Controls; Typical Installation; Application Data - Carrier 50ZH Series Product Data

Sequence of operation
When power is supplied to unit, the transformer (TRAN) is
energized.
Cooling — With the thermostat subbase in the cooling
position, and when the space temperature comes within 2°F
of the cooling set point, the thermostat makes circuit R-O.
This energizes the reversing valve solenoid (RVS) and places
the unit in standby condition for cooling.
As the space temperature continues to rise, the second stage
of the thermostat makes, closoing circuit R-Y. When
compressor time delay (5 ± 2 minutes) is completed, a circuit
is made to contactor (C), starting the compressor (COMP)
and outdoor-fan motor (OFM). Circuit R-G is made at the
same time, energizing the indoor-fan relay (IFR) and starting
the indoor-fan motor (IFM) after a 1-second delay.
When the thermostat is satisfied, contacts open, deenergizing
C. The COMP and OFM stop, and the IFM stops after a 30
second time delay.
Heating — On a call for heat, thermostat makes circuits
R-Y and R-G.

Typical Installation

Application data

Condensate trap — A 2-in. condensate trap must be field
supplied.
1" MIN.

Controls

RETURN
AIR
TOP COVER
POWER AND
LOW-VOLTAGE
ENTRY
COMPOSITE
RUST-PROOF
BASEPAN
Power Wiring
CONDENSATE
DRAIN
Control Wiring
CONNECTION
Condenser Airflow
*Separate disconnect per NEC
(National Electrical Code) required
for electric heater when single-
Evaporator Airflow
point conection is not used.
TRAP
OUTLET
2" MIN.
When compressor time delay (5 ± 2 minutes) is completed,
a circuit is made to C, starting COMP and OFM. Circuit R-
G also is completed, energizing IFR and starting IFM after a
1-second delay.
Should room temperature continue to fall, circuit R-W is
made through second-stage thermostat bulb. If optional
electric heat package is used, a relay is energized, bringing
on first bank of supplemental electric heat. When thermostat
is satisfied, contacts open, deenergizing contactor and relay;
motors and heaters deenergize. The IFM may be controlled
by a time-delay relay that keeps the fan on for 30 seconds.
Defrost — Defrost board (DB) is a time and temperature
control, which includes a field-selectable time period
between checks for defrost (30, 50, and 90 minutes).
Electronic timer and defrost cycle start only when contactor
is energized and defrost thermostat (DFT) is closed.
Defrost mode is identical to cooling mode, except outdoor-
fan motor stops and a bank of optional electric heat turns on
to warm air supplying the conditioned space.
INDOOR
THERMOSTAT
FROM
POWER
SOURCE
DISCONNECT
PER NEC*
(UNIT AND
ELECTRIC
HEATER)
C00008
Maximum cooling airflow — To minimize the possibility
of condensate blow-off from the evaporator, airflow through
the units should not exceed 450 cfm/ton.
Minimum cooling airflow — The minimum cooling airflow
is 350 cfm/ton.
Minimum cooling operating outdoor air temperature —
All standard units have a minimum ambient operating
temperature of 40°F. With accessory low ambient temperature
kit, units can operate at temperatures down to 0°F.
Maximum operating outdoor air temperature — Maximum
outdoor operating air temperature for cooling is 125°F.
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