Bryant DURAPAC PLUS SERIES 542J, Инструкция по установке, запуску и обслуживанию

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VII. OUTDOOR FANS AND MOTORS
Fans and motors are factory set. Refer to Outdoor-Fan
Adjustment section on page 24 as required.
VIII. RETURN-AIR FILTERS
Check that correct filters are installed in filter tracks. See
Table 1. Do not operate unit without return-air filters.
IX. OUTDOOR-AIR INLET SCREENS
Outdoor-air inlet screens must be in place before operating
unit.
X. OPERATING SEQUENCE
A. Cooling, Units Without Economizer
When thermostat calls for cooling, terminals G and Y1 are
energized. The indoor-fan contactor (IFC), reversing valve
solenoids (RVS1 and RVS2 [RVS2 on size 180 only]) and
compressor contactor are energized and indoor-fan motor,
compressor, and outdoor fan starts. The outdoor-fan motor
runs continuously while unit is cooling.
B. Heating, Units Without Economizer
Upon a request for heating from the space thermostat, ter-
minal W1 will be energized with 24 v. The IFC, outdoor-fan
contactor (OFC), C1, and C2 (size 180 only) will be ener-
gized. The indoor fan, outdoor fans, and compressor no. 1,
and compressor no. 2 are energized and RVS1 and RVS2
(size 180 only) are deenergized and switch position.
If the space temperature continues to fall while W1 is
energized, W2 will be energized with 24 v, and the heater
contactor(s) (HC) will be energized, which will energize the
electric heater(s).
When the space thermostat is satisfied, W2 will be deener-
gized first, and the electric heater(s) will be deenergized.
Upon a further rise in space temperature, W1 will be
deenergized.
C. Cooling, Units With EconoMi$erIV
When free cooling is not available, the compressors will be
controlled by the zone thermostat. When free cooling is
available, the outdoor-air damper is modulated by the
EconoMi$erIV control to provide a 50 to 55 F supply-air tem-
perature into the zone. As the supply-air temperature fluctu-
ates above 55 or below 50 F, the dampers will be modulated
(open or close) to bring the supply-air temperature back
within set point limits.
For EconoMi$erIV operation, there must be a thermostat
call for the fan (G). This will move the damper to its mini-
mum position during the occupied mode.
Above 50 F supply-air temperature, the dampers will modu-
late from 100% open to the minimum open position. From
50 F to 45 F supply-air temperature, the dampers will main-
tain at the minimum open position. Below 45 F the dampers
will be completely shut. As the supply-air temperature rises,
the dampers will come back open to the minimum open posi-
tion once the supply-air temperature rises to 48 F.
If optional power exhaust is installed, as the outdoor-air
damper opens and closes, the power exhaust fan will be ener-
gized and deenergized.
If field-installed accessory CO
2
sensors are connected to the
EconoMi$erIV control, a demand controlled ventilation
strategy will begin to operate. As the CO
2
level in the zone
increases above the CO
2
set point, the minimum position of
the damper will be increased proportionally. As the CO
2
level
decreases because of the increase in fresh air, the outdoor-air
damper will be proportionally closed. Damper position will
follow the higher demand condition from DCV mode or free
cooling mode.
Damper movement from full closed to full open (or vice
versa) will take between 1
1
/
2
and 2
1
/
2
minutes.
If free cooling can be used as determined from the appropri-
ate changeover command (switch, dry bulb, enthalpy curve,
differential dry bulb, or differential enthalpy), a call for cool-
ing (Y1 closes at the thermostat) will cause the control to
modulate the dampers open to maintain the supply air tem-
perature set point at 50 to 55 F.
As the supply-air temperature drops below the set point range
of 50 to 55 F, the control will modulate the outdoor-air damp-
ers closed to maintain the proper supply-air temperature.
D. Heating, Units With EconoMi$erIV
When the room thermostat calls for heat, the heating
controls are energized as described in the Heating, Units
Without Economizer section. When the indoor fan is
energized, the economizer damper moves to the minimum
position. When the indoor fan is off, the economizer damper
is fully closed.
E. Defrost
When the temperature of the outdoor coil drops below 28 F
as sensed by the defrost thermostat (DFT2) and the defrost
timer is at the end of a timed period (adjustable at 30, 50, or
90 minutes), reversing valve solenoids (RVS1 and RVS2) are
energized and the OFC is deenergized. This switches the
position of the reversing valves and shuts off the outdoor fan.
The electric heaters (if installed) will be energized.
The unit continues to defrost until the coil temperature as
measured by DFT2 (see Fig. 32) reaches 65 F, or the duration
of defrost cycle completes a 10-minute period.
During the Defrost mode, if circuit 1 defrosts first, RVS1 will
oscillate between Heating and Cooling modes until the
Defrost mode is complete.
At the end of the defrost cycle, the electric heaters (if
installed) will be deenergized; the reversing valves switch
and the outdoor-fan motor will be energized. The unit will
now operate in the Heating mode.
If the space thermostat is satisfied during a defrost cycle, the
unit will continue in the Defrost mode until the time or tem-
perature constraints are satisfied.
DEFROST
THERMOSTAT
NOTE: Defrost thermostat is located at the bottom tee of circuit no. 1
and the top tee of circuit no. 2.
Fig. 32 — Defrost Thermostat Location