Carrier MODU-PAC 50DF - Manual (Page 37)

Guide specifications
Unit shall be of a one-piece air-to-air electric cooling unit and
shall be mounted on a full-perimeter roof curb. Unit shall be UL
listed and carry UL label.
Total cooling capacity of the unit shall be_______ Btuh or greater,
sensible capacity shall be_______ Btuh or greater and the leaving
dry-bulb temperature shall be______ F at conditions of ______ cfm
evaporator air entering unit at______ F wet-bulb,_____ F dry-bulb
and condenser entering air temperature of_______F dry bulb.
Unit cabinet shall be constructed of galvanized steel, bonderized
and coated with baked enamel
Refrigeration system — The unit shall contain serviceable her­
metic compressor(s) with service valves, vibration isolation, crank­
case heater(s), sight glass(es) and filter-drier(s). Electric unloaders,
providing steps of_____ %,_____ %, and _____ .%, shall be factory
installed to provide close control of leaving air dry-bulb tempera­
ture regardless of load variations Compressors shall be of same
manufacture as unit.
Hot gas bypass to the evaporator shall be factory installed to
permit unit operation down to minimum airflow. Evaporator coil
shall always have the full face active to assure proper treatment of
all air flowing thru unit
Controls — The variable volume control network shall be factory
installed and wired in the unit and contain:
• Microprocessor which shall:
— provide precise control of capacity staging.
— contain an adjustable set point for discharge air temperature
— contain a control memory function effectively “remembering”
the previous 50 minutes of system operation and maintaining
a stable, average discharge temperature based on the previous
50 minutes of operation.
— contain the ability to program a reset of discharge air tem­
perature in accordance with temperature readings trans­
mitted from conditioned space. This reset function shall be
adjustable in both amount of reset and point at which reset
is initiated on a preprogrammed schedule.
— contain a control band adjustment (2-16 F) to tune control
system to specific applications •
• Morning warmup thermostat containing 2 stages of control
for demand oriented discriminant energy usage: First stage of
thermostat shall shut down electric heaters (if provided). A “dead­
band” shall exist between first stage and second stage of thermo­
stat. In the “dead-hand” zone, indoor air fan runs but cooling mode
will not energize until return air temperature exceeds the adjust­
able set point of second stage of morning warmup thermostat.
At call for cooling, the morning warmup thermostat shall switch
control of unit to microprocessor.
• Remote control panel containing a 7-day clock and 6 system
status lights.
The clock shall enter system into DAY (OCCUPIED) or NIGHT
(UNOCCUPIED) modes as preprogrammed. Remote control
panel shall contain a 5-hour bypass timer to provide air condi­
tioning during normally unoccupied hours.
50DF Modu"Pac® |
Coils shall be aluminum plate fins mechanically bonded to copper
tubes. They shall be of an intertwined design for equal circuit load­
ing and full active coil on part load operation to assure proper
treatment of conditioned air.
115-volt convenience outlet shall be sized to handle a small
power load or service light.
Modulating outdoor air control package (Economizer) shall
provide “free cooling” with outside air The package shall:
• contain low leak dampers rated at 3% at 3-in. wg static pressure.
• contain spring return motor to close dampers during power
failure.
• use 100% outside air during integrated (simultaneous) econ­
omizer cooling and mechanical cooling.
• utilize discharge air sensor and enthalpy changeover for damper
control.
• contain adjustable outdoor air thermostat to lock out mech­
anical cooling when outdoor air is below its setting
Pre-installed tracks shall be provided to accommodate field-
installed hydronic coils. (Unit without electric heat)
Fans and motors — The indoor air fans shall be of the forward-
curved centrifugal Class
I type, belt driven by a_______ hp motor.
The outdoor air fan(s) shall be of the propeller type, each directly
driven by a 1-hp inherently protected motor
Safety controls — Cooling system shall be protected by: fusible
plug, low and high pressurestat, compressor motor overloads, and
a timing device which will prohibit the compressor motor from
being subjected to a starting current more than once every
5 minutes.
Unit connections — Power wires in the unit shall be powered by
single-point terminal connections All utility connections shall be
routed thru bottom of unit within curb perimeter. Alternate
openings in sides of unit shall also be provided
Dimensions — The unit casing shall have width of not more than
_____in., length of not more than________ in , and height of not
more than_____ inches
Motor and drive to provide higher fan output when job require­
ments exceed standard fan capacity shall be provided.
Bag filters with 50% efficiency (NBS Dust Spot Test) shall be
provided. Bag filter rack shall accept filters of up to 95% efficiency.
Roof Curb — Roof curb shall be of same manufacture as unit,
shall support unit and provide a watertight enclosure to protect
ductwork and utility services Curb design shall comply with
National Roofing Contractors Association requirements.
Static pressure control shall consist of a self-locating damper
assembly and motor/regulator assembly and shall permit bottom
or side connection discharge and shall include a duct transition for
connection of field ductwork.
Head pressure control — An indoor air fan speed control to
permit unit to operate down to -20 F shall be provided.
Number One
AirConditbning
Maker
Division ot
Carrier Corporation
Carrier Parkway • Syracuse NY 13221
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations
Book 1
Tab 1b
Form50DF-2P Supersedes 50DF-1P Printed in U S A 1182 1-82 P C 1 1 1 Catalog No 525-080