Indoor Airflow And Airflow Adjustments; Cooling Sequence Of Operation - Carrier 50SD030 Installation Instructions Manual

INDOOR AIRFLOW AND AIRFLOW ADJUSTMENTS

NOTE: For cooling operation, the recommended airflow is 350 to
450 cfm for each 12,000 Btuh of rated cooling capacity.
Table 4 shows cooling airflows at various external static pressures.
Refer to this table to determine the airflow for the system being
installed.
NOTE: Be sure that all supply- - and return- -air grilles are open, free
from obstructions, and adjusted properly.
WARNING
!
ELECTRICAL SHOCK HAZARD
Failure to follow this warning could result in personal injury
or death.
Disconnect electrical power to the unit and install lockout tag
before changing blower speed.
Airflow can be changed by changing the lead connections of the
blower motor.
All 50SD units are factory wired for low speed, except sizes 030 and
048 which are wired for medium speed.
FOR 208/230v
For color coding on the 208/230v motor leads, see Table 5.
Fig. 16 - - Cooling Charging Chart
Table
To change the speed of the indoor fan motor (IFM), remove the fan
motor speed leg lead from the time delay relay (TDR). This wire is
attached to terminal- -3 of TDR for 3- -phase units. To change the
speed, remove and replace with lead for desired blower motor speed.
Insulate the removed lead to avoid contact with chassis parts.

COOLING SEQUENCE OF 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 thermostat 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 time delay relay (TDR) (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 (OFM). Both motors start instantly.
The set of normally open contacts of energized relay TDR close and
complete the circuit through evaporator blower (indoor) fan motor
(IFM).
17
5—Color Coding for 208/230v Motor Leads
Black = High Speed
Blue = Medium Speed
Red = Low Speed
A05109