Carrier 48DD - Manual

Carrier /У
— 'y
Combination Heating/
Cooling Units
48DD
Gas Heating 275,000 Btuh
Electric Cooling 124,000 Btuh
48DD012
DESCRIPTION
The 48DD012 is a one-piece combination gas heating/
electric cooling unit designed primarily for outdoor rooftop
installation on a factory-supplied curb accessory but can be
installed on grade or conventional steel framework. This
unif combines superior performance with compactness,
versatility of application and ease of installation to supply
year-round air conditioning for commercial and industrial
buildings The unit is completely factory assembled,
charged and tested Requires only natural gas, and suitable
electrical and duct connections for hookup. Air can be
supplied to the building either thru bottom of the unit or
thru the side A manually-adjustable outdoor air intake is
provided Condensers are air cooled Low silhouette design
allows units to be easily hidden from street level view
FEATURES
• Two-Stage Heating and Cooling — Both heating and
cooling stages have 50 percent or 100 percent capacity
ranges of operation This reduces operating costs
• Multiple Choice of Air Flow — Air can be delivered to
the building either thru the bottom of the unit with
separate inlet and outlet air ducts or concentric ducting, or
it can be delivered thru the side of the unit with separate
inlet and outlet air ducts
• Gas Safety Control will shut off the main gas valve in
case of pilot or combustion air failure, or overheating of the
heat exchangers
• Induced Draft Combustion — Unaffected by winds and
drafts Equipped with safety shut-off devices in case of
combustion air failure or blockage
• Automatic Electric Ignition — Pilot flame is auto­
matically relighted in case of interruption of power or gas
• Aluminized Heat Exchangers — Resist corrosion and
provide long, quiet, safe, and efficient operation These
heat exchangers have a full ten-year warranty
• Time Guard Circuit* prevents rapid cycling, extends
compressor life When power to unit is interrupted,
compressor cannot restart for five minutes
• Head Pressure Control automatically cycles one of two
condenser fans, permitting cooling operation down to 35 F
ambient temperature
• Other Quality Components — Crankcase heaters and
accumulators to protect the compressor against flooded
starts, filter-driers and sight glasses for moisture control and
visual inspection of refrigerant charge
ACCESSORIES
• 32LM MotormasterTM Head Pressure Control mod­
ulates speed of condenser fan motor to maintain saturated
condensing temperature at low outdoor temperatures
• Thermostat Assembly is a two-step heating/two-step
cooling thermostat and a matching switch base Either
automatic or manual changeover is available
• Remote Control Center allows manual control of the
unit from a location remote from the thermostat The
thermostat furnished with the remote control center has no
knobs or switches for manual control
• Roof Curb frames roof opening, is watertight connec­
tion between unit and roof Designed so ductwork and roof
flashing may be installed prior to placing the unit
• Modulating Outside Air Control Package (economizer)
can furnish outside air for cooling when outside air
temperature is below 60 F. It can replace operation of the
refrigerant system under these conditions
• LP Conversion Kit used to convert the unit from natural
gas to LP gas usage
• Relief Damper used to relieve positive building pressure
© Carrier Corporation 1970 •Single Feature Sheet Available Form 48DD-1 P