Carrier 48DD User Manual

Carrier

Combination Heating/

/У

— 'y

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

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

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

• 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

•Single Feature Sheet Available Form 48DD-1 P

• 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

DIMENSIONS

PHYSICAL DATA

UN IT 48 D D

OP ER A TI NG W E IG H T (lb )

RE FR IG E RA N T

Op era ti ng C h arg e (Ib )

CO MP R E SS O R

Cyl in de rs ... Rp m (6 0- H z)

OU TD O O R AI R FA N S

No . .. .D iam (in .)

No m Cf m ea c h. ..to ta l

Mo to r H p ...R p m

CO ND E N SE R C OI L

Ro ws ... F ins /i n.

Tot al Fa c e A re a (s q ft)

IND O OR A IR F A N S

No . .. .S ize (i n. )

No m Cf m Rp m Ra n ge (S ta n da rd D riv e ) Ma x A ll ow a ble R p m Bel t T yp e ...L e ng th (i n. ) Mo to r

No . .. .H p. ..R pm

Ma x B ra k e H p Fra m e Sha ft D ia m (in .)

Pul le y P it ch D ia m (in .)

EVA P O RA T OR C O IL

Tot al Fa c e A re a (s q ft) Ro ws ... F ins /i n.

HE AT E XC H A NG E R S

A.G .A . C e rti fie d R ise

No . .. .E lem e nt s (ea c h)

012

169 0

9 ea c h S y ste m

(2) Re ci pr oc ati ng H er m eti c

4 ea c h 3 5 00

Pro pe lle r; Di re ct Dr ive

2 2 2

320 0 .6 40 0

1/ 1 1 40 (3 -p ha se )

107 5 (1 -i^ ha s e)

Pla te Fi n

4 1 3

14 0

Cen tr ifu ga l; Be lt Dr ive

2 10x10

400 0

123 0 to 15 40

170 0

A. 4 4

1 3 17 4 5

3 4 5 182 T

iVs 5 6

Pla te Fi n

10 02

3 1 4

Alu mi niz e cd S tee l

45 to 75 F

2 .5

SELECTION PROCEDURE (With Example)

I Determine cooling and heating requirements at design

conditions.

GIVEN;

Required Cooling Capacity (TO

Sensible Heat Capacity (SHC)

Required Heating Capacity

Condenser Entering Air Temp

Indoor Air Temp Evaporator Air Quantity Electrical Characteristics

External Static Pressure

II Select unit based on required cooling capacity.

Enter Cooling Capacities table at condenser entering air tempera ture of 95 F. The 48DD012 at 4000 cfm and 67 F Ewb will provide a total capacity of 132,000 Btuh and a sensible heat of 96,000 Btuh Calculate SHC correction if required

III Compare the heating capacity of the unit selected with the

design conditions.

Unit 48DD012 provides an input of 275,000 Btuh with a bonnet capacity of 206,000 Btuh

IV Determine fan speed and brake hp requirements at design

conditions.

Enter Fan Performance table. At 4000 cfm and 8 in wg, the fan speed is 1 405 rpm and brake hp is 2.34 The table indicates that standard drive is adequate.

V Select unit that corresponds to available power source.

Refer to Electrical Data table and choose unit as required A 48DD012 230-3-60 is available.

128.000 Btuh 90,000 Btuh

198.000 Btuh

80 F Edb, 67 Ewb

. 95 F

4000 Cfm

230-3-60

8 in. wg

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