Carrier 60 Service Manual download pdf (Page 38)

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4-5

g. Remove refrigerant using a refrigerant recovery sys-

tem.

h. Start vacuum pump and open all valves. Dehydrate

unit to 500 microns Hg vacuum.

i. Cl ose off pump valve, and stop pump. Wait five min-

utes to see if vacuum holds.

j. Charge system. Refer to paragraph 4.8.2

4.8 ADDING REFRIGERANT TO SYSTEM

4.8.1 Checking Refrigerant Charge

The following conditions must be met to accurately

check the refrigerant charge.

a. Coach engine operating at high idle.

b. Unit operating in cool mode for 15 minutes.

c. Headpressure at least 150 psig (10.21 bar). (It maybe

necessary to block condenser air flow t o raise head

pressure.)

d. Under the above conditions, the system is properly

charged when the refrigerant liquid level is at 1/2 to

3/4 of the lower receiver sight glass. If it is not at the

proper level, add or remove refrigerant to bring it t o

the proper level. Refrigerant level should not appear

in the upper sight glass, as this would indicate an

overcharge.

4.8.2 Adding Full Charge

a. Install manifold gauge set at the compressor suction

service valve and service port above the discharge

line check valve. See figure Figure 4-6.

b. Evacuate and dehydrate system. (Refer to paragraph

4.7)

c. Place appropriate refrigerant cylinder on scales. Pre-

pare to charge liquid refrigerant by connect charging

hose from container to center connection on gage

manifold . Purge air from hoses.

d. Note weight of refrigerant and cylinder.

e. Open cylinder valve, backseat discharge valve on

gauge manifold and allow liquid refrigerant to flow

into the high side of the system

f. When correct charge has been added, refer to para-

graph 1.3, close cylinder valve and frontseat man-

ifold discharge valve. At this point, the high side of

the system has been charged but the low sideis still in

a vacuum because the liquid line solenoid is normally

closed.

g. Prepare the cylinder as required to allow vaporcharg-

ing. Backseat the manifold suction valve and charge

vapor to build 20 to 30 psig (1.36 to 2.04 bar) pres-

sure on the m anifold suction gauge. Close cylinder

valve and frontseat suction manifold set.

h. Check chargelevel in accordance with theprocedures

of paragraph 4.8.1.

4.8.3 Adding Partial Charge

a. Install manifold gauge set at the compressor suction

service valve and service port above the discharge

line check valve. See figure Figure 4-6.

b. Place appropriate refrigerant cylinder on scales. Pre-

pare to charge vapor refrigerant by connecting charg-

ing hose from container t o center connection on

gauge manifold . Purge air from hoses.

c. Run unit in cool mode for 15 minutes. With suction

service valve midseated open cylinder valve and add

vapor charge until refrigerant level appears in the

lower receiver sight glass. Under the above condi-

tions, the system is properly charged when the refrig-

erant liquid level is at 1/2 to 3/4 of the lower receiver

sight glass. If it is not at the proper level, add or re-

move refrigerant to bring it to the proper level. Re-

frigerant level should not appear in the upper sight

glass, as this would indicate an overcharge.

d. Backseat suction service valve. Close vapor valve on

refrigerant drum and note weight. Remove manifold

gauge set and replace all valve caps.

4.9 CHECKING FOR NONCONDENSIBLES

To check for noncondensibles, proceed as follows:

a. Stabilize system to equalize pressure between the

suction and discharge side of the system.

b. Check temperature at the condenser and receiver.

c. Check pressure at the compressor discharge service

valve.

d. Check saturation pressure as it corresponds to the

condenser/receiver temperature using the Tempera-

ture-Pressure Chart, Table 4-4.

e. If gauge reading is 3 psig (0.20 bar) or more than the

saturation pressure in step d, noncondensibles are

present.

f. Remove refrigerant using a refrigerant recovery sys-

tem.

g. Evacuate and dehydrate the system. (Refer to para-

graph 4.7.)

h. Charge the unit. (Refer to paragraph 4.8. 2.)

4.10 CHECKING AND REPLACING HIGH PRES-

SURE SWITCH

WARNING

DO NOT USE A NITROGEN CYLINDER

WITHOUT A PRESSURE REGULATOR

WARNING

DO NOT USE OXYGEN IN OR NEAR A

REFRIGERATION SYSTEM AS AN EX-

PLOSION MAY OCCUR.

a. Disconnect wiring and remove switch from unit. All

units are equipped with a schrader valve at the high

pressure switch connection.

b. Connect switch to a cylinder of dry nitrogen. (See

Figure 4-7.)

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