Bryant SINGLE PACKAGED HEAT PUMP UNITS 657A - Manual (Page 23)

remains energized for the delay timing. When the fan switch is in
AUTO, the fan cycles with either the call for heating or cooling.
Cooling- On a call for cooling, 24 v is supplied to the compressor
contactor (C) and IFM simultaneously through the ’’Y’’ and ’’G’’
terminals of the thermostat. Energizing the contactor closes the
normally open set of contacts supplying power to both the
compressor and outdoor (condenser) fan motor (OFM). On the loss
of the call for cooling, 24 v is removed from the ’’Y’’ and ’’G’’
terminals of the thermostat, deenergizing the compressor and
OFM. The indoor fan remains energized for the delay timing.
NOTE: Once the compressor has started and then stopped, it
cannot be restarted again until 5 minutes have elapsed.
J. HEATING SEQUENCE OF OPERATION
PSC BLOWER MOTOR UNITS (024–042)
Heat Pump Heating - On a call for heat, thermostat makes circuits
R-Y and R-G. When compressor time delay (5 +/- 2 minutes) is
completed, a circuit is made to C, starting COMP and OFM.
Circuit R-G also energizes IFR and starts IFM after 1-sec. 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 deen-
ergize. The IFM may be controlled by a time-delay relay that will
extend IFM operation for a matter of sec.
Defrost Mode - Defrost board (DB) is a time and temperature
control, which includes a field-selectable time period between
checks for defrost (30, 50 or 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.
Auxiliary Heating - If accessory electric heaters are installed, on
a call for heat, circuit R-W is made through the thermostat
contacts. Circuit R-G is made which energizes the IFR. If the
heaters are staged, then the thermostat closes a second set of
contacts W2 when second stage is required. When thermostat is
satisfied, contacts open, deenergizing the heater relay and the IFR.
ECM BLOWER MOTOR UNITS (048–060)
Heat Pump Heating - On a call for heat, thermostat makes circuits
R-Y and R-G. When compressor time delay (5 +/- 2 minutes) is
completed, a circuit is made to C, starting COMP and OFM.
Circuit R-G also energizes IFR and starts IFM after 1-sec. 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. At this time, the airflow (CFM) will be
either the AUX HEAT RANGE (VIO) setting or the AC/HP SIZE
(BLU) setting, whichever is greater. This may be a noticeable
change in airflow. When thermostat is satisfied, contacts open,
deenergizing contactor and relay; motors and heaters deenergize.
The IFM has a time delay relay that keeps the fan on for 30-sec.
Defrost Mode - Defrost board (DB) is a time and temperature
control, which includes a field-selectable time period between
checks for defrost (30, 50 or 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.
Auxiliary Heating - If accessory electric heaters are installed, on
a call for heat, circuits R-W and R-G are made through the
thermostat contacts, energizing the heater relay and IFM. If the
heaters are staged, then the thermostat closes the second set of
contacts, W2, when the second stage is required. When the
thermostat is satisfied, contacts open, deenergizing the heater relay
and the IFM.
MAINTENANCE
To ensure continuing high performance, and to minimize the
possibility of premature equipment failure, periodic maintenance
must be performed on this equipment. This cooling unit should be
inspected at least once each year by a qualified service person. To
troubleshoot cooling of units, refer to tables at the back of the
book.
NOTE TO EQUIPMENT OWNER: Consult your local dealer
about the availability of a maintenance contract.
WARNING: The ability to properly perform mainte-
nance on this equipment requires certain expertise, me-
chanical skills, tools, and equipment. If you do not
possess these, do not attempt to perform any maintenance
on this equipment other than those procedures recom-
mended in the User’s Manual. FAILURE TO HEED
THIS WARNING COULD RESULT IN SERIOUS PER-
SONAL INJURY AND POSSIBLE DAMAGE TO THIS
EQUIPMENT.
WARNING: Failure to follow these warnings could
result in serious personal injury:
1. Turn off electrical power to the unit and install lockout
tag 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.
CAUTION: Errors made when reconnecting wires may
cause improper and dangerous operation. Label all wires
prior to disconnection when servicing.
The minimum maintenance requirements for this equipment are as
follows:
TABLE 7—ECM BOARD PIN SELECTION
OPTION DESCRIPTION
30-Sec On/60-Sec Off Delay
Profile (Terminal 1)
Used when it is desirable to allow system coils time to heat
up or cool down prior to airflow
No Delay Option
(Terminal 2)
Used for servicing or when other components are used to
perform the delay function
30-Sec Off Delay
(Terminal 3)
Preset factory setting for 657A units
45-Sec Off Delay
(Terminal 4)
Enhances system efficiency
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