4-in. in Pre-Filters 12 inch, MERV 17 HEPA Filters, 99.99% 12 inch, MERV 17 HEPA Filters, 99.99%
Quantity 19 19
Size (in.) (14) 24x12x12, (5) 24x24x12 24x24x12

7
Fig. 4 — Door Locations
Fan and Belts
Periodically check the condition of fan wheels and housings
and belt tension. When service is necessary, call your dealer.
Evaporator-Fan Motor, Condenser-Fan Motor
and Combustion-Fan Motor
Evaporator-fan, condenser-fan, and combustion-fan motors
have sealed bearings, no lubrication is required.
Fan Shaft Bearings
Charge fittings annually with Shell Alvania No. 2 or equivalent
grease.
Evaporator and Condenser Coils
Cleaning of the coils should only be done by qualified service
personnel. Contact your dealer for the required maintenance as
needed.
Condensate Drain
The drain pan and condensate drain line should be checked and
cleaned at the same time the cooling coils are checked by your
dealer.
Compressors
All compressors are factory shipped with a normal charge of
the correct type refrigeration grade oil in them and should rare-
ly require additional oil. The service technician must be certain
the proper oil level is maintained in the compressor when it is
installed and running.
Condenser Fan
The fan must be kept free of all obstructions to ensure proper
cooling. Contact your dealer for any required service.
Electrical Controls and Wiring
Electrical controls are difficult to check without proper instru-
mentation; therefore, if there are any discrepancies in the oper-
ating cycle, contact your dealer and request service.
Refrigerant Circuit
The refrigerant circuit is difficult to check for leaks without the
proper equipment; therefore, if inadequate cooling is suspect-
ed, contact your dealer for service.
Combustion Area and Vent System
The combustion area and vent system should be visually in-
spected before each heating season. The normal accumulation
of dirt, soot, rust, and scale can result in loss of efficiency and
improper performance if allowed to build up. Accumulation on
the burner crossover tube can result in the burners firing out of
normal time sequence. This delayed ignition is characterized
by an especially loud sound.
See Fig. 1 and 4 and proceed as follows to inspect the combus-
tion area and power-venting system of your unit.
1. Turn off gas supply and then electrical power to your unit.
2. Open gas section access door.
3. Using a flashlight, carefully inspect the burner areas for
dirt, soot, rust, or scale.
4. When you have completed your inspection, follow the
start-up procedures in this manual to restore your unit to
operation.
5. Observe unit heating operation, and watch the burner
flame core to see if it is bright blue. If you observe a sus-
pected malfunction, or if the burner flame cores are not
bright blue, call your dealer. See Fig. 5.
NOTE: Burner flame cores that have a mixture of orange, yellow,
or red flames together with the blue may not be burning gas effi-
ciently. Your dealer may have to adjust the air/gas mixture.
6. Replace gas section access panel.
Fig. 5 — Proper Flame Appearance
FILTER ACCESS DOOR
(OPPOSITE SIDE)
ACCESS DOORS
CONTROL BOX
ACCESS DOOR
AIR HOODS
GAS SECTION
ACCESS DOORS
WARNING
Do not poke sticks, screwdrivers, or any other object into
revolving fan blades. Severe bodily injury may result.
CAUTION
If your unit makes any unusual or especially loud noises
during heating, shut down the heating section and call your
dealer.
CAUTION
If dirt, soot, rust, or scale accumulations are found, call your
dealer and do not operate your heating section.

Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Catalog No. 04-53480193-01 Printed in U.S.A. Form 48N-2SO Pg 8 7-19 Replaces: 48N-1SO
© Carrier Corporation 2019
Unit Panels and Doors
After performing any maintenance or service on the unit, en-
sure all panels and doors are securely fastened in place to pre-
vent rain from entering unit cabinet and to prevent disruption
of the correct unit airflow pattern.
REGULAR DEALER MAINTENANCE
In addition to the type of routine maintenance you might be will-
ing to perform, your unit should be inspected regularly by a prop-
erly trained service technician. An inspection (preferably each
year, but at least every other year) should include the following:
1. Inspection of all flue product passages — including the
burners, heat exchanger, flue collector box, and vent pipe.
2. Inspection of all combustion-air and ventilation-air pas-
sages and openings.
3. Close inspection of all gas pipes leading to and inside your
unit.
4. Adjustment of the air/gas mixture if the burner flames are
not bright blue. (Refer to Fig. 4 and 5 for location of
access panel and proper flame appearance.)
5. Inspection, and if required, cleaning of the condenser and
evaporator coils.
6. Inspection, and if required, cleaning of the evaporator
drain pan.
7. Inspection, cleaning, and lubrication of blower wheel
housing and motor.
8. Inspection of all supply-air and return-air ducts for leaks,
obstructions, and insulation integrity. Any problems found
should be resolved at this time.
9. Inspection of the unit base to ensure that no cracks, gaps,
etc., exist which may cause a hazardous condition.
10. Inspection of the unit casing for signs of deterioration.
11. Inspection of all electrical wiring and components to
assure proper connection.
12. Inspection for leaks in the refrigerant circuit. Pressure-
check to determine appropriate refrigerant charge.
13. Operational check of the unit to determine working condi-
tions. Repair or adjustment should be made at this time.
14. Your servicing dealer may offer an economical service
contract that covers seasonal inspections. Ask for further
details.
Complete Service Instructions can be found in the base unit
Controls, Start-Up, Operation, Service and Troubleshooting
literature.
BEFORE YOU CALL FOR SERVICE, CHECK
FOR SEVERAL EASILY SOLVED PROBLEMS
If insufficient heat or cooling is suspected:
( ) Check for sufficient airflow. Check the air filters for dirt.
Check for blocked return-air or supply-air grilles. Be sure they
are open and unobstructed. Be sure heating and cooling set
points are correct. If these checks do not reveal the cause, call
your servicing dealer.
If your unit is not operating at all, check the following list
for easy solutions:
( ) Check to be sure that heating temperature set point is set
above the indoor temperature during the heating season, or that
cooling temperature set point is below the indoor temperature
during the cooling season. Be sure the unit on/off switch is in
the ON position and not in the OFF position. Be sure unit has
been programmed with the appropriate time schedules and de-
sired operating set points.
( ) Is the electrical supply switch ON? Are any fuses blown,
or have any of the circuit breakers tripped?
( ) During the heating season, check the manual shutoff
valve. Is this lever parallel with the pipe, indicating that the
valve is open? Or is the lever at a right angle, indicating that
the valve is closed? If closed, has the gas been shut off for safe-
ty reasons? Otherwise, you may follow the start-up procedures
listed in this manual and open the valve.
NOTE: Before proceeding with the next check, turn OFF the
electrical power supply to the unit. Open the control access
door.
( ) During the heating season, check the control switch on
the gas valve. It is in the ON position? If it is not, be sure it has
not been turned off for the purpose of safety. Follow the start-
up procedures in this manual.
( ) If your unit still fails to operate, call your servicing dealer
for troubleshooting and repairs. Specify the model and serial
numbers of your unit. (Record them in this manual in the space
provided.) If the dealer knows exactly which unit you have, he
may be able to offer suggestions over the phone, or save valu-
able time through knowledgeable preparation for the service
call.
IN CASE OF TROUBLE
If, after performing the above, unit performance is unsatisfac-
tory, shut off the unit and call your dealer.
Dealer’s Name _______________________________________
Telephone No. _______________________________________
Unit Model __________________________________________
Unit Serial Number ____________________________________
Unit Address _________________________________________
Bus Number _________________________________________