Carrier MODU-PAC 50DF - Manual (Page 24)

I 50DF Modu-Pac® |
Reduced operating cost, energy conservation
and high capacity performance are built into
each unit.
50DF Modu-pac® units contain an advanced solid-state control
system which provides maximum operating economy The “brain”
of the system is a microprocessor that coordinates economizer
operations, sequences cooling stages, and controls system modes
The economizer, standard on 50DF Modu-pac units, provides
“free-cooling” on in-between days When outdoor temperatures
are low, the economizer uses the cool outside air to provide
cooling.
On occasion, the cool outside air may not meet the cooling
demand The microprocessor moves into action. It integrates
economizer cooling with mechanical cooling Cool, outside air
is mixed with mechanically cooled air, providing low-cost comfort
inside. The integrated system supplies only the amount of
mechanical cooling necessary Saves energy, reduces compressor
wear and lowers operating costs.
The microprocessor-reset capability prevents costly over­
cooling of the conditioned space If overcooling occurs, the m.icro-
processor resets the discharge air temperature in relation to the
conditioned space temperature A stable, comfortable tempera­
ture is maintained.
The microprocessor also features an adjustable control band
to tune the control system for specific applications.
At very light loads, when the system experiences minimum
airflows, hot gas bypass maintains capacity control, so space con­
ditions stay comfortable.
The Modu-pac® control system includes a remote control box
that contains a 7-day programmable clock. The clock saves energy
by shutting down the system during unoccupied periods If a field-
supplied thermostat and accessory electric heat are used, unit
starts up only on a call for heating or cooling. There’s no energy
or dollars wasted when building is unoccupied
The clock contains a 10-hour spring carryover for continuous
operation during power failure. No readjustment is necessary.
Standard features for years of energy savings
and convenience
Low-leakage dampers limit infiltration. Rated by the manu­
facturer at 3% with 3-in. wg pressure differential.
Spring return damper motor automatically closes outdoor air
dampers in the event of a power failure.
Enthalpy controller senses total heat content of outside air.
Assures optimum use of outside air for cooling.
2-stage morning warmup thermostat saves fuel by keeping
outdoor air damper closed until morning warmup is completed.
Avoids using energy to warm cold outside air
Status lights on remote control box indicate operating mode
Five-hour manual bypass switch provides unit operation
during unoccupied periods. Located at the remote control box, it’s
a quick and easy way to operate the system temporarily.
Intertwined coil provides cooling of the full air stream with use of
minimum compression.
Options and Accessories
Static pressure control and damper assembly regulates duct
static pressure at rooftop unit to keep the entire system at design
level This assures quiet operation even when maximum static
pressure exists in the duct. The static pressure damper assembly
installs neatly and easily within the roof curb, and may also be used
for side flow connection arrangements All necessary hardware
and mounting fixtures are factory supplied A dial adjustment is
all that’s required to select the desired air pressure setting.
(Accessory)
Roof curb supports entire unit and frames roof openings for
ductwork, wiring and fast connections It provides a strong, water­
tight interface between unit and roof Once the curb is set in place,
the unit may be rigged at any time No need to schedule around
the roofer. The design complies with National Roofing Contractors
Association requirements (Accessory)
Motormaster® head pressure control modulates the speed of
a condenser fan motor to maintain correct condensing tempera­
ture at low outdoor air temperatures. Permits subzero tempera­
ture operation to -20 F if required. (Accessory)
High-efficiency filter. Bag-type filter has 50% filtering efficiency
(NBS Dust Spot Test). Unit bag filter frame also accepts field-
supplied bag filters of up to 95% filtering efficiency.
Filtration not only assures supply of clean air to terminals and
conditioned space, but also reduces frequency of system and
terminal cleaning. (Option)
Higher hp indoor fan motor and drive deliver more fan per­
formance when it’s needed Provide increased performance for
variable volume applications (Option)
Electric heater provides morning warmup following unoccupied
periods Prevents the early morning chill before internal loads
buildup.
ft
MOTORMASTER
HEAD PRESSURE
CONTROL
STATIC PRESSURE
CONTROL REGULATOR
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