Carrier 48TJD Specifications download pdf (Page 36)

UNIT UNIT

48TJ VOLTAG E

208/230

016 460

575

208/230

020 460

575

208/230

024 460

575

208/230

028 460

575

LEGEND

BHP -- Brake Horsepower

BkW -- Brake Kilowatts

Table 25 -- Evaporator-Fan Motor Data

MAXIMUM MAXIMUM MAXIMUM

ACCEPTABLE ACCEPTABLE ACCEPTABLE

CONTINUOUS BHP* CONTINUOUS BkW* OPERATING WATTS

4.25 3.17 3,775

3.45 2.59 3,065

5.90 4.40 5,180

8.70 6.49 7,915

9.50 7.08 8,640

8.70 6.49 7,915

10.20 7.61 9,510

11.80 8.80 11,000

10.20 7.61 9,510

*Extensive motor and electrical testing on these units ensures that the full horsepower (brake kilowatt)

range of the motors can be utilized with confidence. Using your fan motors up to the horsepower (brake

kilowatt) ratings shown in this table will not result in nuisance tripping or premature motor failure. Unit

warranty will not be affected.

NOTE: All indoor-fan motors 5 hp and larger meet the minimum efficiency requirements as established by

the Energy Policy Act of 1992 (EPACT) effective October 24, 1997.

MAXIMUM

AMP DRAW

10.5

4.8

3.9

15.8

7.9

6.0

22.0

13.0

10.0

28.0

14.6

13.0

Table 26 -- Evaporator-Fan Motor Efficiency

UNIT 48TJ MOTOR EFFICIENCY (%)

016 (3.0 Hp) 81.7

016 (3.7 Hp) 65.6

020 (5 Hp) 67.5

024 (7.5 Hp) 66.5

028 (10 Hp) 69.5

NOTE: All indoor-fan motors 5 hp and larger meet the minimum effi-

ciency requirements as established by the Energy Policy Act of 1992

(EPACT) effective October 24, 1997.

CONDENSER-FANS AND MOTORS -- Condenser fans

and motol.'s am factol T set. Refer to Condenser-Fan Adjustment

section (page 42) as required. Be sure that fans rotate in the

proper direction.

RETURN-AIR FILTERS- Check that correct filtel.s are

installed in filter tracks (see Table 1). Do not operate unit with-

out return-air filters.

OUTDOOR-AIR INLET SCREENS -- Outdoor-air inlet

screens must be in place before operating unit.

GAS HEAT -- Verify gas pressmes before turning on heat as

follows:

1. Turn off manual gas stop.

2. Connect pressure gage to supply gas pressure tap (see

Fig. 13).

3. Connect pressure gage to manifold pressure tap on gas

valve.

4. Turn on manual gas stop and set thermostat to HEAT

position. Adjust set point to several degrees above the

current room temperature to ensure a heat demand. After

the unit has mn for sevend minutes, verify that incoming

pressure is 5.5 in. wg or greater, and that the manifold

pressure is 3.3 in. wg. If manifold pressure must be ad-

justed, refer to Gas Valve Adjustment section on page 43.

5. After unit has been in operation for 5 minutes, check tem-

perature rise across the heat exchangers. See unit infor-

mative plate for correct rise limits of the heat supplied.

Air quantities may need to be adjusted to bring the actual

rise to within the zdlowable limits.

Operating Sequence

COOLING, UNITS WITHOLTT ECONOMIZER -- When

thermostat calls for cooling, terminals G and Y I are energized.

The indoor (evaporator) fan contactor (IF(?_), compressor con-

tactor no. 1 (CI) and outdoor-fan contactor (OFC) are ener-

gized, and evaporator-fan motor, compressor no. 1, and both

condenser fans stall. The condenser-fan motors mn continuous-

ly while unit is cooling. If the thermostat calls for a second stage

of cooling by energizing Y2, compressor contactor no. 2 (C2) is

energized and compressor no. 2 starts.

When the thermostat is satisfied, CI and C2 tue deener-

gized and the compressors and outdoor (condenser) fan motors

(OFM) shut off. After a 30-second delay, the indoor (evapora-

tor) fan motor (IFM) shuts off. If the thermostat fan selector

switch is in the ON position, the evaporator-fan motor will run

continuously.

HEATING. UNITS WITHOUT ECONOMIZER -- When

the thermostat calls for heating, terminal WI is energized. In

order to prevent thermostat short-cycling, the unit is locked

into the Heating mode for at least 1 minute when WI is ener-

gized. The induced-draft motor (IDM) is then energized and

the burner ignition sequence begins. The indoor (evaporator)

fan motor (IFM) is energized 45 seconds after a fame is

ignited. On units equipped for two stages of heat, when addi-

tional heat is needed, W2 is enelgized and the high-fire sole-

noid on the main gas valve (MGV) is energized. When the

thermostat is satisfied and WI and W2 are deenergized, the

IFM stops after a 45-second time-off delay.

COOLING. UNITS WITH ECONOMISERIV -- When free

cooling is not available, the compressol_ will be controlled by

the zone thermostat. When free cooling is available, the

outdoor-air &unper is modulated by the EconoMiSerIV control

to provide a 50 to 55 F supply-air temperature into the zone. As

the supply-air temperature fluctuates above 55 or below 50 IF.

the &lmpers will be modulated (open or close) to bring the

supply-air temperature back within the set point limits.

For EconoMiSerIV operation, there must be a thermostat

call for the fan (G). This will move the damper to its minimum

position during the occupied mode.

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Carrier 48TJD Specifications Page 36

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