Bryant 548F User Manual download pdf (Page 40)

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VII. LOSS-OF-CHARGE SWITCH

Located on the outdoor liquid line is a low-pressure switch

which functions as a loss-of-charge switch. This switch con-

tains a Schrader core depressor. This switch opens at 7 psig

and closes at 22 psig. No adjustment is necessary. Refer to

Table 1.

VIII. FREEZESTAT

Located on the “hair pin” end of the indoor coil is a bimetal

temperature sensing switch. This switch protects the indoor

coil from freeze-up due to lack of airflow. The switch opens at

30 F and closes at 45 F. No adjustment is necessary. Refer to

Table 1.

IX. REFRIGERANT CHARGE

Amount of refrigerant charge is listed on unit nameplate

(also refer to Table 1).

Unit panels must be in place when unit is operating during

charging procedure. Unit must operate a minimum of

15 minutes before checking charge.

A. No Charge

Use standard evacuating techniques. After evacuating sys-

tem, weigh in the specified amount of refrigerant. (Refer to

Table 1.)

B. Low Charge Cooling

Use Cooling Charging Charts, Fig. 39-42. Vary refrigerant

until the conditions of the charts are met. Note that the

charging charts are different from type normally used.

Charts are based on charging the units to the correct super-

heat for the various operating conditions. Accurate pressure

gage and temperature sensing device are required. Do not

use mercury or small dial type thermometers because they

are not adequate for this type of measurement. Connect the

pressure gage to the service port on the suction line. Mount

the temperature sensing device on the suction line near the

compressor and insulate it so that outdoor ambient tempera-

ture does not affect the reading. Indoor-air cfm must be

within the normal operating range of the unit.

C. To Use Cooling Charging Charts

This method is to be used in Cooling mode only. Take the out-

door ambient temperature and read the suction pressure

gage. Refer to charts to determine what the suction tempera-

ture should be. If suction temperature is high, add refriger-

ant. If suction temperature is low, carefully recover some of

the charge. Recheck the suction pressure as charge is

adjusted.

Example: (Fig. 39)

Outdoor Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 F

Suction Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74 psig

Suction Temperature should be . . . . . . . . . . . . . . . . . . . . 70 F

(Suction Temperature may vary ± 5° F.)

D. Heating Mode Charge

Do not attempt to adjust charge by cooling methods while in

Heating mode. When charging is necessary in Heating mode,

recover refrigerant and weigh in according to unit data plate

refrigerant data.

Fig. 35 — Cleaning Outdoor Coil

Fig. 36 — Propping Up Top Panel

Fig. 37 — Separating Coil Sections

Fig. 38 — Outdoor-Fan Adjustment

UNIT 548F

FAN HEIGHT — ‘‘A’’

(in.)

036-060 AND

072 (208/230 v)

2.75

072

(460 v and 575 v)

3.50

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Bryant 548F User Manual Page 40

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