Carrier Compressor and Condensing Unit Removing, Inspecting and Replacing Components Fig, No

To Regulate Control Set Point — Turn adjustment nut

clockwise to its bottom stop. In this position, set point is 86 psig. Control set point is then regulated to desired pressure by turning adjustment nut counterclockwise. Each full turn decreases set point by approximately 7.2 psi. Approximately

12 turns counterclockwise		lowers the control				set	point to
0 psig. See Table 5.
Table 5 — Capacity Control
			% Full Load Capacity
	NO. OF		100		67	49		32
UNIT 06E,07E	CONTR			% Full Load kW
	CYL
			100		73	57		46
			Number of Active Cylinders
ALL 4 CYLINDER	2		4		—	2		—
MODELS
ALL 6 CYLINDER	4		6		4	—		2
MODELS

NOTE: Capacity control valve factory settings for 4-cylinder units

are: 59 psig control set point (cylinder load point), 10 psi differential

(59 psig cylinder unload point). Settings for 6-cylinder units are: left cylinder bank control set point is 70 psig, differential is 10 psi; right cylinder bank control set point is 68 psig, differential is 10 psi.

Pressure Differential Adjustment — Turn differential adjust- ing screw counterclockwise to its back-stop position. In this position, differential is 6 psi. Pressure differential is set by turning adjusting screw clockwise. Each full turn increases pressure differential by approximately 0.8 psi. Approximately 10 turns increases differential to 16 psi.

SUCTION CUTOFF UNLOADER OPERATION — The ca- pacity control valve shown in Fig. 9 is the pressure operated type. Refer to Fig. 10 and the following description for valve operation.

Loaded — When suction pressure rises high enough to over- come control set point spring, the diaphragm snaps to the left and relieves pressure against the poppet valve. The drive spring moves poppet valve to the left and it seats in the closed position. See Fig. 10.

With poppet valve closed, discharge gas is directed into the unloader-piston chamber and pressure builds up against the piston. When pressure against unloader piston is high enough to overcome the unloader valve spring, piston moves valve to the right, opening suction port. Suction gas can now be drawn into the cylinders and the bank is running fully loaded.

Unloaded — As suction pressure drops below set point, con- trol spring expands, snapping diaphragm to right. This forces poppet valve open and allows gas from discharge manifold to vent thru base of control valve to suction side. Loss of full discharge pressure against unloader piston allows unloader valve spring to move valve left to closed position. The suction port is blocked, isolating the cylinder bank from the suction manifold. The cylinder bank is now unloaded. See Fig. 10.

Service Replacement Compressors — These compressors are not equipped with capacity control valves. One side-bank cylinder head is a bypass unloading type, plugged with a spring-loaded piston plug assembly. As received, the compres- sor will run fully loaded.

Replacing Suction Cutoff Unloading Heads — When the original compressor is equipped with suction cutoff unloading head(s), the complete cylinder head and control valve assem- blies must be transferred to the service (replacement) compres- sor. See Fig. 10 for typical suction cutoff installation. Where one step of unloading is required, remove the bypass-type unloader head and valve plate assembly from replacement compressor (cylinder head next to terminal box). Remove check valve from the valve plate. Using new gaskets, reinstall the valve plate assembly and install the suction cutoff head from the original compressor. Torque the cylinder head holddown bolts to 90 to 100 lb-ft. For 6-cylinder 2-step suction cutoff unloading, transfer the second unloading head and control valve from the original compressor to the replacement compressor, using the valve plate assembly from the replace- ment compressor. Use new gaskets.

Be sure the new cylinder head gasket is the one shown in Fig. 11, Item 33, when installing suction cutoff unloader head.

Install parts removed from replacement compressor on original compressor and seal all openings to prevent contamination.

Removing, Inspecting and Replacing Components (Fig. 11)

Do not remove the compressor terminal box cover until all electrical power is disconnected and pressure is relieved. Terminal pins may blow out causing injuries, death, and/or fire.

SERVICE NOTES

1.All compressors have interchangeable valve plate assem- blies, unloader valves and oil pump bearing head assemblies. For replacement items use Carrier Specified Parts.

2.Before compressor is opened, the refrigerant must be removed from it by the Pumpdown method:

a.Start compressor, close suction shutoff valve, and reduce crankcase pressure to 2 psig. (Bypass low pressurestat with a jumper.)

b.Stop compressor and isolate from system by closing discharge shutoff valve.

c.Bleed any residual refrigerant. Drain oil if necessary.

3.After disassembly, clean all parts with solvent. Use mineral spirits, white gasoline or naphtha.

4.Before assembly, coat all parts with compressor oil and clean and inspect all gasket surfaces. Replace all gaskets with new factory-made gaskets. See Table 6 for torque values.

5.After reassembly, evacuate compressor and open suction and discharge valves. Restart compressor and adjust refrigerant charge.

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