Carrier 48SX024-048 - Manual (Page 39)

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COOLING SEQUENCE OE OPERATION — With the room
thermostat SYSTEM switch in the COOL position and the
FAN switch in the AUTO, position, the cooling sequence
of operation is as follows:
When the room temperature rises to a point that is slightly
above the cooling control setting of the thermostat, the ther­
mostat completes the circuit between thermostat terminal R
to terminals Y and G. These completed circuits through the
thermostat connect contactor coil (C) (through unit wire Y)
and blower relay coil (BR) (through unit wire G) across the
24-v secondary of transformer (TRAN)
The normally-open contacts of energized contactor (C)
close and complete the circuit through compressor motor
(COMP) to condenser (outdoor) fan motor (OEM). Both
motors start instantly.
The set of normally-open contacts of energized relay BR
close and complete the circuit through evaporator blower
(indoor) fan motor (IFM). The blower motor starts
instantly.
NOTE: Once the compressor has started and then has stopped,
it should not be started again until 5 minutes have elapsed.
The cooling cycle remains “on” until the room temper­
ature drops to point that is slightly below the cooling
control setting of the room thermostat. At this point, the
thermostat “breaks” the circuit between thermostat termi­
nal R to terminals Y and G. These open circuits deenergize
contactor coil C and relay coil BR. The condenser and com­
pressor motors stop. After a 30-second delay, the blower
motor stops. The unit is in a “standby” condition, waiting
for the
next “call for cooling” from the room
thermostat.
MAINTENANCE
To ensure continuing high performance, and to minimize
the possibility of premature equipment failure, periodic main­
tenance must be performed on this equipment. This com­
bination heatlng/cooling unit should be inspected at least
once each year by a qualified service person. To trouble­
shoot heating or cooling of units, refer to Tables 15 and 16.
NOTE TO EQUIPMENT OWNER: Consult your local dealer
about the availability of a maintenance contract.
A WARNING
The ability to properly perform maintenance on this equip­
ment requires certain expertise, mechanical skills, tools,
and equipment. If you do not possess these, do not at­
tempt to perform any maintenance on this equipment
other than those procedures recommended in the
User’s Manual. FAILURE TO HEED THIS WARN­
ING COULD RESULT IN SERIOUS PERSONAL
INJURY AND POSSIBLE DAMAGE TO THIS
EQUIPMENT.
The minimum maintenance requirements for this equip­
ment are as follows:
1. Inspect air filter(s) each month. Clean or replace when
necessary.
2. Inspect indoor coil, drain pan, and condensate drain each
cooling season for cleanliness. Clean when necessary.
3. Inspect blower motor and wheel for cleanliness and check
lubrication each heating and cooling season. Clean and
lubricate (if required) when necessary. For first heating
season, inspect blower wheel bimonthly to determine proper
cleaning frequency.
4. Check electrical connections for tightness and controls
for proper operation each heating and cooling season.
Service when necessary.
5. Check and inspect heating section before each heating
season. Clean and adjust when necessary.
6. Check flue hood screen and remove any obstructions if
necessary.
7. Check vent screen and clean if necessary.
A WARNING
Failure to follow these warnings could result in serious
personal injury:
1. Turn off gas supply, then turn off electrical power
to the unit before performing any maintenance or
service on the unit.
2. Use extreme caution when removing panels and parts.
As with any mechanical equipment, personal injury
can result from sharp edges, etc.
3. Never place anything combustible either on, or in
contact with, the unit.
4. Should overheating occur, or the gas supply fail to
shut off, shut off the external main manual gas valve
to the unit, then shut off the electrical supply.
Air Filter
A CAUTION
Never operate the unit without a suitable air filter in
the retum-air duct system. Always replace the filter with
the same dimensional size and type as originally
installed. See Tables 1 and 2 for recommended filter
sizes.
Inspect air filter(s) at least once each month and replace
(throwaway-type) or clean (cleanable-type) at least twice
during each heating and cooling season or whenever the
filter(s) becomes clogged with dust and lint.
Unit Top Removal
NOTE: When performing maintenance or service proce­
dures that require removal of the unit top, be sure to per­
form all of the routine maintenance procedures that require
top removal, including: inspection of the heat exchanger
area, coil inspection and cleaning, and condensate drain pan
inspection and cleaning.
Only qualified service personnel should perform mainte­
nance and service procedures that require unit top removal.
Refer to the following top removal procedures:
1. Turn off gas supply, then turn off electric power to unit.
2. Remove all screws that secure unit top, including screws
around 4 sides and those on top that screw into internal
divider panels. Save all screws.
3. Lift top from unit carefully. Set top on edge.
4. Carefully replace and secure unit top to unit, using screws
removed in Step 2, when maintenance and/or service pro­
cedures are completed. (Be sure to use original screws
that have rubber washers to seal out water when secur­
ing top to internal divider panels.)
Evaporator Blower and Motor
NOTE: Motors without oilers are prelubricated Do not at­
tempt to lubricate these motors.
For longer life, operating economy, and continuing effi­
ciency, clean accumulated dirt and grease from the blower
wheel and motor annually.
Lubricate the motor every 5 years if the motor is used
intermittently (thermostat FAN switch in AUTO, position),
or every 2 years if the motor is used continuously (thermo­
stat FAN switch in ON position).
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